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UBC Theses and Dissertations

Kinetic study of the gernation and reactions of allyl and cyclopropyl radicals in the gas phase Kambanis, Stamatis M. 1967

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The U n i v e r s i t y of B r i t i s h  Columbia  FACULTY OF GRADUATE STUDIES  PROGRAWiE OF THE FINAL ORAL EXAMINATION FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  ;  of STAMATIS Mi KAMBANIS B.Sc. , U n i v e r s i t y of Athens, 1957  :  .Sc., U n i v e r s i t y o f B r i t i s h Columbia/ 19 THURSDAY, SEPTEMBER 14, AT 3:JO P.M. IN ROOM 225, CHEMISTRY BUILDING  COMMITTEE IN CHARGE Chairman: F.W. Dalby D.C.-Walker D. McGreer  B.N. Moyls N. Basco D.G..L. James F . Aubke  E x t e r n a l Examiner: K.J. Ivin Department of C h e m i s t r y ' Queen's U n i v e r s i t y of B e l f a s t David-Keir Building S t r a m i l l i s " Road,' B e l f a s t 9 Ireland Research S u p e r v i s o r :  D.G.L. James  «*••  •  •  KINETIC STUDY OF THE GENERATION OF ALLYL AND CYCLOPROPYL RADICALS^ ABSTRACT A l l y ! and c y c l o p r o p y l r a d i c a l s were g e n e r a t e d i n the gas phase a t a mean temperature of 140 C by new methods which promise t o be"of g e n e r a l a p p l i c a t i o n . Thus the r a d i c a l R" may be generated by e i t h e r of the two sequences: Addition  :  Dismutation:  C ^  + CH =CHCH C00R 2  2  C^QCOOR  > C^QCOOR >  C  H 5  + 1  0  C  °2  +  R  COOR  + C0  2  + R  The a d d i t i o n - d i s m u t a t i o n sequence was used t o generate the a l l y l r a d i c a l from a l l y l 3-butenoate and from d i a l l y l o x a l a t e , and thei-.cycloprop'yl r a d i c a l from a l l y l c y c l o p r o p y l - c a r b o x y l a t e and from c y c l o p r o p y l 3-butenoate, The m e t a t h e s i s - d i s m u t a t i o n sequence was t e s t e d f o r the g e n e r a t i o n of methyl r a d i c a l s from the methyl e s t e r of c y c l o h e x a - l , 4 - d i e n e - 3 - c a r b o x y l i c a c i d , and a p p l i e d to the rgeneration of a l l y l r a d i c a l s from the c o r r e s p o n d i n g a l t y l ester. The A r r h e n i u s parameters o f the generat i n g sequence r e a c t i o n s f o r e v e r y system were measured and d i s c u s s e d . These methods generate R° r a d i c a l s i n the presence of an excess o f the s e n s i t i z i n g r a d i c a l s , so t h a t the p r e s e n t systems a l l o w the o b s e r v a t i o n o f p a t t e r n s o f R'/C^R°^ i n t e r a c t i o n . A l l y l r a d i c a l s were generated i n the absence o f a p p r e c i a b l e amounts of o t h e r r a d i c a l s , i n the gas phase, by the u n s e n s i t i z e d thermal d e c o m p o s i t i o n :  C H OGCCOOC H 3  5  3  ^  5  log k ( s e c . )  =  _ 1  2 C  H 3  5  +  2  C  0 2  (14 + 1 ) - (37 + 2)10 /2.3RT 3  A l l y l r a d i c a l s were a l s o generated i n the presence of an equal amount of c y c l o h e x a d i e n y l r a d i c a l s i n the gas phase by the u n s ^ n s i t i z e d thermal decomposition:  S=J  C O O G  3  H  5  log k ( s e c . ) _ 1  ~ — f  =  +  co  +  2  C  3  H  ^  ( 1 4 + 1) - ( 3 8 + 3)10 /2.3RT 3  The A r r h e n i u s parameters of these two decompositions i n d i c a t e t h a t a l l the bonds which are f i n a l l y broken are s i g n i f i c a n t l y extended i n the t r a n s i t i o n s t a t e . The combination, d i s p r o p o r t i o n a t i o n , isomerizat i o n , and m e t a t h e s i s r e a c t i o n s were i n v e s t i g a t e d f o r the a l l y l and c y c l o p r o p y l . r a d i c a l s . T y p i c a l r e s u l t s include: (40 + 3 ) %  Combination and Disproportionation  C  +  \ C H + < £ ^ ( 9 + 2)7. 3  Metathesis:  6  [ > + CH =CHCH 00C<—*t>H + CH -CH-CH00C<J 2  2  2  E .= 8.0.+ 0„8-4ccal./mole Isomerization:£>'—;  E^= 20 + 5 kcal„/mole  GRADUATE STUDIES  F i e l d o f Study:  P h y s i c a l Chemistry  Topics i n P h y s i c a l Chemistry Chemical K i n e t i c s  A. Bree D.G.L. James  Topics i n Organic Chemistry  J.P.. Kutney  Seminar i n P h y s i c a l C h e m i s t r y  N. B a r t l e t t .  P h y s i c a l O r g a n i c Chemistry. Molecular Spectroscopy C h e m i c a l Thermodynamics  R. S t e w a r t A. Bree J.R. Sams  A  KINETIC  GENERATION AND  STUDY  AND  OF  THE  REACTIONS  CYCLOPROPYL,RADICALS  IN'  OP THE  A L L Y L GAS  PHASE  by  STAMATIS  KAMBANIS  M.  B . S c ,  U n i v e r s i t y  of  A t h e n s , 1 9 5 7  M . S c ,  U n i v e r s i t y  of  B r i t i s h  A  THESIS THE  SUBMITTED  IN  REQUIREMENTS DOCTOR i n  OF  t h e  C o l u m b i a , 1 9 6 4  PARTIAL FOR  THE  FULFILMENT DEGREE  OF  PHILOSOPHY Department of.  CHEMISTRY  We  a c c e p t t o  THE  t h i s  t h e  t h e s i s  r e q u i r e d  UNIVERSITY  OF  as  c o n f o r m i n g  s t a n d a r d  BRITISH  A u g u s t , 1 9 6 7  COLUMBIA  "  OF  In  presenting  for  an  that  advanced  the  Department  or  my  Department  at  agree  1 9 t h  partial  the  make  or  representatives.  h.i)s  of  written  of  this  thesis  may  for  permission.  Chemistry  September,  Columbia  1 9 6 7 .  be  of  for  granted  It  financial  is  of  the  British  available  permission  purposes  by  fulfilment  University  i t freely  that  The U n i v e r s i t y of B r i t i s h V a n c o u v e r 8, Canada Date  in  scholarly  publication  without  shall  I further  for  thesis  degree  Library  Study.  thesis  this  for  Columbia,  I  reference  and  extensive  by  the  requirements  copying  Head  understood  gain  shall  of  this  my  that  not  of  agree  be  copying  allowed  ABSTRACT Allyl gas phase  and c y c l o p r o p y l  cal  radicals  a t a mean t e m p e r a t u r e  which promise  t o be o f - g e n e r a l  :  application.  2  :  ?  allyl  radical  from a l l y l  late,  and t h e c y c l o p r o p y l and from  thesis-dismutation  radicals  cyclopropyl  and a p p l i e d  of the generating  radicals,  Allyl  oxa-  cyclopropyl-  3-butenoate.  T h e meta-  f o r the generation of  ester'of cyclohexa-1,4-dieneto the generation of a l l y l  sequence  The A r r h e n i u s  reactions These  f o r every  methods g e n e r a t e  i n t h e p r e s e n c e o f an e x c e s s o f t h e s e n s i t i z i n g  so t h a t  the patterns  ciable  and from d i a l l y l  from a l l y l  s y s t e m were m e a s u r e d a n d d i s c u s s e d . R* r a d i c a l s  COOR  was u s e d t o g e n e r a t e t h e  was t e s t e d  from the methyl  •  t L  from t h e c o r r e s p o n d i n g a l l y l , e s t e r .  parameters  of  H  j  COOR  radical  + R*  > ( ( j ) + CO- + R*  3-butenoate  sequence  acid,  P A + .  A  a d d i t i o n - d i s m u t a t i o n sequence  3-carboxylic  C  2  (G X  >  \=z/ COOR  N^/  methyl r a d i c a l s  » C^H^Q + C 0  X X  .Dismutation:  carboxylate  > C'^QCOOR  C^H^COOR  C~H; +  Thus t h e r a d i -  o f t h e two s e q u e n c e s :  2  •  ^  The  b y new methods  + CH =CHCH C00R  iDismutation:  ^Metathesis  were g e n e r a t e d i n t h e  o f 140°C  R* may be g e n e r a t e d b y e i t h e r  rAddition  ' • '  t h e p r e s e n t systems  of R*/C H£ 2  radicals  amounts,of  allow the observation  interaction.  were g e n e r a t e d i n t h e a b s e n c e  other r a d i c a l s ,  o f appre-  i n t h e gas phase,  by the  unsensitized  thermal  C,H OOCCOOC-,H  > 2C E' + 2 C 0 3 5 2  '  c  3 5  decomposition: 7  3 5  log kCsecT )  (14+1) - (37 ± 2 ) 1 0 / 2 . 3 R T  =  1  o  5  Allyl  r a d i c a l s were a l s o  equal  amount  generated  i n the presence  of cyclohexadienyl.radicals  the u n s e n s i t i z e d  thermal  o f an  i n t h e gas phase by  decomposition:  CD^ +  coooyy log k(sec7 ) 1  The that  C 0  >  =  2  °3 5  +  H  (14 + 1) - (38 + 3)10 /2.3RT 5  A r r h e n i u s parameters  of these  two d e c o m p o s i t i o n s  a l l t h e bonds which a r e f i n a l l y  extended The  broken  indicate  are, s i g n i f i c a n t l y  i n the t r a n s i t i o n state. combination,  metathesis reactions cyclopropyl  disproportionation,  were i n v e s t i g a t e d f o r ' t h e a l l y l a n d  radicals.  Typical results include: /  G  Combination  350 H  /7=\ ^  \  and r 5 5 Disproportionation J ^ ' C  H  +  (0 /  v •  3  H l  H  > " + CH =CHCH 00C<] —> 2  2  _  >  /~ \ f\ — / ? \—'  <> 3)# 0 ±  ==  > C  °3 6 Metathesis:  i s o m e r i z a t i o n , and  >H  +  O  (51±4)# < 9±2)So  + CH -CH-CH00C<] li. 2  E = 8.010.8 kcal./mole Isomerization:  [>• — — > C^H^. ; • E = 20 + 5 k c a l . / m o l e  iv T A B L E OF CONTENTS  .Page INTRODUCTION Free r a d i c a l sources Unsensitized decomposition . S e n s i t i z e d decomposition . S e n s i t i z e d decomposition: reaction The a l l y l r a d i c a l ..The a l l y l p o l y m e r i z a t i o n . The c y c l o p r o p y l r a d i c a l The c y c l o h e x a d i e n y l r a d i c a l  sequences  1 2 4 7 11 1 3 1 5 16  . . . .  .  EXPERIMENTAL' METHODS H i g h vacuum t e c h n i q u e s . . . . . . . 18 The h e a t e d s t o r a g e l i n e 2 2 A- t y p i c a l r u n w i t h d i e t h y l k e t o n e a s t h e s e n s i t i z e r . 2 5 A t y p i c a l r u n w i t h acetophenone as t h e s e n s i t i z e r . . 2 9 A t y p i c a l r u n f o r the homopolymerization of d i a l l y l oxalate 3 0 Chromatographic analysis. . . . . . . i . . . 3 0 N.M.R. a n a l y s i s a n d i d e n t i f i c a t i o n . J . !, 3 2 Materials . . . . . . . . / \ 3 3 DISCUSSION A.  B.  Reactions of the e t h y l 3-butenoate . . . . . . Thermal decomposition  - C*~ R e a c t i o n s oxalate D.  , E. / F.  G. H.  of the e t h y l  radical' with . of d i a l l y l radical  allyl 4 3  oxalate  with -  65  diallyl 85  Reactions- o f the e t h y l r a d i c a l with c y c l o p r o p y l 3 - b u t e n o a t e and a l l y l c y c l o p r o p y l c a r b o x y l a t e . . 9 9 Reactions of the e t h y l r a d i c a l with the methyl ester of cyclohexa-1,4-diene-3-earboxylic acid. The u n s e n s i t i z e d d e c o m p o s i t i o n hexa-1 , 4 - d i e n e - 3 - c a r b o x y l a t e  of a l l y l  Reactions of the ethyl r a d i c a l hexa-1 , 4 - d i e n e - 3 - c a r b o x y l a t e .  with a l l y l  .  1 3 9  cyclo167  Photochemical r e a c t i o n s o f acetophenone cyclohexadienic derivatives  cyclo186  with 201  V  W i t h  c y c l o h e x a d i e n e , 1-4  W i t h  m e t h y l  c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e  W i t h  a l l y l  c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e . 2 1 7  '  2 0 1 ..  2 1 1  GENERAL CONCLUSIONS . . .  2 1 9  BIBLIOGRAPHY. .  2 2 9  v i L I S T  OP  FIGURES  F i g u r e 1. 2 .  Page S c h e m a t i c  diagram  of  the  vacuum  Schematic;  diagram  of  the  o p t i c a l  h e a t e d  s t o r a g e  • A d d i t i o n  3 .  and 4.  and  a l l y l .  E t h y l  a p p a r a t u s system  . . . .  and  of  19 the  l i n e  2 0  m e t a t h e s i s  between  the  e t h y l  r a d i c a l  3 - b u t e n o a t e  5 0  r a d i c a l - s e n s i t i z e d  d e c o m p o s i t i o n  of  a l l y l  3 - b u t e n o a t e  5 2  D i s p r o p o r t i o n a t i o n  5 .  between  ethyl., and  a l l y l  r a d i c a l s  ' .  6 .  U n s e n s i t i z e d  7 .  M e t a t h e s i s  d e c o m p o s i t i o n  of  the  a l l y l  of  d i a l l y l  r a d i c a l  o x a l a t e  .,with  .  5 5 .  7 2  d i a l l y l  o x a l a t e  7 6  8 .  M u t u a l  '9.  A d d i t i o n and  i n t e r a c t i o n s  D i a l l y l between  1 0 .  and  d i a l l y l  of  c a r b o x y l a t e 1 2  =  M e t a t h e s i s  m e t a t h e s i s  E t h y l  r a d i c a l s  between  7 7  t h e , e t h y l  r a d i c a l 91  p a t t e r n s of i n t e r a c t i o n s and the a l l y l r a d i c a l  t h e ; e t h y l and of  r a d i c a l  c y c l o p r o p y l  the  ethyl,  p r o p y t - c a r b o x y l a t e 1 3  a l l y l ,  o x a l a t e  .oxalate:— the e t h y l  A d d i t i o n  1 1 .  of  and  to  a l l y l  c y c l o p r o p y l -  3 - b u t e n o a t e  r a d i c a l  w i t h  c y c l o p r o p y l  .  and  .  a l l y l  .  .  of  c y c l o p r o p y l  . 1 1 1  c y c l o -  3 - b u t e n o a t e .  r a d i c a l - s e n s i t i z e d - d e c o m p o s i t i o n  c y c l o p r o p y l — c a r b o x y l a t e  9 2  .  a l l y l 3 -  butenoate 14  P a t t e r n s and  the.  1 1 3 of  i n t e r a c t i o n s  c y c l o p r o p y l  between  r a d i c a l  i n  c y c l o p r o p y l c a r b o x y l a t e / e t h y l p r o p y l 1 5 .  3 - b u t e n o a t e /  M e t a t h e s i s  of  the  e t h y l  I s o m e r i z a t i o n a l l y l  r a d i c a l  of  the  and  the  the  e t h y l  r a d i c a l  systems:  r a d i c a l  and  a l l y l  c y c l o -  r a d i c a l  c y c l o p r o p y l  c y c l o p r o p y l c a r b o x y l a t e 16.  1 1 2  114  r a d i c a l  c y c l o p r o p y l  c y c l o p r o p y l  w i t h  a l l y l  3 - b u t e n o a t e  r a d i c a l  t o  the  1 1 5  . 1 1 9  V l l  L I S T OF FIGURES ( c o n t i n u e d ) Figure  "Page  17.  Decomposition  18.  Formation o f a l l y l r a d i c a l s by d i r e c t t i o n o f OCO2C5H10 5 10 2<] a  19.  20. 21. 22. 23.  24.  n  d  G  H  decomposi-  C 0  1  26.  6  131  P a t t e r n s o f m e t a t h e s i s between t h e e t h y l r a d i c a l a n d m e t h y l , c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e ( a ) •.  151  P a t t e r n s o f m e t a t h e s i s between t h e e t h y l r a d i c a l and m e t h y l c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e ( b ) .  152  E t h y l - r a d i c a l - s e n s i t i z e d decomposition of methyl cyclohexa-1,4-diene-3-carboxylate .  154  P a t t e r n s o f i n t e r a c t i o n s between t h e e t h y l r a d i c a l .and t h e m e t h y l , c y c l o h e x a d i e n y l c a r b o x y l a t e r a d i c a l s I* and I I * -155 Unsensitized decomposition of a l l y l diene-3-carboxylate  cyclohexa-1,4-  Metathesis of the a l l y l r a d i c a l w i t h a l l y l hexa-1 , 4 - d i e n e - 3 - c a r b o x y l a t e . P a t t e r n s o f i n t e r a c t i o n between t h e a l l y l = a n d t h e c y c l o h e x a d i e n y l r a d i c a l ,.  cyclo-  172 182  radical 183  27.  Metathesis, of the ethyl r a d i c a l w i t h a l l y l hexa-1 , 4 - d i e n e - 3 - c a r b o x y l a t e  28. i  P a t t e r n s of decompostion o f the a l l y l dienylcarboxylate radical  cyclohexa-  29.  R e a c t i o n s of the acetophenone t r i p l e t hexadiene-1,4 . . . . .  with  cyclo-  R e a c t i o n s o f the acetophenone t r i p l e t w i t h cyclohexa-1,4-diene-3-carboxylate . .  methyl  30.  2  A d d i t i o n of the e t h y l r a d i c a l to the cyclopropane r i n g o f a l l y l c y c l o p r o p y l c a r b o x y l a t e and c y c l o p r o p y l 3-butenoate '.  ;  25.  123  of energized ethylcyclopropane. . .  cyclo-  192 193 206 215  V X l l  LISO? OF TABLES Table I. II..  III.  IV.  V. VI. VII. V I I I .  IX.  X.. XI. XII. / X I I I .  XIV. XV.  Page R e a c t i o n s o f the' e t h y l r a d i c a l w i t h 3-butenoate  allyl 44  Arrhenius. parameters f o r the p r i n c i p a l r e a c t i o n s of a l l y l 3-butenoate and a l l y l p r o p i o n a t e w i t h the e t h y l r a d i c a l 33 Heats o f c e r t a i n h y p o t h e t i c a l processes assoc i a t e d w i t h t h e t r a n s i t i o n s t a t e o f t h e decomp o s i t i o n o f t h e a d d u c t r a d i c a l RCOOCH2CHC3H7. . 61 P a r t i a l c o n t r i b u t i o n s o f bonds i n v o l v i n g atoms w i t h f r e e e l e c t r o n s , and heats o f f o r m a t i o n o f certain r a d i c a l species  62  Thermal decomposition o f d i a l l y l  68  oxalate  . . .  Heats o f the thermal decomposition r e a c t i o n s o f certain a l k y l oxalates  79  C h e m i c a l s h i f t s ; a n d a r e a s o f t h e N..M.R. p r o t o n p e a k s ; o f d i a l l y l o x a l a t e and. i t s p o l y m e r . . .  82  R e a c t i o n s ^ o f the. e t h y l , r a d i c a l w i t h oxalate  86  diallyl-  C h a r a c t e r i s t i c values of quantities associated ' with the reactions, of,the ethyl r a d i c a l with d i a l l y l oxalate 94 \  Reactions of the e t h y l L r a d i c a l with a l l y l propylcarboxylate Reactions, o f t h e e t h y l r a d i c a l w i t h 3-butenoate  cyclo100  cyclopropyl ;. 1 0 2  Arrhenius parameters o f the r e a c t i o n s of t h e ethyl radical with a l l y l cyclopropylcarboxylate and c y c l o p r o p y l 3-butenoate. 116 Results of the kinetic r i n g opening  study  of the cyclopropyl  R e a c t i o n s o f t h e e t h y l r a d i c a l v/ith methyl cyclohexa-1,4diene-3-carboxylate  133 140  C o m p a r a t i v e N.M.R. s p e c t r a o f IC2H5, I I C 2 H 5 a n d methyl cyclohexa-1,4-diene-3-carboxylate. . . . 145  ix LIST" OF  TABLES' ( c o n t i n u e d )  Table XVI.  XVII.  XVIII.  XIX.  XX.  XXI. XXII. XXIII.  _ A r r h e n i u s parameters of the r e a c t i o n s of the ethyl, r a d i c a l with methyl cyclohexa-1,4—diene3-carboxylate. The u n s e n s i t i z e d decomposition hexa-1 , 4 - d i e n e - 3 - c a r b o x y l a t e  of a l l y l  R e a c t i o n s of the t r i p l e t , cyclohexadiene-1,4  161 .  cyclo168  Reactions of the e t h y l r a d i c a l with cyclohexa-1,A—diene-3-carboxylate.  allyl  acetophenone  188' with 204  R e a c t i o n s of the t r i p l e t acetophenone w i t h methyl cyclohexa-1,4-diene-3-carboxylate . . .  204  Generation of f r e e r a d i c a l s d i s m u t a t i o n sequence  by  220  Generation of free r a d i c a l s d i s m u t a t i o n sequence  by  Modes o f d i s s o c i a t i o n . Patterns of i n t e r a c t i o n  \  an a  additionmetathesis221  . . . /  XXIV.  ,Page  223  /  of f r e e  radicals  . . .  226  X  ACKNOWLEDGEMENT  I w i s h t o thank D r . D. G. L . James f o r h i s g u i d a n c e and encouragement i n t h e c o u r s e o f t h i s i  investigation.  . / c  /  INTRODUCTION  Scope  of Investigation.  This dissertation  k i n e t i c , study of the c h a r a c t e r i s t i c equilibrated  allyl  and c y c l o p r o p y l  b e t w e e n 100 and 2 0 0 ° C . these r a d i c a l s compared, of  from  and t h e k i n e t i c s  the r a d i c a l s  radicals  of thermally  i n t h e gas phase  of the generation of  sources  a r e d e s c r i b e d and  of the c h a r a c t e r i s t i c  themselves  ence t o c o m b i n a t i o n ,  reactions  The k i n e t i c s  appropriate  describes the  reactions  are discussed with s p e c i a l  isomerization,  refer-  and m e t a t h e s i s . i  Free Radical  Sources.  both unsensitized priate  esters.  kinetic  radicals  and s e n s i t i z e d The u n s e n s i t i z e d  study o f the mutual  produced. study  The f r e e  The s e n s i t i z e d  decomposition  of appro-  decomposition  affords the  interactions  decomposition  of the interactions  were g e n e r a t e d b y  of the r a d i c a l s affords  of the r a d i c a l s  produced  sensitizing  species';  of  s i g n i f i c a n t amounts o f t h e d e s i r e d  yielding  much l o w e r of  i t also  temperature  has t h e c o n s i d e r a b l e  than the unsensitized  t h e same s u b s t r a t e .  the k i n e t i c  The e t h y l  with the advantage  radical  at a  decomposition  r a d i c a l was t h e p r i n c i p a l  a  sensitizing state either C H£ 2  agent  was a l s o  used,  used.  but acetophenone i n the t r i p l e t  The s e n s i t i z e d  an a d d i t i o n - d i s m u t a t i o n + CH =CHCH —fCO^R 2  2  CrH^-fCO^R  d e c o m p o s i t i o n f.ollowed  sequence  addition  ^ SrH^-HCO^R  dismutatiori Cr-H  1 Q  +• n C 0  2  + R*  or a m e t a t h e s i s - d i s m u t a t i ' o n sequence COOR (CgH* o r A*) + (I  tt  COOR metathesis  (C H 2  6  o r AH*) + [ J - j J  COOR \i°J\  dismutation^C^H^  2  + R*  n = 1 o r 2, a n d A* i s t h e  ( w h e r e R* i s t h e d e s i r e d r a d i c a l , acetophenone molecule  + C0  i n an' e l e c t r o n i c a l l y . e x c i t e d  triplet  state) Unsensitized Decomposition. been produced  F r e e r a d i c a l s have  at relatively  low temperatures  the u n s e n s i t i z e d decomposition  previously  ( 5 0 - 1 5 0 ° C )  by  o f such t h e r m a l l y u n s t a b l e  compounds a s d i a l k y l p e r o x i d e s , a c y l p e r o x i d e s , p e r e s t e r s , and  a z o compounds.  These d e c o m p o s i t i o n s  a r e based  on t h e  i n h e r e n t weakness o f c e r t a i n bonds i n t h e m o l e c u l e s . tendency  f o r a p a r t i c u l a r decomposition  i n c r e a s e s w i t h t h e energy produced  The  t o take place u s u a l l y  of s t a b i l i z a t i o n of the species  i nthat decomposition.  I n the decomposition  ofd i -  a l k y l p e r o x i d e s , a u n i m o l e c u l a r s c i s s i o n o f t h e weak p e r o x i d e bond (D(R0-0R)=36 k c a l . / m o l e c a l s a r e formed:  RO-OR  > 2R0*  ) o c c u r s and a l k o x y r a d i I t was r e p o r t e d t h a t t h e  n a t u r e o f R does n o t a f f e c t t h e r a t e o f d e c o m p o s i t i o n o f t h e s e compounds.  Two modes o f d e c o m p o s i t i o n  are possible  for the acyl peroxides:^  2RC0-0*  RCO-0-O-OCR . ^ The  importance  o f t h e second  2R* + 2 C 0  2  mode i n c r e a s e s a s t h e e n e r g y o f  stabilization sition  of R  increases.  state involves  This implies that  some s t r e t c h i n g o f t h e C-CO  a d d i t i o n t o s t r e t c h i n g o f t h e 0-0 0 R u n  bond i n  bond^:  0  i C — 0 ' ' ' ' ' 0 — C' ' ' • 'R  I n t h e f o l l o w i n g examples o f t h e u n s e n s i t i z e d of peresters,  the tran-  decomposition  (R'O-O-CO-R),  0  0  t-BuO-O-C-CH^  >t-BuO* + C H ^ C ^ O  ;  k(60°C) = 2 x 1 0 " s e c 8  o  •' .  t-Bu0-0-C-CH</>  >t-BuO* •+ C 0  2  the values o f the rate of  stabilization  CH^C0  9 radical.  2  +' CH</> • ;  2  constants reflect  o f t h e CH<^ r a d i c a l 2  I n the decomposition R-N=N-R  >2R* + N  the rate of decomposition  k(60°C)=4.4x10" 's€ /|  2  the higher  relative  energy  to that  of the  o f a z o compounds  2  a g a i n depends on t h e energy  of  10 stabilization  o f R*..  '  I n t h e p r e s e n t work t h e u n s e n s i t i z e d d e c o m p o s i t i o n s diallyl are  oxalate  and a l l y l  of  cyclohexa-1,4-diene-3-carboxylate  investigated:  CH =CHCH OOCG00CH 0H=CH 2  2  2  -> 2 C H * C H - C H  2  2  ~ C00CK CH=CH 2  The f o r m e r allyl  +  G  of a l l y l  affords  and c y c l o h e x a d i e n y l  2  P + CH -CH-CH  5  interactions of  a study of the i n t e r radicals.  the nature  s o c i a t e d , and by t h e h i g h energy formed.  0  2C0  9  a f f o r d s a study o f the mutual  p o s i t i o n s a r e favoured both.by  species  7  +  ^ /  2  r a d i c a l s and t h e l a t t e r  actions  > AV  2  T h e s e decom-  o f t h e bonds  of s t a b i l i z a t i o n  dis-  ofa l l  4  Sensitized The  Decomposition:  Ethyl  Radical.  Sensitizers  Employed-.  The e t h y l r a d i c a l i s u s e d a s a s e n -  s i t i z e r because i t i s r e a d i l y g e n e r a t e d and h i g h l y  reactive;  the  reactions  mechanism o f i t s g e n e r a t i o n i s s i m p l e , and i t s  1—8  w i t h v a r i o u s s p e c i e s have been w i d e l y  investigated.  E t h y l r a d i c a l s are generated by i r r a d i a t i o n o f pure d i (3130 A) m  e t h y l k e t o n e w i t h U.V. l i g h t  scheme b e t w e e n 50 a n d 250 C  complete r e a c t i o n C ^ C O C ^  + h» 2  2 C  °2 5  +  C  2 5 H  C 0 C  2  2 5  C H^ + C H C0C H 2  2  4  2  5  i s  > CO + 2 C H *  (1)  >'C^_H^Q .  (2)  H ' — > C  H  The  2  2C H^  H  t h e gas phase. o 1-3  >  C  H  2  2 6 H  + C H  4  2  *  6  C H C0C H  +  4  2  2  > C _H COC H Zj  9  2  5  j  (3)  (4)  5  ,  (5)  Above 50°C, t h e d i e t h y l k e t o n e m o l e c u l e i s c o m p l e t e l y  disso-  ciated  i n t o two e t h y l r a d i c a l s and a c a r b o n monoxide mole-  cule.  B e l o w 250°C, a n d a t t h e h i g h i n t e n s i t y o f i r r a d i a t i o n  used, the pentanonyl^radical, an  ethyl radical.  C^^COC^^, only reacts  On t h e b a s i s  with  o f t h e above mechanism, t h e  m a t e r i a l b a l a n c e i n t h e e t h y l r a d i c a l .(M^^.) i s g i v e n b y M^j. n • Experimentally, values found Eo = (R« C iTiT + Rr, 0 THT ) A o00 f o r t h i s e x p r e s s i o n were 0 . 9 8 8 1 0 . 0 2 b y Kutschlce e t a l . , a n d 2  6  4  1 0  0 . 9 9 7 ± 0 . 0 3 b y James a n d S t e a c i e .  These v a l u e s , w h i c h have  55-57 been v e r i f i e d by o t h e r workers,  •  indicate  that  a l l ethyl  r a d i c a l s a r e a c c o u n t e d f o r b y t h e above mechanism. The  ratio of disproportionation  t o combination f o r the .  e t h y l r a d i c a l i s measured by t h e r a t i o o f t h e r a t e s  o f forma-  t i o n o f e t h y l e n e a n d b u t a n e , R^ T /R^ TT , a n d h a s b e e n ^2 4 4 10 T  f o u n d t o have a c o n s t a n t o and. 180  3 4 C.  but  S h e p p g a v e an  kg, 1 0  i t i s now  f o r the  1  g e n e r a l l y accepted t h a t the  rate  constant  r e a c t i o n b e t w e e n e t h y l r a d i c a l s and  5  f o r the  Several  abstraction  d i e t h y l k e t o n e , k^,  from  expression  (where  [D]  =• c o n c e n t r a t i o n  T h e y f o u n d k^_ t o be expression k /k|  =  4  has 7  6 ±  radical with  An  y  '  a l s o been g i v e n :  |io(" -  c o m p o u n d s , and  —1 o f d i e t h y l k e t o n e i n "moleccmT ) 2 55-57  temperature dependent.' '  e x p ( - 7 8 0 0 ± 200)  Addition reactions  of the  I  /RTJ> (molec7 cm?sec7' ) ^ 1  ethyl/radical with  hydrogen a b s t r a c t i o n r e a c t i o n s  compounds c o n t a i n i n g  Arrhenius  labile  1  unsaturated  of the  elsewhere^~''  7 , Z i  ~^ -^~57 In the ,  s t r a c t i o n r e a c t i o n s of the i n v e s t i g a t e d as t h e  tized  The  reactions shown on  of the the  ethyl radical  esters sensi-  with  many w o r k e r s .  d i s p r o p o r t i o n a t i o n and  ethyl radical with  next page.  ab-  esters.  r a d i c a l s h a v e b e e n s t u d i e d by  importance of the  and  a d d i t i o n and  s e n s i t i z i n g processes i n the  k i n e t i c s of i n t e r a c t i o n of the  other.alky1 relative  present study,  ethyl radical with various  decompositions of these  ethyl  h y d r o g e n atoms h a v e  been i n v e s t i g a t e d e x t e n s i v e l y b o t h i n t h i s l a b o r a t o r y  are  .  1  a c t i v a t i o n energy  c o m b i n a t i o n of e t h y l r a d i c a l s i s zero.  w o r k e r s have found the  the  Arrhenius  |5.06x10" exp(-2000+1000)/RT} molec7 cm. sec7  =  2  K u t s c h k e and  for  50  of 0.136+0.010 between  57  '  expression k  55  value  some o t h e r  The  combination  r a d i c a l s are  89^,  °3 8 H  C.-.H*- + CH-*, 2 5 t>  C,pH^  VRefs. 11#J  + CH^  C H CH(CH ) 2  •CHC H * + -CH^ CEL  5  > C H  2  2  5  62°/i  2  + CH =CHCH  6  2  C\ 2  C H  +  5  21#  5  C H* + CH ~CH-CH 2  2  2  CH =C=CH 2  ij  5  CH 5 2  +  C  C  All  H  Ref. 27% V 103  2 5 H  38V  (O)  +  10^  these percent r a t e s are independent of temperature. In the present  with both a l l y l the  2 6  2  35^,  h  C H-  V (40  2  C H _ + CH CH=CH' 2  ,Ref. 17  85^ +  6  ]>Ref. 141 10#  H  >-C H  2  63^  6  ^7 5 10 C  22,132,133  relative  study,  interactions of the ethyl  radical  and . c y c l o p r o p y l r a d i c a l s a r e s t u d i e d , and  importance o f d i s p r o p o r t i o n a t i o n and combina-  t i o n are considered. The  Acetophenone T r i p l e t .  When l i q u i d  acetophenone i s  0  (3130 A ) a t r i p l e t s t a t e i s 87 88 f o r m e d , t h e e n e r g y o f w h i c h i s 74 k c a l . / m o l e : * i l l u m i n a t e d w i t h U.V. l i g h t  C H _C0CH + h v 65 3 extinction coefficient r  The  [  z  a t 25°C i n c y c l o h e x a n e ? ^  > C H C 0 C H ^ (S..65 3 1 a t 3130 A i s 43 l i t r e s / m o l e - c m . c  c  Triplet  acetophenone can a b s t r a c t  a h y d r o g e n atom f r o m a compound ( B H ) c o n t a i n i n g . , . 81,84,85,88 h y d r o g e n atom: ' ' 1  a labile .  7  C H COCH r  c  2  » C H 5 6 ( O H ) C H , + B*  + BH  6  'The o c c u r r e n c e o f t h i s r e a c t i o n was d e d u c e d b y t h e f o r m a t i o n of p i n a c o l  p n  P H  ,  OH  OH  2 C H C(OH)CH  3  6  T h i s c o n v e r s i o n o f acetophenone pinacolization.  No d e c o m p o s i t i o n ' o f t r i p l e t  was o b s e r v e d i n t h e p r e s e n c e detailed kinetic  t o p i n a c o l i s known as  of a hydrogen  acetophenone  donor.  No  s t u d y was a t t e m p t e d , b u t i t was r e p o r t e d  t h a t t h e t r a n s f e r r a d i c a l B* was f o r m e d  i n very large  The d o n o r s u s e d were a l c o h o l s w h i c h f o r m s t a b l e  yields.  transfer  radicals. . I n t h e p r e s e n t gas-phase  study, the donors used are  compounds c o n t a i n i n g t h e c y c l o h e x a d i e n e - 1 , 4 g r o u p , w h i c h a r e more r e a c t i v e t o w a r d s  metathesis than alcohols.  also give thermally unstable transfer radicals, t h a t t h e acetophenone  triplet  Since they i t was h o p e d  could sensitize the  decomposi-  t i o n s o f t h e s e compounds ( b y a m e t a t h e s i s - d i s m u t a t i o n sequence),  and t h a t i t would  ethyl radical. position,  do s o more e f f i c i e n t l y t h a n t h e  I t was h o p e d t o s t u d y t h e k i n e t i c s o f decom-  and t h e e f f e c t  energized species.  on.them o f t h e p r e s e n c e  The l i m i t a t i o n s i m p o s e d  of a highly  on t h i s  study  are d i s c u s s e d i n the a p p r o p r i a t e s e c t i o n of the d i s c u s s i o n . S e n s i t i z e d Decomposition:  R e a c t i o n Sequences.  The  t i z e d d e c o m p o s i t i o n i s c o m p r i s e d o f two e l e m e n t a r y s e n s i t i z a t i o n and d i s m u t a t i o n . p r o c e s s .which y i e l d s  The f i r s t  sensireactions:  i s a bimolecular  a t h e r m a l l y u n s t a b l e s p e c i e s ; the second  8  is  the unimolecular  sensitization If  decomposition  species.  r e a c t i o n s i s p o s s i b l e , then  that i t s transfer radical  be t h e s e n s i t i z i n g  step.  be f a v o u r e d  unless  reaction i s insignificant relative  and  this  However, i f f o r t h e are possible  s t e p s , t h e r e a c t i o n i n v o l v i n g t h e most  transfer radical will  reaction.  provided  i s s u f f i c i e n t l y unstable,  same s u b s t r a t e . b o t h a d d i t i o n a n d m e t a t h e s i s sensitizing  The  r e a c t i o n may be e i t h e r a d d i t i o n o r m e t a t h e s i s .  o n l y one o f t h e s e  reaction will  of t h i s  unstable  the rate of t h i s  t o that o f t h e competing  The t w o p o s s i b l e ' s e q u e n c e s , a d d i t i o n - d i s m u t a t i o n  metathesis-dismutation,  will  now be d i s c u s s e d i n s e p a r a t e  sections. The  Addition-Dismutation  Sequence.  1  Gaylord  and c o -  workers a t t r i b u t e d  evidence  o f decomposition  during i t s benzoyl  peroxide  sensitized polymerization t o the  formation  of- a n u n s t a b l e  adduct r a d i c a l  of a l l y l  acetate  i n the propagation  53 54-  step of the polymerization. R* +. C H C 0 C H C H = C H 5  2  2  > CH^COgCHgCHCH^  2  CH C0 CH CHCH R 5  Using  2  2  > RCH CH=CH  2  2  2  t h e e t h y l r a d i c a l ' as a s e n s i t i z e r ,  + C0  2  + CH*  James a n d T r o u g h t o n 4-9  s t u d i e d t h e k i n e t i c s o f t h i s r e a c t i o n I n t h e gas phase; 39 126 they extended t h e i r study t o a l l y l p r o p i o n a t e " ^ and d i a l l y l . In low  each o f t h e three  systems, decomposition  a d d i t i o n of the ethyl, r a d i c a l  allyl  was f o u n d t o f o l -  t o t h e d o u b l e bond o f t h e  group:  ' C H* + CH-CQ CH CH=CH 2  2  2  GH 00 C H 3  2  $  2  1 0  7-8 * 0• 5> C H ^ C O g C ^ p ^-8±1-Q C H >  5  1 0  + CO^+CH'  C H* + C H^C0 CH CH=CH 2  2  2  2  C H C0 C H 2  5  2  5  1  2  2  2  S H 5  The  1 0  C H 5  8  1  2  1 0  C H' + CH =0HCH CH CE=CH 2  7.7 * 0.5>CgH^COgC^p  ?  6 2  '  ^>.C^H  2  + C H2  C y i ^ C ^  6 1  16 ± 4  5  + C0  1 Q  ,C H 5  1 0  C H-  +  5  a c t i v a t i o n e n e r g i e s i n k c a l . / m o l e a r e g i v e n above t h e  arrows.  The s e n s i t i z e d d e c o m p o s i t i o n s  of these a l l y l i c  com-  pounds a r e good s o u r c e s o f f r e e r a d i c a l s , because t h e t y p e of . r a d i c a l formed  i s completely predictable,  t a t i o n r e a c t i o n s a r e more e f f i c i e n t s e n s i t i z e d decompositions. radical of  i sattributable  i s u s u a l f o r un-  The i n s t a b i l i t y  t o t h e h i g h energy  t h e carbon d i o x i d e and t h e a l l y l In  than  o f t h e adduct of s t a b i l i z a t i o n  radicals  produced.  the present study, the ethyl r a d i c a l  decompositions  o f CH =CHCH C0 CH CH=CH 2  2  CH =CHCH 0 CC0 CH CH=CH 2  2  2  2  2  2  2  2  a r e i n v e s t i g a t e d as s o u r c e s o f  2  radicals.  allyl  r a d i c a l s more e f f i c i e n t l y . t h a n d i a l l y l ,  These systems  s p e c i e s w i t h h i g h energy radicals,  a r e produced 2  are expected t o generate  of s t a b i l i z a t i o n ,  because two  C0  2  and a l l y l  i n the dismutation reactions.  C H'/(>C0 CH CH=CH 2  sensitized  and  allyl  systems  and t h e dismu-  2  2  and C ^ / C H ^ C H C H ^ O ^  i n v e s t i g a t e d as sources o f c y c l o p r o p y l r a d i c a l s . f o u r systems is  investigated the rate  obtained from the r a t e The  earliest  The  are In a l l  of formation of radicals  of f o r m a t i o n o f carbon  M e t a t h e s i s - D i s m u t a t i o n Sequence.  dioxide.  Some o f t h e  examples r e p o r t e d o f s e n s i t i z e d d e c o m p o s i t i o n s by  t h e m e t a t h e s i s - d i s m u t a t i o n sequence were t h o s e o f o r g a n i c 10 peroxides m  the l i q u i d  phase:  10 R*  + R'CHO-OCHR'  > RH + R'CO-OCHR'  R'CO-OCHR*  > R'C=0 + R'CHO*  S i n c e t h e n , many o t h e r e x a m p l e s h a v e b e e n r e p o r t e d . t h e s e f o r gas phase d e c o m p o s i t i o n s  a r e now g i v e n :  Some o f  the methyl  72-77 radical  s e n s i t i z e d decompositions CH'  +• HCOOR  -> C 0  + R*  2  78 carbonate,  dimethyl  C H ; -+ CH^OCOOCH-,  3 . 3  > C H , +' C H 0 C 0 0 C H o  4 2 7 C w,x vuvv,^ H 0w + C00CH-  3  CHgOCOOCH^  o  > C0  COOCHj  aldehydes,  + HCOO j>C0*  a variety  workers;  + CH*  2  > CH  x  3  2  f o r example c y c l o p r o p y l CH*  \  esters,  > C H ^ + COOR  COOR-  and  o f formate  +  4  -> 0-  92  aldehyde, C0<3;  + CO,.--';  E=12.5 k c a l . m o l e a t 174 C  W  U  o f o t h e r compounds s t u d i e d b y T h y n n e a n d c o -  theethyl radical  s e n s i t i z e d decompositions  of d i -  '  a l i y l _ c ar b onat e x  + CH =CHCH 0C0 CH CH=CH  C H^  2  2  2  2  2  CH -CH-CH0C0 CH CH=CH 2  and  2  diallyl  2  2  2  2  2  2  2  2  2  + CH -CH-CH 2  2  2  >C H 2  6  + CH -CH-CH0CH CH=0H 2  2  2  E CH~=CHCH0 + C H - - C H - C H , 2 19.6 + 1.C? 2 kcal./mole  s e n s i t i z e d decomposition of +>  2  2  C H  s t u d i e d b y James a n d T r o u g h t o n ; ^  3  0H -CH-0H0C0 CH CH=CH  ether  CH^-CH-CHOCH" CH=CH  CH;  +  6  > CH =CHCH0 + C 0  2  C H* + CH =CHCH OCH CH=CH 2  >C H  and the methyl  radical  cyclohexadiene-1,4 + CH^; E = 5 . 5  + H*  kcal./mole  ; E=31.2±4.7  kcal./mole  2  11 103 Dy James a n d S u a r t .  studied In  the present study, the s e n s i t i s e d decompositions o f A  compounds o f t h e t y p e  A COOR  w  radicals. ^}-H  (Z/~  <  The  bond:  C  D(C-C)  r  e  u s e d t o g e n e r a t e R*  CD^~ 3  bond i n = 1 1 . 5  a  CH  i  s  w  e  a  k  kcal./mole f o r  D(C-H) = 24 k c a l . / m o l e f o r  e  r  t  n  a  the  n  <^)-GE^  <Q>~H  1  0  2  The p o t e n t i a l p r o d u c t i o n o f CO^ 'in t h e d e c o m p o s i t i o n o f t h e compounds u s e d i n t h e p r e s e n t s t u d y f u r t h e r w e a k e n s t h e C bond.  Therefore, these s u b s t i t u t e d d e r i v a t i v e s o f  c y c l o h e x a d i e n e - 1 , 4 a r e more e f f i c i e n t than cyclohexadiene-1,4 i t s e l f rate  s o u r c e s o f R" r a d i c a l s  i s o f h y d r o g e n atoms. The  o f f o r m a t i o n o f cax^bon d i o x i d e p r o v i d e s a m e a s u r e o f  the r a t e  o f f o r m a t i o n o f R*.  Both  ethyl-radical-  let-acetophenone-sensitized decompositions and  /  X^T)(  a  r  e  i  C0 C H 2 35 o  z  studied,  of  and XZX  and' t h e  tripCO^CH-, ^ 2  c  triplet-acetophenone-sensitized decomposition of cyclohexadiene-1,4 i s i n v e s t i g a t e d of  this  i n p r e l i m i n a r y s t u d i e s on t h e use  sensitizer.  The A l l y l  Radical.  The a l l y l  r a d i c a l has been r e c o g n i z e d as  11-15 an i m p o r t a n t i n t e r m e d i a t e i n t h e p y r o l y s i s , 18-20 21 photolysis, and r a d i o l y s i s of v a r i o u s o l e f i n s  and  cycloalkanes.  shown  Electron  s p i n resonance s t u d i e s have  that the unpaired e l e c t r o n occupies a d e l o c a l i z e d  molecular  23-25 orbital spectrum in  extending over a l l three carbon of the a l l y l  radical  the f a r u l t r a - v i o l e t ;  shows  atoms.  The U.V.  a n a b s o r p t i o n band o n l y  t h e r e f o r e i t i s not expected t o  12 o show a b s o r p t i o n o f t h e 3130 A r a d i a t i o n u s e d i n t h e p r e s e n t study. In the  p r e v i o u s work i n t h i s  l a b o r a t o r y on t h e r e a c t i o n s o f  ethyl radical with various a l l y l i c  compounds, t h e a l l y l  r a d i c a l h a s b e e n r e c o g n i z e d as:-an i m p o r t a n t i n t e r m e d i a t e b y the  appearance o f p r o d u c t s o f i t s c o m b i n a t i o n and d i s p r o p o r 43  tionation reactions with the ethyl  radical:  ^ C,H CH=CH r7  C H* + CH -CH-0H 2 5 2 2 0  o  ' (10)  0  (11)  >C Ii„ + CH =CHCBL 2 4 2 3  o  0  0  • ^CH =C=CH 2  2  + C H 2  (12)  6  The c o m b i n a t i o n r e a c t i o n was f o u n d t o be a p p r e c i a b l y f a s t e r than the d i s p r o p o r t i o n a t i o n reactions.  The p e r c e n t a g e  con-  o f t h e e t h y l r a d i c a l i n t h e r e a c t i o n s 10,11, and  sumptions  12 were r e s p e c t i v e l y 85 ± 5#» 10 ± 2 % , and'4 + 1 $ , independent  of temperature.  a n d were  T h e s e . v a l u e s were i n a g r e e m e n t  w i t h .those c a l c u l a t e d f r o m t h e e m p i r i c a l e q u a t i o n l o g ( k / k ) = . 0 . 1 3 l { ^ S ? ( d i s p . ) - S°(comb.)} - 5.4-7 w h e r e IZ S° i s t h e sum o f t h e e n t r o p i e s o f f o r m a t i o n o f t h e l i 1 Q  d  c  disproportionation products.  Holroyd. and K l e i n ^  u s e (  i  this  e q u a t i o n t o c o r r e l a t e a l a r g e number o f d i s p r o p o r t i o n a t i o n to  combination r a t i o s  (k A ) d  c  f  o  r  alkyl radicals.  They  h a s e d t h e e q u a t i o n on a m e c h a n i s m p r o p o s e d b y B r a d l e y a n d Rabinovitch^  8  w h i c h assumes t h a t b o t h c o m b i n a t i o n and d i s -  p r o p o r t i o n a t i o n have l o o s e l y a s s o c i a t e d , a l t h o u g h n o t n e c e s sarily identical, freely rotating transition states. ing  Accord-  t o t h i s mechanism, t h e c o m b i n a t i o n and d i s p r o p o r t i o n a -  t i o n reactions are not competitive.  Furthermore,  i t i s  13 implied that the a c t i v a t i o n energies at l e a s t e q u a l ,  i f not zero,  of hoth processes are  and t h a t t h e u l t i m a t e  t i o n o f t h e i r p r o d u c t s i s governed by t h e e n t r o p y  distribudiffer-  ences between them. In the present study, a l l y l the  r a d i c a l s are produced i n  s e n s i t i z e d decompositions of d i a l l y l  oxalate,  c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e and a l l y l in  Kinetic studies  of the a l l y l actions the  of the a l l y l  r a d i c a l with  other  and o f t h e i n t e r -  r a d i c a l s present i n  system.  tions  of a l l y l  work i n t h i s  laboratory,  large  ethyl radical;  proportionation allyl  concentra-  r a d i c a l s were g e n e r a t e d from a l l y l i c  s t r a t e s by t h e use o f l a r g e c o n c e n t r a t i o n s  the  two o f t h e s e  a r e made b o t h o f t h e m e t a t h e s i s  r a d i c a l with these substrates  In previous  ing  3 - b u t e n o a t e , and  the u n s e n s i t i z e d decompositions of the f i r s t  compounds.  allyl  of the s e n s i t i z -  however t h e i r m u t u a l c o m b i n a t i o n and  reactions  dis-  c o u l d n o t be i n v e s t i g a t e d , s i n c e  r a d i c a l s were consumed by i n t e r a c t i o n w i t h t h e  ethyl radical.  In previous  i n v e s t i g a t i o n s elsewhere,  r a d i c a l s have n o t been p r o d u c e d i n s u f f i c i e n t l y h i g h trations  sub-  f o r t h e i r m u t u a l i n t e r a c t i o n s t o be 1  allyl concen-  significant.  In the present study, the unsensitized decomposition of d i allyl  oxalate  ficient  gives  a clean  concentration  source of a l l y l  to aliow  a kinetic  r a d i c a l s i n suf-  study of t h e i r  mutual i n t e r a c t i o n s . The A l l y l the  Polymerization.  presence of a l l y l i c  P h o t o l y s i s of d i e t h y l ketone i n  compounds i n t h e g a s p h a s e l e a d s  to  14 addition, metathesis  and  dismutation reactions:  G H: + CH =0HCH X 2 5 2 2 0  o  A yG'd,^! 5 10  o  C JH* + C H = C H C H X 2 5 2 2 0  In  0  r  0  the p o l y m e r i z a t i o n of these  thesis  and  be  related  MT  + CH~=CHCH X _JL^ 2 2  MT  * CH =CH0H X_m  0  2  i  term  2  2  d  2  >  >  ( k ^)  •  i  CH^CH^CH  +  2  has  be  metaprocesses  f°  r  •k K  |  m  ^  c  h  a  i  .  The  2  2  Jtransfer a  "effective"  o r as  variety  i f the  rate  the  "degradative" i f  accepted  explanation for  low r e a c t i v i t y  of  the  p r o d u c e d i n t h e r e a c t i o n s m and  i s a reactive radical  CH =CHCH X s y s t e m i n t h e 2  gas  species. kinetics  phase enables  '  '  An  of the  O^A'^/  prediction  of  d e g r e e o f p o l y m e r i z a t i o n o f CH =CHCH X. T h i s d e g r e e o f p o l y m e r i z a t i o n i s g i v e n by * o p a g a t i o n d e g r a d a t i v e transfer 2  the  2  / k  p r  w h i c h when e i t h e r X"  tive  k./k . M  d  R e a c t i o n d becomes a n ' e f f e c t i v e c h a x n t r a n s 44 49 . 51-54  e x a c t k n o w l e d g e o f t h e m e c h a n i s m and  equals  n  the ' r a d i c a l formed i n the  propagation,  C H - C H - C H X o r -X*  w h e n e v e r X*  propagation ^ °  b e e n shown t o c o v e r  t r a n s f e r ^ r e s t s upon t h e  50 respectively.  2  the  p  +• X'  2  c l a s s e d as  i s markedly l e s s than k  radicals  addi-  i s of magnitude comparable w i t h t h a t of  constant  degradative  fer  M.H  f o r r e - i n i t i a t i o n by  t r a n s f e r process  kri  and  k  M CH CH=CH  o f r e a c t i o n s , w h i c h may  rate  to propagation,  M. CH^CHCfLJC 1 2 2  "chain transfer"  constant  compounds, t h e  44-51):  M CH GHCH X The  allylic  dismutation reactions to chain transfer  (references 1  X*  ?  > C H + CH -CH-CIIX ^ 2 6 2  M  0  t i o n r e a c t i o n can  D v0 3 + 5 10  7  a  h  a  i  n  ,"~  i s r e a c t i v e o r i t s p r o d u c t i o n i-s s m a l l  In t h i s present  since X * — ^ i i y i  c  radical;  w o r k , h o w e v e r , X*  was  t h e r e f o r e , the r a t i o  unreack^/k^  15 represents  o n l y an upper l i m i t  f o r t h e degree  of polymeriza-  tion. The  Cyclopropyl Radical.  Relatively  little  available  on t h e n a t u r e and r e a c t i v i t y  radical.  T h i s i s p a r t l y due t o t h e l a c k  for this  radical.  the photochemical  t h e vapour  0  of the cyclopropyl. of suitable  sources  I t has been r e c o g n i z e d as an i n t e r m e d i a t e  i n many r e a c t i o n s : propane ^;  information i s  chlorination  phase n i t r a t i o n  of cyclo-  of cyclopropane ^; the 0  b r o m i n a t i v e d e c a r b o x y l a t i o n ox s i l v e r  cyclopropane  carboxy-  67 late;  the decomposition  of bis-cyclopropane carboxylic  acid  68 peroxide  ; t h e Kolbe  electrolysis  of potassium  cyclopropane  69 71 carboxylate  '  ; the photolysis  of methyl  cyclopropyl  60 ketone  ; t h e p h o t o l y s i s and p y r o l y s i s 62 6 5  i n t h e vapour- p h a s e  '  ; the photolysis  96 . hyde ; and t h e s e n s i t i z e d cyclopropane The  carboxaldehyde  only kinetic  of phenyl  of cyclopropyl  radical  i n t h e l i q u i d phase  '  '  .  s t u d y o f t h e c y c l o p r o p y l r a d i c a l has been  carboxaldehyde  decomposition 92  i n the. gas phase.  was g e n e r a t e d b y t h e p h o t o l y s i s  the subsequent  alde-  decarboxylation of substituted 29 94- 95  made b y T h y n n e o n the. m e t h y l - r a d i c a l - s e n s i t i z e d of cyclopropane  cyclopropane  The m e t h y l  of- a z o m e t h a n e , a n d  decomposition of the substrate followed a  metathesis-dismutation  sequence:  CH^N^CH, + h u ( A = 3000 A) 3 2 5 CH'  + HC0<] *C0<i  > 2CH* + N ->  0  c-  > CH^ + *C0<l  E=8.7±0.7 | ^ f | *  > CO + «<J  40$  a t 174-°C  .Between m o s t l y c 100 o m b i naendd w200°C i t h m etthhey lc y rc al do ip cr ao lp sy l troa dg ii cv ae l ms e tphryoldcuyc ce ld o -  16 !  CH' + [>•  propane:  >  D> CH^  However, as t h e t e m p e r a t u r e i n c r e a s e d  t o w a r d s 200°C, some  of t h e c y c l o p r o p y l r a d i c a l s i s o m e r i z e d ' .which w e r e consumed t o g i v e  CH*  + CH -CH-CH 2  CH -CH-CH 2  The  2  2  k 2  5  + HC0<]  2  > CH^CH=CH  .ti'on t h a t A.  ISO  = 10  13 y  a s E-  1  2  + *C0<]  2  = 2 0 k c a l . / m o l e o n t h e assump*  ISO  sec.  -1 , a value *  zation of the cyclobutyl  reported *  93  for the isomeri-  radical.  I n t h e p r e s e n t work, g e n e r a t i o n  of the cyclopropyl  radi-  i s attempted by t h e a d d i t i o n - d i s m u t a t i o n - s e n s i t i z e d  d e c o m p o s i t i o n s .of the  \  a c t i v a t i o n energy of t h e i s o m e r i z a t i o n o f t h e c y c l o p r o p y l  r a d i c a l was e s t i m a t e d  cal  ( 7 4 - ° C ) = 560 s e c T 1  i s o  > CH CH CH=CH  2  radicals,  butene-1 and p r o p y l e n e : .  > CH -CH-CH  D>  to allyl  f>C0 CH CH=CH 2  2  agency o f t h e e t h y l r a d i c a l .  portionation reactions  2  a n d CH =CHCH C0 <] 2  The ' c o m b i n a t i o n a n d d i s p r o -  for the f i r s t  time.  t i o n o f t h e c y c l o p r o p y l r a d i c a l and o t h e r processes are also  The  Cyclohexadienyl  The  isomeriza-  p o s s i b l e r i n g open-  studied.  Radical.  I n the present study  dienyl r a d i c a l s are intermediates position of a l l y l  through  2  of the cyclopropyl r a d i c a l with the  ethyl r a d i c a l are studied  ing  2  i n the unsensitized  cyclohexa-1,4-diene-3-carboxylate;  f o r e a b r i e f r e v i e w i s now g i v e n  cyclohexa-  of previous  decomthere-  work i n v o l v i n g ,  these r a d i c a l s . Cyclohexadienyl gas  r a d i c a l s have been g e n e r a t e d i n t h e  phase from c y c l o h e x a d i e n e - 1 , 3 and c y c l o h e x a d i e n e - 1 , 4 .  T h e s e compounds r e a d i l y d o n a t e a. h y d r o g e n atom t o a n a l k y l  17 ,. ,58,103,104,105 radicalf ' ' ' ti'  he  +  <  ; or  R*/  /  \  —H->  + RH  ;  s y s t e m i s a more e f f i c i e n t  of c y c l o h e x a d i e n y l  and  kcal./mole  cleaner  R* / ^~^>  r a d i c a l s than the  a d d i t i o n o f R* t o c y c l o h e x a d i e n e - 1 , 3  6  E ^  system,  t o c y c l o h e x a d i e n e - 1 , 4 i s not  cant;  present  i n the  d i e n e - 1 , 4 a r e u s e d b o t h as radical  itself,  and  as  because  i s a major r e a c t i o n ,  w h e r e a s a d d i t i o n . o f R° therefore  source  study,  e s t e r s of  a source of the  signifi-  cyclohexa-  cyclohexadienyl  sources of s u b s t i t u t e d  cyclohexadienyl  radicals. Previous study • cn  ethyl,  of the  work i n t h i s  r e a c t i o n s of c y c l o h e x a d i e n y l  103 104 methyl, ^ i s o p r o p y l ,  f o l l o w i n g t a b l e gives the hexadienyl  + R*  >  a  kinetic  radicals with  t-butyl  103  radicals.  percentage consumption of reactions  shown:  propyl  t-butyl  (^>- R  35  4-3  36  24  ^3~R  27  39  +' C H 6  6  work, the  r a d i c a l with- t h e  38  '  50  18  i n t e r a c t i o n s of the  allyl radical  are  studied.  The  cyclo-  Methyl  RrH  present  afforded  Ethyl l  In the  and  r a d i c a l s i n each of the _  ^>  l a b o r a t o r y has  19  3 4 - 5 7  cyclohexadienyl  18  EXPERIMENTAL METHODS H i g h Vacuum T e c b n i q u e s . The  measurement o f t h e k i n e t i c p a r a m e t e r s o f t h e  systems s t u d i e d i n t h i s  various  l a b o r a t o r y has. b e e n c o n d u c t e d b y  v e n t i o n a l h i g h vacuum t e c h n i q u e s ,  which are d e s c r i b e d  con-  by  57 B r o w n and  James-;'  o f o x y g e n and  As  against  m e r c u r y c u t - o f f s had of greased taps cell,  the  present  absorption  the  a g a i n s t the  connecting  v e s s e l s and  interference  o f m a t e r i a l s by  been employed by  i n the  storage  study  a precaution  the  low v o l a t i l i t y  these  grease,  authors  i n place  t u b i n g around the  reactor  analytical  In  of c e r t a i n  line.  the  reactants  r e q u i r e d t h a t p a r t s o f t h e h i g h vacuum-' s y s t e m w e r e h e a t e d i n order  t o keep the r e a c t a n t s  Consequently, the the  and  products  mercury c u t - o f f s  s y s t e m were r e p l a c e d by  i n the  gas  phase.  i n the heated p a r t s  suitable  stopcocks  or  of  metal  valves. The  general  f e a t u r e s of the  s c h e m a t i c a l l y i n FIGURES 1 and sections;  the  reaction cell  line,  train.  Only the heated storage s i n c e the  2.  unheated storage  other  c r i p t i o n g i v e n by Brown and  line,  line  s e c t i o n s do  illustrated  There are f o u r  and. o p t i c a l  storage  text,  the  apparatus are  not 57  James. .  component  system, the and  the  i s described  heated  analytical in  this  d e v i a t e f r o m .the d e s -  '  Figure I. Schematic Diagram  of the Vacuum  Apparatus.  Figure 2: Schematic Diagram of the Optical System and of the heated storage line.  ANALYTICAL TRAIN  w  XXt=  UNHEATED STORAGE LINE  21 Key  t o FIGURES 1 a n d 2  A  Silica  B  S i l i c a cell for f i l t e r solution: 0.5$ potassium h y d r o g e n p h t h a l a t e . T h i s f i l t e r does n o t t r a n s m i t A<3000 £, a n d t r a n s m i t s 70% o f t h e i n c i d e n t r a d i a t i o n a t 3130 £.79  C  Neutral density f i l t e r s : partially silvered mirrors. Used o n l y f o r reduced l i g h t i n t e n s i t y e x p e r i m e n t s .  D  S i l i c a window a n d q u a r t z  E  B r i t i s h T h o m p s o n - H o u s t o n ME/D 250 W. medium p r e s s u r e m e r c u r y a r c lamp:. - U.V. l i g h t s o u r c e .  F  Electrically  G  Mercury-sealed standard j o i n t ; t h e mercury i s covered w i t h an a s b e s t o s c u s h i o n f i l l e d w i t h z i n c t u r n i n g s .  H^  E l e c t r i c a l h e a t i n g tape covered by a l a y e r o f g l a s s wool wrapped i n aluminium foil.  H  R e m o v a b l e h e a t i n g m a n t l e o f t h e same make a s H^.  2  reaction  cell.  heated  aluminium  block  Electrically  HVP  H i g h vacuum pump.  I  Removable s t o r a g e t u b e , which  J  A n a l y s i s tube f o r c a r r y i n g p r o d u c t  K  E i t h e r metal needle valves or t e f l o n stopcocks with V i t o n r i n g s o r g l a s s s t o p c o c k s 'with m e r c u r y s e a l s .  L  Pressure adjuster f o r the s p i r a l To l o w vacuum  o i l bath.  furnace.  Hj  _i>LVL  heated  lens.  c a n be h e a t e d mixtures  by H » 2  t o V.P.C.  gauge.  line.  M '  Calibrated pressure  N  Mercury c u t - o f f s connected  0  G r e a s e d h i g h vacuum  P  37 T o e p l e r pump a n d g a s - b u r e t t e . '  Q  /  scale of the s p i r a l  gauge.  t o t h e l o w vacuum  line.  stopcocks.  - T o e p l e r pump a n d t h r e e - w a y g r e a s e d t a p t o e v a c u a t e t h e g a s - b u r e t t e a n d t o - w i t h d r a w t h e g a s sample,. 5 7  R  M e r c u r y d i f f u s i o n pump.  S  Pyrex s p i r a l  S  Space o f a d j u s t a b l e p r e s s u r e , i n which t h e gauge i s s u s p e n d e d .  S  Spiral  T  Removable tube f o r i n t r o d u c t i o n o f  U  Acetone/carbon  V  Spiral  W  Variable  Y  Storage  gauge  gauge. spiral  window.  dioxide  samples.  trap.  trap arranged f o r s o l i d nitrogen temperature  trap  cooling.  ( W a r d - L e Roy s t i l l  14-2 ' ).  vessels.  Wide b o r e m e r c u r y  manometers.  The H e a t e d  Storage L i n e .  The r e a c t a n t s , a n d p r o d u c t s o f l o w  volatility  w e r e t r a n s f e r r e d t o and f r o m t h e r e a c t o r  i n s i d e an e l e c t r i c a l l y h e a t e d l i n e . by a t a p t o each o f t h e r e a c t o r analytical  train,  This line  cell,  was  unheated  metal needle  connected  storage  and s a m p l e - i n s t o r a g e v e s s e l .  f e r e n t t y p e s o f t a p s were t r i e d :  cell  Three  the  Each type had i t s advantages  most e f f i c i e n t  stopcocks.  glass  and d i s a d v a n t a g e s ;  w e r e f o u n d t o be t h e m e r c u r y - s e a l e d  The m e t a l n e e d l e v a l v e s  dif-  valves,  t e f l o n s t o p c o c k s w i t h V i t o n r i n g s and m e r c u r y - s e a l e d stopcocks.  line,  glass  were s a t i s f a c t o r y l e a k -  p r o o f c u t - o f f s p r o v i d e d t h e y w e r e n o t h e a t e d a b o v e 160°C. T h e y t e n d e d t o be b l o c k e d b y l o w v o l a t i l i t y l o n g u s e , and were been completed.  therefore  replaced  Although the l i f e  Glass," t e f l o n s t o p c o c k s was  smaller  materials  a f t e r 15-20  after -  runs had  e x p e c t a n c y o f t h e "Weston than that  of., t h e n e e d l e  valves,  s i n c e t h e i r v i t o n r i n g s h a d t o be r e p l a c e d a f t e r  each r u n , t h e y had t h e advantages placement, few  ly  cleaning  and r e -  a n d o f r e m a i n i n g l e a k p r o o f up t o 2 0 0 ° C .  experiments  by m e r c u r y .  of easy  were p e r f o r m e d  using glass  The  stopcocks sealed  These s t o p c o c k s were l u b r i c a t e d w i t h an  t h i n l a y e r of high temperature  silicon  last  grease.  extreme-  Asbestos  cushions f i l l e d  w i t h z i n c t u r n i n g s covered the mercury t o  prevent vapours  escaping into  s t o p c o c k s had a d e f i n i t e  the laboratory.  advantage  t h e n e e d l e v a l v e s and t e f l o n  i nlife  stopcocks.  t e n d t o be b l o c k e d b y n o n v o l a t i l e  These  expectancy  m a t e r i a l s , and t h e y c o u l d  g r e a s e was c h e m i c a l l y a n d p h y s i c a l l y i n our experiments.  t h a t t h e y o c c u p i e d much s p a c e  •  vessel  quantities  were  of mercury are  temperature  t o the heated  standard j o i n t .  o f an e l e c t r i c a l  products from line  it.  b y means o f a  I t c o u l d be h e a t e d  h e a t i n g tape, the temperature  r e g u l a t e d by a v a r i a c .  was u s e d f o r  substrates into the reactor  and f o r c o l l e c t i o n l o w v o l a t i l i t y  T h i s v e s s e l was c o n n e c t e d  be  i r i e r t under t h e c o n d i -  and i n v o l v e d t h e e l a b o r a t e  of variable  i n t r o d u c i n g the low v o l a t i l i t y  mercury-sealed  silicon  ,  A. r e m o v a b l e  cell  The  Their disadvantages  p r e c a u t i o n s n e c e s s a r y when l a r g e heated.  over  Also, they d i d not  e a s i l y be c l e a n e d a n d r e p l a c e d when n e c e s s a r y .  t i o n s used  glass  b y means  of which  The h e a t i n g t a p e c o u l d r e a d i l y be  r e m o v e d a n d r e p l a c e d b y c o o l i n g b a t h s w h e n e v e r i t was t o use t h e v e s s e l The  heated  could  as a c o l d f i n g e r • o r a sample  l i n e was c o n n e c t e d  wished  remover.  d i r e c t l y t o a pyrex  glass  24 s p i r a l t h e  gauge  image  of  d e f l e c t i o n of  S  was  , w h i c h  was  k e p t  t u b i n g  a t  (Hj) ed  be  by  was Of  o f  g l a s s  l i n e  main  was t a p e d  one  n e a r The  f o l l o w i n g  t i g h t l y wool  measured  was (iii)  t h e  m e r c u r y  by  t h r e e  the  t a p  c l o s e  volume  The  t o of  t h e t h i s  t h e  S  gauge  o i l ' b a t h  a  s p i r a l was  of  h e a t i n g  by  was  h e a t i n g  w h i c h  mantle  was  m e a s u r -  t o  one  w h i c h  by  a  l a y e r  i n s u l a t i o n . c r e a t e  t e m p e r a t u r e  c e l l ,  t a p e  c o v e r e d  and  f o i l  a  of  c o p p e r - c o n s t a n t a n  n e a r  space  of  the  s p i r a l  the  t h e  t e m p e r a t u r e  t h e  t a p e  a l u m i n i u m  l i n e .  t a p s  The  u n i f o r m i n  of  p r e s s u r e  t e m p e r a t u r e of  between  i n s i d e  the  s c a l e  t h e r m o m e t e r .  i t .  the  t h e  The  The  b a t h ,  The  p r e s s u r e  p r e s s u r e  r e f l e c t e d  s c a l e .  e l e c t r i c a l l y h e a t e d  around  by  t h e  s t r a i n .  o i l  m i r r o r  d i f f e r e n c e  and  t e m p e r a t u r e  was  The  c a l i b r a t e d the  v a r i a b l e  wrapped  t o t a l  an  a s s u r e  a l o n g  a t  a  the  The  k e t o n e l i n e  t a p s  v a p o u r  h e a t e d  t h e r m o c o u p l e s ; t h e  v e s s e l  I,  and  e s t i m a t e d  i n  t h e  v e s s e l .  h e a t e d  s p a c e . and  was  I t s were  l i n e  was  a l l o w e d  p r e s s u r e c l o s e d  t o p^  and  f i l l was  t h e  the  c e l l  and  measured. r e s t  of  t h e  l i n e  e v a c u a t e d .  w i t h t a p s K . a l l o w e d  t o  2  and expand  c l o s e d , i n t o  t h e  .  c u s h i o n  way:  d i e t h y l  t h e  t o  was  h e a t e d (ji)  l i n e  end.  i n d e p e n d e n t l y .  i n  the  a  s y s t e m  t h a n  a  i t s  t o  b r e a k i n g  by  b a s e ;  a i r  one  ( i )  a  immersed  w o o l  hot  l a r g e r  c o n v e n t i o n a l  wound  g l a s s  c o n t r o l l e d  a d j u s t e d  The  at  onto  r e a c t i o n  p r e v e n t  i t s  a  m i r r o r  p r o p o r t i o n a l  a l w a y s  t o  a  c r o s s w i r e  t h e  p e r m a n e n t l y c o u l d  a  was  p r e s s u r e a  w i t h  . ••  the  d i e t h y l  l i n e  by  k e t o n e  o p e n i n g  K/>  v a p o u r w i t h  was  25 kept - (iv)  closed.  w i t h Kg  &  Vg,  l i n e ,  the  haviour,  the  P  From  V^  =  V  P  2  our  experimental  (Vg  +  Run  (a) •Diethyl  1  was  V^)  volumes  of  r e s p e c t i v e l y ,  opened  and  the  c e l l ,  the  heated  2>  =  the  has  work,  the then,  r e l a t i o n s h i p  V  +  with  P  3  ( V  new  been  V  has  i d e a l  be-  Vg  V  +  2  and  a l t e r e d  It  assuming  holds:  *  1  volumes  but  ketone  was  vessels  several  runs.  (b)  accurately  measured  part  l i n e  I.  i n .was  to  t o t a l  then of  V^  were  several  never  estimated.  times  during  20$  exceeded  of  the  was  then  into at  closed,  completely  the the  of  low  lowest  taps  vaporized,  into  vessel  T  1  the  I.  of  decimal  to  l i n e : -  one  l a s t  of  .the  f o r  substrate  the on  into  substrate  an  substrate,  or  an  exactly into  the  and  con  by  repeated  b o i l i n g  To  b o i l  substrate,  the  K^  at  which  b o i l i n g were kept  vapour  :  was  a n a l y t i c a l  q u a n t i t a t i v e l y  During  the  to  v o l a t i l i t y  temperature  and  the  de-gassed.  volume  de-gassed  completely. and  ketone  transferred  vessel  S e n s i t i z e r .  quantities  fourth  volume  i t , was  the  thoroughly the  the  as  from  measured  of  evaporated  d i e t h y l  s u f f i c i e n t  exactly  heated  kept  was  I t  back  was  strate  Y  weighed The  Ketone  t r a n s f e r r e d  I t  An  balance.  densing  of  Introduction  l i n e : -  vessel  Diethyl  Introduction  storage  i t  K^  measured.  volume.  T y p i c a l  were  the  r e l a t i o n s h i p  volume  the  are  ( V  was  measured.  vessel,  The  A  was  pg  open,  following  1 1  t h i s  c e l l  :  p^  and  and  pressure  closed,  pressure I f - V^,  The  taps  the Kg  open.  pressure  of  the sub-  and  K^  Whilst the  26 substrate f  was  was  measured.  r e - c o l l e c t e d  jacket Once  Hg  into Z^  at  room  elevated,  heated  l i n e .  H^,  was  ketone  the  sum  ketone,  and  t o keep  d i e t h y l  pressures  ketone  measured  p r i o r  pressure  o f d i e t h y l  measured  previously,  the  *  t h e l a r g e r  was  was  volume  i s a  corrected  ketone  f o rd e f i n i t i o n  was  measured. andt h e  V^)..  both  t h e  t h e i r  (Vg +  o f d i e t h y l  vapour  o f V., V  p  equal t o d i e t h y l  tempersubstrate  mixture;  V^) had  t h e  been  ketone; t h e had  been  f o rexpansion  achieve  mixture  d i -  When  and  Vg, which  t o allow To  t h e  always  s u f f i c i e n t  b u t also  i n t h e volume  (Vg +  t o 100°C,  recorded.  was  mercury  andt h e  opened,  was  ketone  pressure  and t o mix with  i n t h e volume  ketone  vapour  o f t h e substrate  t o t h e i n t r o d u c t i o n  substrate/diethyl  S e e p . 25  K^  pressure  100°C  i n d i v i d u a l l y ,  o f t h e substrate  was  t h e  t h e c e l l  i n t h e gas phase, n o t o n l y  pressure  into  and with  vapour  pressure  t h i s  that  I , t a p  was h e a t e d  ketone  t o evaporate  indicates  t h e heating  and d i e t h y l  into  t h e l i n e  T h e new  substrate  temperature.  o f measured  a t 100°C,  100°C,  was  t o room  i n vessel  introduced  kept  o f t h e p a r t i a l which  ketone  o f d i e t h y l  vapour.  temperature  by removing  closed,  closed,  t h e  away.  and  allowed  b o i l i n g ,  o f t h e substrate  was  a n d H^  the  ature  c o l l e c t e d  d i e t h y l  pressure  I  t o return  With  K g was  Hg,  substrate ethyl  was  temperature  t h e new  With  I  Introduction  t h e c e l l : -  of  and  and allowing  a n d t h e a i r was pumped  (c)  each  i n t h e vessel  t h e substrate  opened  A f t e r  maximum  was  and V,  mixing,  condensed  .  and  27 expanded  several  Then  V^/CV^  the  mixture ing  was  l i n e of  +  V  2  confined  mixture  removed  times  was  from  i nthe. space  +  V^)  the l i n e .  the low v o l a t i l i t y  and  f o r p r o p o r t i o n a t e l y  ture  o f  when  reduced. the c e l l  the f u l l  was  then  l i n e .  vapour  K^.  the vessel  The I ,  remain-  and  thence  re-connected  i t f o r the  mixture:- -  i n t e n s i t y  longer  Throughout was  into  o f the vapour  f o r one  was  c l o s i n g  the  t o the  c o l l e c t i o n  products.  was  s i t y  hy  I  and  o f the t o t a l  out t o prepare  I l l u m i n a t i o n hour  back  Vessel  and't h e a i rpumped  (d)  f r a c t i o n  i n the c e l l  c o l l e c t e d  o f the c e l l  periods each  maintained  o f t h e lamp  when  the  the p a r t i c u l a r  desired.  was  the l i g h t  experiment,  a t  I l l u m i n a t i o n used  inten-  temperatemperature  I /'  (e)  F r a c t i o n a t i o n  i l l u m i n a t i o n tained were and  a t  120°C,  closed  H  allowed  t o  condensed. the i n  vapour  t o  a t  analysis  l i n e .  120°C  was  vessel'  not v o l a t i l e  temperature was  evaporated  closed and  from  was were  (taps  pressure  and  o f  The  2  The  mainand  heating was substrate  temperature  were  and t o  of the  a l l products  removed  the observed  allowed  condensed  K  remaining  a t room  opened,  again,  was  the v e s s e l  substances  estimated Tap  o f the l i n e  I ,  were  t o which  the end  measured.  temperature.  pressure.  a t room  t o t a l  room  was  At  was/opened  The  from  degree  mixture  v o l a t i l e  repeatedly  open).  which The  the t o t a l  the t a p  removed  cool  products  the temperature  v o l a t i l e  was  2  and  and  reactants  jacket  and  /  period,  o f t h e products:-  the  expand  reduction products into  and the condensate by  repeatedly  from  t h e was  heating  28 v e s s e l  I  t o  A f t e r  each  d u c t s  w h i c h  a n a l y s i s performed by  t h e  w h i c h  h a d been  l i n e .  ( u s u a l l y  s p i r a l  e t h y l  r e l e a s e d  t i m e s )  c o o l  t o  room  t h a t  v o l a t i l e  a f t e r  t h i s  t o  a n d t r a c e s  v o l a t i l e  t h e a n a l y s i s  o f  p r o d u c t s  were  p r o d u c t s  l i n e  b y  o n l y  o f  no  s m a l l  were  h e a t i n g , b e i n g  condensate o f d i -  c y c l o h e x a d i e n e s ,  h e x a -  1  s e p a r a t e d  t h e u s e o f  r e g i s t e r e d  amounts  r e t a i n e d .  t h e  was  l o n g e r  t h e  p r o -  i n t o  sequence  a n d a f t e r were  a n a l y s i s  benzene,  expand  t h e p r e s s u r e  b e f o r e  t r e a t m e n t  temperature.  a n d a n y v o l a t i l e  a l l o w e d  u n t i l  w a s t h e same  a n d c y c l o h e x e n e  The  were  G a s c h r o m a t o g r a p h i c  t h a t  t o  was opened,  t h r e e  gauge  k e t o n e ,  d i e n e s  i t  The e v a p o r a t i o n - c o n d e n s a t i o n  i n d i c a t e d  showed  a n d a l l o w i n g  0  c o n d e n s a t i o n ,  r e l e a s e d .  i n  120 C  i n t o  t h e t r a p s  f i v e  U,  f r a c t i o n s  V ,  a n d W a s  57 d e s c r i b e d d u c t s at  b y  w h i c h  Brown  a n d J a m e s . '  a r e n o n - c o n d e n s a b l e ,  t h e t e m p e r a t u r e  under  -200°C  s p e c i f i e d ( a n d w h i c h were c a r b o n monoxide, methane,  CLi)  -170°C  ethane,  e t h y l e n e ,  (iii)  -120°C  butane,  propene,  (Lv)  -  1-pentene  (v)  Room  80°C  F r a c t i o n s  ( i ) - ( i v )  t r a n s f e r r e d a n a l y s i s . e v a c u a t e d  t o  c o l l e c t e d  t h e s a m p l e - o u t  F r a c t i o n v e s s e l  p r e s s u r e  were  I;  (v)  i n  v e s s e l  c l o s i n g  was measured  a n d i t  d i o x i d e ,  i s o m e r s k e t o n e ,  benzene,  a n d o t h e r  was r e t u r n e d  a f t e r  p r e s e n t ) .  a l l e n e .  d i e t h y l  c y c l o h e x e n e ,  p r o -  m a i n t a i n e d ,  s t i l l  c a r b o n  a n d i t s  t e m p e r a t u r e :  c o n t a i n e d  t h e vacuum  (i)  h e x a d i e n e s ,  t o t a l  The f r a c t i o n s  p r o d u c t s .  t h e g a s b u r e t t e , f o r t o  t a p s  g a s  was t h e n  t h e n  c h r o m a t o g r a p h i c  t h e emptied ,  c y c l o -  a n d  IL->, a n d K ^ , i t s removed  from  t h e  29 l i n e t o  f o r g a sc h r o m a t o g r a p h i c  a n a l y s i s  a  s o l u t i o n  a n d / o r  N.M.R.  o f t h e f r a c t i o n  was  a n a l y s i s .  P r i o r  made:  g a s  c h r o m a t o g r a p h i c  a n a l y s i s  t h e s o l v e n t  was  hexane,  heptane,  a n do c t a n e ,  t h e s e l e c t i o n  on  t h er e t e n t i o n  the A  hexane,  s o l v e n t  T y p i c a l When  t i z e r ,  was  Run  time  o f t h ep r o d u c t s ;  d e u t e r a t e d  w i t h  t h e o n l y  i n t r o d u c i n g  in' the  t h er e a c t a n t s  n e c e s s a r y  because  one  meant  t h a t  The  m o d i f i e d  depending  f o r N.M.R.  d i e t h y l  ketone  p r o c e d u r e  was  t o t h e c e l l .  t h er e l a t i v e l y  i t h a dt o -be  method  c y c l o -  a n a l y s i s  a s t h e S e n s i t i z e r  r e p l a c e d  change  from  c h l o r o f o r m .  Acetophenone  acetophenone  chosen  f o r  i s now  low  i n t h emethod  T h i s  change  v o l a t i l i t y  i n t r o d u c e d b r i e f l y  a s t h e s e n s i -  v i a  o f  o f  was a c e t o p h e n -  t h eh e a t e d  l i n e .  d e s c r i b e d . /'  E x a c t l y phenone  were  acetophenone l i n e  known  amounts  i n t r o d u c e d was  t o 100°C,  one.  T h e s u b s t r a t e  t i o n . was  V / h i l s t  measured.  e q u a l l e d (measured,  the  u s e d .  t e m p e r a t u r e added,  T h ep r e s s u r e sum  w h i c h  i n d i c a t e s  were  e v a p o r a t i o n  p r e s s u r e s k e t o n e  t h a t  c o m p l e t e l y  T h e  b y h e a t i n g t h e  t o condense  o f t h em i x t u r e  d i e t h y l  I .  V e s s e l  t h ep r e s s u r e  o f t h ep a r t i a l w i t h  v a p o r i z e d  a n dt h e m i x t u r e  v a p o r i z e d ,  a n d a c e t o -  t h ev e s s e l  measured.  b y r e p e a t e d  i t was  acetophenone  t i o n s  was  mixed  i n runs  acetophenone, the  t o room  t h e s u b s t r a t e  i n t o  f i r s t ,  a n dt h ep r e s s u r e  t o r e t u r n  t h o r o u g h l y  d i r e c t l y  i n t r o d u c e d  lowed  and  o f b o t h  I  was a l -  t h e a c e t o p h e n was  d e - g a s s e d  a n d c o n d e n s a o f t h e m i x t u r e  a t 100°C  always  o f t h e s u b s t r a t e  a s t h e s e n s i t i z e r ) and:  b o t h  t h e s u b s t r a t e a n d  v a p o u r i z e d  under  t h e c o n d i -  30 A  T y p i c a l A  Run  measured  i n t r o d u c e d i n  was  230°C. l y s e d  a  by  to  a  pure  be  polymer  s e a l e d  h e a t e d formed  of  the  a  a  was  r e t a r d e r  of  tube was  l o n g open  where  the was  suspended  the  was  i n t r o d u c e d and  d i a l l y l  m a j o r i t y  of  p r o d u c t s ,  columns  was  p r e f e r r e d .  d e t e c t o r  and  a  packed  i o n i z a t i o n  t h e n  i n  t h a t  a  o x a -  an  at  o i l up  and  t o  a n a -  ' p r i o r  i n s t r u m e n t  t o  w i t h  Leeds  the  e i t h e r  or  2  T h i s  Northrup  Model  whenever  carbon  i n j e c t e d  by  of  s t a n d a r d  t y p e .  were  samples  Gj,  c o n s t r i c -  of  w i t h C^  used  Vapor  w i t h  G,  c o n v e n i e n c e .  by a  1 mV A  %" flame  r e c o r -  t h e r m a l  monoxide  and  measured.  were  loop  and  the  metre  system,  was  l o o p  s t o r a g e  s e a l i n g .  4  d e t e c t o r  s a m p l i n g  i n  measured  P e r k i n - E l m e r  c o n d u c t i v i t y  s a m p l i n g  a  t o  and  d i o x i d e  performed  s e p a r a t e  a c c u r a c y  of  i n  were  s u p e r i o r  l y s i s  T h i s  s e a l e d  C D C l ^ ,  o f f e r e d  a  end.  A n a l y s i s  I.D.  pass  cm.  1.5  temperature  i n t o  o x a l a t e  154C  Gas  was  d i a l l y l  t r a n s f e r r e d  F r a c t o m e t e r  c a r b o n  and  immersed  s p e c i f i e d  O x a l a t e  o x a l a t e  (cyclohexadiene-1,4),  t h o r o u g h l y ,  d e - g a s s e d  Chromatographic  d e r ,  i t s  experiments  r e t a r d e r  d e - g a s s e d  F o r  tube  t o  cm.  at  The  D i a l l y l  d i a l l y l  20  l i n e ,  of  N.M.R.  of  tube  j o i n t  de-gassed.-  h o m o p o l y m e r i z a t i o n  v e s s e l ,  l i q u i d t u b e ,  vacuum  The  c o u l d  p r e s e n c e  amount  of  s t a n d a r d  c o m p l e t e l y  The  In  t e d  w i t h  w h i c h  Homopolymerization  c o n s t r i c t e d  c o n s t r i c t i o n .  b a t h ,  •the  a  was c o n n e c t e d  l a t e the  the  amount  i n t o  d i a m e t e r ,  tube  f o r  grease  m i x t u r e s ,  t a p s a  means  was  l o o p  F o r  a  c a r r i e r  the  adequate, was  gas  l i g h t e s t but  c o n s t r u c t e d  f o r  b y -  gases'a n a -  u s i n g  31 g r e a s e l e s s dermic  t a p s .  s y r i n g e ,  P a c k e d  t h r o u g h  column  F r a c t o m e t e r measured  L i q u i d  was'  f o r  to  an  m a n o m e t r i c a l l y  i n  m i x t u r e  removal  b e f o r e  s t a n d a r d  was  Two low  e i t h e r  v o l a t i l i t y  P e r k i n  E l m e r  c a p i l l a r y  u s i n g  a  P e r k i n  p r o d u c t s  from  f r o m  the  peaks  t h a n  t h o s e of  by  the  x y l e n e  of  m e t h y l  same  benzoate by  f a c t o r :  c l o s e n e s s ate  and  of  the  Flame  or  was  an  t h i s  were  a- p a c k e d  g r e a t of  a  e t h y l  packed  The  second  i n t e r n a l  f o r  and  on  f i n e r  by  f a c t o r  were  a l s o  t o  c h o i c e  s t r u c t u r e s  measure  0.01"  had  a  t e m of  r a d i c a l s c h r o m a t o of  Q u a n t i t a t i v e  c a r b o x y l a t e s )  and  150',  r e s o l u t i o n  s t a n d a r d .  a r b i t r a r y  the  the  a n a l y s i s  column.  a  on  s u b s t r a t e  The  areas  used  p r o d u c t  a  methyl  peak  was  measured  i n t e r n a l  w h i c h  The  t i m e s  were  u s i n g  g l y c o l  ( e t h y l c y c l o h e x a d i e n y l  i o n i z a t i o n  the  v o l a t i l i t y ' , compounds  an  was  performed  r a d i c a l s .  m u l t i p l i e d  was  Vapor  154C  column  u t i l i t y  gave  c a l i b r a t i o n . '  r e t e n t i o n m e t h y l  low  as  run  Chromatograph,  the  hypo-  c y c l o h e x a n e .  on  column  the  ( e t h y l c y c l o h e x a d i e n y l the  of  a  P r o d u c t s  t o  l i n e .  p o l y e t h y l e n e  Gas  by  w h i c h  added  vacuum  c a r b o x y l a t e  t h e s e  and  k i n e t i c  w i t h  samples.  s t a n d a r d ,  F r a c t o m e t e r ;  c a p i l l a r y  d e t e r m i n a t i o n  d e t e r m i n e d  the  one  226  from  P e r k i n - E l m e r  l i n e  i n t e r a c t i o n  c y c l o h e x a d i e n y l  grams  was  each  f e a t u r e  the  the  gaseous  n - h e p t a n e  E l m e r  program  of  f r o m  column  p e r a t u r e  use  a l l  i n t r o d u c e d  septum.  i n t e r n a l  Vapor  154C  on  vacuum  f o r  were  r u b b e r  p r o d u c t s :  G o l a y  w i t h  the  a n a l y s e s  a  a n a l y s i s  used  r e l a t i v e  samples  of  was The  of of  a c h i e v e d peak  a r e a w h i c h  1-52, the  methyl  m u l t i p l i e d based  on  m e t h y l  by the  b e n z o -  c a r b o x y l a t e s ) . a l l  p r o d u c t s  e x c e p t  32 carbon the  c a r r i e r  flame 12  monoxide  a n d carbon  g a s ; hydrogen  i o n i z a t i o n  p . s . i .  d e t e c t o r b r a t e d  t o  each  comparing The  peak  areas  comparison  w i t h  diene-1,5,  benzene,  i n g  t o  p r o d u c t s  pure  m i x t u r e s  were  methyl  N.M..R.  o f t h e  w a s  c a l i -  t h e compounds,  i d e n t i f i e d  p r o p y l e n e ,  p r o d u c t s  a n d  a n d measured  1-pentene,  c y c l o p r o p a n e , w e r e . i d e n t i f i e d  q u a n t i t i e s  s p e c t r a ;  COOCH^  m i x t u r e  a t  r a t i o s .  benzoate,  l a r g e  t h e  p l u g s ,  The response  o f  a s  i n t o  s i n t e r e d  a n a n a l y t i c  samples:  T h ef o l l o w i n g  t h e i r  porous  t h e known  c h r o m a t o g r a p h i c a l l y  o b t a i n i n g  o f  w a s used  a i r p a s s e d  r e s p e c t i v e l y .  s y n t h e t i c  f o l l o w i n g  c y c l o p r o p a n e .  t h r o u g h  component  b y r u n n i n g  N i t r o g e n  g a s a n d pure  d e t e c t o r  a n d 30 p . s . i .  d i o x i d e .  '  from  h e x a -  and  e t h y l -  b y  i s o l a t -  runs,  a n d  C2H5  ;  1  l o n g  b y  H  CgH^ , -• .;• DOOCH,  H  H  The  r e m a i n i n g  p r o d u c t s  the  r e t e n t i o n  t i m e s  were  H i d e n t i f i e d  a n d c o r r e c t i o n  f a c t o r s 39  workers were  who used  carbon  butane, N.M.R.  A n a l y s i s  s e l f .  a n d  s p e c t r a  d e r i v a t i v e s  D e u t e r a t e d t u r e s  monoxide,  ethane,  m i n a t i o n  were  *  e t h y l e n e ,  o t h e r  these, carbon  p r o d u c t s  d i o x i d e ,  a n d hexadiene-1,5.  o b t a i n e d  b y u s i n g  e i t h e r  T h e method  b y  u s i n g  I d e n t i f i c a t i o n  c h l o r o f o r m  o b t a i n e d  g i v e n  b y  57 1 0 3  i n s t r u m e n t s *  c y c l o h e x a d i e n e - 1 , 4  N.M.R. d i e n y l  these  a n d measured  o f  i s d e s c r i b e d  t h e V a r i a n  w a s used from  f o r a  i d e n t i f i c a t i o n  o f  A - 6 0N.M.R.  t o d i s s o l v e  t h e v e s s e l  i n d e t a i l  v a r i e t y  I  c y c l o h e x a instrument.  t h e p r o d u c t  o r from  t h e c e l l  a n d q u a n t i t a t i v e  i n t h e r e l e v a n t  m i x i t -  d e t e r -  s e c t i o n s  o f  • 33 The same A - 6 0 instrument was employed f o r  the d i s c u s s i o n .  the i d e n t i f i c a t i o n o f the s u b s t r a t e s t h a t were o b t a i n e d by organic  synthesis i n t h i s laboratory.  used as a standard shifts  Tetramethylsilane  f o r the d e t e r m i n a t i o n  was  o f the chemical  (S) r e p o r t e d i n t h i s t e x t .  Materials Most o f the k i n e t i c  experiments i n v o l v e d p h o t o l y t i c s y s -  tems c o n s i s t i n g o f a p h o t o s e n s i t i z e r and a s u b s t r a t e , but some experiments i n v o l v e d o n l y a dark thermal r e a c t i o n o f a substrate.  The p h o t o s e n s i t i z e r s employed were d i e t h y l  and  acetophenone.  These ketones absorb U.V. l i g h t  The  s u b s t r a t e s were a l l y l  cyclopropylcarboxylate,  ketone o  o f 3130 A.  3-butenoate, d i a l l y l o x a l a t e ,  c y c l o p r o p y l 3-butenoate,  allyl  cyclohexa-  d i e n e - 1 , 4 , methyl c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e , and cyclohexa-1,4-diene-3-carboxylate.  allyl parent  These were t r a n s -  t o 3130 2 l i g h t .  The  p h o t o s e n s i t i z e r s and the s u b s t r a t e s were e i t h e r syn-  t h e s i z e d i n t h i s l a b o r a t o r y o r purchased from c h e m i c a l companies.  They were p u r i f i e d  column.  After purification,  i a l was analyzed  a sample o f the p u r i f i e d  mater-  on s e v e r a l chromatographic columns, and  N.M.R. s p e c t r a were t a k e n . cation  i n a s p i n n i n g band d i s t i l l a t i o n  The s y n t h e s i s , o r i g i n ,  purifi-  , and i d e n t i f i c a t i o n o f p h o t o s e n s i t i z e r s and sub-  s t r a t e s are now  discussed.  D i e t h y l Ketone.  Eastman Kodak, White L a b e l grade;  puri-  f i e d on a s p i n n i n g band d i s t i l l a t i o n column a t atmospheric pressure.  A n a l y s i s showed no s i g n i f i c a n t  impurities.  34 Acetophenone. v i r t u a l l y E l m e r  t o  b y a n a l y s i s  (£ = 2.5)  t h e f i v e r a t i o s  a n d a  were  a m p l i f i c a t i o n D i a l l y l  l a t i o n  column  N.M.R.  spectrum  ( C 0 0 - C H i n g  - C H = C H  a r e a  h i g h  2  )  2  ,  g a s s e d w i t h  r a t i o s  o f  t h e f o u r  (£ = n o  t a p s  a n d  a  p r e v i o u s  the  o f  a t  t h e sample  p o l y e t h y l e n e  2  c o r r e s p o n d -  a f t e r  t o  a t room ( P I G , 1)  No i m p u r i t i e s  were  c o l l e c t e d  l a b o r a t o r y ,  B e f o r e  w a s examined  g l y c o l  p a c k e d  The 0 . 6 7 . t h e  d e -  immersed i n  b y passage  u s e i n t h i s  .  t e m p e r a t u r e ,  Company;  Megachrom  2  =  b e i n g  U  )  r e v e a l  I  C h e m i c a l  2  5.7)  t o  t r a p  7 5 ° C  atoms,  - C H = C H  appeared  t h e v e s s e l  o n t h e Beckmann  Chromatograph  d i s t i l -  (£ = 4.7 t o  h y d r o g e n  ( C 0 0 - C H  o x a l a t e  column  Gas  p u r i t y  J  peaks  A l d r i c h  o f t h e  d o u b l e t  4.9):(S= 5-2  i n t h i s  A p i e z o n  h i g h  T h e  ( £ = 5 . 2 t o 5.7)  w o r k e r  12'  A t  band  a n d w i t h  C y c l o h e x a d i e n e - 1 , 4 . by  t o  D i a l l y l  open,  n i t r o g e n .  m e t h y l e n i c  4.7  i n  .  a n d t e m p e r a t u r e .  atoms,  o t h e r  o v e r n i g h t  3:5  s p i n n i n g  s t r u c t u r e d  m u l t i p l e t  h y d r o g e n  were  o f  T h e peak  L a b o r a t o r i e s  o n a  p r e s s u r e f i n e l y  i m p u r i t i e s .  w a s l e f t  l i q u i d  a  atoms  c o r r e s p o n d i n g  r i n g .  t o 8 . 0 ) =  a  appeared.  p u r i f i e d  a n d a  a m p l i f i c a t i o n  p r e s e n c e  i n  showed  t o t h e s i xv i n y l  peak At  2  t h e benzene  P e r k i n  showed  h y d r o g e n  t o 8 . 0 )  Monomer-Polymer  a t r e d u c e d  t o  o f  peaks  Company;  c o r r e s p o n d i n g  (6 = 7 . 2  t o be  i n t h e  spectrum  t h e t h r e e  2.5):(S=7-2  ( £ =  O x a l a t e .  C h e m i c a l  4.9)  atoms  n o o t h e r  Borden  t o  shown  columns  The N.M.R.  m u l t i p l e t  h y d r o g e n  Company;  o n c a p i l l a r y  c o r r e s p o n d i n g  C H j group,  a r e a  S c i e n t i f i c  2 2 6 G a s Chromatography  s i n g l e t the  pure  F i s h e r  t h e  p u r i f i e d , t h r o u g h  P r e p a r a t i v e work,  t h e  g a s c h r o m a t o g r a p h i c a l l y -  column.  t r a p .  The A-60"  N.M.R.  o n  a  35 spectrum f o u r  r e v e a l e d  m e t h y l e n i c  due  t o t h e f o u r  was  j u s t  o f  w a s c e n t e r e d  o l e f i n i c  p r o t o n s ,  about  M e t h y l .  s p l i t  ,  a  a t 8 = 2.6;  w a s a t  S = 5-6.  t r i p l e t  w i t h  t h e  o t h e r ,  E a c h a  peak  c o u p l i n g  C y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e . Merck  QOOCH  R  i n t o  o n e , d u e t o t h e  c . p . s .  0.2  H  H  t w o a b s o r p t i o n s ;  p r o t o n s ,  p e r c e p t i b l y  c o n s t a n t  H  o n l y  Sharp  p u r i f i e d  a n d Dohme  o n a  (Canada)  s p i n n i n g  band  L i m i t e d ;  d i s t i l l a t i o n  3 column t u r e .  A  p u r i f i e d  sample  w a s a n a l y z e d  a n d i t  w a s found  col,  p a c k e d  column  The  N.M.R.  spectrum  t o  t h e t h r e e  (6" =5-7)  showed  hydrogen  t o  i m p e r c e p t i b l y , t r i p l e t e d the  t w o n o n - e q u i v a l e n t  and  a  <*.-methylenic l i s h e d  hydrogen  'CH =CH-CH -C00CHj 2  2  r a t i o s  (6 These  o f  t h e  t h e f o u r  peaks  (6=  g e r m i n a l  atom. o f  t h i s  p r e s s u r e o n a  o f  (6=3-6)  COOCH^  a n d t e m p e r a -  p o l y e t h y l e n e  t o be f r e e  s i n g l e t  (6=3-8)  peak  b y comparison  a  atoms  c o r r e s p o n d i n g  m u l t i p l e t  a t r e d u c e d  i m p u r i t i e s .  c o r r e s p o n d i n g  group,  a  v i n y l ' h y d r o g e n 2.5  t o 2.7)  m e t h y l e n i c  s i n g l e t atoms,  hydrogen  a n d c y c l o h e x a d i e n e - 1 , 4 .  s i n g l e  were  e s t a b -  t h e s p e c t r a The peak  t o  atoms,  t o t h e  s h i f t s  spectrum, w i t h  t w o  c o r r e s p o n d i n g  c o r r e s p o n d i n g  T h e c h e m i c a l  g l y -  o f  a r e a  were  = 3.6):(6 = 2 . 5 t o 2.7):(S = 3 - 8 ) : ( 6 = 5-7) a r e e x a c t l y  a m p l i f i c a t i o n  t h o s e  r e v e a l e d  e x p e c t e d . f r o m n o more  p e a k s ;  The d o u b l e t  n o t i n d i c a t e d .  t h a t  t h e m e t h y l e n i c  t h e y  a r e i n t h e c y c l o h e x a d i e n e - 1 , 4  hydrogen  t h e f o r m u l a . t h e r e f o r e  (6=2.5  were  atoms  = 3:2:1::4  t o  2.7)  H i g h  i m p u r i t i e s i n d i c a t e s  a r e n o t e q u i v a l e n t , m o l e c u l e .  T h i s  a s  s u g g e s t s  36 that  the cyclohexadiene  carboxylate Allyl H g  /  =  ring  has the boat  shaped  cyclohexa-1,4~diene-3-  s t r u c t u r e o f Cg.^ symmetry.  cyclohexa-1,4— diene-3-carboxylate. H  x  o f methyl  <—r  COOCH CH=CH  temperature. was l e f t  After  o  n  a  s  P i  n  n  i  n  S  band  liquid  impurities  i t had been de-gassed  overnight  with taps in  and  distillation  nitrogen.  were c o l l e c t e d  to  the four v i n y l  to  5 . 5 ) corresponding  sample  i n the trap.  hydrogens  ( £ = 4-.5) c o r r e s p o n d i n g  of the  to  (£=2.5  2.7)  methylenic  (S= 3 - 8 )  atom.'of t h e r i n g .  were e s t a b l i s h e d b y c o m p a r i s o n  (S = 5 - 0  t o t h e two  non-equivalent  a multiplet  t o t h e s i n g l e oc-hydrogen  shifts  corresponding  three vinyl-hydrogens  t o t h e two g e r m i n a l  spectrum  a multiplet  1  h y d r o g e n atoms- o f t h e r i n g , a n d  cal  (8=5.8)  of the ring ,  to-the  u n t i l no  The N.M.R.  h y d r o g e n atoms o f COOCH^, a d o u b l e t  corresponding  line,  temperature  was r e p e a t e d  showed a p e a k  group, a m u l t i p l e t  ponding  i n t h e vacuum  i n t h e v e s s e l I a t room  T h i s procedure  the p u r i f i e d  methylenic  p r e s s u r e and  ( F I G . 1 ) open, and w i t h t h e t r a p U immersed  of  allyl  Sharp  a n d Dohme ( C a n a d a ) L i m i t e d ; p u r i f i e d  column a t r e d u c e d  it  Merck  corresThe c h e m i -  o f t h e spectrum  with the s p e c t r a o f methyl cyclohexa-1,4—diene-3-carboxylate and  allyl  oxalate.  diene-3-carboxylate  The i d e n t i t y was f u r t h e r  of a l l y l  cyclohexa-1,4—  e s t a b l i s h e d by t h e peak  area  ratios: (£ = 5.0  By  to  5.5>:(S  = 5.8):(S =  t h e same r e a s o n i n g u s e d  4-.5):($ = 2 . 5  to  2.7):(£ =  3.8) =  3:4:2:2:1  f o r the s t r u c t u r e of methyl  h e x a - 1 ,4— d i e n e - 3 - c a r b o x y l a t e ,  cyclo-  we b e l i e v e t h a t t h e c y c l o h e x a -  37 diene t u r e  r i n g of  C  2  of .  v  A l l y l . from  the  a l l y l  a l s o  has  the  boat  shaped  b u t e n o i c  a c i d  by  the  2  (CH =CHCH C00CH CH=CH ). 2  and  2  a l l y l  2  a l c o h o l  S y n t h e s i z e d  2  (both  from  K  and  +  2  SQClg  a>CH =CHCH C0C1 + S 0 2  2  +  2  column.  were  T h i o n y l  (a) J e f f e r y  p u r i f i e d c h l o r i d e  . P r e p a r a t i o n and  p l a c e d  i n  joint),  w i t h  o i c  +  2  r e a g e n t s  V o g e l  a  a  was  added  r e f l u x e d  f o r  30  a l l - g l a s s  60  g.  of  d i s t i l l e d  g.  150  m i n u t e s ,  of  t h e n  hour.  m i x t u r e  the  3-butenoate  method  c h l o r i d e  of  of  was  (ground  g l a s s  pure  b u t e n -  The  m i x t u r e  was  r e p l a c e d  was by  f r a c t i o n a t e d .  98-99°C w a s  b.p.  a l l y l  by  g.  condenser  the  d i s t i l l a t i o n  f i t t e d 95  HC1  q u i n o l i n e .  t h i o n y l  f l a s k  one  the  and  c h l o r i d e , of  over  condenser.'  d u r i n g  band  c h l o r i d e  pure  bottomed  column  P r e p a r a t i o n  s p i n n i n g  3-butenoyl  s l o w l y  Dufton  the  was  round  3-butenoyl  (b)  on  d:ouble-surface  a c i d  an  of  :  m l .  500  L a b -  HC1  CH =CHCH 00C1 + C^^CHCHgOH-k^CHg^CHCHgCOOCH^H^CHg A l l  K  method  CH =CHCH C00H 2  s t r u c -  symmetry. 5-Butenoate  o r a t o r i e s )  e s t e r  by  o b t a i n e d . the  method  of  144 B a r n e t t  and  B u t l e r  added  dropwise  mole)  and  throughout  The a  I t  the  l a y e r  s a t u r a t e d  w a t e r .  of the  and  e t h e r  a  p y r i d i n e  temperature  removed  t o  :  the  s t i r r e d  r e a c t i o n  of  s o l u t i o n  mole)  (0.21  i n  3-butenoyl of  m i x t u r e  was  a f t e r  w h i c h  m i x t u r e  s t i r r e d  f o r  an  100  m l .  was  then  washed of  w i t h  sodium  d r i e d  over  a l l y l  nil.  125  a d d i t i o n ,  s o l u t i o n was  mole  0.2  of  c h l o r i d e a l c o h o l  d r y  c o o l i n g  c a r b o n a t e , anhydrous  w a t e r , and  t h e n  sodium  at  b a t h  a d d i t i o n a l of  (0.22  e t h e r .  m a i n t a i n e d  the  was  f o u r t h e n  The 0.5°C was h o u r s . w i t h  a g a i n  " s u l p h a t e .  .  w i t h  38 . D i s t i l l a t i o n on t h e s p i n n i n g band column gave t h e d e s i r e d ester completely pure. tured doublet  The N.M.R. s p e c t r u m  showed a s t r u c -  (6 = 3.1) c o r r e s p o n d i n g t o t h e t w o m e t h y l e n i c  h y d r o g e n a t o m s o f t h e g r o u p CHg-COO-, a s t r u c t u r e d d o u b l e t (6=4.5) of  c o r r e s p o n d i n g t o t h e t w o m e t h y l e n i c h y d r o g e n atoms  -COOCHg* a n d a m u l t i p l e t  (6 = 5.0 t o 6.0) c o r r e s p o n d i n g t o  t h e s i x v i n y l h y d r o g e n atoms o f t h e a l l y l tity  groups.  The i d e n -  o f t h e e s t e r was f u r t h e r s u p p o r t e d b y t h e p e a k  ratios:  ( S= 3 . 1 ) : ( 6 = 4 . 5 ) : ( S = 5.0 t o 6.0) = 1:1:3  .  a m p l i f i c a t i o n r e v e a l e d n o more p e a k s t o i n d i c a t e .  Allyl  2  Company) a n d a l l y l  alcohol.  .band d i s t i l l a t i o n  the f o u r plet  ft-hydrogen  (Aldrich  3 - b u t e n o a t e was u s e d .  column, u n d e r r e d u c e d  showed a m u l t i p l e t  (6=1.9)  2  The m e t h o d d e s c r i b e d f o r  c y c l o p r o p y l c a r b o x y l a t e was p u r i f i e d  spectrum  impurities.  cyclopropanecarboxylic acid chloride  s t e p ( b ) o f the. s y n t h e s i s o f a l l y l allyl  High  C y c l o p r o p y l c a r b o x y l a t e . ( [>C00CH CH=CH ).  Synthesized from Chemical  area  The  on t h e s p i n n i n g  pressure.  The N.M.R.  (£=0.6 t o 0.9) corresponding t o  atoms o f t h e c y c l o p r o p y l r i n g ,  a multi-  c o r r e s p o n d i n g t o t h e s i n g l e oc- h y d r o g e n  atom o f  the c y c l o p r o p y l r i n g , a s t r u c t u r e d doublet-(6=4.5) c o r r e s ponding and  t o t h e two m e t h y l e n i c hydrogens o f t h e a l l y l  a multiplet  group,  (6=5-0 t o 5-8) c o r r e s p o n d i n g t o t h e t h r e e  v i n y l hydrogens o f the a l l y l  group.  The i d e n t i t y o f t h e  e s t e r was f u r t h e r s u p p o r t e d b y t h e p e a k a r e a  ratios:  (6= 0 . 6 t o 0 . 9 ) : ( 6 = 1-9):(6 = 4.5)::(6= 5.0 t o 5.8) = 4 : 1 : 2 : 3 - I m p u r i t i e s were n o t i n d i c a t e d , s i n c e h i g h r e v e a l e d no f u r t h e r  peaks.  amplification  39 Cyclopropyl  3-butenoate  (CH =CHCH C00<]). 2  2  O b t a i n e d by t h e s y n t h e s i s CH|CHCH C00H + S 0 C 1 2  (CF CO) 0 + 2H 0 5  2  2  CH =CHCH C0C1 + S 0  2  2  *>  2  2  2CF' C0 H + E y )  >  5  5  OH i  [>COCH  + CF^CO^H  5  c  OH  CH^C<3  y  CF C0 3  >CFjCOg +  CH|CHCH C0C1 +  OOH _ e _  2  (a) cribed  i n step  <_>  CH C X  >  0<  CH COO<] + C F , C 0 H > 0 <x  o  > [>0H CH =CHCH C00<] 2  2  P r e p a r a t i o n o f 3-butenoyl. c h l o r i d e :  (b) in  X  OH  0+  LJA1H4  3  +  CH C<1  5  G i r a r d ' s Reagent c CH COO<]  + HC1  2  (a) of the synthesis of a l l y l  method d e s 3-butenoate.  P r e p a r a t i o n o f p e r o x y t r i f l u o r o a c e t i c a c i d (CF^CO^H)  s o l u t i o n i n methylene  Materials:  chloride.  trifluoracetic  methylene c h l o r i d e  a c i d anhydride  (CH C1 ) (both 2  from Eastman O r g a n i c  2  Chemicals);  90$ hydrogen p e r o x i d e  Method:  0.48 m o l e 'of t r i f l u o r o a c e t i c  ^  ( ( C F ^ C O ^ O ) and  (fmc C o r p o r a t i o n ) .  t o 0.4 m o l e o f 9 0 $ h y d r o g e n p e r o x i d e  anhydride  dissolved  was a d d e d  i n methylene  chloride. (c)  Oxidation of methyl cyclopropyl ketone.  Materials::  methyl c y c l o p r o p y l ketone  •Inc.); G i r a r d ' s Reagent T chloride, hydrazide: Organic  ( A l d r i c h C h e m i c a l Co.  ((carboxymethyl)trimethyl  |(NH NHCOCH )N(CH ) Cl|) 2  2  5  5  ammonium  (Eastman  Chemicals). 145  M e t h o d (Emmons a n d L u c a s s o l u t i o n prepared  " j : the peroxytrifluoracetic  i n ( b ) was a d d e d o v e r a t w e n t y f i v e  acid  minute  4-0 period  t o a w e l l s t i r r e d m i x t u r e o f 1.0  h y d r o g e n p h o s p h a t e a n d 0.2 i n 200 the  mole o f m e t h y l c y c l o p r o p y l  m l . o f methylene c h l o r i d e .  m i x t u r e was h e a t e d u n d e r r e f l u x f o r one h o u r .  of methylene c h l o r i d e ,  ketone  A f t e r a d d i t i o n was c o m p l e t e ,  s a l t s were t h e n c o l l e c t e d on a f i l t e r  with  mole o f d i s o d i u m  The m i x e d  and washed w i t h  100 m l .  The c o m b i n e d f i l t r a t e s w e r e w a s h e d  150 m l . o f 10/o s o d i u m c a r b o n a t e s o l u t i o n a n d d r i e d  magnesium s u l p h a t e .  Most o f t h e methylene c h l o r i d e  moved b y d i s t i l l a t i o n ,  over  was r e -  a n d t h e r e s i d u a l l i q u i d was d i s s o l v e d  i n a m i x t u r e o f 1 8 0 m l . o f m e t h a n o l a n d 20 m l . o f a c e t i c  acid  containing  solu-  37.4- g . o f G i r a r d ' s  R e a g e n t T.  The r e s u l t i n g  t i o n was b o i l e d f o r 12 h o u r s a n d p o u r e d i n t o 6 0 0 m l . o f i c e water.  I t was p a r t i a l l y n e u t r a l i z e d  b i c a r b o n a t e i n 100 s i x 50.0  25.2  g. o f sodium  m l . o f w a t e r , a n d was t h e n e x t r a c t e d  ml. portions  were washed w i t h  with  o f methylene c h l o r i d e .  The e x t r a c t s  50 m l . o f 10$ b i c a r b o n a t e s o l u t i o n ,  o v e r m a g n e s i u m s u l p h a t e , a n d most o f t h e s o l v e n t at atmospheric p r e s s u r e . a t e d on a s p i n n i n g pressure.  8.0 g . o f c o l o u r l e s s 5  The  (lit.  cyclopropyl n  2 5  D =  a c e t a t e , b.p.  1.4-059 °  N.M.R. s p e c t r u m showed a. m u l t i p l e t  (6"=2.1)  was d i s t i l l e d  column a t atmospheric  7  ) , was o b t a i n e d .  (6=0.8)  t o t h e f o u r ^ - h y d r o g e n atoms o f t h e c y c l o p r o p y l let  corresponding ring, a sing-  c o r r e s p o n d i n g t o t h e t h r e e h y d r o g e n atoms o f t h e  m e t h y l g r o u p (CH^COO-), a n d a m u l t i p l e t  (6 = 4-.1)  correspond-  i n g t o t h e s i n g l e ot-hydrogen atom o f t h e c y c l o p r o p y l The  dried  The r e s i d u a l l i q u i d was f r a c t i o n -  band d i s t i l l a t i o n  109-111 °C, V D = 1.4-060  with  i d e n t i t y of cyclopropyl  a c e t a t e was a l s o  ring.  confirmed by t h e  41 peak a r e a The  ratios:  (S = 0 . 8 ) : ( g = 2.1):(£ = 4*1) * 4 : 3 : 1 .  p r o d u c t was r e m a r k a b l y , f r e e f r o m i m p u r i t i e s .  repeated acetate  several times i n order f o r use i n subsequent  (d)  t o o b t a i n enough c y c l o p r o p y l  steps.  Hydrolysis of cyclopropyl acetate  aluminum h y d r i d e ( f r o m  British  by l i t h i u m  Drug Houses L t d . ) .  M e t h o d (De P u y a n d M a h o n e y ^ ) : 0  l i t h i u m aluminum  (1.1M, 3 3 ^ 1 . , 0 . 0 3 8 5 m o l e ) i n e t h e r  a t a r a t e t o keep a g e n t l e  of sodium sulphate tion,  of the hydride and  was c o m p l e t e .  About 5 g.  aqueous s o l u -  immediately after the a d d i t i o n The e t h e r s o l u t i o n was f i l t e r e d !  d r i e d over anhydrous sodium s u l p h a t e .  ed b y d i s t i l l a t i o n  i n 35 ml. o f  reflux.  w e r e made i n t o a s a t u r a t e d  and added t o t h e m i x t u r e  hydride  was a d d e d t o a s o l u t i o n  o f 6 . 2 0 g. ( 0 . 0 6 2 0 mole) o f c y c l o p r o p y l a c e t a t e anhydrous ether  ( c ) v/as  Step  Solvent  on a s p i n n i n g band column.  was r e m o v -  The r e s i d u a l  l i q u i d was shown b y c o m p a r a t i v e r e t e n t i o n t i m e s a n a p o l y ethylene  glycol  cyclopropanol. preparative column. was  I s o l a t i o n a n d p u r i f i c a t i o n was e f f e c t e d b y  2 g. o f p u r e c y c l o p r o p a n o l  glycol  were o b t a i n e d .  Step (d)  s e v e r a l t i m e s t o o b t a i n enough c y c l o p r o p a n o l f o r  (e). (e)  Preparation  of c y c l o p r o p y l 3-butenoate:  similar t o the preparation chloride by  e t h y l a l c o h o l , and  gas chromatography on a p o l y e t h y l e n e  repeated  step  column t o c o n t a i n e t h e r ,  and a l l y l  cyclopropanol.  pure butenoyl  of a l l y l  3-butenoate from  alcohol, but with a l l y l S p e c i a l care  chloride.  was t a k e n  The y i e l d  t h i s was butenoyl  alcohol replaced • to obtain  extremely  of c y c l o p r o p y l 3-butenoate  42 did  n o t e x c e e d ' 2 0 $ a f t e r p u r i f i c a t i o n on t h e s p i n n i n g band  distillation  column.  The p u r i f i e d  s a m p l e was i n t r o d u c e d i n t o  t h e vacuum l i n e where any r e m a i n i n g v o l a t i l e pumped away.  impurities  were  The N.M.R. s p e c t r u m o f t h e p u r i f i e d c y c l o p r o p y l  3 - b u t e n o a t e showed a m u l t i p l e t  (£=0.8-) c o r r e s p o n d i n g t o t h e  f o u r ^ - h y d r o g e n atoms o f t h e c y c l o p r o p y l r i n g , a m u l t i p l e t (•£ = 5.3 t o 6.0)  corresponding t o the three v i n y l hydrogen  atoms o f t h e a l l y l responding  group, a s t r u c t u r e d doublet  (6=3.I) c o r -  t o t h e two m e t h y l e n i c h y d r o g e n atoms o f t h e  group, and a m u l t i p l e t  ( £ =4.2)  corresponding to the single  <x-hydrogen atom o f t h e c y c l o p r o p y l r i n g .  The i d e n t i t y o f  c y c l o p r o p y l 3 - b u t e n o a t e was a l s o c o n f i r m e d b y t h e p e a k ratios:  (6=  allyl  area  ' 0.8)::(£ = 5.3 t o 6.0):(6= 3.1):(S - 4.2) = 4^3:2:;1  DISCUSSION In  this  c h a p t e r a r e p r e s e n t e d t h e r e s u l t s and d e t a i l e d  d i s c u s s i o n o f t h e v a r i o u s t h e r m a l and p h o t o l y t i c were i n v e s t i g a t e d .  These  types:  allyl,  ted  cyclohexadienyl.  more) o f t h e r a d i -  c y c l o p r o p y l , c y c l o h e x a d i e n y l , and s u b s t i t u I n e a c h s y s t e m , t h e k i n e t i c s were  t i g a t e d both of the production of these r a d i c a l s i n t e r a c t i o n with other r a d i c a l s A.  inves-  and o f t h e i r  present.  Reactions of the Ethyl Radical with A l l y l It  which  s y s t e m s were s e l e c t e d because t h e y  were e x p e c t e d t o p r o d u c e one- ( o r s o m e t i m e s cal  systems  has been p r e v i o u s l y o b s e r v e d i n ' t h i s  3-Butenoate laboratory  that  when e t h y l r a d i c a l s a r e p r o d u c e d i n t h e . p r e s e n c e o f a l l y l pionate vapour a t r e l a t i v e l y an e t h y l r a d i c a l  pro-  l o w t e m p e r a t u r e s (100°C t o 1 6 0 ° C ) ,  sensitized decomposition of the a l l y l  propio-  39 nate takes place  . (A study of the reactions of the ethyl 3 - b u t e n o a t e was u n d e r t a k e n i n t h i s w o r k t o  radical with a l l y l  s e e i f , i n t h e same way, e t h y l r a d i c a l s c a n s e n s i t i z e t h e d e 3-butenoate.  composition of a l l y l CgH^-  + CH =CHCH C0 CH CH=CH 9  2  2  2  2  -> C H C H C H C H C 0 C H C H = C H > 5 2 2- - 2 2  C  5  H  2  +  2  C 0  +  2  C H  2  C H  2  C H  1 0  If  they do, a l l y l  r a d i c a l s w o u l d be p r o d u c e d , a n d t h e decompo-  s i t i o n would p r o v i d e a c o n v e n i e n t and r e l a t i v e l y  low tempera-  ture source of these r a d i c a l s . Results. the  TABLE I s u m m a r i z e s  ethyl radical with a l l y l  range between  9 7 ° C a n d 162°C.  the results of the reactions of 3-butenoate i n t h e temperature The g a s e o u s m i x t u r e ' o f  allyl  TABLE I REACTIONS OF THE ETHYL RADICAL WITH A L L Y L 5-BUTENQATE* RUN  °K  (C H  )  [D]  (CO)  [B]  (co )  <Vio>  #  2  4  1  0  (0 H^ 2  0  Rio$ Rl1a$ 11b#  )  R  K  M  A11  k  A  Me  D  K  k  Ma  0.11  0.136  —  0.710  49.6 9.9  1.8  -  0.12  0.136  -  0.749  54.5 13.1  3.0  -  0.19  0.136  -  0.693  71.0 15.2 .  4.1  0.03 0.01  0.35 .  0.142 0.006  0.743 0.916.  76.0 15.2  2.78 0.78  0.05 0.02  0.40  0.144 0.008  0.728 0.798  89.1 19.2  6.4  2.97 0.76  0.05 0.02  0.55  0.147 0.011  0.704 0.832  108.6 19.4  7.8  11.53 0.97  5.20 ' 2.94 1.61 0.76  0.04 0.02  0.64  0.145 0.009  91.0 6.7  0.703 0.845  110.4 19.0  12.16 1.12  5.11 1.94  3.52 0.76  0.05 0.02  0.83  0.147 0.011  91.5 •6.1 2.4  0.713 0.983  112.6 22.3  6.32 0.34  2.29 0.86  ' 2 • .; 377  5.19 1.96  9.91 0.29  5.20 0.41  2.23 0.71  3  378  4*95 2.05  10.26 0.49  4*91 0.68  2.21 0.67  4  : 385  5.12 1.46  9.98 0.48  4.98 0.83  2.43 0.71  5.  388  5.03 1.48  11.21 0.66  5.37 1.06  6  392  4.85 1.38  11.48 0.87  5.15 1.42  7  392  4.80 1.35  8  400  4.75 1.35  *  1  -  12.11 0.23  I  H  4  5*81 2*78  •i  5  (C H )  370  1  D(C  2  89.7 7.7 O ft c. • o 86.4 10.4 ^ o 88.0 8.8 2, o p. d  10.9  The d u r a t i o n o f each r u n was 60 minutes. Continued..  E I °K  RUN #  9 10  .  [D]  (CO)  (C H )  (C H^  [B]  (co )  (C H ) 1Q  (C H^  (C H )  4.79 1.23  11.08 0.95  4.97 1.67  3.43 0.78  0.12 0.03  0.66  4.25 2.76 ,•  3.71 0.69  0.12 0.04  1.16 —  0.163 0.027  ..  400 408  (continued)  2  11.26 4.85 • 1.05 ... '1-58  4  5  10  D(C H )  2  2  5  5  4  10  (  D k  —  V 3,2  0.156 0.020  11  408  4.93 1.03  11.98 1..64  4.57 2.75  3.92 0.74  0.14 0.04  1.11 0.02  0.162 0.026  12  417  3.76 0.81  10.35 1.69  3.94 2.69  3.44 0.62  0.11 0.03  1.03 0.03  0.154 0.018  417  3.97 0.81  11.52 1.91  4.34 3.16  3.75 0.70  0.14 0.04  1.25 0.03  0.160 0.024  14  425  4.02 0.79  12.16 2.76  3.90 4.33  4.27 0.68  0.23 0.05  1.57 0.09  0.170 0.034  15  455  4.50 0.65  12.76 2.50  4.00 3.92  5.37 0.69  0.30 0.05  1.42 0.15  0.173 0.037  Rio$' R  11b# 82.5 13.1 4.4 88.0 8.8 3.2 87.5 9.4 p. 91.0 . 6.5 2.5 90.0 7.4 2.6 89.5 7.8  U  Et '  U  A11  '2.7'  A  k  D  k  Me  k  Ma  0.756 0.966  . 100.4 25.1.  12.4  0.700 1.030  149.0 28.5  19.0  0.706 0.951  165.3 31.4  0.718 0.852  184.0 34.5  27.0 1.3  0.700 0.943  107.9 34.2  25.6 1.2  0.677 0.914  246.0 39.5  44.9 2.3  0.729 0.975  267.5 45.3  60.4 4.0  1  88.0 9.1 2.9  k  Key  —  —  .  18.6 0.6  overleaf.  . K E Y TO TABLE  I —•'17  [DJ  =  Concentration  o f d i e t h y l  [B]  =  Concentration  o f a l l y l  ketone  10"  x  3-butenoate.  x  -3  'molec.cm. •~17 ~z 10"" ' m o l e c . c m T  —12 —3 1 10" molec.cnu^sec. —  (  )  =  BRc H 5  D  C 3 H  R  (  j  k  D k R  )  2  0  6  =  R  =  R  ^  =  =  =  11b#  =  E t A11  M  k  k  D  k  M  a  C 3 H  6  5  C  1  1  °  o f formation -  0  " C  3  o  2  2  2  R  C4.H  1 0  ?  D  )  2  C  R  (R  0.136  -  5  H  2  l  C  l  0  o ^  n  D  0 5 H l O  R  + C He 2  1 0  1  k  5  k  =  =  10~  =  1 0  1  5  5  +  R  / k  /  k  k  8  k | / k  k  1  4  6  2  R  2  H  4  R  + 1 0  C3H6  ?  C3H4 + C  R  C3Hi|. +  ~ ^ 3 % ) /  R  C5Hio  R  1  R  1 0  +  - 0.136  Rc4H o)/CD C5H o  -0.136  4  C3H4/(D C5H  2 R  D R  2  R  R  (  x  H 4 -0-^36  R  ^ Czj.H  =  RC0  H4/ C4Hi  2  ( k  10  =  Me  1  ' "  =  A  H  C  R  =  11a$  M  k  2  10$.  R  R  5  )  1  Rate  +  R  1  R  R  C  2  +  R  C  % - 0.136  R  C  4  H 4 + C  H  R  5  2  1  0  )  H4-0.136  R  C  4  H  ) 1  0  RO^Q)  C0  C3R7,.)/ C0 R  2  (cm?molec?sec\!)^  2  (cm.molecsec?)^  7  k ^ / k  •  ,  (cm^molec.sec.)^  a  1  "•  Q  (cm.molec^sec?)^  o^  4-7 3-butenoate  and t h e e t h y l r a d i c a l s o u r c e , d i e t h y l k e t o n e , o  illuminated  with  3130  The p o s s i b i l i t y in  A light  at f u l l  i n t e n s i t y f o r one  of thermal decomposition of a l l y l  since  no c a r b o n d i o x i d e  system, the f o l l o w i n g  was  a n d U.V.  p r o p y l e n e and a l l e n e .  hexadiene-1,5  are  consistent  Although the presence  was  the f o l l o w i n g  >  2 5  C  2  C  2 5* H  +  investigated,  mechanism:  C H C0C rL-2 5 2 5 o  R  o  C  C0C  (2)  4  2 4H  + C H 2  G 0 C  2 5 H  C H C0C H  ^2 4- 2 5~ H  CO  H  2  5  +  5  4 10  C H  2C H ** +  of acro-  The natux^e a n d d i s t r i b u t i o n o f t h e p r o d u c t s  with  5  carbon  found.  2  0  1-pentene,  These a r e t h e o n l y p r o d u c t s  2C H *  C H 2  I n the s e n s i t i z e d  a n d 3 - b u t e n o i c a c i d were  none o f t h e s e p r o d u c t s Kinetic Analysis.  after.allyl  p r o d u c t s were i d e n t i f i e d and measured:  found i n s i g n i f i c a n t y i e l d s . lein,  found  radiation.  carbon monoxide, e t h y l e n e , ethane, butane, dioxide,  3-butenoate  170°C f o r two h o u r s i n t h e a b -  3-butenoate had been h e a t e d a t sence of d i e t h y l ketone  hour.  (97°C t o 162°C)  the temperature range of the experiments  was e l i m i n a t e d ,  was  H  4  9  2  (3)  6  +  C  (4)  2 6 H  (5)  -  5  CH =CIICH C00CH-CH-CH o  C H 2  5  + CH =CHCH C00CH CH=CH, 2  2  2 6 il  2  +  2\  or  (6)  CH -CH-CHC00CH CH=CH i 2  •CH =CHCH C00CH-CH-CH, 2  2  ^  2  2  2  CH =CHCH COOCH(C H )CH=CH 2  2  2  5  CH =0HCH C06CH=CHCH C H 2  C H-  .  o  2  2  2  2  ]  5  +<)  (6a) CH -CH-CHC00CH CH=CH : ^ C H = C H C H ( C H ^ ) C 0 0 C H C H = C H G H CH CH=CHCQ0CH CH=CH2  2  2  2  2  5  2  2  2  2  2  2  | >  48 0 H + CH~=CHCH~C00CH CH=CH 2 5 2 2 2 o  C H 2  c  5  o  ^  C H -CH gHCH C00CH CH=CH 5 ^ 2 2 (7) 2-^CH =CHCH C00CH GHGH„C H 2 2 22 2 5 2  o  2  2  t  o  o  o  + C H^CH CHCH C00CH CH=CH 2  o  2  o  o  o  2  o  o  c  2  C H CH CH(C H )CH C00CH CH=CH 2 5 2 ^ 2 5' 2 2 2 0  CoH,25  C  0  0  C  o  o  (  o  7 a  )  + CH =CHCH C00CH CHCH C H,o  o  2  o  d  o  2>  o  2 2 o  C H = C H C H C 0 0 0 H C H ( CgH^ ) C H ^ H ^ ) 2  2  2  2 5 22 2 J T C c H ^ + C 0 + CH -CH-CH C H = C H C H C 0 0 C H C H C H C H — ^ 5 10 2 2 2  o  2  2  2  2  2  0  0 2  • C H - C K - C H • + C' H^-—>CH =CHCH 0 H^ 2  2  CH -CH-CH 2  2  2  CH -CH-CH '+ 2  2  2  + C H ":—>CH CH=CH  2  2  CH -CH-CH 2  5  2  5  (10)  2  + C ^  2  C H " — » CH =C=CH  2  + C. H  + S H — » CH CH=CH  2  +S*  2  (8)  5  5  2  5  2  (11a)  #  (11b)  6  (14)  3-butenoate o r d i e t h y l  ( w h e r e SH r e p r e s e n t s e i t h e r a l l y l  ketone) T h i s mechanism i s s u p p o r t e d by t h e m a t e r i a l and e t h y l r a d i c a l s w h i c h a r e d i s c u s s e d The  following reactions  g i v e n above detectable  later i nthis  were n o t i n c l u d e d  because t h e r e l e v a n t  balances i n a l l y l section.  i n t h e mechanism  p r o d u c t s were n o t f o r m e d i n  quantities:  CH =CHCH COOCH-CH-iOH —> CH =CHCH C0 + 0H =CHCH0 2  2  2  2  2  CH =CHCH C0—>CH -CH-CH 2  2  2  2CH -CH-CH —>C H 2  2  6  The r e a c t i o n s  2  9 a n d 9a a r e e l i m i n a t e d  f o u n d among t h e p r o d u c t s . the  2  reaction  s e q u e n t l y r e a c t i o n 13 c a n a l s o be In hydrogen a b s t r a c t i o n from a l l y l  (9) (9a)  + CO  (12) 2  + CH CH=0H  since  3  2  (13)  no a c r o l e i n was  The a b s e n c e o f h e x a d i e n e - 1 , 5 among  products indicates that  removed  2  1 Q  2CH -CH-CH —->CH =C=CH 2  2  12 d o e s n o t o c c u r ;  con-  eliminated.  ( r e a c t i o n 6 ) , t h e hydrogen  atom  3 - b u t e n o a t e i s e x p e c t e d t o be one o f t h o s e  49 attached vinyl  t o a c a r b o n atom a d j a c e n t  groups.  Since  the hydrogen  replaced with deuterium, the  r a t e s o f a b s t r a c t i o n f r o m t h e c a r b o n atoms on e a c h  s i d e o f t h e c a r b o x y l group rate  activating  atoms o n one o f t h e cx-  c a r b o n atoms were n o t s e l e c t i v e l y relative  t o one o f t h e  of hydrogen  c o u l d n o t be d e t e r m i n e d .  The t o t a l  a b s t r a c t i o n f r o m b o t h c x - c a r b o n s was  obtained  from 6  R  This  =  R  C H 2  +  2  R  4  C H 3  " 4  .  R  4  (  A  1  )  e x p r e s s i o n has been d e r i v e d u s i n g t h e e x p e r i m e n t a l  dence t h a t t h e r a t i o the  " C H R  6  of the rate of production  rate of production  expression k  R  _ k  *  2  0 H . " C H, 2 6 2 4 E  o  +  0  2 R  L  [B] . H »  =  0  H  k^:  C.H, ' ^ 4 3 4 . , [B] k " k  [D] =  concentration of diethyl  and  [B] =  concentration of a l l y l  2  )  3-butenoate whichcK-  was a b s t r a c t e d i n r e a c t i o n 6, i t i s n o t p o s -  t o determine  butenoate  A  ketone  J u s t a s i t was n o t p o s s i b l e t o d e t e r m i n e f r o m  sible  . (  2  where  carbon hydrogen  constant  o f 3 . 0 . A1 c a n be u s e d t o d e r i v e a n  f o r the rate constant  6  of propylene t o  of allene was'approximately  and h a d an average v a l u e  evi-  t o w h i c h o f t h e d o u b l e bonds o f a l l y l  the ethyl radical  i s a d d e d i n r e a c t i o n 7.  3-  Therefore,  o n l y t h e t o t a l r a t e o f a d d i t i o n c a n be m e a s u r e d : E  7  From t h i s  '  E  00 - \ H  expression,  - C H R  1  0  2  +  H  6  an e x p r e s s i o n  3  -  2  H  C0 - % H  - C H H  1  0  2  6  S^io  4  ' U3>  f o r t h e r a t e c o n s t a n t kr,"  c a n be d e r i v e d : !L  C H  *  50 Figure  3.  A d d i t i o n and m e t a t h e s i s b e t w e e n t h e e t h y l cal  and a l l y l  3-butenoate.  radi-  The  expression  f o rthe material " 4 1Q, C  Et  H  +  R  balance of the e t h y l r a d i c a l  °2 6 H  ~  =  R  can  be s u b s t i t u t e d  , . • < 5)  H  ~  C0  i n A4 t o o b t a i n  5 4  R c  A C  —  2  A  an e x p r e s s i o n  f o r the rate  c o n s t a n t ~k i n t e r m s o f n  k  7  H  k~  The cates  '  ( 1  =  —  -  Et^ CO  M  R  % p  presence o f carbon dioxide  that  among t h e p r o d u c t s  pentene and a l l y l  t o r e a c t i o n 8, t o y i e l d radicals.  The r a t e  r e a c t i o n , kn, must e q u a l t h e r a t e i ti s therefore  given  2  k  7a  R  of this  decomposition  of formation  4  of carbon d i -  (A7)  1 Q  7a  When, a s i n t h e e x p e r i m e n t a l c o n d i t i o n s tion of ethyl radicals i shigh,  used, t h e concentra-  i t i s r e a s o n a b l e t o assume  a l l a d d u c t r a d i c a l s w h i c h do n o t decompose ( r e a c t i o n 8)  combine w i t h the  c a r b o n d i o x i d e , 1-  by  .R )° C H  that  indi-  t h e a d d u c t r a d i c a l p r o d u c e d i n r e a c t i o n 7 decom-  poses, according  oxide;  (A6)  [BJ .R TT  rate  e t h y l . r a d i c a l s t o give  stable products.  Then  o f t h i s c o m b i n a t i o n r e a c t i o n , Ro_, i s g i v e n b y <  R  7a  =  R  "  7  S u b s t i t u t i o n i n A7 f o r R  n  R  a  co2  ( A 8 )  gives  the following expression  in-  /a volving kg: k  8 2 k  R  C0* % H ,  i  = k  7a  n  R  C0  " C H R  4  _LJ0 " C H C H^ " C0 R  1 0  +  2  6  R  (  R  5  2  A 9  )  F i g u r e 4.  Ethyl-radical-sensitized allyl  3-butenoate.  decomposition of  . The The  . decomposition r e a c t i o n 8 generates a l l y l  5 5 radicals.  presence o f these r a d i c a l s i s deduced d i r e c t l y from t h e  appearance o f p r o p y l e n e and a l i e n e and i n d i r e c t l y f r o m t h e fact that the rate of formation the  rate  of formation  o f 1-pentene i s l a r g e r  of carbon d i o x i d e .  of the experiment, e t h y l r a d i c a l s t i v e l y high should and  Under t h e c o n d i t i o n s  are always present i n r e l a -  so t h a t  a l l e n e and p r o p y l e n e ,  be f o r m e d m a i n l y i n t h e d i s p r o p o r t i o n a t i o n r e a c t i o n s 1 1 a  11b.  tical  concentrations,  than  Some o f t h e p r o p y l e n e may be f o r m e d i n t h e m e t a t h e The a b s e n c e o f h e x a d i e n e - 1 , 5  r e a c t i o n 14.  i s strong  e v i d e n c e t h a t p r o p y l e n e and a l l e n e a r e n o t produced i n a mutual, i n t e r a c t i o n o f a l l y l over carbon dioxide  radicals.  The e x c e s s , o f 1 - p e n t e n e  i s .most p r o b a b l y d e r i v e d  from r e a c t i o n 10.  i  The  rates  the  of reactions  R  R  The  rate  10  ,"  D S  C H 5  11a  =  R  11b  =  R  by  C H $  6  C H  4  5  "  1 0  0  R  5  H  1  0  r  R  C0  (  A  )  ^  R  (A12)  the metathetical  does, n o t e n t e r o  r e a c t i o n 14 c a n be  into metathetical  eliminated.  reactions with  radi-  cyclopen-  29  t a n e b e l o w 200 C lity  0  - 14  R. M c N e s b y a n d A. S. G o r d o n h a v e shown t h a t t h e a l l y l  cal  1  2  o f t h e d i s p r o p o r t i o n a t i o n r e a c t i o n 1 1 a c a n n o t be  known u n l e s s  .  of the a l l y l o  O t h e r w o r k e r s have s u p p o r t e d t h e i n a b i -  radical to abstract 30 31 32  o l e f i n s b e l o w 200 C the  given  expressions R  J.  1 0 , 1 1 a a n d 11b a r e t h e r e f o r e  '  '  .  a h y d r o g e n atom f r o m  The i n c i d e n c e  o f r e a c t i o n 14 i n  p r e s e n t s y s t e m was t e s t e d b y e x a m i n i n g t h e i n f l u e n c e o f  54 temperature  on t h e r a t i o R  „ /R . S i n c e CH,. i s f o r m e d 0 4 3 6 ^ o n l y , i n t h e d i s p r o p o r t i o n a t i o n r e a c t i o n 11b, i t s r a t e c o n s t a n t n  n  TT  of f o r m a t i o n i s n o t e x p e c t e d t o depend on t e m p e r a t u r e . C^Hg i s f o r m e d  r e a c t i o n 11a,  i n the disproportionation  n e i t h e r must i t s r a t e  then  c o n s t a n t o f f o r m a t i o n be d e p e n d e n t o n  B e l o w 135°C, t h e r a t i o R„ r /R r was f o u n d t o °3 ' 4 °3 6 independent o f t e m p e r a t u r e and t o have an average v a l u e o f  temperature.  T  i  be  I f  0.36  ± 0.10.  with  A b o v e 135°C, t h e r a t i o R  i n c r e a s i n g temperature  produced natural results,  i n a temperature  /R 3 4 H  Q  decreased  H  3 6  i n d i c a t i n g t h a t p r o p y l e n e ' was a l s o  dependent r e a c t i o n  c h o i c e i s r e a c t i o n 14. the rate  c  T  n  i  (FIG. 5).  I n o r d e r t o c o n f i r m t h e above  o f f o r m a t i o n of. e t h y l e n e was  Ethylene i s produced  The  m a i n l y by t h e mutual  examined.  disproportionation  ( r e a c t i o n 3), and i t s r a t e • o f f o r m a t i o n i n 2 t h e a b s e n c e o f s u b s t r a t e s h a s b e e n r e p o r t e d t o be 0.136 R ^4^10 I n t h e p r e s e n c e o f a l l y l 3 - b u t e n o a t e , i t was f o u n d t h a t R„ -j- > 0.136 R^ TT , b e c a u s e e t h y l e n e was n o t o n l y p r o d u c e d of e t h y l r a d i c a l s  n  °2  4  v  4 10  in reaction 3  ?  b u t a l s o i n r e a c t i o n 11a.  Therefore, the d i f -  rj , w h i c h i s e q u a l t o E „ „ - 0.136 R„ TT , c a n °2 4 2 4 4 10 be c o n s i d e r e d , e q u a l t o t h e r a t e o f r e a c t i o n 11a. The r a t i o R T r /DR~ TT i s f o u n d t o be e q u a l t o 0.36 t 0.07 a n d t o b e 3 4 2 4 independent o f temperature throughout t h e temperature range. f e r e n c e DR  n  n  T h e r e f o r e , below  135°C, R  Q  H  /UR  34 T h i s e q u a l i t y shows t h a t , b e l o w duced  i n r e a c t i o n 11a a n d t h a t  within the limits  C  /R . 2 4 3 4 3 6 135 0 , a l l p r o p y l e n e i s pro-.. H  i s equal t o R  i t s rate  c  H  H  of production i s , .  o f e x p e r i m e n t a l e r r o r , e q u a l t o DR  A b o v e 135°C, t h e r a t e d i f f e r e n c e  c  „ . ^2 4 DR„ n = B„ - DR~ p i s 3 6" 3 6"~ 2 *4 TT  n  55 Figure  -  5«  Disproportionation allyl  between e t h y l  and  radio a ls •  0.5  @  3  0  0"  IK  0.3  o  O  N  3 U  0.2 0.1  Y  2.6  25  23  2.4  10 / T 3  B  Rx  Rc  ©  Rx  RC H -0.136 Rc H  H  3  2  4  6  4  IO  56 temperature  d e p e n d e n t ; t h e r e f o r e , i t must be e q u a l t o t h e r a t e  of r e a c t i o n 1 4 .  Reaction 1 4 includes metathesis  r a d i c a l w i t h both d i e t h y l ketone strate  ( r e a c t i o n 1 4 D ) and t h e sub-  (reaction 14B): +.C H COC H 2  C A '  5  2  5  + C,H -C0 C-.H [  55  Therefore  O  C  > C-Ji  6  > C-,H  R  552^5  R^  then If  of the a l l y l  =  1Zj  k  1  4  2  w  5  2  X  /L  (14D) •  4  + C H C0 C-,H  56  = R^-g + R ^ j } *  R _  + C H C0C H O  (14B)  C:  •3 4 d p5  e  a  s  s  u  m  that  e  p H | {[B] + C k / k ) [D]}  B  2  / f  6  t h e above e x p r e s s i o n i s t a k e n i n t o a c c o u n t ,  the rate  cons-  t a n t , k^,- c a n be g i v e n b y  % k  % ^  {[B] + ( k / k | [ D ]  1 Q  4  .DR  6  '  (A13)  °5 10 H  The A r r h e n i u s p l o t E  1iL  o f t h e above  21 ± 5  =  q u a n t i t y gave t h e p a r a m e t e r s  kcal./mole  13 + l o g | A , A | / A ( c m 3 o l e c 7 s e c T ) ^ } 1  1 i  1 0  1  m  =  10 ± 4  The v a l u e o f t h e a c t i v a t i o n e n e r g y E ^ d o e s n o t a g r e e t h a t o f 11.5 k c a l . / m o l e  o b t a i n e d from  with  Polanyi's empirical  130  formula, to  11.5 - 0.25  be a p p r o x i m a t e l y 4  A^^i  , where  zero.  M o r e o v e r , we c a n e s t i m a t e  that  6  1 0 * Ag o n t h e a s s u m p t i o n  of A ^  was e s t i m a t e d  i s unacceptably  of propylene  high.  t h a t A^Q = A ; s u c h 2  We c o n c l u d e  a value  that the formation  i n r e a c t i o n 1 4 i s s i g n i f i c a n t , b u t t h a t t h e pre-__  c i s i o n o f measurement i s i n s u f f i c i e n t  to provide  reliable  values f o r the Arrhenius parameters of r e a c t i o n 1 4 . The m a t e r i a l b a l a n c e ^  M  A11  =_ {  R  C  5  H  1  0  "  R  f o r the a l l y l C0  + 2  R  C  3  H  + 6  R  r a d i c a l c a n be g i v e n  C HJ/ C0 R  5  2  •  (  A  1  4  )  57 F^A  11  was f o u n d t o be  .0.89 ± 0„09,  b e t w e e n 97°C a n d 162°C.  This  independent o f temperature  shows t h a t 89 ± 9$ o f t h e a l l y l  r a d i c a l s produced i n r e a c t i o n 8 a r e accounted f o r by the f o r mation o f p r o p y l e n e , a l l e n e and 1-pentene. m a t e r i a l - b a l a n c e does n o t d e c r e a s e w i t h ture; therefore, is  there  The v a l u e  increasing  ofthe  tempera-  i s no e v i d e n c e t h a t t h e a l l y l  added t o t h e s u b s t r a t e .  The d e f i c i t  radical  indicates that  allyl  r a d i c a l s may. be consumed b y c o m b i n a t i o n r e a c t i o n s w h i c h a r e analogues o f r e a c t i o n s Discussion.  6 a a n d 7a«  TABLE, I I shows t h e A r r h e n i u s  main r e a c t i o n s  of the ethyl r a d i c a l with  and  propionate.  with  allyl  parameters of the allyl  3-butenoate  The l a t t e r w e r e p r e v i o u s l y  found  39 in  this  laboratory^  .  The . c o r r e s p o n d i n g p a i r s o f  parameters f o r these substrates stated limits  Arrhenius  show a g r e e m e n t w i t h i n t h e  of error for the dismutation  o f t h e adduct  radicals. In both the a l l y l  propionate  and a l l y l  tems, m e t a t h e s i s w i t h t h e e t h y l r a d i c a l  3-butenoate  i s associated  sys-  with  a  l o w e r - a c t i v a t i o n energy than t h e a d d i t i o n of t h i s r a d i c a l t o the  d o u b l e bond.  The f a c t t h a t E g i s s m a l l e r  t h a n E ^ c a n be  a t t r i b u t e d t o t h e resonance s t a b i l i z a t i o n o f t h e adduct cal  produced i n the m e t a t h e t i c a l CH =CHCH C00CH-CH-CH 2  2  2  or  reaction  (6):  CH -CH-CHC00CH CH=CH 2  radi-  2  2  The  adduct r a d i c a l produced i n t h e a d d i t i o n r e a c t i o n 7 does  not  show a n y s u c h s t a b i l i z a t i o n . 7  of octene-1 tivity.  and d i a l l y l  The c o r r e s p o n d i n g  126 a l s o show t h i s p a t t e r n •  "  reactions of reac-  TABLE I I ARRHENIUS  PARAMETERS FOR THE P R I N C I P A L R E A C T I O N S PROPIONATE  OF A L L Y L 3-BUTENOATE AND  WITH THE E T H Y L R A D I C A L  E kcal/mole  49 Allyl  log A  propionate  E kcal/mole 8.7  ± 0.4  6.9,  7.4  ± 0.3  5.4  17.0  ± 0.5  Addition Metathesis  w i t h C H^'  k  2  Dismutation  l  Where  k. ME k  D  ME  D  7.7  ± 0.5  5.8  ± 0.2  5.8  ± 1.4  4.1  ±  0.8  18.2 ± 2.6  11.1  ±  1.5  10.4 ± 0-.3  10^"-^kr,/k2 c m ? m o l e c . s e c 7 13 \ % _ i _ 10 k^/kg cm* molec7 sec7 2  2  k  gk /kr-; 2  2  a  ±.0.3  2  2  10  log A  0.3  ±  /  '  A l l y l 3-butenoate  Reaction  ALLYL  2  i  cmT^molecfsec"  Vn co  59 The  d i f f e r e n c e i n t h e a c t i v a t i o n e n e r g i e s o f t h e meta-  t h e s i s and a d d i t i o n r e a c t i o n s i s f o u n d f o r a l l a l l y l i c compound/free r a d i c a l  s y s t e m s , a n d i t i s known t o he  c i a t e d w i t h the degree o f a l l y l i c  polymerization.  asso-  As h a s  been d i s c u s s e d i n t h e i n t r o d u c t i o n , t h e r a t i o o f t h e r a t e constants of propagation t o degradative t r a n s f e r , which can be u s e d a s a m e a s u r e o f t h e d e g r e e o f p o l y m e r i z a t i o n f o r l o n g c h a i n s t e r m i n a t e d by mutual d i s p r o p o r t i o n a t i o n , i s a p p r o x i mately equal to the r a t i o  of the rate constant  of the addi48 49  t i o n r e a c t i o n , 7, t o t h a t o f t h e m e t a t h e s i s  reaction, 6  That i s ,  '  i  k^/kg  =  k  p/ t k  cl- S  =  e  r e e  of. p o l y m e r i z a t i o n  T h e r e f o r e , t h e v a l u e o f k ^ / k g c a n be u s e d t o p r e d i c t t h e d e g r e e o f p o l y m e r i z a t i o n o f a l l y ! 3-butenoate.,  T h i s v a l u e was  f o u n d t o be k /k ?  6  = . =-  To  10^ * 1  5  1  Oo5  )exp(-1..3< t 0 . 4 ) 1 0 / R T 5  5-0 ± 0.4  a t 80°C  t h i s d a t e , no i n f o r m a t i o n on t h e a c t u a l d e g r e e o f p o l y -  m e r i z a t i o n i s a v a i l a b l e f o r comparison w i t h t h i s value of k^/kg; k^/kg  however, t h e v a l u e i s comparable w i t h t h e v a l u e s o f w h i c h have been r e p o r t e d f o r a l l y l  a c e t a t e and a l l y l  propionate. These a r e g i v e n i n t h e f o l l o w i n g t a b l e : SUBSTRATE ^/kg DEGREE OF POLYMERIZATION ( c a l c . f o r 80°C) ( o b s e r v e d a t 80°C) Allyl  acetate  A l l y l propionate Allyl The  3-butenoate  4.4  4  9  14  5  5  3.9  4  9  10  5  4  5.0  t r e n d i n t h e r e l a t i v e v a l u e s o f k ^ / k g and t h e degree o f  .  60 p o l y m e r i z a t i o n observed has  may  indicate that a l l y l  a s l i g h t l y h i g h e r degree of p o l y m e r i z a t i o n t h a n have  o t h e r two The adduct agree  Arrhenius parameters  r a d i c a l s from  allyl  v/ithin the l i m i t s  f o r the decompositions  3 - b u t e n o a t e and  allyl  of  for  t h e s e two  are  t r a n s i t i o n s t a t e s c a n be  indistinguishable  I f i t i s assumed t h a t t h e s e  a c h i e v e d b y one  h y p o t h e t i c a l processes, the heats  of the  following  of these processes  w i t h the a c t u a l a c t i v a t i o n energy,  Eg-, may  compared  i n d i c a t e which  them g i v e s t h e b e s t a p p r o x i m a t i o n o f t h e t r a n s i t i o n ^5 10 H  Add*  >  "^"^  from  level.  compounds i n d i c a t e s s i m i l a r t r a n s i t i o n s t a t e s i n  t h e i r decomposition reactions.  w h e r e a,b,c  the  propionate  o f e r r o r a t t h e 5$ p r o b a b i l i t y  f a c t t h a t t h e a c t i v a t i o n e n e r g i e s Eg  allyl  the  monomers.  The  of  3-butenoate  +  M  o  n  o  r  a  Monoradical C  3 -io * H  C0  2  3-i  |  c  a  M  o  c o r r e s p o n d t o Add"  n  o  r  a  state.  ( a , a ' ,a")  x  + Diradical +  one  d  i  c  a  l  (b,b',b") ( c , c ' , c " )  = C^H^COOC^H^Q,,derived  from  p r o p i o n a t e , a ' , b ' , c ' t o Add*-. C ^ H ^ C O O C ^ H ^ Q , d e r i v e d allyl  3 - b u t e n o a t e , . and  d e r i v e d from  allyl  a" , b , c " n;  3-butenoate.  The  t o Add"= C ^ Q C O O C ^ , heats  of t h e above p r o -  c e s s e s have been c a l c u l a t e d u s i n g the p a r t i a l bond  contribu-  101 t i o n s method heats  and  t h e y a r e t a b u l a t e d i n TABLE I I I .  of f o r m a t i o n of a l l r a d i c a l  The  s p e c i e s i n v o l v e d i n the  c e s s e s a p p e a r i n g i n TABLE I I I , t o g e t h e r w i t h t h e p a r t i a l t r i b u t i o n s o f c e r t a i n b o n d s i n v o l v i n g atoms w i t h f r e e  procon-'"  elect-  r o n s , arid a m e t h o d o f c a l c u l a t i n g them a r e g i v e n i n TABLE I V . An Eg,  i n s p e c t i o n o f TABLE I I I shows t h a t t h e a c t i v a t i o n e n e r g j , r  for allyl  propionate l i e s  c l o s e t o , and  slightly  exceeds  TABLE I I I H E A T S OF C E R T A I N H Y P O T H E T I C A L P R O C E S S E S A S S O C I A T E D WITH T H E T R A N S I T I O N S T A T E O F T H E D E C O M P O S I T I O N OF T H E ADDUCT R A D I C A L RCOOCHpCHC^Hy SUBSTRATE: Adduct r a d i c a l (AH o f adduct radical kcal/mole)  Hypothetical  AH*  products  f  ALLYL  .  kcal/mole  8  kcal/mole  3-BUTENOATE:  CH =CHCH C02CH2CHC H 2  :3  2  (-57.5)  7  CH =CHC-3H 2  CH iCH*-CH  -  2  CH *CH-CH 2  7  2  + CH =CHCH C0 2  2  2  7  + CH2CHC3H7  2  (a )  28.7  (b»)  68.0  (C)  -7.6  1  2  + g0 CH CHC3H + C0  2  2  r C3H CHCH C0 CH CH=CH 7  2  2  2  (-57.5)  2  C3H CH=CH  2  + C0 CH CH=CH  CH --CH-CH  2  + C3H CHCH C0  7  2  2  2  ALLYL  2  7  CH -CH-CH2 + C 0  2  (a")  2  2  "  2  +CH =CHC3H 2  7  (b" )  17.0 + 0.5  26.9 80.8  (c")  -7.6  (a)  15.7  (b)  73.2  (c)  -3.8  PROPIONATE:  CH CH C0 CH CHC3H 3  E  2  2  2  (-69.7)  7  CH =CHC3H 2  7  + CH3CH C0 2  CH^CHg + C0 CH CHC3H 2  2  2  7  CH3CH - C 0 + C H = C H C 3 H 2  2  2  7  The h e a t s o f f o r m a t i o n o f t h e r a d i c a l s p e c i e s were c o n t r i b u t i o n s method a s shown i n TABLE I V .  calculated  » 18.2 ± 2.6  using the partial  bond  TABLE IV PARTIAL CONTRIBUTIONS OF BONDS INVOLVING ATOMS WITH FREE ELECTRONS AND HEATS OF FORMATION OF CERTAIN RADICAL SPECIES Bond  XH  (A-B)  kcal/mole  AH (XH) F  (co-o*)  +  -»X  CH^COgH  AH  H.  102  102  kcal/mole  Partial contribution of (A-B) i n k c a l mole  112.0  -18.0  ->-C0 H + H*  90.0  -22.2  > ( C H ^ C H + H*  9^.5  40.6  > CH^COg' + H  -103.8 (CO-O)  HC0 H 2  2  -88.5 (C-H) + 2(C-C)  CH^CHgCH^  METHOD :  AH (X* ) F  =  1  .  -24.8  A H  -  X  AH(H*  = y~{Partial  ) + AH(XH)  bond c o n t r i b u t i o n s  A l l other bond c o n t r i b u t i o n s RADICAL SPECIES: AH  F  kcal/mole  :  CH =CHCH C0 ' 2  2  -23.8  2  obtained from v a l u e s r e p o r t e d  C0 CH CHC H 2  2  -22.5  i n c l u d i n g t h a t o f (A-B)  3  ?  C-H^CHCHgCOg -20.7  C0 CH CH=CH 2  2  -25.6  by Benson 2  101  CH CH C0 3  2  -49.0  2  cn ro  63 the  value  ofA H  .  0  This  i n d i c a t e s t h a t model a i s a  close  oa  approximation t o the t r a n s i t i o n ching  of only  state;  therefore,  one b o n d n e e d s t o be c o n s i d e r e d .  the stret-  In contrast,  the v a l u e o f Eg f o r a l l y l 3-butenoate i s c o n s i d e r a b l y than e i t h e r A H , or A H ... T h i s i n d i c a t e s t h a t more oa' oa 0  lower than  Q  one b o n d i s s t r e t c h e d  i nthe t r a n s i t i o n  model f o r t h e t r a n s i t i o n  state i s given  CH *CB>CH  either  0  <-  or  C  5 10 H  1  state.  0  c-  An  appropriate  by  • • « i i iC-=rO< » • i « > « • > > « ' C ^ H ^ |/; 3 10 0  '•'•«•'« •C ^ Oi i i i i i CH -CH-CH 2  2  0 It  i s possible  transition allyl  state.  and C 0  transition Ag = I O  1 0  t h a t b o t h o f t h e s e models c o n t r i b u t e  2  I f the loss of i n t e r n a l rotations i nthe  segments i s t a k e n i n t o c o n s i d e r a t i o n ,  states are consistent  ' ' 4  the rates  actions  with  the estimated  these value,  ±  In the k i n e t i c that  to the  a n a l y s i s of. t h i s  s e c t i o n i t was shown  of the combination and d i s p r o p o r t i o n a t i o n r e -  o f t h e e t h y l and a l l y l  r a d i c a l s c a n be g i v e n  by t h e  relationships \  R  10 R  R  =  D  1 1 a ^ 11b  =  R  G H 5  C  R  R  2  1  H  Q  4  =  E  '  C R  5  H  1  -  0  R  C 0  G "°A  2  136  Vlo'  CUEL  Between 97°C and 162°C,  the r a t i o s  R 1  1  b  /  R  a 1  0  n  d  R  11a  / / R  '10  w e r e f o u n d t o be i n d e p e n d e n t o f t e m p e r a t u r e a n d t o h a v e average values tively. cates  o f 0.030 ± 0.012 a n d 0.098 1 0.033  respec-  The t e m p e r a t u r e i n d e p e n d e n c e o f t h e s e r a t i o s  that  indi-  t h e e x c e s s o f 1 - p e n t e n e , DR~ „ , the excess of °5 10  64 e t h y l e n e , b i n a t i o n and  D R „ , °2 4 r e a c t i o n n  and a l l e n e  c a n be  10  d i s p r o p o r t i o n a t i o n  and t h e  11b r e s p e c t i v e l y .  of  r e a c t i o n s . 1 0 ,  88  ±  4 ,  w i t h  9  t h e  ±  The p e r c e n t a g e  1 1 a a n d 11b were  and 3  3  produced  ±  1 .  c o r r e s p o n d i n g  These  r a t e s  o f  i n  t h e c o m -  r e a c t i o n s t h e  t o t a l  1 1 a r a t e  t o  be  r e s p e c t i v e l y  v a l u e s  a r e  i n  c l o s e  ± 4 ,  1 1 + 3  values,85  found  o n l y  and 4  agreement ±  1 ,  r e -  40 p o r t e d  f o r  l a t t e r  v a l u e s  have  been  r a d i c a l  does  n o t  a l l y l  t h e  d i e n e - 1 , 5 . the  T h i s  r a t i o s  R~ C  pendent  e t h y l  o f  „  /R  C  w i t h  e t h y l  r a d i c a l  t o  and  o f  t h e  t h e  a l l y l  adduct  r a d i c a l s  parameters  were  w i t h  o f  those  a n d R  H  „  n  C  3 6  t h e  o f  t h e t h e  Approximate  t i o n  s t a t e s  e t h y l  convenient The  o f  s u b s t r a t e ,  and t h e  i n t e r a c t i o n  r a t e  carbon  o f  c o n f i g u r a t i o n s  t h e  p r o p i o n a t e The  t h a t i n d e -  o f o f  s u b s t r a t e ,  and t h e i r  o f  o b t a i n e d  e t h y l  t h e  t h e  t h e  r a t e s  t h e  m e t a -  d e c o m p o s i t h e  and  e t h y l  A r r h e n i u s  agreed  r a d i c a l  w i t h  c l o s e l y a l l y l  ,  /  a l l y l  a d d i t i o n  the  p r o p i o n a t e .  h e x a -  used  w i t h  t h e  t h e  '  o f  o f  from  t h e r e a c t i o n s  The r e s u l t s  t h e r e a c t i o n s  t h a t  t h e f a c t  bond  observed  measured.  b y  H  3-butenoate  r a d i c a l ,  atom  The  h a d remained  5 10  range  s t u d y  r a d i c a l  were  /DR~ „ C  .  assumption  hydrogen  H  w i t h i n  a l l y l  a  t h e  system  was j u s t i f i e d  t h e double  e t h y l  on  a b s t r a c t  t h e k i n e t i c  r a d i c a l  t i o n  3 4  temperature  e t h y l  o f  TT  n  H  I n  d e r i v e d  a s s u m p t i o n  3 6  C o n c l u s i o n .  t h e s i s  r a d i c a l / h e x a d i e n e - 1 , 5  d e c o m p o s i t i o n  and a l l y l  g e n e r a t i o n  dioxide..''  Among  o f  proposed t h e  adduct  3-butenoate o f  g e n e r a t i n g  g i v e n  b y  t h e r a t e  t h e  t h e  t r a n s i -  r a d i c a l s  system  method  i s  f o r  o f  3-butenoate.  r a d i c a l / a i l y l  and e f f i c i e n t  were  s u b s t r a t e s  w h i c h  p r o v i d e s  a l l y l  r a d i c a l s .  o f "formation on  a  o f  s e n s i t i z a t i o n  6 5  with e t h y l r a d i c a l s generate has  c e r t a i n advantages a)  diallyl  b)  diallyl  126  allyl  radicals, allyl  3-butenoate  over  , because R Th 86  oxalate  p  is  simply i n d i c a t e d by.-R  , because  decomposition. 39 d i a l l y l e t h e r ^ , because  there i s  no  p n  2 '  .  unsensi-  tized c) B.  Thermal Decomposition Oxalic  t h e mechanism i s  much s i m p l e r .  of D i a l l y l Oxalate.  a c i d and a l a r g e number o f i t s  esters  show a  n i t e t e n d e n c y f o r t h e r m a l d e c o m p o s i t i o n i n t h e gas phase  1 0 6  '-  1 0  ?-"  1 0 8  or  liquid  .  The d e c o m p o s i t i o n o f o x a l i c a c i d v a p o u r h a s b e e n over the range  defi-  127°C  to  157°C  by L a p i d u s  studied  and c o - w o r k e r s .  Only  j  equimolecular q u a n t i t i e s of carbon dioxide,.and formic  acid  w e r e p r o d u c e d , a n d t h e k i n e t i c s were f i r s t o r d e r w i t h r e s p e c t to oxalic acid. •E =  3 0 . 0  authors  ±  The o b s e r v e d A r r h e n i u s  parameters  k c a l / m o l e and l o g ( A , s e c . ' )  1 . 3  assumed  = - 1 1 . 9  were  ±  These  0 . 7 -  a u n i m o l e c u l a r mechanism v i a a c y c l i c a c t i v a -  ted, complex.  0  {  \  . 0  ,  The d e c o m p o s i t i o n , o f a s e r i e s  a c i d i n the l i q u i d phase t u r e range  of a l k y l e s t e r s  of  oxalic  was s t u d i e d , m a i n l y i n t h e t e m p e r a -  b e t w e e n 14-0°C a n d 1 6 0 ° C ,  by K a r a b a t s o s  and  co-  10R workers  .  decomposed oxalic  Dialkyl oxalates  of o n l y the t e r t i a r y a l c o h o l s .  i n t h i s temperature range  acid.  Those  d e c o m p o s i t i o n up t o  of primary.and 325°C.  giving  secondary  only o l e f i n s alcohols  A l t h o u g h no m e c h a n i s m i s  and  resisted explicitly  66  s u g g e s t e d , t h e r e s u l t s i m p l y t h a t t h e mechanism must i n v o l v e a hydrogen t r a n s f e r from t h e ^ - c a r b o n atom o f t h e a l c o h o l group to  t h e c a r b o n y l group o f t h e o x a l a t e m o l e c u l e i n a p r o c e s s  where two seven membered r i n g s a r e formed i n d i s t i n c t and separate r e a c t i o n s : 0 ^  . . 0 — C~CH,  CH, ' i 3 ^ C ^ / CH,-C-0 ^0---H -... 5 i CH, 5 , H — 0 ^ > 0 C^ CH |  C  H  0 ^ x 0  2  +  .  0 ^  OH  A r r h e n i u s parameters  H  =  C  r  u  OH  '  5  a r e n o t a v a i l a b l e f o r , any o f t h e decompo;  s i t i o n reactions of d i a l k y l oxalates. In  C  0  2  CH,-C---0'^ 3 t CH,  .CH, ' 2 \ i 3 ^C CH, CH,-C-0 OH 5 i CH, 5 : HO^ . 0 C ' ^ C H3 > I + .. ,0112=0  >  /  the present study, the thermal decomposition of d i -  a l l y l o x a l a t e , which i s n o t d e s c r i b e d i n t h e l i t e r a t u r e , has been i n v e s t i g a t e d i n t h e e x p e c t a t i o n t h a t t h e p r i m a r y p r o c e s s involves the production of a l l y l r a d i c a l s .  This~expectation  was based on t h e l o w e n d o t h e r m i c i t y o f t h e r e a c t i o n COOC^Hn CJOOC H 3 5  . >  2  C  0  2  +  2  G  3 5  AH  H  =' 3.  kcal./mole  compared w i t h t h e e n d o t h e r m i c i t y o f t h e r e a c t i o n COOCJH,COOH COOC^H,^COOH 5 5  +  CH =C=CH 2  2  AH  = 4 .5' 5  kcal./mole  which i s the counterpart of t h a t i m p l i e d f o r the decomposition of  a l k y l o x a l a t e s by t h e work o f K a r a b a t s o s .  I f the primary  p r o c e s s c o u l d g e n e r a t e a l l y l r a d i c a l s , t h i s system would be w e l l s u i t e d t o t h e -study o f t h e p a t t e r n o f mutual  combination  67 and d i s p r o p o r t i o n a t i o n i n t h e  i n t e r a c t i o n o f two a l l y l  radi-  cals. Results.  TABLE V s u m m a r i z e s t h e r e s u l t s  composition of d i a l l y l  o f the thermal de-  o x a l a t e v a p o u r b e t w e e n 130°C a n d 200°C.  The  major products  and  hexadiene-1,5, w i t h m i n o r a m o u n t s o f p r o p y l e n e ;  temperatures, experiments  of this  decomposition  are carbon d i o x i d e  v e r y s m a l l amounts o f a l l e n e  were p e r f o r m e d ,  at higher  a r e formed.  Two  one a t 140°C a n d t h e o t h e r a t  160°C, w i t h a v a p o u r m i x t u r e  of diallyl  h e x a d i e n e - 1 ,4.  o b t a i n e d were carbon d i o x i d e ,  The p r o d u c t s  hexadiene-1,5, and p r o p y l e n e . it  o x a l a t e and c y c l o -  A l l e n e was n o t f o u n d ,  although  would have been d e t e c t e d under e q u i v a l e n t c o n d i t i o n s i n  the absence o f p r o p y l e n e . A series of qualitative performed diallyl  oxalate i n evacuated  hours  formed. or  b e t w e e n 100°C" a n d 160°C w i t h h i g h l y p u r i f i e d break-seal tubes.  d e t e c t e d a b o v e 120°C, a n d i n a d d i t i o n ,  was  24  e x p l o r a t o r y • e x p e r i m e n t s were  This polymer d i d n o td i s s o l v e  Chloroform  was u s e d  a f t e r more  than  was b r i t t l e ,  solve and d i l u t e  i n either chloroform .  w i t h t h e m f o r one week.  f o r the removal  lower molecular weight  form.  Carbon d i o x i d e  i n c u b a t i o n a b o v e 150°C, a t r a n s p a r e n t p o l y m e r was  benzene even a f t e r t r e a t m e n t  itself  liquid  o f t l a e monomer a n d t h e  p r o d u c t s from the polymer.  non-extendable,  The p o l y m e r  and im'soluble i n c e l l o -  i n o r g a n i c a c i d s b e s i d e s i n benzene and c h l o r o -  To o b t a i n i t s N.M.R. spectrum.,  i t mas i m m e r s e d i n a n  a p p r o x i m a t e l y . e q u a l v o l u m e o f d e u t e r a t e d c h l o r o f o r m f o r one day.  During this,time  i t became s w o l l e n , , t h u s a c h i e v i n g a  c e r t a i n degree o f i n t e r n a l m o b i l i t y .  I t s JN.M.R. s p e c t r u m was  TABLE V THERMAL DECOMPOSITION OF D I A L L Y L O X A L A T E °K  (C0 )  [DAO]  (C H  2  6  1 0  )  (G H ) 3  6  (C3H4)  1 0 ^  M  10*3*!* k  l O  A  2.43  0.01.'  traces  2.45  -  0.02  0.01 ;  -  -  -  413  2.45  -  0.03  0.0 2  -  -  -  419  2.45  • -V  0.05  0.02  -  -  -  423  2.53  429  2.58  -  437  . "2.43  448  2.43  456  2.54  463  2.54  423  2.48  443  2.48  408  :  [DAO]  •  GH  )  •  .  -  0.23  0.12  traces  traces  -  -  O.I5  0.08  traces  traces  -  -  -  1.13  0.60-  0.01  O.OO5  8.35  -  1.34  0.68  0.0.1'.  0.005  6.1.6  3-10  0.05  4.10' 5  1.97  2.84  0.17;  2.84'  0.99  -  ..'  1.00  2.1  1.30  4.1  1.00 ••  6. 0  ;  . 0.85  10  . 1.03  48;.  1.11  29  0.160  1.08  229  7.40  0.250  1.03  275  0.030  9.68  0.450  1.02  1210  0.05  0.015  7.60  0.980  0.99  804  0.03  0.07  -•  -  -  1.18  0.05  0.55  -  -  -  1.21  (Concentration of d i a l l y l  o x a l a t e ) x 10""-'•''molec.cm?;  .  =  •.  .( C3H 2R  .34-  ZOO  +  R  6  C02  (Concentration of cyclohexadiene-1,4) x l O ' ^ m o l e c c m ? ;  C 1,4] (  .  -  .  :  R a t e o f f o r m a t i o n x 10  molec.cmisec.  •* u n i t s :  ^  (see?*  2  2  403  8  cm*molec7 sec7 5  2  . 69 compared w i t h t h a t o f d i a l l y l with respect  oxalate.  t otetramethylsilane  The c h e m i c a l  shifts  a n d t h e peak a r e a s o f b o t h  s p e c t r a a r e shown i n TABLE V I I * . The s p e c t r u m o f t h e p o l y m e r gave a b r o a d peak w i t h s i t i o n u s u a l l y assigned in  8=  1.2 t o 1.8.  This peak, a t t h e p o -  t o t h e (C-C)-H p r o t o n ,  d i d not appear  t h e s p e c t r u m o f t h e monomer. . An  unsuccessful  of d i a l l y l  a t t e m p t was made t o o b t a i n t h e p o l y m e r  oxalate by heating  diallyl  oxalate i n the presence  o f c y c l o h e x a d i e n e - 1 , 4 f o r a p e r i o d o f 48 h o u r s a t 160°C. failure  confirms  that the homopolymerization o fd i a l l y l  late i s a r a d i c a l addition process, degradative  the  thermal  radical  scavenger.  The r e s u l t s o b t a i n e d  decomposition o fd i a l l y l  w i t h t h e r e a c t i o n scheme I .  oxalate  CH CHCH2 2  Schemes I I a n d I I I c a n b e c o n s i -  Decomposition t o give a l l y l 2  I  C  0'  2 heat., C0 2  •0 2CH -CHiCH . 2  2  2  2  . CH -CH-CH 2  The  2  + 2CH -CH-CH 2  2  2  CH CH=CH  resonance  2  2  henceforth  p . 82.  + CH =C=CH 2  (3)  2  G00CHCH=CH + ooOH CH=CH 2  -> CH CH=CH 3  2  C  2  (4) 2  o  C00CH CH=CH  o rI I " )  (2).  2  C00CH=CHCH  2  (I*  2  structures C00CHCH=CH  will  2  (D  2  ^ CH =CHCH CH CH=0H  2  2  mechanism.  radicals.  5  C00CH CH=CH + C00CH CH=0H "  from .  are consistent  dered as p o s s i b l e minor contributors,, to t h e o v e r a l l Scheme I .  oxa-  w h i c h may be i n h i b i t e d b y  c h a i n t r a n s f e r t o an e f f i c i e n t  K i n e t i c A n a l y s i s and D i s c u s s i o n .  This  C00CH CH=CH  2  2  2  be d e n o t e d 1* and. I I * r e s p e c t i v e l y . + CH -CH-CH 2  2  > ( I o r II)-CH CH=CH 2  2  (5)  70 C00CH CH=CH 2  CH -CH-CH 2  +  2  C  CH=CH  2  C00CH CHC..H  N  0  0  C  H  O  un -on-on 2  +  2  C  0  0  C  H  C H S B  CH  2  2  2  C00CH CH=CH 2  0^  ^C  C00CH CHC H  7  C00CH CH=CH  2  2  >  4  2  o  X  "~ 2 w  o  T  + CJBL- + C H v  0^  2  6"10  of  3  X  5  (8)  C  diallyl.  2  •^2C0 0^  o  2  •» 2 C 0  2  c  2  2  CH CH=CH  z  C00CH CH=CH  Intramolecular elimination  / 0  ^  C00CH CH(C H )C,,H  2  COOCH CHCH CH CH=CH  Scheme I I .  2  + CH =GHCH CH CH=CH  2  2  2  2  (1")  2  2  Scheme I I I , CH =0  /  o  d  \  C  CH-  I  | ^  ^ 0 ^  and  acid,  > 0^  hexadiene-1,5 r u l e  Therefore, d i a l l y l  ^0H  transfer  oxalates  o x a l a t e does n o t decompose  studied  oxalic acid"'^ or 108  by K a r a b a t s o s  I n t h e m e c h a n i s m scheme I , a l l y l primary process  propylene,  o f a h y d r o g e n atom  t h e same t y p e s -of m e c h a n i s m a s e i t h e r of the a l k y l  (1")  C3  o u t m a j o r p a r t i c i p a t i o n o f t h e mecha-  (Scheme I I I ) .  the  + 2CH =C=CH.  and t h e appearance o f c a r b o n d i o x i d e ,  intramolecular  any  .  o f f o r m a t i o n o f a l l e n e , 'the a b s e n c e o f  nism i n v o l v i n g  by  •  I  2  The l o w r a t e oxalic  C^  r a d i c a l s are formed i n  (reaction  1 ) . Hexadiene-1,5 i s s t a b l e 12 under the r e a c t i o n c o n d i t i o n s . The r a t i o • 2R „ /Rrjn » ' °6 10 2 representing the material balance f o r the products of the d e c o m p o s i t i o n i n scheme I I , a n d t h e r a t i o ( 2 R „ + 2R„ ) / R n  n  n  V  °6 10  n r  °3 6 n  representing the material balance f o r the a l l y l r a d i c a l i n scheme I , w e r e f o u n d t o h a v e t h e a v e r a g e v a l u e s 1.03 i 0.10 and  1.06  ± 0.10.respectively.  This indicates  that  either  .  c o  ,  2  7  scheme I , o r scheme I I , o r a m i x t u r e confirm t h e presence  of a l l y l  t h e r m a l l y decomposed  i n the presence  in and  of both i s p o s s i b l e .  radicals, diallyl  the expectation that metathesis  1  To  o x a l a t e was  of cyclohexadiene-1,4,  between a l l y l  radicals  cyclohexadiene-1,4 would i n c r e a s e t h e r e l a t i v e y i e l d o f  propylene. C H  2  - C H - C H  The r a t i o R  n  C  25 a t 150  3  2  tr / H  6  +  R  » CH CH=CH 5  n  -j  °6 10 H  +  2  (6)  i n c r e a s e d by a f a c t o r g r e a t e r  C a n d b y a f a c t o r g r e a t e r t h a n 6 0 a t 170  than  C .  This  c o u l d n o t h a v e b e e n p o s s i b l e i f hexadiene-1,5 h a d n o t b e e n produced i n the mutual combination f o r e , we must c o n c l u d e allyl  radicals.  There-  that the thermal decomposition  of d i -  oxalate produces a l l y l  of, a l l y l  r a d i c a l s i n the primary  t h e r e f o r e , scheme I makes t h e m a j o r  process;  contribution.  The r a t e c o n s t a n t o f t h e d e c o m p o s i t i o n / r e a c t i o n C00C-.H,-  .  >  COOO3H5  c a n be g i v e n b y k^ where  2 C 0  2  +  2C  .  5 5  \  =  .  H  ( 1 )  -  0.5  R  C Q  •  / [DAO]  (E1)  [DAO] d e n o t e s t h e c o n c e n t r a t i o n ' o f d i a l l y l  oxalate.  The A r r h e n i u s p l o t of- k^ g a v e t h e p a r a m e t e r s E^ = 37 * 2 k c a l . / m o l e ; ' The e n t h a l p y c h a n g e j A H ^  log(A ,sec" ) 1  1  = 3-0  kcal./mole,  a b l y l o w e r t h a n t h e a c t i v a t i o n ' e n e r g y E^. l a r g e v a l u e o f E^ may s u g g e s t the decomposition the simultaneous C'-C bond.  = 14 + 1 i s consider-  The r e l a t i v e l y  that the t r a n s i t i o n state i n  of the d i a l l y l  o x a l a t e does n o t i n v o l v e  s t r e t c h i n g o f t h e t w o C-0 b o n d s a n d t h e one  The t r a n s i t i o n s t a t e i n v o l v i n g  simultaneous  F i g u r e 6.  Unsensitized oxalate.  decomposition  of  diallyl  73 stretching  of a l l three  CH -CH-CH i 2 d 0  would imply a h i g h reflected  i  0  bonds  i' i i 0~C  • > « . . CTSS-0 ' « ' ' > CH -CH~CH ^\| \{T d d 0 0 0  degree o f s t a b i l i z a t i o n ,  i na relatively  The l a r g e  value a c t u a l l y found  f o r t h e a c t i v a t i o n energy i n d i c a t e s t h a t  CjH^  w h i c h s h o u l d be  lov; a c t i v a t i o n e n e r g y , c o m p a r a b l e  to t h e heat of t h e r e a c t i o n .  may i n v o l v e  thet r a n s i t i o n state  e i t h e r incomplete s t a b i l i z a t i o n  fragments o r i n i t i a l  o r two o f t h e t h r e e  0  o f t h e C 0 and 2  p r e f e r e n t i a l s t r e t c h i n g o f o n l y one  bonds.  The f o l l o w i n g h y p o t h e t i c a l  tions represent the l i m i t i n g  c a s e s i n w h i c h t h e bonds  ched p r e f e r e n t i a l l y i n t h e t r a n s i t i o n s t a t e  reacstret-  are respectively  C - 0 , 2 C - 0 , C-C, C-0 a n d C-C, a n d b o t h 2 C-0 a n d C-C. CH =CHCH 00CC00-CH CH=CH -^ ^CH =CHCH 00CC00* + CH -CH-CH a  o  O  2  2  2  o  o  o  2 C)i Q  O  2  #  d  d  C H = C H G H - 0 0 C C 0 0 - C H C H = C H ^ ^ > 6 0 C C 0 6 /+ 2 C H - C H - C H 2 2 2 M39.6 o  O  o  o  2  2  0  D  CH =CHCH 00C-C00CH CH=CH 2  2  ^  c  d  0  > 2C00CH CH=CH 2  D  0  0  2  C H = C H C H 0 0 C - C 0 0 - C H G H = C H ^ ^ 0 H = C H 0 H 0 0 C + C 0 . + CH -CH-CH 2  2  2  2  2  CH '=0HCH -00C-C00-CH CH=CH *S§»2C0 2  2  (the  heats of r e a c t i o n  An i n s p e c t i o n &EL  <<Es <&B.£<&& l  2  2  c  2  2  2  2 0 ^ '  are i n kcal./mole*)  of thereactions A-I .  2  a,b,c,d, a n d e shows  Although E ^ A R " ,  that  i ti s u n l i k e l y  D  * The h e a t s o f t h e s e r e a c t i o n s w e r e c a l c u l a t e d u s i n g t h e p a r t i a l bond c o n t r i b u t i o n s m e t h o d . F r o m A H - P ( G H 3 C O O H ) = -103.8" D ( G H C 0 0 - H ) = 112, a n d Z ^ i f C C O O C H j ) =-45.7 , the partial b o n d c o n t r i b u t i o n s (CO-0*)=-22.2 a n d ( * C 0 - 0 ) = - 1 8 . 0 w e r e calculated. Use o f t h e s e v a l u e s , w i t h d e r e a l i z a t i o n i m p l i c i t l y c o n s i d e r e d , gave £H (CH?=CHCH200CC00') =-68, £ H f ( * 0 0 C C 0 0 * ) =-51.4, a n d A H f ( C H 2 = C H C H 2 0 0 C * ) = - 2 5 . 6 . A l l these q u a n t i t i e s are i n kcal./mole. 1 0  1  5  f  0  2  74 t h a t t h e r i g h t hand s i d e o f e q u a t i o n sition  state,  since this  'd' r e p r e s e n t s t h e t r a n -  e q u a l i t y w o u l d i m p l y t h a t t h e CC^  a n d C H r fragments had a c h i e v e d t h e i r f u l l 3 5 7  Therefore,  i t i s more l i k e l y  volves a p a r t i a l  that the t r a n s i t i o n state i n -  s t r e t c h i n g o f a l l t h r e e bonds, and t h a t t h e  CC^ a n d C^H^ f r a g m e n t s a c h i e v e lization  stabilization.  about h a l f  of t h e i r f u l l  stabi-  energy.' 14. + i  The  pre-exponential factor  which i s compatible The  has a value  o f 10  -  with a unimolecular decomposition  pre-exponential factor f o r the decomposition  _  sec.  process.  of butane t o  g i v e e t h y l r a d i c a l s h a s b e e n e s t i m a t e d b y B e n s o n t o be 10^  secT  7  1  123,  Our v a l u e  i s lower by a f a c t o r o f 1 0  3  pos-  s i b l y i n d i c a t i n g that the t r a n s i t i o n state of the d i a l l y l l a t e decomposition  i s achieved with a smaller gain of entropy  ( a r i s i n g from changes i n t h e n a t u r e than  i s the t r a n s i t i o n  14 5 to  10  —1  *"sec.  o f / t h e degrees o f freedom)  s t a t e of the butane decomposition.  s i m i l a r s i t u a t i o n has been observed s i t i o n of d i a l l y l ,  oxa-  with the thermal  which has a p r e - e x p o n e n t i a l f a c t o r  A  decompoequal  IDX  '<?  T h i s lower v a l u e has been a t t r i b u t e d t o a  loss of i n t e r n a l rotations i n the a l l y l p a r t l y o f f s e t s the large gain i n entropy  groups.  This  loss  r e s u l t i n g from the  weakening of t h e r e s t o r i n g f o r c e s f o r the r o c k i n g f r e q u e n c i e s of the a l l y l tor  groups.'  The r e l a t i v e l y  f o r the decomposition  of d i a l l y l  low pre-exponential  ;  fac-  o x a l a t e c a n be r a t i o n a - _ _ .  l i z e d by a s i m i l a r argument, s i n c e t h e t r a n s i t i o n s t a t e a l s o involves a l l y l It  groups.  was o n l y a b o v e 150°C t h a t t h e e x p e r i m e n t a l  were s u f f i c i e n t l y s e n s i t i v e  techniques •  t o detect the formation of allene.  The  value of the ratio R  75  „ / R~, was e q u a l t o °3 4 °6 10 a n d i n d e p e n d e n t o f t e m p e r a t u r e b e t w e e n 150 C n  u  M  (8 ± 3) x 10 a n d 190°C.  The t h e o r e t i c a l v a l u e o f t h e r a t i o  of the rate  c o n s t a n t s f o r t h e d i s p r o p o r t i o n a t i o n and c o m b i n a t i o n r e a c t i o n s of  the a l l y l  r a d i c a l , k^/k , was f o u n d f r o m t h e e q u a t i o n u s e d b y  I i o l r o y d and K l e i n the  4 1  ,  l o g ( k / k ) = 0 . 1 3 1 ( r s ° - S°) - 5.47, a n d d  c  entropies of formation:  S°(C H ) =63 5  S°(CH2=C=CH2) = 50 e u ,  eu, and S ( C H P  6  6  1 Q  ) = 90 e u  1 0 1  .  The v a l u e  -3 k^/k tal  = 8 x 10  y  was f o u n d , w h i c h a g r e e s w i t h t h e e x p e r i m e n -  value. R e a c t i o n 3 w o u l d be e x p e c t e d t o p r o d u c e , i n a d d i t i o n t o  allene,  a n e q u i m o l a r amount o f p r o p y l e n e .  P r o p y l e n e was f o u n d  among t h e p r o d u c t s a t t e m p e r a t u r e s a b o v e 150°C, b u t i n l a r g e r q u a n t i t i e s t h a n w o u l d be e x p e c t e d . i f i t w e r e p r o d u c e d o n l y i n r e a c t i o n 3. allyl  T h i s e x c e s s p r o p y l e n e c o u l d be p r o d u c e d when a n  r a d i c a l a b s t r a c t s a hydrogen  ( r e a c t i o n 4).  atom f r o m d i a l l y l  T h i s a b s t r a c t i o n w o u l d be e x p e c t e d t o be t e m -  p e r a t u r e d e p e n d e n t . ^ When t h e r a t e from t h e e x p r e s s i o n 4 k  R  C H 3  6  -  R  C H 3  c o n s t a n t k^ i s e s t i m a t e d  4  °6 10  2  it  H  i s f o u n d t o be t e m p e r a t u r e d e p e n d e n t .  Thus t h e p r o p o s a l  that reaction 4 takes place i s supported. p a r a m e t e r s were  = 25  1  m  The A r r h e n i u s  5 k c a l . / m o l e and  ±  13 ± l o g | A / A | ( c m 5 o l e c 7 s e c 7 ) ^ } = 4.7 4  oxalate  1  + 3.0  .  The p r e -  e x p o n e n t i a l f a c t o r i s o f t h e same m a g n i t u d e a s t h o s e o f o t h e r m e t a t h e t i c a l r e a c t i o n s i n v o l v i n g an a l k y l r a d i c a l and an  allyl  Figure  7.  Metathesis • diallyl  of the  oxalate.  allyl  radical  with  77  F i g u r e 8.  . Mutual i n t e r a c t i o n s  of  allyl  radicals  78  e s t e r ^  T  The  55  h  allyl  r a d i c a l to a b s t r a c t a hydrogen  atom f r o m c e r t a i n s u b s t r a t e s ,  i n s p i t e of i t s s t a b i l i z a t i o n ,  is  ability  of the  a l s o p r o v e d by t h e  increase  i n the  amount o f  p r o d u c e d when c y c l o h e x a d i e n e - 1 , 4 i s p r e s e n t . buted t o the nic  a b i l i t y , of t h i s  h y d r o g e n atoms t o t h e  e f f e c t i v e l y t h a n can A d d i t i o n of the detected,  s i n c e the  the  radical  diallyl  is  ( r e a c t i o n 6)  oxalate  attri-  more  (reaction 4).  r a d i c a l t o the  d o u b l e b o n d was  m a t e r i a l b a l a n c e f o r the  remained c l o s e to u n i t y .  This  compound t o d o n a t e i t s m e t h y l e -  allyl  allyl  propylene  allyl  not  radical  However, i t i s p o s s i b l e t h a t  the  reaction C,H".  +  » 0,^6-^0000000^ .  GxHcOOCCOOCUHc-  3 5  3 5  does o c c u r , t i o n of the  3 5  3  5  3  5  which keeps the  3  >2C0  r e a c t i o n of. t h e i n the  o  2  5  5  i  3 5 ,  a. c o m p l e t e  + C^H.  +•  n  6 10  material balance unaltered  T h i s p o s s i b i l i t y i s s u p p o r t e d by  discussed  3  but t h a t i t i s f o l l o w e d by type.  0,^0,^0000000,^ 3  5  the  each of the diallyl and,  compounds:  oxalate.  to  unity. the  oxalate, which  are  (C). of O x a l i c  oxalic acid, di-t-butyl  I t a l s o g i v e s the  modes o f d e c o m p o s i t i o n c a n be  general  reactions:  Acid.  d i f f e r e n t modes o f d e c o m p o s i t i o n f o r oxalate,  and  heats of these reactions..-  whenever t h e y are known, t h e i r a c t i v a t i o n e n e r g i e s .  three ing  shows t h r e e  equal  for  Modes o f T h e r m a l D i s s o c i a t i o n o f C e r t a i n - E s t e r s TABLE V I  5  r e s u l t s obtained  ethyl radical with d i a l l y l next s e c t i o n  C,H* 3  and  decomposi-  represented •  by  the  The  follow-  \  TABLE V I  H E A T S OF T H E THERMAL D E C O M P O S I T I O N R E A C T I O N S OF C E R T A I N A L K Y L O X A L A T E S  Substrate  Oxalic  acid  Di-t-butyl oxalate  Diallyl oxalate  A H  F  kcal/mole (substrate)  -175  -198  -127  calc. A H ; kcal/mole  Products  C0  2  + HC0 H  2C0  2  + 2H*  2C0  2  +  H  -  ,  2  30.0  6.7  ± 1.3  91.4  -'  -  -13.0  2 .  ?  20.6  CI+HQ*  25.0  G2O4H2 + C H = C ( C H o ) C H o 2C0  2  +  2C0  2  + C(CH ) (CH )  C20^H  2  + CH =CH=CH  2C0  2  + 2C H *  2C0  2  3  2  3  •E kcal/mole  3  3  2  43.5  ;  -40.0  : 106 •* '•••* •  108  -40.0  3.0  5  + C6H10  3  Reference (*hypothetical)  -  ^  -  •*  *  *  f  37.0  ± 1.5  - -  this thesis •»  80  1)  Esters.of  2) . E s t e r s 3)  oxalic acid oxalic acid  > olefin + oxalic acid > f o r m i c a c i d + CO, '2  of oxalic acid oxalic acicL-—?  Esters  of oxalic acid oxalic  f  r  e  r  a  d  i  c  a  l  s  +  C  > d i a l k y l + COp  acid  > H  +C 0  2  2  t h e t h i r d mode o f decompo-  a l t h o u g h t h i s i s , i n e a c h c a s e , t h e most  e a c h o f t h e compounds f o l l o w s  exothermic;  whichever o f t h e f i r s t and  s e c o n d modes i s t h e most e x o t h e r m i c ; t - b u t y l oxalate  -  0 2  None o f t h e t h r e e compounds f o l l o w s sition,  e  this i s the f i r s t  l a t e t h i s , i s t h e s e c o n d mode.  f o r o x a l i c a c i d and  mode, a n d f o r d i a l l y l  Plausible  oxa-  t r a n s i t i o n states f o r  e a c h compound i n t h e t h i r d mode o f d e c o m p o s i t i o n a r e t h e s e : / O  ,  S  co co ^  H H  GO '  0 ^  co ^  for oxalic acid  C(CH^) C(CH,) 0  ^  Although the f i r s t  involve  »  a  c.  ;  °.,co /• ^ ' 0 — C H  f o rd i a l l y l •'/'.'  '• .  three  7  - . C H ^  cd  ^C,H,^ 0 ^  (as they are written  the unusual d e r e a l i z a t i o n  oxalate,  7f electrons, conclusion,  follow  a  cja  2  2  — C H ^  involves  'CH  9  .CH  5  •  E L  oxalate  above) o f these  complexes a r e f a v o r e d by a six-membered r i n g ,  diallyl  tions  ^ . 0 - C H  0  of cr electrons.  complex o f t - b u t y l oxalate  hindered by bulky groups.  In  n  0  t i o n of the activated  for  /O.  co  for t-butyl oxalate  activated  •  The s e c o n d a c t i v a t e d  they  The f o r m a -  i s sterically c o m p l e x shown  a l t h o u g h f a v o r e d by t h e p a r t i c i p a t i o n o f t h e f o r m a t i o n o f a ten-membered r i n g .  i tappears that  t h e f a i l u r e o f t h e decomposi-._-  of o x a l i c acid, t - b u t y l oxalate  and d i a l l y l  oxalate  to  t h e t h i r d mode o f d e c o m p o s i t i o n c a n be e x p l a i n e d b y a n  unfavorable t r a n s i t i o n state.  81 The  Unsensitized Polymerization of D i a l l y l Oxalate.  purified  liquid diallyl  oxalate polymerized  cubation  ( 2 4 h o u r s o r m o r e ) a t 160°C.  no' p o l y m e r was o b t a i n e d . ted  that decomposition The  concurrence  z a t i o n suggests the  generation  of d i a l l y l of thermal  7  oxalate a l s o took  radicals  3 5  indica-  place.  and p o l y m e r i -  s t e p i n t h e l a t t e r may be  i n the thermal > 2C0  c  a long i n - .  Below t h i s temperature .  decomposition  C H OOCCOOC,,H,-  Highly  o f carbon d i o x i d e  that the i n i t i a t i o n of a l l y l  reaction:  Formation  after  .  3 5  decomposition  + CJ3*  o  3 5  2  However, i t i s p o s s i b l e t h a t t h e i n i t i a t i o n s t e p i n v o l v e s t h e . generation  of diradicals:  •2C,H 00CC00CH CH=CH c  o  > C-,H -00CC00CH CHGH CH CHCH 00CC00C- H -  o  £  o  o  o  o  c  c  35  2 2 2 5 2 2 2 2 35 or C00CH CH=CH . 000CH CHCH i 2 2 > i 2 i 2 j C00CH CH=CH C00CH CHCH T h i s type o f i n i t i a t i o n has been suggested f o r t h e u n s e n s i o  o  o  o  2  2  2  2  t i z e d polymerization of styrene In t h e propagation add  to diallyl  oxalate t o generate  2  2  ( w h e r e R" = ^3^5 radicals  '  o  r  former,, because t h e y  allyl  a polymer 2  can e a s i l y  a l l y l oxalate. an a l l y l i c  To a l i m i t e d  (7)  nor a l l y l  efficient sensitizers; terminate  2  the  themselves by i n t e r - ,  because o f t h e h i g h  a d d i t i o n t o the double bond o f d i degree, propagation  may s t a r t  with,  r a d i c a l produced i n t h e m e t a t h e t i c a l r e a c t i o n  CH =CHCH 00CC00CH=CHCH 2  2  Neither diradicals  t o be v e r y  energy o f t h e i r  radical:  2  or mutual c y c l i z a t i o n , and t h e l a t t e r , activation  or d i - radicals  >RCH CHCH 00CC00CH CH=CH  2  diradical).  a r e expected  *.  step, either  R" + CH =CHCH 00C000CH 0H»CH 2  bles 139 140  2  2  + CH CHCH 00CC00CH CH=CH 2  2  2  2  > CH CHCH 00CC00CH=CHCH CH CHCH 00CC0QCH CH=CH 2  2  2  2  2  2  2  • (4p)  \ • - \  .-.  TABLE V I I  •  C H E M I C A L S H I F T S AND A R E A S OF T H E N.M.R. PROTON P E A K S OF D I A L L Y L O X A L A T E AND I T S POLYMER*'  SAMPLE  8  (PPM)  (C-C)-H  (O-C)-H  (C=C)-H ,a; J *  2  6  (PPM)  a?  £  (PPM)  a#*  2  \  Diallyl  oxalate  P o l y m e r p r o d u c e d a f t e r 24 h o u r s i n c u b a t i o n a t 160°C  P o l y m e r p r o d u c e d a f t e r 72 h o u r s i n c u b a t i o n a t 160°C  5.4 t o 6.2 multiplet split i n t o two groups  61  multiplet split i n t o two g r o u p s ; b r o a d peak  39  4.5 t o 5.0 broad peak  37  1.2 t o 1.8 broad peak  17  4.4 t o 5.1  38  1.2 t o 1.8 broad peak  21  doublet  5.0 t o 6.5 46 multiplet split i n t o two g r o u p s ; b r o a d peak 5.0 t o 6.5  4.7 t o 4.9  41  broad  peak  M e a s u r e m e n t s made o n b o t h d i a l l y l o x a l a t e a n d t h e p o l y m e r t e t r a m e t h y l s i l a n e was u s e d a s a s t a n d a r d . *  a% - 100 x a r e a o f p e a k  f o rproton specified/total  a s 1:1  m i x t u r e s w i t h CDCI3:  peak a r e a f o r a l l p r o t o n s  00 ro  An  interesting possibility  through a c y c l i z a t i o n .CL  i s a propagation  process:  /CH CH CH  0. ^C  N  P  I 0^  X  0  >  NCH I CHpC^Hc-  .0. ^CH ^CH \ .OHp 9  I  0^  0  CH i CHoC^H,-  2 3 5  T h i s p r o c e s s y i e l d s an a c t i v e p r o p a g a t i n g  7,  (7p')  d  235  The  proceeding  species.  f r e e r a d i c a l mechanism i m p l i e d i n t h e r e a c t i o n s  4p a n d 7p'  was t e s t e d b y i n t r o d u c i n g a n i n h i b i t o r ,  h e x a d i e n e - 1 ,4,  i n t o t h e system.  This  can replace  or r e a c t i v e polymer r a d i c a l s by u n r e a c t i v e radicals:  cyclo-  allyl, di-  cyclohexadienyl  1  C^H,- +  3^5  d i - or polymer radical  r> C,H ' 3"6  \=J  v  /  \  —  v  +  6  . .+  .s ts at ba lb el e "> p r o d u c t  +  <fO  (6a)  /r~\ %ZJ  (c-w\ (6b)  P o l y m e r i z a t i o n was n o t o b s e r v e d i n t h e p r e s e n c e o f c y c l o h e x a d i e n e - 1 ,4;  t h e r e f o r e , i t must be c o n c l u d e d b o t h t h a t ' t h e  polymerization  i s s e n s i t i z e d by e i t h e r a l l y l  and  t h a t , a t the temperature of the experiment, t h e c y c l o -  hexadienyl  r a d i c a l does n o t undergo any a p p r e c i a b l e  sition: If  or d i - radicals  C H*  > CgHg + H*  6  such a decomposition had occurred,  w o u l d have i n i t i a t e d  a new p o l y m e r  H* + CH =CHCH OOCCOOC H 2  2  5  H*  +  C H 6  o  69  The  2  o  2  polymerization  5  t h e h y d r o g e n atoms  chain:  > CH^CHCHgOOCCOOCjH^ > C H*  8  C H l + CH =CHCH 00CC00C-,H c  decompo-  6  c;  > C.H C-,H -00CC00C H Q  3 5 . 6 9 3 5  of d i a l l y l  c  oxalate  x  (  35  involved the  84 conversion  o f 27$ t o 30$ o f t h e h y d r o g e n atoms f r o m v i n y l t o  saturated chain mer  (TABLE V I I ) .  I f i t i s assumed t h a t t h e p o l y -  m o l e c u l e i s produced o n l y by an i n t e r - m o l e c u l a r propaga-  t i o n without  ( r e a c t i o n 7p)  cyclization  5  and i s , t h e r e f o r e ,  c o m p o s e d o f t h e same' monomer u n i t w i t h p e n d e n t a l l y l  groups,  CH =CHCH 00CC00CH CH 2  2  2  CH  2  CH =CHCH 00CC00CH CH 2  2  2  0H i t h e n a 50$ c o n v e r s i o n  o  2  from v i n y l t o s a t u r a t e d chain  g e n s w o u l d be e x p e c t e d .  Incorporation of cyclic units (re-  a c t i o n 7p')  or d i r a d i c a l u n i t s c a n n o t l o w e r  conversion;  therefore, the experimental  a complicated  the-percentage  value  indicates that  polymer c h a i n i s formed by t e r m i n a t i o n  u n l i k e polymer r a d i c a l s  of various  sizes.  The  oxalate  molecules. insolubility  buted t o extensive f o r m e d when a l l y l corporated three  between  I t i s a l s o posr- -  s i b l e t h a t t h e polymer has i n c l u s i o n s o f d i a l l y l monomer  hydro-  of the polymer can probably  c r o s s - l i n k i n g between chains  various solvents  attri-  , which i s  groups o f dead polymer m o l e c u l e s a r e i n -  i n growing chains.  dimensional  be  T h i s would g i v e a two o r even  network, which would r e s i s t the a c t i o n o f and p o s s e s s g r e a t  rigidity.  Conclusions. (1) the  The u n s e n s i t i z e d d e c o m p o s i t i o n g a s p h a s e i s a. u n i m o l e c u l a r E. = 37 ± 2- k c a l . / m o l e  and  of d i a l l y l  process  oxalate i n  with  l o g A ( s e c " ) = 14 + 1 1  These p a r a m e t e r s - a r e c o n s i s t e n t w i t h a t r a n s i t i o n s t a t e i n  85 which three  bonds a r e s i m u l t a n e o u s l y  C^H^ a n d C 0  the  2  f r a g m e n t s have g a i n e d  t i o n of the d e r e a l i z a t i o n energies (2)  extended, and i n which an a p p r e c i a b l e  of the free  The s y s t e m i s w e l l s u i t e d t o t h e s t u d y  of the a l l y l  (3)  species.  of the reactions  " r a d i c a l , s i n c e no o t h e r r a d i c a l i s p r e s e n t i n  significant allyl  frac-  amounts, and s i n c e t h e r a t e o f g e n e r a t i o n  r a d i c a l i s equal  to the rate of formation  o f the.  o f CC^.  The p a t t e r n o f m u t u a l d i s p r o p o r t i o n a t i o n a n d c o m b i n a -  tion of the a l l y l . k,/k (4)  r a d i c a l i s g i v e n by  = 0.008 + 0.002  (from  150°C t o 190°C)  An e x c e s s o f propene o v e r a l l e n e . i n d i c a t e s t h a t t h e a l -  lyl  r a d i c a l may a b s t r a c t a h y d r o g e n atom f r o m t h e j  oxalate molecule. (5)  The p o l y m e r i z a t i o n o f p u r e l i q u i d d i a l l y l  ved  on p r o l o n g e d  diallyl  heating  oxalate  obser-  a b o v e 150°C was i n i t i a t e d b y f r e e  radicals. C.  Reactions .. D i a l l y l  o f the', E t h y l R a d i c a l w i t h D i a l l y l  o x a l a t e was i n v e s t i g a t e d , a s a n a l t e r n a t i v e t o  allyl3-butenoate  as a source o f a l l y l ' r a d i c a l s by t h e a d d i -  t i o n — d i s m u t a t i o n sequence. allyl to  oxalate  The s t r u c t u r a l s y m m e t r y o f d i -  ( C H = C H C H 0 0 C - C 0 0 C H C H = C H ) w o u l d be e x p e c t e d 2  2  2  give i t an advantage over a l l y l  (CH =CHCH C00CH CH=CH ) 2  2  2  2  2  3-butenoate  i n the kinetic  as t h e t e m p e r a t u r e i n c r e a s e s  analysis.  However,  any such advantage would  r e a s i n g l y be o f f s e t b y t h e t h e r m a l oxalate.  Oxalate.  instability  inc-  of d i a l l y l '  TABLE REACTIONS  [Dl,  (CO)  ( C ^ Q )  OF T H EETHYL  ( C ^  (C H ) 3  6  V I I I  RADICAL  DR(C H 5  [B]  (co )  $88  6.14 1.48  13-36 8.48  4.85 7.77  4.41 1.06  0.36 0.12  3.52  394  6.14 1.30  12.77 8.04  4.11 7.06  5.03 0.85  0.40 0.14  3.06  401  5.87 1.18  12.32 7.58  3.70 6.83  5.26 0.82  0.32 0.14  3.05  408  5.87 1.18  12.48 9.50  3.15 8.55  5.11 0.88  0.44 0.18  3.79  413  6.33 1.08  13.55 8.66  3.30 7.93  6.02 0.77  0.28 0.12  3.60  421  5.81 1.02  15.09 10.95  3.28 9.95  6.35 0.83  0.39 0.15  4.45  428  5.67 1.08  12.97 11.64  1.90 10.26  5.62 0.78  0.51 0.15  4.44  433  5.26 1.12  13.67 11.05  2.25 9.85  6.45 0.77  0.50 0.15 :  4.35  2  The d u r a t i o n  (C H 5  of each  1 0  )  (C H ) 2  / J  r u n was 60  1  4  minutes.  DIALLYL  OXALATE  ( 6 1.0> flio# 11a# DRCCpH^) 1lb# C A 0.06 88 0.227 0 . 4 0 . 1.54 9 3 0.06 0.231 85 1.60 0.38 11 4 0.05 0.217 87 0,30 9 . 1.41 4 0.10 86 0.279 1.44 0.45 10 •4 0.10 90 0.239 0.34 1.56 7 3 0.250 0.20 89 1.41 0.38 8 3 0.416 0.22 87 1.46 0.52 10 3 0.16 0.345 87 0.47 1.35 10 3  0 ^ 3 ^  ( C H ) DR(C^Hg) 5  WITH  C  H  *  M  E t  k  M  A  k  R  1  0  R  R  A  R /R 7  8  Me'  0.685 0.970  128 41  0.993  0.700 0.935  149 63 •  0.970  0.715 0.950  154 69  0.925  0.647 0.985  210 76  0.926  0.680 0.970  222 96 '  1.005  0.630 0.980  302 95  1.020 i:.020  0.570 0.950  375 110  0.964  0.625 0.968  316 126  0.932  Key  CO  o v e r l e a f . . . •»  KEY TO T A B L E  VIII  Concentration  of diethyl  ketone  [B]  Concentration  of d i a l l y l  o x a l a t e x 10  (  Rate  )  DRC H 5  D R  G H 3  1 0  .  of formation  Rc H 5  H 6  CjH  1  2  R  C H 2  R  C I I 4 - 0.136  R  R  D R  R R M  11a$ 11b$ Et  M,  C6H10 C4.H10 R  C5H10 ^ /  D R  R /DR  C3H4/^ C5H^io DR  ^. C/j.Hio R  ( D R  +  C5H10  10  1 5  R  +  -12  - 3 - 1 molec.cm.sec.  R  H  C 4  +  H  C3He  C H6  +  R  3  +  R  +  R  R  C 3 H  +  6  C3H6  C3H4^  RC3H4) ECJHZJ.)  +  R  +  R  C3H/f  R  +  2 R  C6Hio^ "  7  A  \  *" C 3 H 4 ) / C 0  k / k | (cm?molec?sec?)^ 5  1 0  1 0  1 0 - k A o (cmJmolec^sec?)^ 1  -3 molec.cm.  C5H10  02 6 R  H  C 4  C5H10  RCjHe/CDRc^H-io R  -17  1 0  2  4  R,  10$  4  -3 molec.cm.  2  " RC2H4 " ° - 5 6  6  RC H4/RC H D  Rco  - 0.5  1 0  x 10  x 10  -17  [D]  0  5  R  C0  2  ,  38 Results• of  the ethyl radical with d i a l l y l  range of  TABLE V I I I s u m m a r i z e s t h e r e s u l t s  a n d 160°C.  oxalate i n the temperature  The p r o d u c t s o f t h i s  series  e x p e r i m e n t s were c a r b o n m o n o x i d e , b u t a n e , e t h a n e ,  ethyl-  ene,  b e t w e e n 115°C  of the reactions  carbon d i o x i d e , 1-pentene, p r o p y l e n e , a l l e n e  d i e n e - 1 , 5.  and hexa-  The m e a s u r e d r a t e s o f p r o d u c t i o n o f c a r b o n d i -  o x i d e , h e x a d i e n e - 1 , 5 , p r o p y l e n e a n d a l l e n e were  corrected  by s u b t r a c t i o n o f an e s t i m a t e o f t h e i r r a t e s o f p r o d u c t i o n by t h e r m a l d e c o m p o s i t i o n .  The e s t i m a t e s were made u s i n g t h e  f o l l o w i n g r e l a t i o n s h i p s , which a r e based  on t h e r e s u l t s o f  the'study of the thermal decomposition of d i a l l y l (section B);  (R^therm.  % H 6  1 0  = k^ [DAO]  Wm. =  R  (R  6  C-H,, therm. )  =  0.495(R 0.00 (R  < C H >tHerm. = 3  oxalate  5  °-  0 0 5 ( R  C0  ) o  c 0 2  0 0  O  )  t h e r m  t h e r m  . .  therm.  At t h e temperatures pf these experiments  ( b e l o w 160°C) i t  was f o u n d t h a t , w i t h t h e e x c e p t i o n o f t h e one f o r t h e p r o d u c t i o n o f c a r b o n d i o x i d e , t h e s e c o r r e c t i o n s were  unimportant,  s i n c e t h e m e a s u r e d r a t e s o f p r o d u c t i o n w e r e s o much l a r g e r than the thermal.rates at corresponding temperatures. Kinetic Analysis.  The n a t u r e a n d d i s t r i b u t i o n o f t h e p r o -  ducts are consistent with the f o l l o w i n g C H C0C H 2 5 2 5 o  c  r)  I  2  5  >C H  1 0  2C H*  >C H  4  2  5  (1)  0  2  C H* + C H C O C H 2  > 2 C H * + CO 2 5  2C H* 2  mechanism:  4  2  • + C H 2  >C H C0C R" 2  4  2  5  '  (2) " (3)  6  + C ^  (4)  89 C H £ + CpH^COCgH^  -» C H C O C H  2  C0 CH CH=CH | 2 2 2 C0 CH CH=CH  jr. ^2 5  o  r  n  o  2  2  o  4-  1  2  ^ °2 6  o  2  -> 2  d  °2 5  d  2  2  00 CH CH=CH 2  C  2 5 H  +  2  2  2  2  Q  o  C0 CH-CH-CH  2  o  o  (6)  o  2  C0 CH CH=CH o  i  o  d  d  2  2°  2  2  o  2  2  (6a)  2  o  d  2 2  C0 CH GH=CH  (7)'  5 .  2  C0 CH CH(C H )CH C H 2  5  C0 CH CH=CH i d d d C0 CH CHCH C H -o  +  C0 CH CH=CH i 2 2 2 . C0 CH=CHCH C H^  2  2  C0 QH CHCH C H 2  ->  d  C0 CH CH=:CH  n  C0 CH CH=CH  2  CO-CH-CI^CH|  (5)  5  5  2  G0 GH-CH-CH  TT"  p  2  n  2  o  2  9  o  C0 CH CH=CH  r H°2 5  4  2  2  5  2  2  5  (7a)  o  2  2  2  r  ->2C0 C  C H*-  +  0  + C H  2  5  + CH -CH-CH,  1 0  2  )  (10)  5 10 H  (11a)  C-TH"-  25  55  * C H 2  35 2 C  (8)  C  3  (11b)  4  (12)  H  3  E  C H  +  6 10  -> C H  3 5  6  + 0 H  4  3  (13)  6  C o n s i d e r a t i o n o f a l l r e a c t i o n s i n which ethane i s p r o d u c e d g i v e s t h e r a t e o f t h e m e t a t h e t i c a l r e a c t i o n 6: R  6  =  R  C H 2  " 3 ." 1 1 b ~ R  6  R  (d)  4  R~ TT / R TT indicate that C H C H i s n o t p r o d u c e d o n l y i n r e a c t i o n 3; t h e r e f o r e , i n  The h i g h v a l u e s o f t h e r a t i o  n  2  ethylene  R  4  4  1 Q  o r d e r t o e s t i m a t e R, t h e l i t e r a t u r e v a l u e o f t h e r a t i o 3 0.136 was u s e d . T h u s , R-7 = 0.156 Rp TT • S i n c e k /k 3  R  13  2  c a n be e s t i m a t e d a s 0.008 R  is- always s m a l l , duction of allene.  TT ( a s i n s e c t i o n B ) , and °6 10 was s e t e q u a l t o t h e t o t a l r a t e o f p r o N  H  T h u s , e x p r e s s i o n G1 becomes (C2)  90 The  rate  c o n s t a n t o f r e a c t i o n 6 c a n now b e g i v e n  k .  C H  E  6  kj  2  " °' 56 H ^ .  "  0  '  The. r a t e  - R  1  6  H  q  ^  c  ^  by .  ^  [B] Rp TT  [B] k*  J  of addition of the ethyl r a d i c a l t o d i a l l y l  ( r e a c t i o n 7) c a n be d e r i v e d production  by subtraction  )  oxalate  from t h e r a t e o f  o f p a i r s o f e t h y l r a d i c a l s , t h e sum o f t h e r a t e s  o f f o r m a t i o n o f a l l t h e m e a s u r e d p r o d u c t s w h i c h a r e known t o . have a r i s e n from p r o c e s s e s i n w h i c h p a i r s o f e t h y l • r a d i c a l s have been consumed. E  7 • "  E  Thus,  C0 - ( C H R  4  +  R  1 0  C H - 0 H >  .  E  2  6  3  4  corresponds t o t h e consumption o f a.pair since  one i s added t o d i a l l y l  combines d i r e c t l y w i t h allyl  oxalate  < > W  of ethyl radicals  and t h e o t h e r  t h e adduct r a d i c a l o r r e a c t s  either with the  r a d i c a l formed by decomposition,/of t h e adduct.  the  rate  o f f o r m a t i o n o f ethane i s reduced by H  the  rate  o f f o r m a t i o n o f e t h a n e i n r e a c t i o n 1 1 b . The  material  the rate  ( V  -  k§ 2  half thus,  +  E  C H 2  E  6  C0  +  R  C  $  i y  \ H  1  C H > 5  / CO E  4  4  rate  Q  -  R  C H 2  <°5>  6  (C6)  [ B ] RJ; TT  C H  1 0  of the decomposition reaction 8 i s equal t o  the rate  o f formation of carbon d i o x i d e ,  the rate  .  0  ~  constant k  g  c a n be g i v e n b y  k kf/k  ? a  =  0.5 R o - ^ H  R  ? a  =  R  8  where  1  c o n s t a n t k^ b y R  The  „ , which i s  b a l a n c e f o r t h e e t h y l r a d i c a l c a n be g i v e n b y "fit  and  p  I n C4,  R  C  ?  2  - 0.5 R Q  0  1 0  /  R  7a  Rg = 0 . 5 R Q Q '  Figure 9 .  Addition radical  and and  m e t a t h e s i s between the diallyl  oxalate.  ethyl  92 Figure  10.  Diallyl  oxalate:—  a c t i o n s between the allyl  radical,.  patterns ethyl  of  and  interthe  93 r a t e s o f r e a c t i o n s 10,11a a n d 11b  The  c a n be shown ( b y  a s i m i l a r a r g u m e n t t o t h a t u s e d i n s e c t i o n A) t o be g i v e n b y the R  following expressions:  10  TT - m  =  R  °5 10  i R  = ' W3 '°  11a  =  la  R  =  C  R  i  2  o u  f  C,H> C,H " C H + 5 o 5o 2 4 depend on t e m p e r a t u r e ; D E  R  H  <  4  S  I  N  C  E  R  If.hexadiene-1,5 of  two a l l y l  °4 io» n  }£ 12 2: k  Vio"  008  R^ . R^ 6 10* 4 10 LC  H  .  G  D  R  d  C  5  H  1  0)  o  e  s  n  o  t  *  by t h e mutual  ( r e a c t i o n 12),  •  io  °-  =  C,H > .4 10  i f DR~ TT d e p e n d s o n t e m p e r a t u r e ; 3 6.  n  i s produced  =  k  w  13  radicals k  H  combination  the expression , y  0  w o u l d be e x p e c t e d t o be t e m p e r a t u r e retical  R  R  P  4  5  ;  ° 5 10  u - 0.136 R o ti . 2  11b  = DR  rCj  M  independent  and o f t h e o -  interest.  Discussion.  TABLE I X shows t h e A r r h e n i u s p a r a m e t e r s  main r e a c t i o n s o f t h e e t h y l r a d i c a l w i t h d i a l l y l  of the•  oxalate,  a n d t h e a v e r a g e v a l u e s o f t h e q u a n t i t i e s k^Q,/(k^Q+ k^^ + k^,^, a  R  C  H /  5  R  C  k^ k /k 2  2  3  H  1 0  6  >  .  R  C  3  H /  D  R  C  FIG. 9  2  H  4  '  k  11a  / ( £  10 11a 1'lt> ' + k  + k  )  a  n  d  g i v e s t h e A r r h e n i u s p l o t s o f k / k ^ and &  1/  ky/k^.  FIG.10 shows t h e p a t t e r n s o f i n t e r a c t i o n o f t h e e t h y l  and t h e a l l y l The  radical  i n t h e r e a c t i o n s 10,  Arrhenius parameters  11a  and  of the metathesis reaction 6  and t h e a d d i t i o n r e a c t i o n 7 a r e s i m i l a r t o t h o s e found f o r a l l y l For  3-butenoate  11b.  previously  and a l l y l . p r o p i o n a t e (TABLE I I ) .  t h e s e r e a c t i o n s , no s i g n i f i c a n t d i f f e r e n c e s c a n be  94-  TABLE  CHARACTERISTIC  VALUES  OF  OF QUANTITIES  THE ETHYL  RADICAL  Expression  10  1  10  1  5  1  Q  )  kcal/mole  0.3  k  *  6.8  ±0.2  -?.5  ±  0.2  /k  ^  2  +  1  )  0  R(C H ) + 3  R(C H^)  6  1  0  )  6  3  R(C H^)  6  3  5  1  0  )  +  R(G H ) + 3  R(C H^)  6  6  R(C H^)/DR(C H 3  R*(C H 6  .  2  1 Q  )  .  i +  5  1 Q  )  —  * (cm^molec^secT)^  -  0.88  o.o  -  0.09 - 0.03  o.o  -.  0.03 - 0.01  0.0  -  0.38  . *  0.05  0.38  t  0.05  0.0  )  R*(C^H  gR(C H  0.0  t O.OJ.  3  •R(C H4)/R(C3H ) 3  -  3  R(C %)DR(C H  value  3  R(c H ) +  +  REACTIONS  Average  ±  3  5  l o gA  -6.5  7  THE  OXALATE  + 0.2  R(C H ) DR(C H  DIALLYL  7.8  5  5  WITH  WITH  *  2  DR(C H DR(C H  E  ASSOCIATED  k /k * 6  5  IX  1 0  -  -  .  ) °'°  "  ±  0  '  0  2  95 d i s t i n g u i s h e d between the r e a c t i v i t i e s -C00CH CH=CH 2  and  2  For d i a l l y l tion reaction  groups  CH =CHCH C00-. 2  2  oxalate, theratio  (7) t o the r a t e  at80°C.  o f the  is  2.4  of  homopolymerization  of therate of the addi-  o f the metathesis r e a c t i o n ( 6 )  This value predicts a r e l a t i v e l y ofdiallyl  l o w degree  o x a l a t e and f o l l o w s t h e  HQ 52 53 g e n e r a l t r e n d e x h i b i t e d b y v a r i o u s a l l y l i c monomers The  property ofd i a l l y l  from the o t h e r a l l y l i c far  V 8 R  R  3  the r a t e  \ H  E  t o decompose i n t h e p r e s e n c e o f  I  O  -  since R  C  2  H ^  - 5  0  K  C 0  o f d e c o m p o s i t i o n o f the adduct  nearly equal t o i t s rate  y  oxalate that singles i t out  Infact,  ^CCT C V  =  °'  8  =  All  5  R  .  compounds w h i c h h a v e b e e n s t u d i e d s o  i s i t s s t r o n g tendency  the e t h y l r a d i c a l .  '• '  2  -  =  0.97  radical  ± 0 . 0 4  (Rg) i s  of formation (Ry); therefore  co 2  adduct  radicals  ofdiallyl  o x a l a t e decompose t o  give carbon dioxide,'1-pentene anda l l y l r a d i c a l s .  A pos-  s i b l e mechanism f o r t h i s d e c o m p o s i t i o n i s t h a t s u g g e s t e d b y 125  Trotman-Dickenson radical  formed  Dickenson  x  f o r the decomposition o f the  by a d d i t i o n o f N F  2  t o an o l e f i n .  concluded t h a t t h e adduct  adduct Trotman-  r a d i c a l was v i b r a t i o n a l l y  e x c i t e d a n d c o u l d decompose e i t h e r d i r e c t l y o r a f t e r v a t i o n by c o l l i s i o n w i t h a molecule its  excess energy.  lyl  o x a l a t e adduct  c a n be w r i t t e n :  deacti-  (M) c a p a b l e o f r e m o v i n g  Thus, f o r the d e c o m p o s i t i o n o f the radical  (Add*) t h e f o l l o w i n g  dial-  sequence  96 either  Add'*  or  > 2C0  Add** + M  f o l l o w e d by  o  (8*)  + C H . „ + C_H * d ID 2 3 0  d  > A d d ' + M*  Add*  > 2C0  I f - t h e h y p o t h e t i c a l case  (8')  + Cyi  2  1 0  + C^H*  (8)  where E > 0 i s c o n s i d e r e d ,  then  A  under a h i g h c o n c e n t r a t i o n o f e t h y l r a d i c a l s r e a c t i o n 7 a Add* + C H * 2 5  >AddC H 2 5  0  0  t  w o u l d c o m p e t e ' e f f e c t i v e l y w i t h r e a c t i o n 8; t h e r e f o r e RQ w o u l d be l e s s t h a n R y .  S i n c e Rg was f o u n d  R i s known t o be n e g l i g i b l e ; • - /a  t o be n e a r l y e q u a l . t o R^.,  therefore, the effective  acti-  - v a t i o n e n e r g y E g must be v e r y l o w a n d i s p o s s i b l y z e r o .  This  0  is.justifiable  by t h e h i g h e x o t h e r m i c i t y o f the.  decomposition  r e a c t i o n 8: — 2 2 5  CO:CH,CHCHJ H  2  2. -88.7 V  >  2  C  2  0  P  CH =CHC H  +  2  2  C H ^ C H ^ ; ^=-70 5 . kcal./mole / 34.0 '  +  -188.2 -5.0 i n kcal./mole  - — A H  F  R e a c t i o n 8, w h i c h d e s c r i b e s t h e o v e r a l l d e c o m p o s i t i o n the  adduct r a d i c a l ,  Decomposition  i n v o l v e s t h e r u p t u r e o f t h r e e bonds. .  proceeds e i t h e r by simultaneous  t h r e e bonds o r by t h e i n i t i a l The p r o c e s s  of  rupture ofa l l  r u p t u r e ' , o f one o r t w o o f t h e m .  involving the i n i t i a l  r u p t u r e o f b o t h t h e C-0  b o n d n e a r t h e f r e e e l e c t r o n , a n d t h e OC-CO b o n d , C0 CH CH=CI-I • C0^4cH0Hi H^ 2 2.. 2 2 5 P  o  9  is  C  H  2=  H  0  H  2  0  0  0  "  +  C 0  2  +  C ^ ;  A H =-36.0  (AHj= -25.6 k c a l . ) mole  h i g h l y exothermic.  initial  C  kcal^ mole  The o t h e r p r o c e s s e s , w h i c h i n v o l v e the.,  b r e a k i n g o f one o r t w o b o n d s , c a n a l l be shown t o be  endothermic;  ' therefore they  are -incompatible w i t h the  97 experimental cess.  evidence  suggesting a s t r o n g l y exothermic  I t must, t h e r e f o r e , ' b e  t i o n o f t h e adduct r a d i c a l by t h e s i m u l t a n e o u s  concluded  of d i a l l y l  that t h e decomposi-  oxalate either  bond, i s t h a t w h i c h i s s t r e t c h e d i n t h e t r a n s i t i o n 3-butenoate adduct r a d i c a l  t h e C-0  relationship  of vibrationally  ofthe  excited species, the following  of the adduct r a d i c a l :  where E i s t h e e n e r g y c o n t e n t t h e number o f e f f e c t i v e  ofthe  kg= Ag ((E - E g ) y / E ) ~ s  of the energized r a d i c a l  oscillators  .fied w i t h t h e average v i b r a t i o n a l The  treatment  c a n be u s e d t o e s t i m a t e t h e r a t e c o n s t a n t  decomposition  is  state of  decomposition.  According t o the Rice-Ramsperger-Kassel decomposition  proceeds  r u p t u r e o f t h r e e bonds o r by t h e i n i t i a l  r u p t u r e o f t w o b o n d s ( a s shown a b o v e ) one o f w h i c h ,  the a l l y l  pro-  125 . .  1  ;  and s  Ag c a n be l d e n t i 13 —1  frequency  10  sec.  ).  e n e r g y c o n t e n t , E , c a n be c o n s i d e r e d e q u a l t o t h e e n e r g y  imparted t o t h e adduct r a d i c a l by t h e f o r m a t i o n o f t h e CH^CH^CR^CH- b o n d . ^ T h u s , we c a n assume t h a t E .= D ( C H C H - C H C H ) = 25.5 5  The in  2  2  kcal./mole  2  high exothermicity of the processes the t r a n s i t i o n  102  presumably i n v o l v e d  s t a t e o f r e a c t i o n 8 suggested  Therefore, k g ^ A g , which i s j u s t i f i e d  that  Eg«E.  by t h e v e r y h i g h r a t e  o f r e a c t i o n 8. The  instability  very convenient  of the d i a l l y l  f o r production of a l l y l  t u r e s a s l o w a s 115°C. radicals  even a t t h i s  radicals  a t temper-  Because o f t h e h i g h y i e l d s low temperature,  oxalate' as a s u b s t r a t e enabled combination  o x a l a t e adduct r a d i c a l i s  t h e use o f  of a l l y l - • diallyl  t h e d i s p r o p o r t i o n a t i o n and  reaction of the ethyl  radical with the a l l y l  98 r a d i c a l t o be s t u d i e d w i t h use  of other The  M  A11=  allylic  facility  K H 5  + 1 0  E  C H * 5  than d i d the  substrates.  material balance for. the a l l y l  This value  6  E  CV 3  2 E  C H 6  radical  >°-5 00 E  1 0  2  -  0-97 ±0.03  i s n o t s i g n i f i c a n t l y d i f f e r e n t from u n i t y , and  thereby confirms p.  a greater  the v a l i d i t y  o f t h e mechanism a d o p t e d on  86. I n t h e t e m p e r a t u r e r a n g e b e t w e e n 115°C  percent f r a c t i o n s of the a l l y l  a n d 160°C, t h e  radicals interacting with  e t h y l r a d i c a l s t o g i v e 1-pentene, p r o p y l e n e and a l l e n e were, r e s p e c t i v e l y , 8 8 . 0 + 3 . 0 , '9.0 ± 3 . 0 , firm values  previously obtained  a n d 3 . 0 ±0.5.  These c o n 40 126  f o r t h e same r e a c t i o n s  B e c a u s e b o t h o f t h e r a t i o s R- TT /R  n  u  '  a n d R . , /DR„ n  T  u  .  showed no t e m p e r a t u r e d e p e n d e n c e ( b o t h , f l u c t u a t e d a b o u t t h e same a v e r a g e v a l u e ,  0.38+0.05) f o r m a t i o n  of propylene i n the  r e a c t i o n s 14B a n d 14D c o u l d n o t be d i s t i n g u i s h e d : C^H* +\ B  > C^Hg + B*  (14B)  CjH* + D  > C H  (14D)  5  6  + D*  Formation of hexadiene-1,5 i n d i c a t e d t h a t  recombination  o f a l l y l r a d i c a l s was t a k i n g p l a c e . Because t h e r a t i o R~ -rr . R^ /DR TT was t e m p e r a t u r e i n d e p e n d e n t , h e x a d i e n e TJ  V" 10  ^ l O  x  P  °5 10 M  1,5 c a n o n l y be f o r m e d i n a r a d i c a l i n t e r a c t i o n p r o c e s s , w h i c h must be t h e m u t u a l c o m b i n a t i o n r e a c t i o n 1 2 ; t h e r e f o r e expression  07  i s v a l i d : . t h e r a t i o had an average v a l u e o f  0.15±0.02. The  r a t i o k-,/k c o u l d n o t be m e a s u r e d s i n c e i t was n o t d c  possible to d i s t i n g u i s h the rates of formation  of propylene  99 and  a l l e n e i n the mutual d i s p r o p o r t i o n a t i o n of a l l y l  Conclusion.  The s t u d y o f t h e r e a c t i o n s o f t h e e t h y l  with d i a l l y l  oxalate  t i o n of t h i s  compound g i v e s  ducing  r a d i c a l s a t l o w t e m p e r a t u r e s from an  allyl  combination with other  a very  e f f i c i e n t method o f p r o -  Diallyl  oxalate  a r e needed. •  Reactions ate  c a n he u s e d i n  and t h e o t h e r  .  of the Ethyl Radical with Cyclopropyl  and a l l y l  5 - b u t e n o-  cyclopropylcarboxylate.  We h a v e shown i n S e c t i o n A t h a t t h e a l l y l conveniently  allylic  r a d i c a l sources i f c e r t a i n combination  or d i s p r o p o r t i o n a t i o n products of the a l l y l  D.  radical  h a s shown t h a t t h e s e n s i t i z e d d e c o m p o s i -  compound i n t h e g a s p h a s e .  radical  radicals.  be g e n e r a t e d f r o m a l l y l  radical  may  3-butenoate by a  sequence o f t h e a d d i t i o n o f t h e e t h y l r a d i c a l f o l l o w e d by the  dismutation  the  generation  of t h e adduct radical'I o f any g i v e n  The p o s s i b i l i t y o f  r a d i c a l R* b y a p p l y i n g  t h e same  s e q u e n c e o f r e a c t i o n s t o e i t h e r CH =CHCH C00R o r R C 0 0 C H C H = C H 2  o f f e r s an a t t r a c t i v e g e n e r a l radicals.  This  chapter  describes  esters:  (CH. =CHCH C00<]) a n d a l l y l 2  2  ([>C00CH CH=CH ). 2  by  2  2  method f o r t h e g e n e r a t i o n  of t h i s method t o t h e g e n e r a t i o n from the corresponding  2  2  of  the.successful application of the cyclopropyl  cyclopropyl  radical  3-butenoate  cyclopropylcarboxylate  The g e n e r a t i o n  of the cyclopropyl  radical  the m e t h y l - r a d i c a l - s e n s i t i z e d decomposition of cyclopropyl 92  carboxaldehyde,  w h i c h was d e s c r i b e d  i n the Introduction,  f e r s from t h e disadvantage t h a t t h e intermediate may h a v e s u f f i c i e n t  stability  t o complicate  suf-  [>C0 r a d i c a l  the k i n e t i c  TABLE X REACTIONS OF THE ETHYL RADICAL WITH A L L Y L CYCLOPROPYLCARBOXYLATE * °K  362  ED]  (CO)  [B]  (co )  5.85 . 4.26  378 385  2  9.47  (C H )  (P K£  % 10>  (C H )' D ( C H  4  10  H  5.73  (0)  2  2  5  4  1 0  )  ( C ^  -  2.55 0.79.  3,2  R  3,2>  R  D k  (k  —  10# 11a*  0.137  0.769  _  100.0.  0.846 0.286 0.129 0.835 0.817  6.00 3.85  12.39' 0.14  6.25 0.16  4.24 0.85  0.04 0.02  —  0.136  5.87 3.65  12.82 0.24  6.05 0.24  4.66 0.86  0.15  0.06  0.006 0.142  79.8 20.2  0.06  0.006 0.142  80.5 19.5  —  . 5.94 3.50  13.37 0.24  .6.37 0.27  4.97 0.89  394  5.43 3.27  13.26 0.50  5-50 0.63  5-32 0.79  0.19 0.12  0.08  0.008 0.144  80.8 19.2  398  5.83 3.00  14.38 0.61  5.71 0.70  6.15 0.85  0.32 0.09  0.12  0.012 0.148  82.-5 17.5  403  5.80 2.85  13.39 0.58  5.17 0.60  5.89 0.80  0.42 0.02.  0.18  0.018 0.154  81.7 18.3  408  5.04 2.49  12.49 0.67  4.75 0.75  5.56 0.74  0.40 0.08  0.17 0.01  0.019 0.155  81.6 18.4  duration  o f each  r u n was  60  minutes.  ' —  •- .  388  The  '^11  — —  0.16 0.03  *  J|Et  0.848 0.906 0.110 0.815 0.526 0.270 0.824 0.728 0.148 0.826 1.029 -  0.826 0.859 0.139  k k  D  A  .k  M  ..  C  S  k k  11.6 14.0 19.8 23.0 2.1 23.5. 25.1 3.2 23.0 25.3 3.4 3-1.9 33.8 6.0 35.1 37.8 7.7 35.9 35.8 7.5 40.2 40.9 9.6  I  s  A«  —  0,19 5.4  —• —  4.7  0.48 0.34  6.2  1.71 1.63  6.0  0.67 1.26  6.9  0.10 0.28  .  -  7.6  Continued  0.51 1.71  TABLE X ( °K  [D]  (CO)  (C H )  (0 H^  '((>C H^ ( [>)  [B]  (C0 )  (0 H 9  (C H )  D(C H ) (CjHg)  2  4  5  1Q  1C  2  2  4  2  5  1Q  .tinued) D k  3,2  fc > 5j2  R  10$  R  11a#  413  4.95 2.49  • 12.57 0.86  4.57 0.94  5.89 0.73  0.47 0.09  0.21 0.02  0.024 0.160  80.9 19.1  418  4.85 2.49  13-04 1.15  4.25 1.29  6.13 0.68  0.57 0.14  0.23 0.02  0.024 0.160  84.7 ' 15.3  423  5.-03 2.10  1:3.04 1.39  3.96 1.58  6.46 0.68  0.68 0.19  0.35 0.03  0.034 0.170  85.0 15.0  425  4.-97 2.14  '14.34 1 .49  4.35 1.79  7.19 0.74  0.64 0.30  0.32 0.04  0.033 0.169  84.5 15.5  430 '  4.85 2.50  14.68 1.89  4.04 2.36  7.44 0.72  0.37 0.05  0.044 0.180  83.0 17.0  435  4.79 2.49  14.55 2.01  3.63 2„56  7.63 0.69  0.47 0.04  0.054 0.190  82.5 17.5  0.66 . 0.47 0.68 0.55  JjEt M  .  k  MC  k  All  k  0.815 44.5 0.787 42.6 0.123 11.9 0.796 51.5 0.690 48.1 0.112 15.7 0.802 61.3 0.748-55.6 0.154 23*6 0.804 62.6 0.641 59.O 0.222 24.0 0.780 64.8 0.543 57.2 0.271 28.0 0.775 69.4 0.575 61.9 0.293 30.2  Key  ls A'  7.4  0.48 1,93  7.7  0.59 3.14  1%7 11.4  •  0.62 5.07 1.08 7.45  11.91-56 10.24 14.7  on  1.65 12.40  p. 104..  TABLE X I REACTIONS OF THE ETHYL RADICAL V/ITH CYCLOPROPYL CD]  4  : [B]  (co) ( C H ) ( 0 H ^ (co) <Vio> ( C H ) 1 Q  2  2  4  ( OCpH^) D(C H ) 5  1 Q  2  0  ( 3 6> C  R  R  H  10$ 11a$  —  -  100.0  0.134  • —  0.10 0.05  0.04 —  0.005 0.141  76.9 23.1  5.39 0.76  0.24 0.07  0.09  -  0.009 0.145.  83-3 16.7  4.89 0.58  5.69 0.75  0.31 0.07  0.12  0.014 0.150  81.0 19.0  14.62 0.63  4.91 0.71  6.57 0.77  0.38 0.08  0.17 0.005  0.020 0.156  80.8 19.2  5-13 3.96  12.47 0.48  4.13 0.57  5.-68 0.63  0.24 0.09  0.11 0.005  0.016 0.152  80.0 : 20.0  5.00 3.02  10.79 0.63  3.56 0.75  5.12 0.58  0.33 0.11  0.16 0,01  0.027 0.163  79.3 20,7  12.38 0,16  6.37 0..17  4.20 0.85  0.07 0.-01  5.86 4.49  13.13 0..24  6.18 0.29  4.83 . 0.87  394  5.40 4.53  13.16 0.40  5.25 0.47  398  5.42 4.49  13.49 0.51  403  5.45 4.10  408 413  385  Dk, 3,2  _  5.78 4.54  378  (0)  —  3-BUTENOATE  Mo M  A11  0.854 0.340 0.838 0.605 0.213 0.809 0.812 0.175 0.793 0.827 0.127 0.784 0.871 0.119 0.787 0.722 0.189 0.804 0.757 0.189  '  k k k  A Me D  15.8 19.3 0 ^ 2.p 19.0 21.4. 3.1 24.3 26.5 4.4 27.7 27.8 5.0 34 ..8 37.0 5.532.0 30.0 8.1 37.3 35-1 8.1  k  MC  k  ls  . V  —  0.39 0.09  3.6  1.24 0.45  4.3  0.67 0.67  4.8  0.49 0.65  5.8  0.47 0.83  5.4  0.77 1.11  7.7  0.7'1 2.10  Continued...  o  TABLE XI ( c o n t i n u e d )  v;  [D]  (CO)  (C H )  (C H^  [B]  (oo )  (C H )  (0 H^D(0 H^  418  5.01 3.22  11.58 0.81  3.56 0.95  423  4.90 3.50  12.52 1.43  428  • 5.35 3.25  4  1Q  2  (>C H^)  D k  2  3,2  R  10#  **Et  R  11a$  M  5  ( C ^  5.65 0.61  0-45 0.15  0.23 0.02  0.03 0.17  81.8 18.2  3.20 1.68  6.11 0.61  0.63 0.25  0.36 0.03  0.05 0.19  80.7 19.3  14.14 1.60  3.48 1.97  7.33 0.65  0.59 0.37  0.35 0.03  0.05 0.19  81.0 19.0  2  5  1Q  2  435  4.98 3.02  12.89 1.66  2.95 2.12  6.91 0.59  0.52 0.46  0.34 0.05  0.06 0.20  78.2 21.8  443  5-00 2.79  14.66 1.91  3.13 2.53  8.20 0.63  0.47 0.62  0.25 0.07  0.07 0.20  77.0 23.0  A11  0.795 0.851 0.206 0.744 0.690 0.196 0.764 0.590 0.250 0.759 0.515 0.307 0.773 0.428 0.320  k  A  k  D  39.0 37.0 9.6 51.2 40.5 14.3 54.8 47.0 17.4 60.2 49.5 19.5 67.3 58.2 23.8  Key  k  MC  k  Is k  A'  8.2  0.69 2.70  8.2  0.81 4.50  8.5  1.24 6.55  9.0  1.69 9.80  11.0  2.60 14.00  overleaf.... .A  o  KEY TO TABLES X AND X I ID]  Concentration of d i e t h y l ketone x I O  [B]  Concentration of substrate x 10~ raolec.cm7 )  =  C Hio  R  M  M  M  - C0 R  5  1 0  2  ( k ) - 0.136  10^  =  DR  11a#  =  Et  =  ^ C4H10  0  =  ( D>C H  A11  =  C D R C  =  1 0 \ / k | (cmjmolec^sec )^  =  lO^kg/k*^ ( c m f m o l e r f s e c ) ^  =  10~ k k^/k  k k  C H  R  =  2  A  Me  k  D  R  2  R  H  C 5  /(DRC H  1 0  C K /(D C H 6  5  R  +  2  5  H  + C H ) 5  C H )/ C0  R  6  R  6  + [>)/ C0  2  R  2  + C H / C0 R  1  R  $  0  6  R  R  5  3  1 0  1  &  2  1  7  1  5  8  88  1  k  Is  =  /10  °  14B 2  7 a  (cmjmolec.sec?)^  10  (cmJmolec^lsec )^  ~' ^ 1 5 / 1 0  (cni^olec.sec )^  1 5 k  k  1  k  k  10  1 3  k  / k  k  2  =  R  1 0  2  R  + C H  5  R  5  MC  A  1 0  2 3  k  k ,  3  3  Rc H4/ C4H  Dk-^ R  1 2  =  )  5 ) 2  3  Rate o f f o r m a t i o n x 1 0 ~ m o l e c . c m s e c l  =  5  (k  molec.cm7  17  ( D S  - 1 7  1  1  / k | (cmfmolec^sec )^ 1  1 7 a  o  105 i n t e r p r e t a t i o n o f systems of  this  w h i c h use t h i s method.  The method  c h a p t e r h a s no s u c h d i s a d v a n t a g e , a s t h e C00<] a n d  [>C00* f r a g m e n t s  are unstable.  P a r a l l e l d i s c u s s i o n s a r e made o f t h e c y c l o p r o p y l 3-butenoate and a l l y l they d i f f e r of  c y c l o p r o p y l c a r b o x y l a t e systems,  s i g n i f i c a n t l y only i n the rates of decomposition  the adducts  radicals.  R e s u l t s and K i n e t i c A n a l y s i s .  TABLE X g i v e s t h e d a t a  f o u r t e e n one h o u r r u n s , p e r f o r m e d o e f f e c t i v e wavelength ketone  and a l l y l  A, a g a s e o u s m i x t u r e o f d i e t h y l  89 t o 162°C.  tempera-  TABLE X I g i v e s t h e c o r r e s -  d a t a from twelve runs w i t h a gaseous m i x t u r e o f d i -  e t h y l ketone  170°C.  o f 3150  from  by i l l u m i n a t i n g , v/ith an  cyclopropylcarboxylate at various  t u r e s i n t h e range ponding  since  a n d c y c l o p r o p y l 3 - b u t e n o a t e b e t w e e n 105 a n d  When e i t h e r s u b s t r a t e was s e p a r a t e l y i l l u m i n a t e d a t  170°C f o r one h o u r i n t h e a b s e n c e o f d i e t h y l k e t o n e , showed a n y d e c o m p o s i t i o n t o g i v e v o l a t i l e Both t h e e t h y l r a d i c a l / a l l y l  products.  c y c l o p r o p y l c a r b o x y l a t e and  t h e e t h y l r a d i c a l / c y c l o p r o p y l 3-butenoate systems same p r o d u c t s :  neither  carbon monoxide, butane,  ethane,  gave t h e ethylene,  1-pentene, c a r b o n d i o x i d e , e t h y l c y c l o p r o p a n e , c y c l o p r o p a n e and p r o p y l e n e .  Small peaks,  s a i d p r o d u c t s , appeared chromatograms. was  other than those of the a f o r e -  and d i s a p p e a r e d e r r a t i c a l l y  I t was e s t a b l i s h e d t h a t none o f t h e s e  due t o a n y o f t h e p o s s i b l e p r o d u c t s a c r o l e i n ,  butene  i s o m e r s , and t h e pentene isomers,-2-pentene  methyl-1-butene.  i n a l l  The t o t a l  peaks  allene, a n d 2-  a r e a o f t h e s e peaks" n e v e r  106 exceeded The  10$  of the peak a r e a of 1-pentene.  l a r g e y i e l d s of ethane  cal abstracts ial  a hydrogen  i n d i c a t e that the e t h y l  atom f r o m t h e s u b s t r a t e .  balance f o r the e t h y l r a d i c a l ,  tively  w h i c h was  as M- ,= (R  f o r these systems  TT  n  t?  c o n s i s t e n t l y l e s s than u n i t y , which radical The  the adduct cannot  of carbon d i o x i d e  tentaW A S  i n d i c a t e s t h a t the  and  ethyl  substrate.  1-pentene i n d i c a t e s  r a d i c a l decomposes; the s o u r c e of c a r b o n  be t h e u n s e n s i t i z e d  mater-  TJ  n  a l s o d i s a p p e a r s through a d d i t i o n t o the  appearance  The  defined  + R  radi-  decomposition of  that  dioxide  the'substrate,  s i n c e no d e c o m p o s i t i o n o c c u r r e d i n t h e a b s e n c e o f d i e t h y l ketone.  The  presence  o f e t h y l c y c l o p r o p a n e c a n be e x p l a i n e d  most s i m p l y b y c o m b i n a t i o n o f c y c l o p r o p y l The  presence  of the c y c l o p r o p y l  and  ethyl radicals.  r a d i c a l c a n a l s o be  from the f o r m a t i o n of c y c l o p r o p a n e , which  c a n be  produced  e i t h e r b y d i s p r o p o r t i o n a t i o n b e t w e e n t h e e t h y l and propyl  r a d i c a l s o r by a b s t r a c t i o n o f a hydrogen  the o r i g i n a l reactants  by t h e c y c l o p r o p y l  deduced  cyclo-  atom  radical;  from  evidence  of the d i s p r o p o r t i o n a t i o n i s a v a i l a b l e , s i n c e the y i e l d ethylene i s l a r g e r than that predicted (0.136) of the r a t i o R  „  n  °  2  /R 4  n  of  by t h e c o n s t a n t v a l u e  T i n the absence of °4 10 T  sub-  n  s t r a t e s f evidence of the a b s t r a c t i o n i s a v a i l a b l e since yield  of ethylene i n the d i s p r o p o r t i o n a t i o n r e a c t i o n ,  m a t e d f r o m DR„ „ = L „ - 0.1J6 °2 4 2 4 the y i e l d of propane. If  L  „ 4  , i s always  esti-  less  10  a l l i n d i c a t i o n s d i s c u s s e d above a r e t a k e n i n t o  a c c o u n t , t h e f o l l o w i n g r e a c t i o n scheme c a n be  the  proposed:  than  107 C  2  H  5  C0C  2  H  2 C  2  H  > 2C H°  5  3  — > C  Z  H '  2  +  C H*" 2  C H2  H  C H COC H^  > C  2  H  5  2  + C  H  2  C0C  * ZL 9  2 5  C  H  +  t>-xC0 -)-CH CH=CH  +  0—4C0 ^-CHCH=CH  2  2  C  + [> - ^ c O p ^ -  H  3  C H  6 H C H  2  C H  2  C H C H  2  C  2  H  +  3  C H-  C [>•  2  0  0  H ;  +  2  2  H  C  2  H  2  cal  2 5  (5)  H  +  - ( C 0  CHCH=CH  [> - ^ C O ^  CHCH=CH  +  > - C  2  C 0 H  5  2  group.  This  (7)  >  C  > C  0  H  C  2  H  4  C H ( C +  2  C  H  5  5  1  ) C H  2  C  2  H  C?a)  5  (8)  Q  (11)  0  C H = C H  2  ' +  (12)  0  d CH_CHCH  2  > [> + t> -6C0 -4-  2  >  2  >  H  2  [> ,  C H  25  2  (10)  2  > - 4 C 0  2  > C H ( C  CH -CH-CH  only a methylenic  2  2  . (13)  2  CHCH=CH H  5  (14)  2  ) C H = C H  . 04a)  2  (15)  2  radi-  h y d r o g e n atom o f t h e a l l y l  assumption i s based on t h e e x p e r i m e n t a l  dence r e p o r t e d  ( 6 )  (6a)  2  r e a c t i o n scheme, i t i s assumed t h a t t h e e t h y l  abstracts  .  5  > C H^_ +  0  2  ^ - C H  2  > > .  >• In t h i s  0  5  2  2  + [> — ( C 0 - > -  (4)  5  [> . _ H »  0-4C0 ->-'CH CH=CH 2  +  5  CH^HCH^H^  CH--CH-CHV  2  C0C  H  2  (3)  6  > [ > - ( C O ^  2  d  C O C  4  H  2  2  CH--CH-CH  2 5  +  C H*  2H :5 +  C  C  +  4  CH(C H )CH==CH  + [>.  2  C  2  (2)  > [>—00^-  -> t> - £ C 0 - ) -  (1)  (  2  2  2  H  CO  0  > CgHg  2  2  + 0-^'C0 4-CH CH=CH  2  1  2  C Hc 2  _ H  > C  °2 5 2 4 H  ]  2C H * 2  C  +  2  by Trotman-Dickenson that  evi-  the methylenic  hyd-  r o g e n atoms o f t h e c y c l o p r o p a n e g r o u p a r e n o t a b s t r a c t a b l e 94 by  alkyl  radicals  However t h e r e  a tt h e temperatures of this'experiment.  i sa p o s s i b i l i t y  that  the tertiary  a t o m o f t h e c y c l o p r o p y l g r o u p c a n be a b s t r a c t e d : *  A-{-C0 -}-B 2  i s either  A C 0  2  B  or  B C 0 A. 2  hydrogen  -  108 C H* 2  The  + |>-fC0 4-CH CH=CH 2  2  substituted  >  C  2  cyclopropyl  H 2  6  +  O^ 2^~ C0  CH CH=CH 2  r a d i c a l may t h e n  (6')  2  undergo  decomposition:  >-^C0p4- C H C H = C H 2  > CH -C=CH  2  2  2  + C0  2  + CH -CH-CH 2  This r e a c t i o n , although thermodynamically  ©')  2  favoured,  (AH ^ + 4 . 0 k c a l . / m o l e * ) , d o e s n o t seem t o o c c u r , b e c a u s e n o a l l e n e was f o u n d that 9'  reaction  possible-  the rate sidered  among t h e p r o d u c t s .  6' i s n o t s i g n i f i c a n t But since  this  T h e r e f o r e , one s u s p e c t s e n o u g h t o make  suspicion  reaction  c a n n o t be c o n f i r m e d ,  o f t h e h y d r o g e n a b s t r a c t i o n r e a c t i o n must b e c o n as t h e combined r a t e  of reactions  6 a n d 6'. The  r a d i c a l p r o d u c e d i n r e a c t i o n 6 c a n be consumed i n e i t h e r r e a c t i o n 6ao r [>-4C0 -^CHCH=CH 2  > ( > C 0 ' + CH =CHCH=0  2  (9)  2  However, t h e absence o f a c r o l e i n i n d i c a t e s t h a t  reaction'9  does n o t o c c u r .  6 a n d 6' c a n  The c o m b i n e d r a t e , o f r e a c t i o n s  therefore  be g i v e n b y  and  R  since  =- 0 . 1 3 6 R  x  5 Therefore, the rate >6  +  k  6-  R =  ;  „ - 0.1$6R - R. °a io 2 6 °4 10 c o n s t a n t k g c a n be g i v e n b y n  „  R^ + R^, = R^ ^ - R^ -R^  , R^ + E c ,  = R  P  r TJ  Jri  C.H " ° __2_6  U  1 3 6 R  C H, M fL™ j a  CB]Rg  4'  0  k  4 —  . (  D  1  )  [B] k |  * To d e t e r m i n e t h i s h e a t o f r e a c t i o n , a d i s s o c i a t i o n e n e r g y o f 8 9 . 5 k c a l . / m o l e was a s s i g n e d t o t h e t e r t i a r y h y d r o g e n bond^ A H f ( [>-4CG27-CHCH=CH ) was e s t i m a t e d t o be - 5 4 . 0 kcal./mole. From t h e r e a c t i o n t>-fC02^-CH CH=CH -^ [>-HC02^-CH2CH=CH2 +' > AHf(OHC027-CH2CH=CH ) was e s t i m a t e d t o be - 1 6 . 5 k c a l . / m o l e . F r o m t h i s v a l u e t h e h e a t o f r e a c t i o n 9 ' was e s t i m a t e d t o be 4 . 0 k c a l . / m o l e , w h i c h i s a n u p p e r l i m i t s i n c e t h e l o w e s t poss i b l e v a l u e was c h o s e n f o r t h e d i s s o c i a t i o n e n e r g y o f t h e hydrogen bond. 0 2  p  H  ?  2  2  10^ It  f o l l o w s d i r e c t l y from t h e p r o p o s e d mechanism t h a t t h e  r a t e o f a d d i t i o n o f t h e e t h y l r a d i c a l t o t h e d o u b l e bond o f the  substrate,  R^, i s g i v e n b y  R = R -R - -R "7 C0 X 10 2 6 ' T h e r e f o r e t h e r a t e c o n s t a n t k,-, c a n be g i v e n b y K  V 2 " k  ( H  M  co - \ n  ^  -  w  For.reasons given the  C  W  /  later,  M  ^  (D2)  i t i s c o n v e n i e n t t o measure  r a t e o f decomposition o f the-adduct r a d i c a l formed i n R Q , "fry "the r a t e  r e a c t i o n 7,  of formation  o f carbon  dioxide  r a t h e r t h a n o f C ^ H ^ Q ; t h u s k g c a n be g i v e n b y k k /k 8  2  where  R  = R o R C  ? a  = R  n  R  and k  2  C z i  - R  n  C0  R  H /- 7aR  1 0  Q  C H^ Z J  R Q  C Hg  R  2  C0  .-'  2  therefore 8 2 k  / k  7a  =  R  C0  R 2  C  Z l  _H  / ( R 1 0  C0~ % H  The d e c o m p o s i t i o n o f . t h e pyl radical,  "C H  " C0  R  1  0  2  R  6  )  (  D  3  )  2  adduct r a d i c a l y i e l d s t h e c y c l o p r o -  the further reactions  of which give  c e r t a i n k i n e t i c problems, which include  rise to  the relationships  TT 0 a n d R„ T > R , a n d w h i c h w i l l be d i s c u s s e d i n 3 6 ° 5 10 °°2 the supplementary s e c t i o n (p.117). Here, i t i s s u f f i c i e n t  R  T  c  rn  d  t o m e n t i o n t h a t t h e above r e l a t i o n s h i p s a r e c o n n e c t e d the  formation  of the a l l y l  the  e t h y l r a d i c a l t o give  r a d i c a l and i t s r e a c t i o n s  with  pentene-1 and p r o p y l e n e :  CHp-CH-CHp.+ c H ; P  5  I U  C H 5  The c y c l o p r o p y l  with  6  + C H 2  4  (13)  r a d i c a l interacts with the ethyl r a d i c a l  110 to give  e t h y l cyclopropane•and  ^  cyclopropane:  t>_C  2 5  . (10)  H  * ~ " ^ D> + C.H^ '24  (11)'  5  The  r a t e o f r e a c t i o n 11 i s e s t i m a t e d  excess ethylene: R  13. = C H ' R  3  a  n  R  The E  - R^^ + R ^  since R j = 0.156  d  6  =  11  R  i n d i r e c t l y from t h e  \  ^  E  - 0.136  0 H 2  - C H ' R  Q  3  C L 4  t  h  e  n  6  rj  R  4  + R^ , and  3  -  R  1 Q  TT  C ii 3  6  ratio H^10  -  ( R  C H - O" ' 1  2  V l O  6  4  has  t h e average values  and  0.23  E  0  H  3  )  /  6  V 0  2  H  W  5  0.21 ± 0.02 ( s u b s t r a t e : ' [> C 0 A 1 1  )  2  ± 0.06 ( s u b s t r a t e :  90  temperature between  _  ), both independent o f  A11C0 <3 2  a n d 170°G.  !  Cyclopropane i s formed n o t o n l y i n t h e d i s p r o p o r t i o n a t i o n r e a c t i o n 11, b u t a l s o i n m e t a t h e s i s o f t h e c y c l o p r o p y l r a d i c a l w i t h d i e t h y l ketone and w i t h t h e s u b s t r a t e : [>•  +.^BH  >[> + B*  (14B)  [>.  + DH  -> 0  (14D)  ( w h e r e BH = s u b s t r a t e  a n d D H =• d i e t h y l  The  rate of these m e t a t h e t i c a l  *K  - 14B E  +  E  * |>  1«  = Since  -  R  DE  + D"  E  reactions  C H * °- 5S  c a n be g i v e n b y  R c ^ ^  1  2  ketone)  4  E  C H 3  6  [>  r e a c t i o n s 14B a n d 14D a r e r e l a t e d t o r e a c t i o n s 6 a n d 4  r e s p e c t i v e l y , we c a n assume t h a t .  V 6 k  = K , /  then (k or  k  [DH]  +  k|/k  1 0  1 4 D  1 4 B  4 I )  A  ,  1 4 B  k ^  B  therefore  [BH] ) k | / k  1 Q  k -  1  4  D  D  = m ^ ^ J ^ J ^ m  = R  +  (k^/k^k^s ^  [BH])  T  ^  R  ^  ^  ^  (D5)  112 F i g u r e . 12.  Metathesis of the e t h y l r a d i c a l c y c l o p r o p y l c a r b o x y l a t e (•) propyl  3-butenoate Q  '•  with  and w i t h  allyl  cyclo-  113  Figure  13.  Ethyl radical-serisitized allyl propyl  decomposition  cyclopropylcarboxylate 0 3-butenoate  of  and c y c l o - .  Figure  14.  Patterns ethyl cal  of i n t e r a c t i o n s between  r a d i c a l and  i n the  systems a l l y l  • carboxylate/ethyl cyclopropyl ( 0 , 0 ) .  the c y c l o p r o p y l  the radi-  cyclopropyl-  radical (A,©)  and  3-butenoate/ethyl r a d i c a l  TABLE X I I ARRHENIUS PARAMETERS OF THE REACTIONS OF THE ETHYL RADICAL WITH A L L Y L CYCLOPROPYLCARBOXYLATE AND CYCLOPROPYL: 3-BUTENOATE 1  \  k Rate constant relationship x  Allyl  Units lo  1 3  logA  3-butenoate  kcal/mole  log A  ± 0.2  5.5 ± 0.5  4 . 5 ± 0.2  5.8 ± 0.2  7.6 ± 0.3  5.6 ± 0 . 2  6.4 ± 0.3 . 5 . 1  2  -  — " , SUBSTRATE " cyclopropylcarboxylate Cyclopropyl EY " Ey  kcal/mole  k /k * 6  -  x  x  cm^molec. sec. 2  10  1 3  k A V , -\  7.8±0.3  2  ?  L _A cm?molec. s e c . •  10-5k k Vk 8  2  ? a  cm. ''molec. 2 s e c 7 10 3k 1  1 4  k Vk 2  1 0  cm?molec7 sec7 2  k  lla/ 10 k  ".  16.0 ± 0.6  9.6 ± 0.3  8.0 ± 0.8  . 5-3 ± 0.5  .-  -r-  -  • •  12.3  ±0.6  7.5  ±0.5  7.5  ± 0.8  4 . 8 ± 0.6  2  .  2  0.210 ± 0.020  5  0.230 + 0.025  -A -A cn  117 The  Arrhenius  carboxylate linearity,  and c y c l o p r o p y l with  Substrate  2  2  3-butenoate (FIG.  cyclopropyl19)  show g o o d  parameters  , f l 4 ^ .kcal./mole  C0 -A11 A11-C0  p l o t s o f D5 f o r b o t h a l l y l  i  E kcal./mole  ; ^ ^ / ^ • (cmvmolec.'sec. ' ) ' 5  6  +  5  8.0 ± 0.8  6.4 ± 0.3  5-3  7.5  5-5  4.8 ± 0.6  ± 0.8  ± 0.5  ± 0.5  The  linearity  are  c o n s i s t e n t w i t h a m e c h a n i s m w h i c h i n c l u d e s r e a c t i o n s 14B  and  14D.  values  o f t h e s e p l o t s and t h e v a l u e s ' o f t h e p a r a m e t e r s  T h e r e i s no s i g n i f i c a n t d i f f e r e n c e b e t w e e n t h e  of E^  4  f o r t h e two s u b s t r a t e s .  The o b s e r v e d v a l u e s o f  E^-E„„ a r e - 1 . 6 ± 1 . 1 a n d -2*0±1.1 k c a l . / m o l e f o r >-C0„-All and  All-C0 -<3 2  ship, E = The  respectively.  According  11.5 - 0.25Q, E g - E ^ a  excess of E ^  should  to Polanyi's be  +0.75  relation-  kcal./mole.  o v e r E g may s u g g e s t t h a t t h e t r a n s i t i o n  s t a t e s o f r e a c t i o n s 14 a n d 6 do n o t i n v o l v e t h e same t y p e o f bonding.  ' .  Expressions  D1 'to ©5 f o r k g , k^, k g , k ^ / k ^  based on t h e s i m p l e  reactions  1 t o 8 a n d 10 t o 14 o n l y . following,  i t will  Q and k ^ a r e  scheme c o m p r i s e d o f r e a c t i o n s  I n the supplementary  be s e e n t h a t t h i s  simple  section  scheme must be  extended t o account f o r p r o d u c t s and r a t e r e l a t i o n s h i p s n o t so f a r d i s c u s s e d . date the expressions  However, t h i s  extension  D1 t o 3)5.  '  Supplement t o t h e K i n e t i c A n a l y s i s .  does n o t i n v a l i • '  The p r e s e n c e o f b o t h  p r o p y l e n e a n d e x c e s s 1 - p e n t e n e (R~. T - S „ . = DR~  *> 0 )  T  .  °5  suggests that the cyclopropyl ing.  The e x a c t  10  2  5  10  group i s undergoing r i n g  mechanism o f t h e r i n g  opening i s - n o t  open-  118  i m m e d i a t e l y o b v i o u s ; t h e r e f o r e a number o f p o s s i b l e  processes  must be e x a m i n e d : Cl)  >C H£ 5  . 0«  (II)  + Cy-Ic—>[>-C H*—> C H 2  5  [>-C H* + M—>[>-C H 2  2  f>. +  (III)  C  [>-C H* 2  0  H ° — >  I > C  25  + Fi* ( d e a c t i v a t i o n )  r  0  H * — > C  25  + M—>>-C H^ 2  + M  5  .  C0  +  2  4- C H 5  1 0  CE 7  4- [>-<-C0p^-CpH,Cr* 2  2  CH  3 5  ^ ^ ^ - ^ C O ^ C ^ Q  ^  E a c h o f t'hese f i v e the  25  (deactivation)'  ^ ^ H '  (V) P  4- C D H °  H ;  X  J  ^ ^  C H-  isomers  1 0  5 10  —  >>.+ C 0  2 2  35  + C H 5  1 0  schemes i s d i s c u s s e d s e p a r a t e l y i n t h e  Supplements I t o V f o l l o w i n g .  Supplement  I . The p r e f e r r e d scheme i s I , i n w h i c h t h e a l l y l  r a d i c a l i s formed from t h e c y c l o p r o p y l r a d i c a l by d i r e c t u n i molecular  isomerization: fs.  15 r-,H ; A H >  1  5  = -23  kcaL/mole  T h i s view i s supported by t h e v a l u e s o f t h e r a t i o R  C  H /( C H R  3 "6  °5 1 0  " C 0 ^' ^ R  2  =  ^ ^ c ^ '  gether with the value for a l l y l System  w  h  i  c  n  a  r  e  S  i v e n  T h  3-butenoate"  > >  below t o -  :  k^/k^ ( A H * E t " )  temperature range  0.11 ± 0.3  above 150°C  All-C0 -<]  0.09  ± 0.3  above 1 5 0 ° C  A11-C0 -A11  0.09  ± 0.3  100 t o 165°C  [>  C0 -All  2" o  2  2  +  '  T h e s e v a l u e s i n d i c a t e t h a t i n t h e t>—(-CO,-,-)-All s y s t e m s 150°C,. p r o p y l e n e a n d e x c e s s p e n t e n e - 1 reactions  above  a r e d e r i v e d from t h e  11-9 Figure  16.  Isomerization to  the a l l y l  of the c y c l o p r o p y l  radical  radical.  y  10  T  o  Allyl. cyclopropylcarboxylate  •  Cyclopropyl  3-butenoate  system  system  .  120 C,H* > Several  C  +  ?  C  H-—^  (12)  5 10 H  C H -+ 0 H 5  6  2  i n v e s t i g a t o r s have r e p o r t e d  (13)  4  that  cyclopropyl radicals 90-92  can  undergo r i n g  f i s s i o n t o give  who s t u d i e d t h e r e a c t i o n s gas  allyl  radicals.  Thynne,  of the cyclopropyl radical  i n the  phase m e t h y l - r a d i c a l - s e n s i t i z e d d e c o m p o s i t i o n o f c y c l o -  propyl  carboxaldehyde, reported  ring fission  that  i s a minor process, o  o n l y a b o v e 174  i n this  system such a  w h i c h becomes  noticeable  92  C.  He e s t i m a t e d  t h a t the a c t i v a t i o n energy  o f r e a c t i o n 15 was 20 k c a l . / m o l e . Nov-/, i f i t i s a s s u m e d t h a t Ry,c= VR H + Rp TT , t h e r a t e c o n s t a n t o f t h i s r e a c t i o n , k.,-, n  12  is  5 io  °3 6  "-.S^AlO  > (  O  r i  given by  A straight line quantity only  °  D R  C H 5  + E 1 0  C H > ^H E  3  c a n be f i t t e d  a b o v e 150^0  6  / t>C H  CD6)  R  1 0  2  5  t o the Arrhenius  (FIG.  17).  plot of this  The A r r h e m u s  para-  meters a r e System  \  k  !>C0 -A11 2  All-C0 -<l 2  (A = 2  The  5^10  —10  c  a  i ^  m  o  i e  l o  S  <1 A  s e c 7 l ) 5  22 ± 5  12 ± 5  18 ± 5  10 + 2  —1 5 — 1 molec.cm.sec. and i t i s assumed t h a t A »*-^Q) 2  values  o f E^^ a r e i n c l o s e  agreement w i t h t h e v a l u e o f 92*  20 k c a l . / m o l e r e p o r t e d b y T h y n n e . The v a l u e s o f A ^ a r e reasonable f o r a unimolecular rearrangement(isomerization). Both t h e k i n e t i c parameters o f the radical  i n r e a c t i o n 15  and t h e r a t i o  generation.of the R^ ^ / ^ R Q H  36 t o t h e r e a c t i o n s 12  15,12,13 ~  value  a n d 13,  as a s u f f i c i e n t  allyl  relating  5 10  s u p p o r t t h e sequence o f r e a c t i o n s  s u p p l e m e n t a r y scheme t o a c c o u n t f o r  o f 22 k c a l . / m o l e now r e p o r t e d  ^7  1  121 the  f o r m a t i o n o f p r o p y l e n e and excess  the  range  150°C). tions the  A d o p t i o n o f Scheme  not•accounted  V, w h i c h  pentene-1  over  carbon  i s formed  f o rthe calculation of a n o  dioxide  ^ ^14.*  ^  n  observed  I ; however, t h i s  as t h e d i f f e r e n c e  e  e  r  7  excess  b e t w e e n much  may a c c o u n t  small 150°C must  larger  i snecessarily very low.  a r e d i s c u s s e d below,  The  schemes I I  f o r t h e excess  150°C.  Supplements  I I and I I I .  supposition  that  Schemes I I and I I I a r e based  the energized  by the combination  isomerize to yield and e t h y l  v  below  o f one o r more o f t h e s u p p l e m e n t a r y  below  (above  n o .changes i n t h e e q u a -  X  so t h e p r e c i s i o n  participation  allyl  Analysis"  f o r b y Scheme  be m e a s u r e d  quantities,  may  I requires  r  o f pentene-1  formed  propylene  c o n s t a n t s kg,lc -,,kg,k j^/k^2»  rate  always  to  i nwhich  given i nthe "Kinetic  excess is  o f temperature  1-pentene throughout  molecules,  and c y c l o p r o p y l  pentene  isomers  radicals,  (scheme H ) o r  (scheme I I I ) .  S c h e m e 31 i s p a r a l l e l methylcyclopropane  of ethyl  either  radicals  ethyl cyclopropane  on t h e  to the isomerization  to yield  a mixture'.of butene  of energized isomers  111 •(Butler  and K i s t i a k o w s k i  ) and i s r e p r e s e n t e d b y t h e equa-  t i o n s 10,10ia,10ib,10ic and.10q: . [><- + C p H * >[>CpH * (vibrationally  excited)  (10)  (lOia)  122  5  2 [>C H" *^ 2  ^ CH CH=CHC H  5  5  2  '  5  (10ib)  2- 5  i  C>-C H * 2  >  5  !^>C?IC H 2  [>C H * 2  5  2  + M•  5  —^>C H 2  (where M i s a m o l e c u l e c a p a b l e energy o f . e t h y l c y c l o p r o p a n e considered  equal  J  > CH =CC H  5  2  (lOic)  5  + M»  .  (10q)  of removing the e x c i t a t i o n  a n d whose c o n c e n t r a t i o n c a n be  t o t h e w e i g h t e d sum o f t h e c o n c e n t r a t i o n s  o f d i e t h y l k e t o n e 'and a l l y l  cyclopropylcarboxylate.)  mechanism e x p r e s s e s a c o m p e t i t i o n , b e t w e e n the  This  alternative,  i s o m e r i z a t i o n r e a c t i o n s ( 1 0 i a , 1 0 i b , and 1 0 i c ) and t h e dee n e r g i z a t i o n r e a c t i o n (10q),  and i s c o n s i s t e n t w i t h t h e r e l a -  tionship k  10i/ 10q= k  [M] c ^ H D R  / / R 1 0  [>C H 2  where, assuming t h a t B and D a r e e q u a l l y ' energizers,  [MJ =  [Bj + [D] .  ™ )  r  The A r r h e n i u s  e f f i c i e n t deplots of ^oi^ 10q k  k  are n o t l i n e a r throughout t h e complete temperature range, t o 170°C, f o r e i t h e r s u b s t r a t e linearity perature.  a b o v e 140°C, b u t t h e y The A r r h e n i u s  the p l o t s are 1  OC0 -A11 2  All-C0 -<] 2  (FIG.  18).  100  T h e y show a g o o d  a r e e r r a t i c below t h i s  tem-  parameters f o r the l i n e a r p a r t s o f -  , ?10i'-. kcal./mole 25 + 4 16' ± 4 •  &'( 10i/Al0q) molec.cmr?  l o  A  .50  + 3  25 ± 2  log A seer"  1 0 i  20 + 5 '^15  ± 2  Figure  1 7 .  Decomposition of  O  Allyl  0  Cyclopropyl  energized'ethylcyclbpropane.  cyclopropylcarboxylate 3-butenoate  system  system  124 The  effective  a c t i v a t i o n energy f o r the i s o m e r i z a t i o n process  •10i  i s approximately  20 k c a l . / m o l e , w h i c h i s 45 . k c a l . / m o l e  l e s s than the value expected  f o r the pure thermal  isomeriza-  112 tion.  T h i s d i f f e r e n c e i n d i c a t e s t h a t a b o u t one h a l f o f t h e  energy r e l e a s e d on the f o r m a t i o n o f t h e C-C bond i n r e a c t i o n 10  i s a v a i l a b l e f o r the i s o m e r i z a t i o n ; t h i s i s a reasonable  fraction.  However, t h e ' v a l u e s o f t h e A - f a c t o r s ' a r e h i g h f o r h y d r o g e n t r a n s f e r a n d C-C r i n g  processes  with simultaneous  opening.  A l s o , the simultaneous  10ic  r e a c t i o n s 10ia,. 1 0 i b , a n d  some 2 - p e n t e n e , b u t o n l y 1 - p e n t e n e was d e -  should y i e l d  tected. p a t t e r n l e s s A r r h e n i u s p l o t s below 140°C, the  The  A - f a c t o r s , t h e absence o f 2-pentene, and the f a i l u r e mechanism t o account  of the  f o r the f o r m a t i o n o f p r o p y l e n e , i n d i c a t e  t h a t , a t t h e m o s t , scheme I I c a n o n l y be a v e r y m i n o r S u p p l e m e n t HE p r o p o s e s t h a t p r o p y l e n e  process.  and excess  1-  s e q u e n c e o f r e a c t i o n s 10,10d,10q,  pentene a r e formed i n the  12,  high  a n d 15a: [SCpHr-*  1  |>C H * + M 2  C , H ;  1  5  +  C  0  t> 5  H  *  -  25  ^  '  ° > CjH' + CpH';  AH  d  °q ^  1 0 d  =  65 k c a l . / m o l e *  ^ C p H ^ + M*  >  5  L  13->C H 5  6  U  4- C L 2  4  T h i s scheme h a s t h e a d v a n t a g e s o v e r Scheme H t h a t i t p r e d i c t s both the f o r m a t i o n o f propylene and  that i t involves thea l l y l  mediate,  and the absence o f 2-pentene, r a d i c a l as t h ep r i n c i p a l  which i s c o n s i s t e n t w i t h the values o f R  n  3 *  A H ( [>C H ) f  2  5  = -Ikcal./mole  1 1 0  .  inter-  -n /DR„ TT , 6  C  5 10  125 0.11 ± 0 . 0 3  and 0.09  ±0.03  forallyl  cyclopropylcarboxylate  c y c l o p r o p y l 3-butenoate r e s p e c t i v e l y .  and  This  r a d i c a l mechanism e x p r e s s e s a c o m p e t i t i o n  r e a c t i o n 10d and t h e d e - e n e r g i z a t i o n  between  r e a c t i o n 10q, and i t i s  consistent with the r e l a t i o n s h i p . k  W  h  e  r  But  10d  e  R  s i n c e DR~ „  10q  / k  10d  » E  relationship  =  D  M 10d R  C H,  R  R  / R  +  N  10q  '  R  '  3 6  3 o TT  5 10  D8 i s v i r t u a l l y  k  a  r  e  q u a n t i t y k^Q^/k^Q^.  v  ^ * r  u  a  ^ y  The v a l u e  The v a l u e  of the a c t i v a t i o n energy  of the A-factor,  although extremely high  parameters of the  i d e n t i c a l t o those of the  (20 k c a l . / m o l e ) i s c o n s i s t e n t w i t h •10d.  ; therefore the  i d e n t i c a l t o the r e l a t i o n s h i p  D7 ( S u p p l e m e n t H ) , a n d h e n c e t h e A r r h e n i u s q u a n t i t y ^^od^ 10q  ^  C^H,  5 10  „ , t h e n R ^ ^ , « DR-,  P  5 10 '  =  the decomposition  10  15 y  reaction  -1 ?0 -1 s e c . t o 10 sec. ,  f o r t h e i s o m e r i z a t i o n r e a c t i o n 10^  ( S u p p l e m e n t H ) , i s more a c c e p t a b l e  f o r a simple  bond  dis-  s o c i a t i o n r e a c t i o n such as 10d. If  Schemes H a n d HE a r e o f m a j o r R  10  =  R  O C  2  H  +  5  D  R  C  5  H  h o w e v e r , t h e r a t i o R^^/R^Q S* and This  this  + 1  1011  condition i s f u l f i l l e d  implies that the energized  deactivated  by c o l l i s i o n ,  o f more t h a n m i n o r Supplement I V . generation radical  0  R  C  3  importance, H  6  -^ be t e m p e r a t u r e o n l y i f R^Q  =  R  independent,  I V Q J.J  OCpJE,- m o l e c u l e s a r e l a r g e l y  a n d t h a t Schemes H a n d HE c a n n o t be...  importance.  In this  of a l l y l  i s examined.  supplement, the p o s s i b i l i t y  of d i r e c t  r a d i c a l s , by d e c o m p o s i t i o n o f t h e adduct This  r e a c t i o n ( 1 6 ) w o u l d be i n  126 F i g u r e 18.  Formation  of a l l y l  decomposition -' C H 5  1 0  of  C0 < . ( • ) • 2  radicals  ^002^1-1^  by (0)  direct and  127 c o m p e t i t i o n w i t h the g e n e r a t i o n of c y c l o p r o p y l r a d i c a l s i n r e a c t i o n .8: mole kcal.^ mole If  we j u d g e  only by the  e x o t h e r m i c i t i e s o f these r e a c t i o n s ,  r e a c t i o n 1 6 a p p e a r s t o be more f a v o u r e d  t h a n r e a c t i o n 8; how-  ever i t i s d o u b t f u l i f i t i s also favoured k i n e t i c a l l y . - I n o r d e r t o i n v e s t i g a t e whether c o m p e t i t i o n between r e a c t i o n s 16  and 8a i s c o n s i s t e n t w i t h t h e e x p e r i m e n t a l r e s u l t s ,  examined t h e temperature  W for no  k  both  8  dependence o f t h e r a t i o  ' ^ \ n ^ \ E  substrates.  6  ^ 0 0  -  2  The•Arrhenius  D  E  0  5  plot  H  1  0  -  R  C H ) 3  of this  6  ratio  p a t t e r n b e l o w 155°C ( F I G . 1 9 ) , b u t i t i n c r e a s e s  above t h i s linear  temperature.  we  The A r r h e n i u s p a r a m e t e r s  p a r t o f t h e p l o t were E . - E f t  shows  linearly forthe  = 11±4 kcal/mole and /  p  * The h e a t s o f t h e s e r e a c t i o n s w e r e e s t i m a t e d u s i n g t h e p a r t i a l b o n d c o n t r i b u t i o n s method'"'01 a n d t h e h e a t s o f f o r m a t i o n AHf ( > ) = 12.7 - k c a l . / m o l e H O and A t l f ( [ > — C H 3 ) = 5-5 k c a l . / m o l e d ™ F r o m t h e s e v a l u e s t h e p a r t i a l c o n t r i b u t i o n s ([>—-H) = 2 . 1 k c a l / m o l e a n d ( [ > - C ) = 4.5 k c a l . / m o l e w e r e o b t a i n e d . Assuming t h a t (O-H)-(O—0) = ( C - H ) - ( C - O ) , a n d t h a t ( > - H ) - ( [ > - C 0 ) = ( C - H ) - ( C - C O ) t h e p a r t i a l c o n t r i b u t i o n s (>—0) =-10.2 k c a l . / m o l e a n d ([>- CO) = - 1 2 . 6 k c a l . / m o l e were f o u n d . To estimate t h e heat o f f o r m a t i o n o f t h e adduct r a d i c a l , t h e f o l l o w i n g p a r t i a l c o n t r i b u t i o n ( c a l c u l a t e d i n S e c t i o n A) was u s e d : ( C g - H ) + 2 ( C o - C ) = 41 k c a l . / m o l e . T h u s , we f i n d A H f ( [>- CO2C3H5C2H5) =• A H f ( C 2 H 5 C 3 H 5 C O 2 <| ) = - 5 4 k c a l / m o l e T h i s v a l u e , t o g e t h e r w i t h t h e f o l l o w i n g v a l u e s was u s e d t o f i n d AH16 a n d A H s : A H f ( C H 0 - C H - C H 2 ) = 5 8 . 0 k c a l . / m o l e 1 ° ; 4 H f ( 0 ) = 6 0 . 0 kcal./mole127; A H f ( C ^ H ^ n ) = - 5 . 0 k c a l . / m o l e ( r e f . 102); A H f ( C 0 ) = -94 k c a l . / m o l e . e c  e c  2  1 0 2  2  128 A^^/A  lo o= Q  6 2 10 - .  surprising,if  The d i f f e r e n c e b e t w e e n Y,  and E  l  we c o n s i d e r t h a t  imparted t o t h e adduct  i s not  oo  Ar  0  i n r e a c t i o n 16 t h e e n e r g y  radical  b y t h e f o r m a t i o n o f a C-G  b o n d , t o g e t h e r w i t h t h e t h e r m a l e n e r g y , must be s u f f i c i e n t to  cause  which  t h e s i m u l t a n e o u s r u p t u r e o f t h r e e C-C b o n d s , t w o o f  a r e a t r e l a t i v e l y d i s t a n t p o i n t s i nt h e adduct '  radical  ^-CI-L _ 2 L  CH^CH CH„CH-^-CH » ' > '• • C 0 ' • • » • CH 0  5  d  0  c.  o  d  c.  \  -CtL 2  T h i s i s an e n e r g e t i c a l l y v e r y demanding p r o c e s s ; t h e r e f o r e would  be e x p e c t e d t o be g r e a t e r t h a n E g b y a t l e a s t  11 k c a l . / m o l e .  On t h e o t h e r h a n d , i t i s e x t r e m e l y  unlikely  6 t h a t A^g w i l l therefore  be l a r g e r t h a n Ag b y a f a c t o r o f 1 0 .  conclude  that  We must  a mechanism i n c l u d i n g t h e e f f e c t i v e  c o m p e t i t i o n between r e a c t i o n 16 and r e a c t i o n 8 i s v e r y  / unlikely. S u p p l e m e n t V. excess  A. f u r t h e r - ' r a t i o n a l i z a t i o n o f t h e p r e s e n c e , o f  1-pentene and,of  propylene  of a d d i t i o n o f t h e e t h y l r a d i c a l  c a n be a t t e m p t e d  i n terms  t o the cyclopropane  function  w i t h subsequent d e c o m p o s i t i o n o f t h e r e s u l t i n g adduct C H * + [>—£C0 -)- C H,- — ^ H 1 7 * — v C3H ^ _£ 2 5 ^ \ 2 3 5 -13 k c a l / m o l e -cH;f o  0  J  7  7  CvHr, ^CH-fCO^C.H,-  A  H-ift* '—  0  > CJ3-  *  G E  £  2  3 5 -22  + ^^CH-eCOp^C.H.  C H  >  G ' L l ,  5  kcal/mole 2Z£  >  r  C O 2  C0  +  i  radical v  o  +  TT  " 5  C-jr  2  10  c  c  55  ^^CH-fCOpt-C.H,-""  A H ^ r ? _ and A H . g  -56  kcal/mole  were f o u n d u s i n g A H f ([>—tC025-CjH5) = and A H f ^ 3 7^CH—(-C02v-C3H^j ? l ' / C  H  =  k  a  m  o  l  e  and i n f o r m a t i o n from t h e p r e v i o u s f o o t n o t e . The h e a t s o f r e a c t i o n were" f o u n d b y t h e p a r t i a l b o n d c o n t r i b u t i o n s method';-  129 T h i s m e c h a n i s m was c o n s i d e r e d p o s s i b l e b e c a u s e t h e C-C of t h e cyclopropane  g r o u p must, p o s s e s s - c e r t a i n  character since cyclopropane  bonds  unsaturated  undergoes a d d i t i o n r a t h e r than.  substitution reactions with a variety of ionic  and r a d i c a l  113-115 species.  F o r example, Kharasch  y  bromine r a d i c a l propyl r a d i c a l  reported that the  adds t o t h e c y c l o p r o p a n e 1 1 5  :  0  + Br*  r i n g t o form  a bromo-  > CHgCHpCHgBr  I n a n ' e f f o r t t o p r o v i d e an e x p l a n a t i o n f o r t h e u n u s u a l p r o p e r t i e s o f c y c l o p r o p a n e s , Walsh c o n s t r u c t e d a model o f cyclopropane  i n which  t h e C-C b o n d s a r e f o r m e d f r o m t h e i n t r a 2 ' • a n n u l a r o v e r l a p o f one o f t h e s p h y b r i d i z e d o r b i t a l s o f - e a c h 115 c a r b o n atom a n d t h r e e p - o r b i t a l s . y  T h i s model suggests t h a t t h e r e is'more, p c h a r a c t e r i n t h e C-C b o n d s o f c y c l o p r o p a n e pounds.  t h a n i s u s u a l f o r s a t u r a t e d com-  T h i s i n c r e a s e d p c h a r a c t e r i s a l s o supported by  d i p o l e moment a n d n u c l e a r q u a d r u p o l e  resonance  studies of  116 1 1 7 chloride. ' ' 119 1 2 0  cyclopropyl :. C o u l s o n  and Goodwin,.  '  , followed  hy Randic  1  and  121 Maxsic',  applied  t h e p r i n c i p l e o f maximum o r b i t a l  by v a r y i n g  the state  of h y b r i d i z a t i o n of the o r b i t a l s u n t i l  t h e sum o f t h e o v e r l a p i n t e g r a l s was m a x i m i z e d . ed t h e optimum c o n f i g u r a t i o n 5 C-C b o n d s w e r e s p 2 were sp  "' . hybridized.  on each  They  obtain-  when t h e o r b i t a l s f o r m i n g t h e  hybridized  and those  This type  bent-bond s t r u c t u r e . orbitals  overlap  f o r m i n g t h e C-H b o n d s  of h y b r i d i z a t i o n leads t o a 5  The a n g l e b e t w e e n t h e a x e s o f t h e s p  carbon  i s 101° 3 2 ' , w h i c h  i n d i c a t e s a bend-  i n g o f 20° 4 6 ' :  118 Bernett  h a s shown t h a t  t h e W a l s h m o d e l c a n e a s i l y be  c o n v e r t e d i n t o t h e b e n t - b o n d m o d e l , and t h a t b o t h m o d e l s port the p o s s i b i l i t y go  addition The  that  function  can under-  reactions.  above e x p e r i m e n t a l and t h e o r e t i c a l e v i d e n c e , a l t h o u g h  not r e f e r r i n g s p e c i f i c a l l y c a l t o the cyclopropane and  the cyclopropane  sup-  t o t h e a d d i t i o n o f an a l k y l  function, renders reactions  radi-  1 7 , 18",  17a p l a u s i b l e . . \ The r a t e  o f r e a c t i o n 18 c a n be g i v e n b y R. IS  Q  = DR u  n  „  5 10  + R  n  p-  > 3 6  : ' F i g u r e 19.°  ' -  A d d i t i o n of the e t h y l r a d i c a l propane r i n g (0)  of a l l y l  •  1.31.  to the c y c l o -  cyclopropylcarboxylate  and c y c l o p r o p y l 3 - b u t e n o a t e  (El).  132  The  t h e i r p r o d u c t s are  we  c a n n o t be  measured,  i n d i s t i n g u i s h a b l e from those of  H o w e v e r , i f we t a k e  7 and - 8 . and  18  r a t e s o f r e a c t i o n s 1 7 and  0,  assume t h a t R^y^  into  because  reactions  account that A H ^ C A H ^ ,  then R^r^  and  k , / k ^ = (DR •+ R ) / [ B ] P ^ TJ 17 2 • C H C H C H 2  7  5  Above 1 4 0 ° C , for  the  Arrhenius  3  6  show l i n e a r i t y . E^r,  Arrhenius  2  a linear  plot  parameters =  12  ±  for allyl  2  k c a l . / m o i e '. 1  cyclopropylcarboxylate  of the  plot  are  t h a n w i t h the  f o r c y c l o p r o p y l 3-butenoate slope  widely  of the  plot  with  below  f o r b o t h "compounds  140°C.  high temperature l i n e s  both substrates,  ably higher  than the  such a process.  temperature l i n e 10"^^  10  not  consistent with  2  ~  - 1 3  cyclopropyl 1  •. The  factors  m o l e c . cm.sec. ) are  pre-exponential  a  -1  c o l l i s i o n number < ? 1 0 The  of  y  +  * ^ *^molec7^cm?sec7' f)±s  process.  are  process because t h e i r p r e - e x p o n e n t i a l - 5  lar  1  h o w e v e r , t h e i r p a t t e r n i s more c o n s i s t e n t  bimolecular  of  parameters are  = 23 ± 3 kcal./mole .  1  points  The  (for  median A r r h e n i u s  ir  scattered;  above  20)  + log(A -,/A|)(cm?molec7 sec7 )^ = 6.5 ± 1 . 2  13  140°C,  (FIG.  cyclopropylcar-  cyclopropyl 3-butenoate gives  E  slope  allyl  1  w h i c h has  the  quantity  1 7  B e l o w 14-0 °.C,  the  The  1 0  + log(A /A|)(cm?molec7 sec7 )^ = 13 ±  13  but  4  p l o t s of t h i s  b o t h c y c l o p r o p y l 3 - b u t e n o a t e and  boxylate  ,(  1 0  1 0  consider-  (cm? m o l e c .  f a c t o r of the  sec. low  3-butenoate consistent with  activation-.energy  for this  line  a  bimolecu-  TABLE X I I I : Reaction  0-  RESULTS OP ,'THE K I N E T I C STUDY OF THE CYCLOPROPYL RING Relationship  k  >150°C  15 2^ 10 k  temp.  k  Arrhenius parameters E kcal/mole l o g A a 22 ± 5 12± 3 Consistent 18± 5  All II  ( c m ^ m o l e c . s e c ? ft  2  5  10i C H 5 10 i s o m e r s  i n  D>C H * 2  5  10d All* iv  10± 3  ^and of  >C H *  k  10i  y / k  10q  >140°C  4  a  >140 C 0  10d/ 10q k  C  25 ± 4  a  16± 4 °  molec.cm.^  251 2  5  1 0  *135°C  16^ 8 k  11  l F  C H -{>C0 A11 2  17 C  5  H  1  0  +  R  2  temperature  c  Inconsistent independent  R e j e c t e d scheme.  IP  with  DRc H^/R[>C2H5 2  o f temperature.  scheme.  Inconsistent  with  A^g=10^Ag.  scheme,  k  1 7  /k|  >140°C  23 3° 1  0 ± 2  C  - Inconsistent  with Arrhenius  parameters.  R e j e c t e d scheme.  (cm^molec? s e c ? ft  OP + A l l 2  <140°C  12 ± 2 °  -6 ± 2 ° ' P o s s i b l e  scheme  3-butenoate a= a l l y l  and t h e absence  a  25± 2 61  RQ^JJ^/DRQ^JJ^Q  C^H^Q  2  5  150°C).  2  Rejected k  Preferred  DRc H4/ [>C H5 i n d e p e n d e n t  ^Rejected  A11-+ C 0 +  2  (above  J o f 2-pentene.  30±3  16  V  ^and  C  2  2  temperature.  a  + C H*  [>co c H  R  30 ± 3 ^ I n c o n s i s t e n t w i t h of  k  RQ^J^/DRC^JJ^Q ,  with  D R c 2 H 4 / [ > C2H5 i n d e p e n d e n t  scheme  25± 4 16i  m o l e c . cm.7^.  Remarks  C  (  #  OPENING  cyclopropylcarboxylate  system;  c= cyclopropyl  f o r cyclopropyl  (below  3-butenbate system.  140°C). V>J  134 .(12  ±2  kcal./mole) i s j u s t i f i a b l y  tion 7  (7.6 kcal./mole),  than r e a c t i o n 7;  since  2  C H*. + C H = C H C H C 0 < 2  2  reaction 17 i s less  for  reac-  exothermic  > C^CT^CHCf^CO^  2  AH 2  than that  '  CpH* +• C H = C K C H C 0 < 2  higher  = -24.6  7  (7)  kcal./mole*  > CH =CHCH C0 CHCH C Ey  2  2  2  2  2  (17)  2  •CH2 AH Also,  i t i s reasonable to  character  i n the  1 7  =  -13.0  kcal./mole*  .  e x p e c t t h a t E^^E,-,, s i n c e  cyclopropane  function,  although  the  p  pronounced  e n o u g h t o make a d d i t i o n p o s s i b l e , i s n o t  as p r o n o u n c e d as  the  be  double bond.  qualitative 17  b a s i s , f o r the  b e l o w 140°C i n t h e  since of  A similar  the  this  propyl  trend  system  cyclopropyl  allyl  shown b y resembles  ring  with  propylcarboxylate Arrhenius  system,  scattered low  low  3-butenoate are  trend. are  the  Arrhenius  partially  results for allyl  p l o t s f o r both substrates  cyclo-  addition to  B e l o w 140°C, t h e  the  for  points  '  h a v e shown t h a t  and  temperature  temperature l i n e -  show a s i m i l a r  consis--. cyclo-  A b o v e 140°C, inconsistent  the with  process.  Conclusion  t o the  cussion  five  propyl  cyclopropylcarboxylate  is possible.  such a process,  a  reaction  the  s u p p l e m e n t we  a d v a n c e d , on  occurrence of  the  parameters f o r cyclopropyl  s u c h a.  possible  3-butenoate.  In this  tent  argument can  in  of  ring.  Supplement.  possible  Scheme I on  TABLE X I I I  summarizes the  mechanisms f o r o p e n i n g of the i t s own; p r o v i d e s  * E s t i m a t e d by p a r t i a l b o n d c o n t r i b u t i o n s information.in previous footnotes.  the  most  dis-  cyclo-  probable  ,101 method from  135 explanation III,  IV,  and  o f p r o p y l e n e a b o v e 140°C, a l t h o u g h  make a m i n o r c o n t r i b u t i o n . scheme, w h i c h on i t s own  provides  they  experimental- data  and  same p r o d u c t s  allyl  Since  both c y c l o -  cyclopropylcarboxylate  i n t h e i r r e a c t i o n s w i t h ''the e t h y l  Therefore,  we  d e r i v e d the  tionships f o r both substrates.  gave  whether our  experimental  f a c t o r i l y , , and two  see  substrate  data  f i t thes.e  whether there  are  mecha-  s e c t i o n we  rela-  examine  relationships satisd i f f e r e n c e s between  systems.  TABLE X I I g i v e s t h e A r r h e n i u s t i o n s of the  any  the  radical,  same r a t e c o n s t a n t  In t h i s  rela-  influence  r e a c t i o n s were b e l i e v e d - t o p r o c e e d by p a r a l l e l  nisms.  have  t c derive  to i n v e s t i g a t e the  o f t e m p e r a t u r e on v a r i o u s r a t e c o n s t a n t s ' .  these  the  I n t h e k i n e t i c a n a l y s i s we  3 - b u t e n o a t e and  may  • •  t i o n s h i p s w h i c h w o u l d e n a b l e us  propyl  of  Alternatively, this  an i l l u s i o n a r i s i n g f r o m i n s u f f i c i e n t p r e c i s i o n i n  Discussion.  parameters f o r the  e t h y l r a d i c a l w i t h t h e two  c a l c u l a t i o n of these  p a r a m e t e r s was  m e c h a n i s m c o m p r i s e d o f r e a c t i o n s 1-8 not  only  a plausible explanation  r e l e v a n t measurements.  the  may  a r i s e from a combination of sources or  t r i e d t o i n t e r p r e t our  IX,  excess  Scheme V i s , h o w e v e r , t h e  e x c e s s o f . 1 - p e n t e n e b e l o w 140°C.  e x c e s s e i t h e r may be  Schemes  V were e l i m i n a t e d as u n i q u e s o u r c e s o f  1 - p e n t e n e and  the  above 150°C.  of the r e s u l t s o b t a i n e d  substrates.  b a s e d on t h e and  t a r y r e a c t i o n s 15-18, u n l e s s  r e a c t i o n 18  is  The  simple  1 0 - 1 4 , and  a f f e c t e d by t h e p o s s i b l e p a r t i c i p a t i o n o f t h e  reac-  i t is  supplemen-  significant,  136 •when R^Q = Rg + R ^ g  a n d t h e sum k ^ g + k g must be s u b s t i t u t e d  5  f o r k g i n e x p r e s s i o n D3; confirmed, The and  this  e x c e p t i o n cannot  h o w e v e r ' be  s i n c e t h e A r r h e n i u s - p l o t f o r r e a c t i o n 8 was  linear  p a i r s of Arrhenius parameters f o r the r e a c t i o n s 6  7 do n o t v a r y s i g n i f i c a n t l y when t h e s u b s t r a t e i s c h a n g e d  Thus, w i t h i n t h e l i m i t s o f e x p e r i m e n t a l butenoate.,  allyl  ( S e c t i o n A)  e r r o r , c y c l o p r o p y l 3-  c y c l o p r o p y l c a r b o x y l a t e and a l l y l  show t h e same r e a c t i v i t y  3-butenoate  towards the e t h y l  radi-  c a l i n b o t h hydrogen a b s t r a c t i o n and a d d i t i o n t o t h e double bond. The  Arrhenius parameters f o r the decomposition  adduct r a d i c a l Eg  of a l l y l cyclopropylcarboxylate A  = 16.0 ± 0.6 k c a l . / m o l e ;  10?*  Q  ^ °* sec7'  6  5  are i n good agreement w i t h t h e c o r r e s p o n d i n g 39 • parameters f o r a l l y l Eg and  f o rallyl  A  Q  A  Q  '  10  1  1  *  •in U-  +  ,0.5. k c a l . / m o l e ;  However, t h e h e a t s  Arrhenius  /  3-butenoate  = 17.0  1  propionate-^'  = 18.2 1 2.6 k c a l . / m o l e ;  Eg  of the  10  of the corresponding  1  * sec~  1  5  1  o 3 -1 - * sec. u  9  dismutation reactions  o f these- t h r e e s u b s t r a t e s [>C0 C H 2  C  5  !>• + C 0  1 0  2 5 °2^5 10 H  C  °2 5  H  H  G H C0 G H 3  5  2  5  show t h a t A H  1  g i  0  C "H  ^ E  E - « E --^E .... 0  0  ol  o l  has  5  Q  8 i  5  +  C  0  + C H  2  ?  5  +  + C0  5 10 H  ; A H  8ri All  + C^Q,  , and t h a t A H  8 i  Qm  Q i  =  =  15  ~ * 5  8  k  kcal./mole cal./mole  =-7-5  > AHg^, AH  g i i i  ,  kcal./mole whereas  T h i s c a n be e x p l a i n e d o n l y i f r e a c t i o n 8 i  OH1  a distinctly different  8xi and 8 r J i .  2  C  ;A H  1 Q  The t r a n s i t i o n  transition  s t a t e from r e a c t i o n s  s t a t e o f 8 i must i n v o l v e a n  137 almost complete s e p a r a t i o n  o f t h e 0°,  and C^H^Q g r o u p s ,  C0  o  whereas t h e t r a n s i t i o n s t a t e s o f 8iL and 8 m , discussed  i n s e c t i o n A, a r e t h o u g h t t o i n v o l v e a l a r g e r b e t w e e n t h e C^H^Q  separation and  £2^5  The for  o  r  ^3^5  Arrhenius  cyclopropyl  =12.3  Eg  a n d CC^ g r o u p s t h a n b e t w e e n t h e  groups. parameters of the dismutation  - 0 . 6 kcal./mole;  C H C0 <|; 10  > 5 10 C  2  H  Although these value  A  Q  = 10 * 7  +  G 0  2  +  t>* 5 ^ 8  =  1  °* secT 5  5  k  c  a  1  be s o , s i n c e l  -/  m  o  l  e  o f E g a n d A-g' a p p e a r a n o m a l o u s , t h e  o f kg from which they are d e r i v e d  nitude  t o the corresponding  The  5 ±  should  values  pionate  reaction 8  3-butenoate a r e d i s t i n c t l y l o w  T h e r e i s no p a r t i c u l a r r e a s o n why t h e y 5  as has been  a r e o f s i m i l a r mag-,  rate constants  of the a l l y l pro-  system. t r a n s i t i o n s t a t e f o r r e a c t i o n 8 i n each o f t h e a l l y l  cyclopropylcarboxylate,  c y c l o p r o p y l /3-butenoate a n d a l l y l  butenoate systems i s c o n s i s t e n t i  3-  with  o f b o n d s o n b o t h sides'- o f t h e C0  (a)  extension  (b)  considerable  (c)  v e r y l i t t l e d e l o c a l i z a t i o n i n t h e r a d i c a l t o be r e l e a s e d .  Conclusion.  derealization'.'energy  The s t u d y o f t h e r e a c t i o n s  boxylate. leads (1)  to the following  i n t h e CO2 g r o u p .  of the ethyl  w i t h c y c l o p r o p y l 3-butenoate and w i t h a l l y l  group.  2  radical  cyclopropylcar-  conclusions:  t h e r e a c t i v i t y o f t h e d o u b l e bond and  methylenic  h y d r o g e n atoms o f the' a l l y l g r o u p t o w a r d s t h e e t h y l  radical  d o e s n o t a p p e a r t o be i n f l u e n c e d , s i g n i f i c a n t l y e i t h e r b y t h e presence of the carboxyl  g r o u p o r b y t h e n a t u r e "of i t s  138 linkage  to the a l l y l  group.  Er, f o r t h e s u b s t r a t e s for  126 hexadiene-1,5.  The a c t i v a t i o n e n e r g i e s  studied  and  so f a r i n t h i s t h e s i s , and a l s o  and octene-1  4  , are not s i g n i f i c a n t l y  different. (2)  cyclopropyl r a d i c a l s are obtained  i n good  yield  f r o m t h e s e n s i t i z e d d e c o m p o s i t i o n s o f b o t h c y c l o p r o p y l 3butenoate. and a l l y l  cyclopropylcarboxylate.  The r a t e o f  formation  o f c y c l o p r o p y l r a d i c a l s i s measured by t h e r a t e o f  formation  of carbon d i o x i d e .  duct,  and a l l y l  1-pentene i s a l s o a major  r a d i c a l s a r e formed i n small y i e l d .  sources of cyclopropyl r a d i c a l s , both substrates vantage over cyclopropylcarboxaldehyde, the r e s p e c t i v e dissociate  intermediates  completely,  a t 174°C, w h i c h i s a h i g h e r  As  have an a d -  OGO^  a n d [/"C^C  i n t h e i r decomposition  reactions  whereas  since  pro-  [>C0' i s o n l y 4 0 $ d i s s o c i a t e d  temperature than any used i n t h i s  study. (3)  the ratio p f the rates of the disproportionation to  •the c o m b i n a t i o n r e a c t i o n s b e t w e e n e t h y l a n d c y c l o p r o p y l c a l s has a median v a l u e  o f 0.220 ± 0 . 0 3 0 ,  t e m p e r a t u r e b e t w e e n 110 a n d 170°C.  This  t e m p e r a t u r e i m p l i e s t h a t t h e m o l e c u l e 'of  radi-  i n d e p e n d e n t ofindependence of ethylcyclopropane,  formed by combination,ox t h e e t h y l and c y c l o p r o p y l r a d i c a l s , is  s t a b i l i z e d by c o l l i s i o n before  i t can undergo e i t h e r i s o -  m e r i z a t i o n . o r d i s s o c i a t i o n , v/ith o r w i t h o u t i s o m e r i z a t i o n o f the  cyclopropyl (4)  substrate  fragment.  Metathesis  between t h e ' c y c l o p r o p y l  was,observed and measured.  r a d i c a l and t h e  The a c t i v a t i o n e n e r g y  139 E^  e x c e e d e d E ^ by 2 ± 1 k c a l . / m o l e .  Z|  (5) allyl  The  propylene  radical,  1-pentene are d e r i v e d from  i s most p r o b a b l y f o r m e d i n t h e  [> .  > CH -CH-CH 2  formation of a l l y l n  w  excess  which  /BR TJ = 0.10 °3 6 °5 10 b e t w e e n 140 and 170  R„  and  reaction  2  r a d i c a l s i s v e r i f i e d by t h e  ± 0.03,  the  independent  of  ratio  temperature  C.  E. R e a c t i o n s o f t h e E t h y l R a d i c a l w i t h t h e M e t h y l E s t e r o f Cyclohexa-1,4-diene-3-carboxylic  Acid  P r e v i o u s work i n t h i s l a b o r a t o r y has hexadienyl r a d i c a l s are produced 57 103 with cyclohexadiene-1,4. ' y  R* w h e r e R*  i s CH^  +  <  o r C H^ 2  )  shown t h a t  cyclo-  when a l k y l r a d i c a l s r e a c t •  > RH  +  o r sec-C-^H,*;. I t h a s 7  a l s o been  found  t h a t t h e c y c l o h e x a d i e n y l r a d i c a l t h u s f o r m e d i s consumed, t o a m a j o r e x t e n t by i n t e r a c t i o n w i t h R"  radicals,  and  m i n o r e x t e n t b y d e c o m p o s i n g t o y i e l d b e n z e n e and  t o a'  a hydrogen  10-5 atom. ^  I n the present study, cyclohexadiene-1,4  by c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e , radical.  T h i s r e a c t i o n system  these reasons: activity  (a)  t h e c a r b o x y l g r o u p may  two  i s the  ethyl  i s of t h e o r e t i c a l i n t e r e s t f o r  of the s u b s t r a t e towards (b)  and R'  xs r e p l a c e d  the e t h y l  i n f l u e n c e the r e radical;  t y p e s o f r a d i c a l s may  be  generated  when t h e e t h y l r a d i c a l a b s t r a c t s a h y d r o g e n atom f r o m t h e strate  sub-  TABLE X I V REACTIONS OF THE ETHYL RADICAL WITH METHYL CYCLOHEXA-1,4-DIENE-5-CARB0XYLATE * °K  383 393 398 405 410 41? 421 428 433. 444 450  [D]  (CO)  [B]  (COp)  5.21 1.30 6.27 1.35 5.05 1.44 5.14 1.50 4.95 1.47 5.27 1.65 5.64 1.15 5.85 1.40 5.51 1.21 6.27 1.50 5.14 1.15  13.22  (C H ^(C H^ 4  ( C  2 4 H  1 C  )  • 6.75 0.90 16.61 7.31 1.00 0.03 13.50 5.37 0.06 0.75 14.58 5.55 0.81 0.07 5.00 13.50 0.12 0.79 16.04 5.71 1.10 0.17 15.95 4.69 0 . 3 5 0.98 4.00 14.70 0 . 5 0 1.15 3.60 13.97 0.61 0.91 21.94 4.75 1.11 . 1.05 3.21 17.11 1.40 0.09  2  (C HQ) 3  6.81  -  —  11.13 —  10.38 —  11.90  -  10.91 0.01 15.33 0..03 14.20 0.06 15.00 0.09 14.19 0.11 21.68 0.15 17.88 0.20  (CH ) CECpH^) CECH^ ClMBzO) 4  (CgHgXttCpH^ OICH^) — — —  0.02 0.03 0.06 0.05 0.08 0.05 0.11 0.07 0.16 0.13 0.32 0.23 0.45 0.30 0.51 0.37 0.96 0.44 1.33  0.54 1.64 0.84 2.04 0.61 2.11 0.80 2.66 0.61 2.22 1.27 3.89 0.72 2.47 0.94 2.81 0.66 1.95 1.08 3.30 0.87 2.38  _ -  1.-15 1.44  — —  1.39  —  -  —  1.76  —  1.56  — —  2.06  —  —  0.05 0.02 0.10 0.05 0.15 0.16 0.24 0.25 0.42  M  M  — —  . Et  1.47 2..13 1.96 2.21 1.95  c  0.94 0.75 1.02 0.86 1.06 0.79 1.07 0.94 1.06 0.86 1.18 0.99 1.09 0.77 1.14 0.82 1.13 0.73 1..10 0.75 1.16 0.79  (bl/aD M ... M E Me (a/c) ( W a l l ) D k  k  MEI  k  k  MEH  H  _  0.53  -  0.50 0.50 0.51 0.72 0.51 0.50 0.55 0.55 0.53 0.67 0.47 0.88 0.57 1.00 0.52 0.92 0.47 0.94 0.50  • 1.42 0.23 1.15 0.24 1.52 0.22. 1.46 0.22 1.70 0.23 1.10 0.18 1.36 0.20 1.50 0.25 1.97 0.33 1.36 0.22 1.49 0.27  132 —  138 3.6 158 5.3 160 7.1 158 11.2 191 10.3 271 28.2 282 32.4 320 50.1 324 63.1 447 100  Key *  The d u r a t i o n  o f e a c h r u n was 60 m i n u t e s .  24.5 74.2 34.7 81.1 27.5 97.3 34.0 116 28.2 106 49.1 155 47.2 145 53.7 174 39.8 155 50 ..1 182 . 67.1 251  MEI K  MEIE 38 60 44 70 . 46 79 56 95 49 86 67 130 68 132 85 141 . 87 136 78 153 106 212  overleaf.. •4>  o  KEY TO TABLE XIV [  ]  =  -17 -3 Conc.xlO 'molec.cm.; D = d i e t h y l k e t o n e ; -12 -3 —1  (  )  =  Rate o f f o r m a t i o n x 10  MBzO Et  =  M e t h y l benzoate  =  ( C^H  .=  ( C H  M Me  R  R  6  +  R  1 0  +  H  R  R  2  2  R  5  8  ic H5  5  + ICH ; + IICH ; + R M B z Q . . ) / ( R  5  5  IIC H );  yb MBzo  y  =  C IC H + IIC H )/ IC H  (bl/al)  =  2yb MBzO  ME  =  10l3(k Af)  k  MEI  =  io  k  MEII.  .  i o ^ k  k  k  a  MEI k' MEI I  R  =  2  2  R  2  2  / 3 R l  5  (k  6  (  1  5  (k  io 3 1  (  k  6  6  I  .  2  Af)  I  I  A f )  A|) i  A  5  A ) 2  [B]Rc H 4  1 0  2  a  + IIC H R  5  6  2  (bU/alE) =  + ICH R  5  y R b  5  M B z 0  + RlICHj)/3RlIC H 2  5  (  l  i  2  C H ;  6  l  5  k  yb = 1 - 6 y a / ( 1 + o - 6 y . ) '  5  R  5  R  io  1  / ( R  R  5  + RlICH )/RC0  =  +  R  5  (d/c)  R  . •.  R  (RCHzj. + R C H + I C H  =  molec.cm^sec.  ° 2 6 ~ MBzO)/ CO  IC H5 + I I C H  R  6  B - substrate  |)  (1 +  (d/c))Ric H /[B]R^H 2  5  1 0  (1 + ( d / c ) ) R n c H / [ B ] R ^ H i o s «, 2  0  5  + (bI/aI)>R ic H /[B]Rg 2  (1 + ( > I I / a I I ) ) R  5  I I C 2 H r 5  , 3 -1" - 1 . % (cm.molec.sec.)' <  4 H l 0  /[B]R^  H l 0  142  CpH* +  > ^j^-COOCH^  <^~Y  COOCH  or  3  I f t h e r a d i c a l s I * and I I * a r e produced, i t i so f i n t e r e s t t o know how t h e y i n t e r a c t w i t h t h e e t h y l (c)  radical.  e i t h e r o f t h e r a d i c a l s I * o r I I * may d e -  c o m p o s e , i n a n a n a l o g o u s way t o t h e c y c l o h e x a d i e n y l to give  a hydrogen  ^VcOQCH^  o  r  atom a n d a s t a b l e p r o d u c t  (f^X  > * H  COOCH-,  +  3  COOCH, I*  I I *  3  methyl  benzoate  The r a d i c a l I I * , b u t n o t t h e r a d i c a l I * , may a l s o t o y i e l d benzene,  decompose  caroon d i o x i d e , and a methyl r a d i c a l  O —'  O . —  COOCH-,  N  This  radical,  3  alternative i s l i k e l y  +  /  C  0  2  +  CE  i  t o be t h e p r e d o m i n a n t  r e a c t i o n by  which I I * decomposes, s i n c e i t i n v o l v e s b o t h t h e f i s s i o n o f a weaker bond* and t h e p r o d u c t i o n highly  o f carbon d i o x i d e , which i s  stabilized.  Results.  TABLE X I V s u m m a r i z e s  theresults, of eleven experi-  ments, each performed under f u l l . , l i g h t  i n t e n s i t y .for s i x t y  minutes, and each l y i n g i n t h e temperature range *  110-177°C.  The*"^^-COOCHj- b o n d i s e x p e c t e d t o b e w e a k e r t h a n t h e  <^>-CH b o n d b e c a u s e 3  dissociation;  of thepotential release  i t i s known t h a t t h e <C)~~ p- b o n d (DC^y-CH^) =  11.5 k c a l . / m o l e ) i s w e a k e r t h a n t h e /^V-H b o n d 24.0  o f COp o n i t s  CH  10?  kcal./mole).  (J)(<T^\-E)  =  143 The p o s s i b i l i t y  of u n s e n s i t i z e d thermal or photo-  decom-  p o s i t i o n o f m e t h y l c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e was e x a m i n e d b y i l l u m i n a t i n g i t w i t h U.V. l i g h t  ( 3 1 3 0 £) i n t h e  a b s e n c e o f d i e t h y l k e t o n e , f o r a p e r i o d o f 60 m i n u t e s a t t h r e e d i f f e r e n t t e m p e r a t u r e s , n a m e l y a t 1 3 0 , 1 5 0 a n d 180°C. The  experiments performed  at  130  and 1 5 0 ° C d i d n o t r e s u l t i n  the p r o d u c t i o n o f any c a r b o n d i o x i d e ;  a t 180°C a v e r y  amount o f c a r b o n d i o x i d e was p r o d u c e d .  small  On t h e b a s i s o f t h e s e  r e s u l t s , we c a n s a f e l y c o n c l u d e t h a t t h e r m a l a n d p h o t o - decomp o s i t i o n of methyl cyclohexa-1,4-diene-3-carboxylate are negligible  i n the temperature range, 110-177°C used t o study  its: reactions with the ethyl  radical.  Throughout the temperature range, the r e a c t i o n s o f the e t h y l r a d i c a l with methyl cyclohexa-1,4-diene-3-carboxylate gave t h e p r o d u c t s :  c a r b o n monoxide, c a r b o n d i o x i d e , , methane,  ethane, e t h y l e n e , propane, and  butane, benzene, methyl  certain other high b o i l i n g point  compounds.  I d e n t i f i c a t i o n of High B o i l i n g Point Products. p r o d u c t s were c o l l e c t e d vacuum l i n e  benzoate,  The h i g h b . p .  i n the cold f i n g e r , w h i l s t the heated  was k e p t ' a t 100°C.  A sample from t h i s  was i n j e c t e d o n t o a p o l y e t h y l e n e g l y c o l  mixture  c o l u m n , w h i c h was  t h e n h e a t e d t o 160°C w h i l s t n i t r o g e n g a s a t 12 p . s . i . passed through.  was  S m a l l amounts o f t h e l o w b o i l i n g p o i n t p r o -  ducts, w h i c h had been r e t a i n e d i n t h e h i g h b.p. m i x t u r e , were eluted within the f i r s t  t e n minutes.  No p e a k s a p p e a r e d  i n t h e t i m e d u r i n g w h i c h t h e p r o d u c t s CpH^CgH,-,  anc3  -  G H  3 5 7 C  103 would have been e x p e c t e d  ( 1 0 t o 30 m i n u t e s  with-  ).These  H  144 s u b s t a n c e s were t h e n  eluted:  E l u t i o n Time (minutes) 4J  methyl cyclohexa-1,4-diene-3-carboxylate (reactant)  53 55  methyl I' II' I II  62 66  70  The  identification  benzoate L  products  J product I and the minor product I ' , and the p r o d u c t I I  and t h e m i n o r p r o d u c t I I ' , w e r e shown t o be a s s o c i a t e d v / i t h the  r a d i c a l s I * and I I * r e s p e c t i v e l y ,  by the f o l l o w i n g  17 A m i x t u r e , o f about  4.5x10  -3 ' molec.cm. m e t h y l 1 7 - 3  method.  d i e n e - 3 - c a r b o x y i a t e a n d 7x10 illuminated  at f u l l  molec.cm.  cyclohexa-1,4-  d i e t h y l k e t o n e was  i n t e n s i t y f o r 24 h o u r s , and t h e h i g h b . p .  p r o d u c t f r a c t i o n was c o l l e c t e d .  T h i s p r o c e s s was r e p e a t e d  t h r e e t i m e s , w i t h t h e same r e a c t i o n c o n d i t i o n s , a n d t h e g a t e h i g h b.p.  p r o d u c t s were i n j e c t e d  aggre-  onto a p o l y e t h y l e n e  oe l r ec o lc u o ny, i tm hm ee r sp ir no gd u tc ht es Io u, t lI eIt , In e' e, dalned Ig Il 'y c w om ln l e. c t eOn d fs re ap ca tr ai to en la yt i b o f t h e V.P.C. i n t o s e p a r a t e N.M..R. t u b e s c o n t a i n i n g C D C l ^ , • w h i c h were i m m e r s e d i n a n i c e b a t h .  1  The N.M..R.. s p e c t r u m o f  e a c h o f t h e s e e l u t e d p r o d u c t s was o b t a i n e d a n d c o m p a r e d the  spectrum o f methyl  d i l u t e d i n CDC1-,.  with  cyclohexa-1,4-diene-3-carboxylate  The c h a r a c t e r i s t i c c h e m i c a l s h i f t s a n d  5  r e l a t i v e peak areas f o r the s p e c t r a o f I , I I , and methyl cyclbhexa-1,4-diene-3-carboxylate  a r e g i v e n i n TABLE XV.  T h e s e t h r e e s p e c t r a a l l ' p o s s e s s t w o p e a k s i n common:  one o f  t h e s e h a s been a s s i g n e d t o t h e v i n y l p r o t o n ; the. o t h e r t o  TABLE XV COMPARATIVE N.M.R. SPECTRA OF  IC2H5,  I I C H ^ AND METHYL CYCLOHEXA-1-4-DIENE-3-CARBOXYLATE* 2  $ i n PPM  Sample  C H 2  IC H 2  d COOCH3  5  H  H  OR  5  H  l  H  Multiplicity  % Area  H, where x is  5.5 t o 6.1 2.2 t o 2.6 3.5 t o 3-6 3.4 -  multiplet multiplet multiplet singlet  42 18 9  a b c d  5. 5 t o 6. 1 2. 2 t o 2. 6 3. 5 t o 3- 6 3:4 1. 0 t o 1.4  multiplet multiplet multiplet . singlet multiplet  25  a b c d e  5. 5 t o 6.1 2. 2 t o 2.6  multiplet multiplet multiplet singlet multiplet  31  19  0 22 34  COOCH3  aH I I C 2H5 •  #  SOLVENT:  OR  H  3. 5 t o 3.6 3.4 0 1. t o r . 4  H  CDC1  3  .  STANDARD:  tetramethyl  silane  28 8 7  21 36  a b c d e  vn  146 the p r o t o n s o f t h e methyl e s t e r group.  The c h e m i c a l s h i f t s  o f t h e p e a k s a r e 5.5 t o - 6 . 1 a n d 3°4 PPM r e s p e c t i v e l y .  The  s p e c t r a o f I and methyl c y c l o h e x a - 1 , 4 - d i e n e - 3 - c a r b o x y l a t e b o t h p o s s e s s a p e a k w i t h 8 = 2.2 t o 2.6, w h i c h i s a s s i g n e d t o the methylenic protons n o t adjacent t o t h e carboxyl The  s p e c t r a o f I I and methyl  group.  cyclohexa-1,4-diene-3-carboxy-  l a t e b o t h p o s s e s s a peak w i t h S  =3„5  t o 3.6, w h i c h i s a s s i g n -  ed t o t h e p r o t o n a d j a c e n t t o t h e c a r b o x y l g r o u p .  The s p e c t r a  o f I a n d I I b o t h h a v e a p e a k w i t h 6 = 1.0 t o 1.4, w h i c h i s ^ n o t present i n t h e spectrum o f methyl boxylate;  cyclohexa-1,4-diene-3-car-  t h i s peak c a n be a s s i g n e d t o t h e e t h y l group.  A  comparison o f t h e areas o f t h e v a r i o u s peaks i n these t h r e e spectra v e r i f i e s these assignments  P r o m t h i s N.M-E.,- e v i -  d e n c e , we c o n c l u d e t h a t t h e p r o d u c t s I a n d I I p o s s e s s t h e basic s t r u c t u r e of methyl cyclohexa-1,4-diene-3-carboxylate, but w i t h , i n a d d i t i o n , an e t h y l group a t t a c h e d t o a m e t h y l e n i c c a r b o n atom. The  above e v i d e n c e i n d i c a t e s t h a t t h e p r o d u c t I c a n have  either of the structures ..' %  C H 2  5  V/-w 2 5 G  EL o  X  X  V-C00CH  7  H, b  H  COOCH, 5  N e i t h e r o f t h e s e s t r u c t u r e s p o s s e s s e s a c - t y p e h y d r o g e n atom, but t h e y b o t h p o s s e s s a t l e a s t two b-type  ( s e e TABLE X V ) .  B o t h o f t h e s e s t r u c t u r e s may be d e r i v e d f r o m t h e c o m b i n a t i o n of an e t h y l r a d i c a l w i t h t h e r a d i c a l I " :  147 H •H. °2 5 H  H  X3^  +  H The  H  \ A  * X^~  3  _ C 0 0 C H  CpH^  C 0 0 C H  C H  2"5 0  X^X  °r  3  _  fl  H  COOCH  p r o d u c t I I c a n have e i t h e r o f t h e s t r u c t u r e s  ^2^5  H 5  >D<COOCH-,  H, h The  i  common f e a t u r e  possess  ~  ^  \/ H  DCCOOCH  3  -  of these structures  i s that they  a c - t y p e h y d r o g e n a t o m ( s e e TABLE X V ) .  t u r e s - may be d e r i v e d cal with  7  both  Both  struc-  from t h e combination o f t h e e t h y l r a d -  the radicalI I " : H G  c  +  2 5 h  O  X  2 5  —>  COOCH,  W  _  H  H  3  -  H  _V  ;  XIX  -'  __  o r  COOCH,  3  H COOCH,  5  T h e r e f o r e , we c a n c o n c l u d e t h a t  t h e p r o d u c t s I and I I a r e  IC H  S i m i l a r l y , by comparison o f  2  3  a n d IICpJH^ r e s p e c t i v e l y .  t h e N.M..R. s p e c t r a  f o rI', I I  diene-3-carboxylate I C H j and I I C H ^  p r o d u c t s I ' and I I  with  2 2  > C H  2C H'  > C H  C H* + C H C O C H  5  2  2  4  2  2  3  2  2C H* —  5  5  (1)  o  5  C H* + C H C O C H  scheme:  > 2 0 H * + CO  4  2  2  .  were i d e n t i f i e d a s  1  the following reaction  C-Hr-COC-H,- —=  2  cyclohexa-1,4-  The n a t u r e a n d d i s t r i b u t i o n o f t h e p r o -  ducts are consistent  5  , and m e t h y l  respectively.  Kinetic Analysis.  2  1  2  :  (2)  1 Q  4  + C H 2  -> C H C 0 C H 2  4  2  4  9  2  + C H  5  -> C H C 0 C H  (5)  6  2  5  (4)  6  "  . (5)  148 ^  C H 2  (61)  COOCH-  +  6  ( d e n o t e d 1°) G  2 5 H  +  C H COOCH , 6  7  5  (611)  2 b COOCH  5 ( d e n o t e d 11°) C  (  V  x  2 5 H  >  -  C  O  O  C  H  (eia^  5  C H* + I * 2 5 0  (6Ia^ COOCH-  (6II ) a i  C~H  '  2 5  CpH^ + 11°  x  —1 C O O C H x  . . 5  x  C Hr- .•' 2  de  ^Ila^  'X300CH  C H' + I * 2  %  (61b)  C H  6  +• C H C 0 0 C H  •> C H  6  +:.C0 +. CH*  2  6  5  $  (6IIb)'  C H'-.+ I I ' 2  II"'  &  (9)"  2  (10) C Hrt 2  -h C H j . CH  C  H  :  +  C  H  *  3 5 CHJ + C H C O C H 2  CH*  +  5  2  C H COOCH 6  7  5  5  + C H  4  -> C H 2  2  (11)  4  (12)  6  CH  4  + GgH^COCgH^  CH  4  + 1°  CH^ + I I '  (14D) (141) (1411)  } (14B)  149  COOCH CH* +: I "  .. "(141a,,)  3  (14Ia ) 2  COOCH,  (1411a,,) COOCH, CH* + I I '  (I^IIap)  COOCH,  (141b)  CH,, + C. H COOCH, 4-  The m a t e r i a l  5  c  (1411b)  b a l a n c e f o r t h e e t h y l r a d i c a l c a n be d e r i v e d  by t h e f o l l o w i n g is  b p c  considerations.  One,pair of ethyl  radicals  g e n e r a t e d f o r e a c h m o l e c u l e o f CO p r o d u c e d , a n d one p a i r  o f e t h y l r a d i c a l s i s c o n s u m e d f o r one m o l e c u l e o f p r o d u c t formed •  i n the reactions  "  R  But  C0  2,3,4, a n d 6 ;  =  R o  Rp  =  R  3  +  R  4-  +  R  6  and  R  where y  b  =  R 6  b  / ( R  6  b  +  R  S  u  M  C H "* 6 b " 1 2 R  2  R  V  +  °4 10  d  and  V  +  2  R  therefore  6b +  R  6  " b C H C0 CH y  R  6  R  1  4  b  5  and  )  2  R  6  5  +  b  R ^  = R  b  c  H  c  o  C  b 3 Thus  M. Et  =  (  C'4"10 A n  R  +  y ^ was c a l c u l a t e d k /k (CH*,C H*) d  c  6  V2 H y b ^C 6H 5O ^ O 2, C H3 ' 6 " ~ 103 R  v  X i  u  r  n c  u  u n  from S u a r t ' s r e s u l t s  R  E  2  1^2" C  U  o  ) / R  0  0  ^ a c c o r d i n g t o which'  = 0.24 a n d k ^ k ^ C ^ , C H * ) = 0 . 3 8 . 6  I f we  150 k,/k ( C X . C X ) d ' c 2 5 6 y  assume t h a t  = k,/k ( C J a * C ^ H C 0 C H , ) and d' c 2 5 o 6 2 3 o  c  k /k (CH',C H°) = k / k ( C H , C H C 0 C H ) , then d  c  6  d  R  Defining  y  c  3  R  R  7 y  14a^'  i s a measurable q u a n t i t y , y  For  a  =  IC H,-  ( R  +  25  9  R  II0 H. o  ) / ( R  25  » w  =  b  6  1  6b/ 6a ^  = ^ a ^ ^ a *  a  6  2  W 14a  6 ]  e  c  5  R  a  n  w  1.6 y  r  '  since * ICH 25 ^ I C - H25  IC H, 0  +  R  + X  5I I C E U 3 R  }  m o s t e x p e r i m e n t s , y ^ was f o u n d t o be u n i t y ; o n l y a t h i g h  2  + R  3  )  J  i  R ^  2  / ( R  1  + R  0  to which the value ratio  1  1  ) . =  smaller  R  12  from t h e q u a n t i t y 2  3  2  2  as a p o s s i b l e  a l l experiments R,j  1  2  2  \  10  + k  1  1  )  statistical  factors for the interactions  and two u n l i k e r a d i c a l s . = ^ »  than u n i t y .  k A?J /(k  (k +  was a s s i g n e d  of thepre-exponential  between two l i k e  For  e  a  r a t e o f r e a c t i o n 1 2 was e s t i m a t e d (R  t  / ( 1 + 0.6 y )  a  t e m p e r a t u r e s d i d i t become s l i g h t l y The  i  .  E  /  ^  '  ^  Thus  R  6  C  A  o  was f o u n d t o be n e g l i g i b l e .  I f we t a k e i n t o a c c o u n t t h e a b o v e d i s c u s s i o n , we c a n w r i t e the  material balance f o r the e t h y l r a d i c a l i n t h e s i m p l i f i e d  form  M  E t  = (R  H  M-  This  +  10  R  H  - R 2 6  H.CO.CH > C0 6 5 2 5 / R  Q  m a t e r i a l b a l a n c e was- f o u n d t o be v i r t u a l l y  t e m p e r a t u r e and t o have t h e average v a l u e value  '  (  E  1  constant  1.05 - 0 J 0 5 .  )  with This  indicates that the addition of the ethyl r a d i c a l to  the  substrate  the  p r o p o s e d mechanism i s r e a s o n a b l y c o n s i s t e n t w i t h t h e e x -  perimental The  c a n n o t be s i g n i f i c a n t .  Also,  i t shows  that  results.  a b s t r a c t i o n o f a h y d r o g e n atom f r o m m e t h y l  cyclohexa-  • Figure  2.1'.  Patterns cal late  and  of m e t a t h e s i s between the e t h y l methyl  (b).  152  radi-  cyclohexa-1,4-diene-3-carboxy••• .  '153 -1,4-diene-3-carboxylate the  generation  by t h e e t h y l r a d i c a l w i l l , lead t o  o f e i t h e r o f t h e r a d i c a l s 1° o r 1 1 ° .  a s s . u m p t i o n was s u p p o r t e d b y t h e f o r m a t i o n  o f the combination  p r o d u c t s IC^H^. a n d I I C ^ H ^ C m a j o r p r o d u c t s ) , (minor  This  a n d l C H ^ and IICH^  products).  The m a i n s o u r c e o f e t h a n e i s r e a c t i o n 6, b u t i t i s a l s o  3,4,12  produced i n r e a c t i o n s C H  R  =  2  R  and t h u s  R  6  6  +  * R  6  R  Q  and 6b.  3 . 4 +R  E, = E  c  R  +  R  6b  R^  0.12 R  =  a  a  n  d  R  R p  =  6b  =  J  -  TT  0.12 R  b C H C0 CRy  y  R  6  132-134 8 •  H  Q  24 R  TT  n  w  h  e  r  ^ b  e  2  5  R^  -  2  6  - R ^ ,and s i n c e  H  12  +  - R^ -. R^ - R  H  2  But  Therefore,  *  = 1  y  =  y  6  R  a  /  (  °*  1+ L  a  6 a ^ 6 a R  a  6 y  2  the following expression i  reaction 6 k ^  R 6  C B * °2  1 2 H  6  '  d  we c a n  f o rthe rate constant of  . E  C H 3  C V  yb 0 H C0 CH  .tB] ^ H  =  ^  S  2  8  6  g  2  1  ;  ,  B  The r a t e  n  * W  +  and. R^ . h a s b e e n shown t o b e n e g l i g i b l e ; t h e r e f o r e derive  }a  Q  "  (E2)  ^  c o n s t a n t s f o r t h e r e a c t i o n 61 a n d 611 c a n be  given by k  6  I  W*! It  =  (RO H I 2  R  2  that  ^ I b ^ M ^ I i ^  +  5  " ( 0 H II  was a s s u m e d  bination the  Af  5  +  E  6IIb  +  E  •  (EJ)  C H >/M C H,, E  6  6  4  t h e r a d i c a l 1° c a n o n l y  (61a) and d i s p r o p o r t i o n a t i o n  0  enter  reactions  i n t o com-  (61b),  whilst  r a d i c a l I I * c a n a l s o u n d e r g o d e c o m p o s i t i o n ( r e a c t i o n 9).  :• V . . Figure  25.  .  •  P a t t e r n s of i n t e r a c t i o n between the cal  and  radicals  the  ..'155 ethyl  radi-  methyl•cyclohexadienylcarboxylate  I * and I I * ' .  10 / 3  156 .The s e p a r a t e  rates of production  o f methyl benzoate i n t h e  r e a c t i o n s 61b a n d 6 I I b c o u l d n o t be measured t h e y were e a c h e s t i m a t e d (a)  The.ratios  combination  experimentally;  i n t w o d i f f e r e n t ways:  (a) and ( b ) .  of the rates of disproportionationt o  o f t h e r a d i c a l p a i r s (CgH^",!*) a n d ( C H ° , I I * ) 2  were b o t h t e n t a t i v e l y s e t e q u a l 6bl  R  R  6bII  6al  where ( d / c ) =  R  0  6aII  7* B  ^Cc-Hc-CO C H , 6 5 2 3  -  r^j. R  t o t h e i r w e i g h t e d mean:  C H I. 2 5  R  0  +  _  0 BvII 2 5  R  C  o  J(-W.I  VH.IP  +  CEC0GE  6 5 2 9 2 5 2 5 mean o f t h e t r u e r a t i o ' s . The q u a n t i t y ( d / c ) was f o u n d t o be constant 0.52  w i t h t e m p e r a t u r e , and t o have t h e average  value  ± 0.04. i  (b)  I f we compare t h e number  o f a v a i l a b l e H atoms i n  each o f the r a d i c a l s I * and I I " ' E  •  R  R  y  R  6  R  R  6bl  6bII  The r a t i o  R  / R  / R  5  6al  =  2  2 y  t  =  5 ][/ 6 i> R  b  a  n  d  5  H  n  e  r  R  e  y  o  r  e  R  6  5  2  5  b C H -C0 CH-/ C H I 6 5 2 y 2 3 R  5 R  c  6aII  a  1  COQCH, 6bII' ' f ^ 1 6 b I I ^ 3 b C H" C0 CH  2 R  b  and  '  5  H ' seems l i k e l y t h a t g j & 2 6 b l ^ 3 b C H C0 CH  Thus,  H  Y^)VcOOCH , 2H a n d I I * : V^Y  I*: it  ,  c  o  o  c ;  ^ C g l ^ C O ^ H ^ ^ C ^ I I although  i t ' f l u c t u a t e s w i d e l y , does n o t  show a n y d e p e n d e n c e o n t e m p e r a t u r e ; i t h a s an' a v e r a g e v a l u e o f 1.46 ± 0 . 2 5 reasonably value  The r a t i o  constant  0.24 + 0 . 0 6 .  R 6  b  I  I  /R  6  a  I  I  —  was a l s o f o u n d t o b e  w i t h t e m p e r a t u r e , a n d t o have t h e average  1 5 7  Based on t h e f i r s t  assumption  ( a ) , the rate constants of the  r e a c t i o n s 61 a n d 6 1 1 c a n he g i v e n b y  The  A.rrhenius p l o t s o f t h e s e  Eg-j- = 4 . 5 t 0 8  kcal./mole;  o  13 13  q u a n t i t i e s gave t h e 5 j j = 5 * 9 ± 0.^5  E  parameters:  kcal./mole  + 1 O S | A / A | (cm?molec7 sec7 )^} = 3 o 9 ± 0 . 5 1  1  6 I  + log<ji\  /A| (cm?molec7 sec7 )^} = 5-3 1  6 I I  Based on t h e second assumption  0.3  1  (b), the rate constants of the  r e a c t i o n s 61 a n d 6 1 1 c a n be g i v e n b y k k  The  /kf  = (1  6Il/ 2  = {0  6 I  k  (H  +  6  b  I  + CR  A  6  6 B I I  a  I  ))R  /R  Eg-j. = 5 . 0 ± 0.7  13 Both  + 1OS|A  assumptions  6 I  /A|  H l/[B]^H 5  '  0  a  E  5 L I  C6  R  6  4  1 0  parameters:  kcal./mole  ( c m ? m o l e c 7 s e c 7 ) ^ } = 4.4 1  d  R H }/ t ^ C H  +  = 5»8 ± 0 . 5  gjj  n  B  2  +  1  0.8  / A | (cm?molec7 sec7 )^ = 5 . 2 + 0 . 5 1  6 I I  1  q u a n t i t i e s gave t h e  kcal./mole;  13 + l o g { A  2  ))Rc H  6 a I I  Arrhenius p l o t s of these  C  1  lead t o acceptable results f o r the Arrhenius  p a r a m e t e r s o f r e a c t i o n s 61 a n d 6 1 1 , b u t n e i t h e r o f them g i v e s values  of ^ h l ^ ^ a l  a  n  d  R  6bII  / / R  6aII  w n i c  -  l a  w o u l d  -  b  e  expected  103 from p r e v i o u s work; 0.38  ± 0.03  James and S u a r t  f o r the r a t i o  ^ have r e p o r t e d a v a l u e  o f d i s p r o p o r t i o n a t i o n to, combina-  t i o n o f t h e c y c l o h e x a d i e n y l and e t h y l r a d i c a l s . n o t i n g t h a t . ( d / c = 0 . 5 2 ± 0.04)  i s worth  ( d / c ( C H - , C H - ) = 0.38 2  which R  6bl  6  + 0.03)  > (R bII 6  / R  However, i t  > 6aII  =  °' ^ 2  1  p r o b a b l y may i n d i c a t e t h a t t h e . t r u e r e l a t i o n s h i p a  n  d  R  6bII  l s  '  2 R  6bII  >  R  6bI  > R  6bII  .  °'  0 6 )  between  I f this i s true  158 then  6 j/ 6 i  R  high  will  R  D  a  value The  of  1.46  somewhat s m a l l e r  D e  ±  carbon dioxide  evidence that  going decomposition. the  rate  since  The  of production  these  One II* or  k of  i s the  ^ A  9  the  6  a  I  m e t h a n e and  -  I  c a l s has R.  which can  substrate  = 0.12  the  to  been found t o R  TT °3 8  .  n  9»  If  present,  either  -we  11  and a  10)  to  the  rate  negligible.  The  ratio  combination of 132-134 ^ ;  0.12  y  form  hydrogen form  also possibly  but  be  radical  disproportionate  abstract  i t could  we  ( E 1 0 )  or d i e t h y l ketone to  ( r e a c t i o n 12),  e s t i m a t e d t o be  1 1  species  to  benzene,  the d e c o m p o s i t i o n of the  propane r e s p e c t i v e l y , or  disproportionation  the  ^ o / c ^ H ^ I I C ^  methane ( r e a c t i o n s e r i e s 1 4 ) ;  of  or  i n reaction  ethyl radicals (reactions  atom f r o m e i t h e r the  t i o n v/as  b e n z e n e among  of d e c o m p o s i t i o n i s equal  for a l l transient  products of  mutual combination  •  t r a n s f e r r a d i c a l I I * v/as u n d e r -  produced only  methyl r a d i c a l ,  combine w i t h  and  e i t h e r carbon dioxide  compounds a r e  write  the rate  of  assume a s t e a d y s t a t e can  remarkably  0.25.  presence of  p r o d u c t s was  than the  '  undergo  of t h i s of  e t h y l and  the  reacrates  methyl  radi-  therefore,  From t h i s e x p r e s s i o n  , we  can  estimate  U  rate  of  difference o f .the  f o r m a t i o n of methane i n r e a c t i o n R  - 0.12  R„  „  methyl r a d i c a l with  e t h y l ketone Defining R  n T J  14B  ( 1 4 D ) , and  R ^ +  = R ^ R  14D  =  R  m u s t be b o t h the  possibly to  11.  a t t r i b u t e d to substrate  (14B)  reaction  14b.  +-H^-  CH " °* 4  1 2  R  C Hg" 5  R  The  14bl ~  R  14bII  rate  metathesis and  di-  159 R ^  where  + R ^  = (1  -  y  )  R  C H "  ^  c  5  6 Thus, R  + R^^j) - ^ C H ^  1 4 B  =  °°  -  CH  D R  1 2  5  R  14B  = k  1 4 I )  =  k  W  ' 14.D R  B  1 4 B  ]  (k [CH  +  R  Z j  _/k ),  3J  14B  » {  =  we  "  2 y  b  p  ) R  C H C0 CH 6  5  2  assumed t h a t k^/kg  and t h a t  6  8  1  5  4  In order to determine R ^ g , or k  R  =• k ^  since  4 D  = k^^/k^-g [D] [ C H J  and  t h e n  1 4 B  k  (  W  W  +  k  f  14B^}  CH  5  ]  Therefore  The  Arrhenius plot  of t h i s  w h i c h i s p r o b a b l y due  q u a n t i t y gave an e r r a t i c  to c e r t a i n i m p r e c i s i o n i n measuring  s m a l l chromatographic peaks, f o r example,those t o I C H j and I I C H ^ . proposed The  pattern,  T h u s , we  corresponding  must a d m i t t h a t t h e  f o r t h e r e a c t i o n s e r i e s 14 g i v e s  mechanism  inconclusive results,  m a t e r i a l b a l a n c e f o r t h e m e t h y l r a d i c a l was  b y c o n s i d e r i n g t h a t m e t h y l r a d i c a l s w e r e consumed t o methane, -propane, M  This  Me  =  (  R  C  and t h e c o m b i n a t i o n p r o d u c t s I C H ^  V \ E  +  R  ICH  + 3  ^  C  O  methyl, r a d i c a l s  form and  IICH^:  p  material balance v a r i e s e r r a t i c a l l y with  and i s below u n i t y ; t h e r e f o r e  the  W  derived  (  E  1  a s i g n i f i c a n t p o r t i o n of the of  M u t u a l c o m b i n a t i o n o f m e t h y l r a d i - : _„  12 cals it  h a s p r e v i o u s l y b e e n shown t o be n e g l i g i b l e ;  i s possible that  GH^  may  be  however  consumed by c o m b i n a t i o n w i t h  C^HT-COCOH, : d  5  C H C0C H 2  5  )  temperature,  i s consumed i n r e a c t i o n s o t h e r t h a n t h o s e  p r o p o s e d mechanism.-  1  2  4  + CH*  > CgH^COCjH,-,  (5')  160 S i n c e C H -G0C H -, c o u l d n o t be m e a s u r e d , t h i s r e a c t i o n 2 5 3 7 ' o  be  c  7  c o n s i d e r e d when c a l c u l a t i n g  the low values o f  I t i s also possible  peaks o f ICH^ and IICEU,  a t l o n g r e t e n t i o n times-, w h e r e t h e y a r e f o u n d , t o give reproduceable The  that  ' a r e due t o a c e r t a i n i m p r e c i s i o n i n  r e c o r d i n g the chromatographic  fail  cannot  r  since  s m a l l amounts  responses. (MQ) i n m e t h y l c y c l o h e x a d i e n y i c a r -  material balance  b o x y l a t e r a d i c a l s is, d e r i v e d by c o n s i d e r i n g t h a t these  radi-  c a l s a r c consumed t o f o r m b e n z e n e t o g e t h e r w i t h c a r b o n d i o x i d e , methyl benzoate,  and t h e c o m b i n a t i o n p r o d u c t s  IC H^ 2  }  IIC' H , I C H j , and I I C H ^ ; 2  5  R  C^H.  +  R  I0 H o  +  r  R  IIC H _  where t h e d e n o m i n a t o r  0  +  ICH  R  I  +  R  X  IICH  + 7  R  C<-H,-C0 CH o  z  r e p r e s e n t s t h e r a t e o f h y d r o g e n atom  a b s t r a c t i o n by t h e e t h y l r a d i c a l ' f r o m t h e s u b s t r a t e .  This  r a t e has been c o n s i d e r e d a p p r o x i m a t e l y , e q u a l t o t h e r a t e o f f o r m a t i o n o f t h e r a d i c a l s I * and 11°, s i n c e . t h e r a t e a t i o n o f these r a d i c a l s by methyl  of form-  radical sensitization i s  much l o w e r t h a n R^:  (k Af) 5  [B] B  * ^ »  (k,  4  B  ^A  1  0  )  (B H /R^ ) 0 3  6  O  [B]  T h u s , t h e q u a n t i t y E 1 2 c a n be - c o n s i d e r e d a s a n u p p e r l i m i t o f M . C ;  T h i s m a t e r i a l b a l a n c e had an average  and d i d n o t show a n y d e f i n i t e  v a l u e 0.810 + 0 . 0 8 0 ,  trend with temperature,  somewhat l o w e r v a l u e s w e r e f o u n d  although  f o r high temperatures.  l o w v a l u e s o f M'^. may be a t t r i b u t e d t o a m u t u a l  or inter  The com-  b i n a t i o n o f I * and I I " . r a d i c a l s t o form products- l i k e I - I ,  TABLE' X V I  ARRHENIUS  PARAMETERS  OF T H E REACTIONS  OF THE ETHYL  D I E N E - 3 - C A R B O X Y L A T E ' AND  System  C  2 5 H  /  C  Plotted  6 7 H  C  0  0  C  H  '  10  1 3  variable  OTHER  RADICAL  RELATED  PHOTOLYTIC  k. x  6  6  I  / k f  (cm.molec.sec.;  C H - / C H - 1 , 4 57 2  6  8  103  C H - / C H - 1 , 4 103 3  6  8  C H - / C H - 1 , 4 57 2  6  8  i o  5  1  k  .  i  i  /  k  |  10 • " ^ 9 2 ^ 6 I I a  C  10  (cm^molec^sec^')^  r  1  5  k  k  6  /k|  s  METHYL  c m  »  r a o l e c  »  s e  ° » )^  CYCLOHEXA-1.4-  SYSTEMS  log  k /k^  1 0 ^ k  WITH  A  x  E  kcaL/mole  5-6 ± 0,4  6.0 i 0 . 7  3.9 ± 0 . 5  4 . 5 ± 0.8  5.3 * 0 . 3  5.9 i 0.5  4.4 ± 0.8  5.0 ± 0.7  5.2 i 0 . 5  5.8 i 0 . 5  12.0  i 0.6  20.5 i  1.5  5.7 ± 0.1  5.8 ±  0.1  .  II-II,  and I - I I ,  w h i c h we w e r e n o t a b l e  .  162  to-detect.  ' The. p o s s i b i l i t y was c o n s i d e r e d t h a t t h e r a d i c a l s I " a n d II*  may u n d e r g o d e c o m p o s i t i o n t o g i v e , h y d r o g e n a t o m s a n d  methyl benzoate:  /^^-COOGH^  or  \f^X —  (i")  ^  < f | ^  C  0  0  C  H  3  +  H  •  COOCHj  ( 1 5 1  &  1511)  , ( I D  However, i f s u c h r e a c t i o n s were o f m a j o r i m p o r t a n c e i n o u r s y s t e m , we w o u l d h a v e e x p e c t e d t h a t t h e f o l l o w i n g  subsequent  r e a c t i o n s would have been o b s e r v e d :  H +  (^^COOCHj  COOCH-,  COOCH-,  +  I or isomers  >  COOCH-,  > I  ^-COOCH^ and. i s o m e r s  X COOCH-.'  + \i'i  o  COOCH;.  r  or isomers  S i n c e m e t h y l c y c l o h e x e n e c a r b o x y l a t e was n o t d e t e c t e d among t h e p r o d u c t s , we c a n c o n c l u d e t h a t r e a c t i o n s 1 5 1 a n d 1 5 1 1 a r e not  significant.  Discussion. reactions  TABLE X V I shows t h e A r r h e n i u s p a r a m e t e r s f o r t h e  of the e t h y l r a d i c a l with methyl cyclohexa-1,4-  diene-3-carboxylate thetical  .•  The A r r h e n i u s p a r a m e t e r s f o r t h e meta-  r e a c t i o n 6 o f t h e C^^/CgH^COOCH^ s y s t e m a g r e e v e r y -  c l o s e l y w i t h t h o s e o b t a i n e d f o r t h e C2H£/cyclohexadiene-1,4 103 5 7 ) ,CH*/cyclohexadiene-1,4 and C^H'/cyclohexa103 diene-1,4 systems. Thus i t a p p e a r s t h a t t h e - t o t a l (ref.  y  163 lability the  of the methylenic  h y d r o g e n atoms i s n o t a f f e c t e d by  i n t r o d u c t i o n of the carboxylester  hexadienyl  ring.  group i n t o the c y c l o -  However, t h e p r e s e n c e o f t h e  carboxylester  g r o u p must be t h e r e a s o n t h a t f o r o u r s y s t e m kg- .. > kg-,T  independently  r  o f t h e method employed f o r t h e e s t i m a t i o n o f  k^-r-r a n d k . oil 61  I n f a c t , f o r r e a c t i o n 611 t h e r e '  r T  a r e two  a b s t r a c t a b l e h y d r o g e n a t o m s , w h e r e a s f o r r e a c t i o n '61 t h e r e is  o n l y one, w h i c h i s p r o b a b l y H  °2 5 H  C  2 5 H  H  +  H H  +  sheltered.  A=A  COOCH,-  6 I I  has  COOCH,  ,H C  2 6 H  A j J /  +  C 0 0 C H  i t i s a n t i c i p a t e d t h a t k^-j-^.2k . &1  ( p . 154)  6 I  a wide s c a t t e r without  1  6II  «(1.58  definite  trend:.  of k  6 I  ,  k  6 I I  , E  by t h e f i r s t  t h a t J%j< 6xi> E  6 I I  / k j ) vs  T"  6  6 I  E  6 I I  method.  ± 0.8  ,  A  6 I  ,  and A  6  I  I  more r e l i a b l e  1  method 6 I j  /fc ) 6 I  kcal./mole  These r e s u l t s . s h o w  s e c o n d m e t h o d must be c o n s i d e r e d obtained  first  t o 2.00)xk ; the p l o t of l o g ( k  - 0.5. 6 I ?  The  the second  h a s t h e p a r a m e t e r s . E g j j - E g j =-1.2  and. log(Ag-j-j/Ag-r) = 0.9 values  ( 6 I )  gave  ^ ( 2 o 3 4 t o 3.90)xk ; the p l o t of l o g ( k  T"  3  COOCH, 3  (p.154) g a v e k vs  (611)  5  m e t h o d o f e s t i m a t i n g k^-j- a n d k ^ j k  <f^Y  5  >cx  Therefore,  — ^» °CJBL. 2 6 + H  X-A  H  H  that the  obtained than  by t h e  those  I t i s r e a s o n a b l e t o expect-  s i n c e t h e r a d i c a l 1°  shows a more  extensive  d e - l o c a l i z a t i o n than the r a d i c a l I I " . W.e h a v e assumed p r e v i o u s l y t h a t o n l y t h e r a d i c a l undergo decomposition t o g i v e  carbon d i o x i d e .  This  II"can  assumption  164 is  reasonable  and  s i n c e the  rates  of production  benzene are n e a r l y e q u a l . . I f the  d e c o m p o s i n g a t an  appreciable  s i n c e b e n z e n e c a n n o t be tion  of t h i s  radical,  radical  rate to give  produced i n the  the  rate  have been s m a l l e r t h a n t h a t  of carbon I * was  dioxide also  carbon d i o x i d e ,  would-be  of p r o d u c t i o n  decomposi-  of benzene  would  of carbon d i o x i d e .  103 Previous sition is 31.2  of the  27o3 I 4 . 7 t. 4„7  radical 20.5  1  11°  cyclohexadienyl  radical,  kcal./mole,  the  In this  kcal./mole,  mole" ): 1  D(H^Q>)  energy i s found that  the  which i s c o n s i s t e n t w i t h the  greater  exothermicity  probably  c a l c u l a t e d i n the  reaction  energy,  to a high negative can  heat of  decompo-  a much l o w e r a c t i v a t i o n  (AH^-  = -5-6  energy i m p l i e s t h a t the  b e a r i n mind t h a t the  d i o x i d e , we  the  w o r k , i t was  s t a t e imposes a d e f i n i t e  m a i n l y due  that f o r the  activation  of i t s decomposition  activation  transition  *  and  decomposes w i t h  1.5  low  have r e p o r t e d  kcal./mole.  exothermicity The  workers  s t r u c t u r e of  energy b a r r i e r .  envisage a t r a n s i t i o n  = 70.5 ° ; 1  5  i f we  If  the we  of t h i s r e a c t i o n i s  heat of f o r m a t i o n  f o l l o w i n g way  kcal./mole*)  of  carbon  state i n which  ( a l lquantities i n  kcal.  assume t h a t D ( H - ^ ) )  =  D(H~(Z}~C00CH ..), and t h a t t h e a c t i v a t i o n e n e r g y f o r c o m b i n a t i o n o f I I " arid H i s z e r o , t h e n t h e h e a t o f d e c o m p o s i t i o n o f t h e s u b s t r a t e t o g i v e I I * and H i s 70.5* Prom t h i s v a l u e and t h e v a l u e s A H f ( s u b s t r a t e ) = -55 ( f o u n d by t h e P a r t i a l Bond C o n t r i b u t i o n s M e t h o d ' ' ) , and A H f ( H ) = 5 2 „ 1 \ t h e v a l u e o f A H f ( I I * ) was f o u n d t o be - 3 6 . 6 . A H O was c a l c u l a t e d f r o m AHf ( I I * ) and t h e v a l u e s A H ( C 0 2 ) = - 9 4 . 1 , AHf (CH*.) = 3 4 . 0 , A H f ( 0 H ) = 19.8101. ;  10  1  1 0  f  0  6  6  1  the  d e r e a l i z a t i o n of carton  This  dioxide  i snot f u l l y r e a l i z e d .  transition states:  COOCH^ HX, <Tj)  •+ COOCH^; A H - = 10 k c a l . / m o l e '  <^^-C00  ^^-•COOCHj  + CH^;  AH =85 ji  kcal./mole*  A comparison o f the heats o f these h y p o t h e t i c a l  estimated  AHi  as follows  t o representing  6  5  COOCH3 + H;  A H  kcal./mole):  =-3&16 ( f r o m  AH=70.5 ), A H ( C 0 0 C H ) = 90 °5), a n d A H f ( C g H t s ) = 1 9 . 8 105  f  =  5  -  1  4  ( f r o m HC00CH ->  6  1 0 2  CgHrjCOOCHj-* 5  .  A  v a l u e s A H f ( C H C 0 0 C H ) = - 3 6 . 6 ( a s a b o v e ) , A H f (CH3) 5  6  5  and A H f ( C g H g C O O " ) = 2 3 ( e s t i m a t e d butions  Method as d e s c r i b e d  (0-H) (C .(<2MH)  from t h e  U  = 34 °2,13g 1  b y t h e P a r t i a l Bond C o n t r i -  contributions  (O-H) + 5 ( O H ) of the p a r t i a l  H  below).  AHf(CgHgCOO*)=sum o f p a r t i a l Estimation  indicates  the t r a n s i t i o n  ( a l l quantities•in  f r o m t h e v a l u e s AHf(CgHgCOOCH^)  C H C00CH +H; 6  reactions  t h e a c t i v a t i o n e n e r g y (20.5 i 1*5 k c a l . / m o l e )  that reaction ( i ) i s closer  *  5  s i t u a t i o n may be r e p r e s e n t e d b y e i t h e r o f t h e f o l l o w i n g  hypothetical  with  6  +  (O-co) + (co-o-)  contributions:  =-3.4: f r o m A H f ( Q ) = 4(>-H) + 4 ( C - H ) + 4 ( C - C ) - H ) = 3.2, ( C - C ) = 6.7 ; (>-H) a s s u m e d = ( 0 ~ H ) V  V  101  v  v  =10:  f r o m A H f (O)  (O-CO) =-13: (C-H)  = -3.9,  = 5 (OH)  +  2 (©-H) = 4  1 0 2 5  (O-H) -  >  1 0 3  (O-CO) a s s u m e d = ( C - H ) - ( C - C O ) ; mi (C-CO) = - 1 4 . 4  (CO-0*) = - 1 8 ( w i t h d e o l c a l i z a t i o n ) : f r o m AHf(CH3C00*) =sum o f p a r t i a l c o n t r i b u t i o n s ' ' 3(C-H) + (CO-0*) + (C-CO) = 4 5  1 5 1  166  of r e a c t i o n 9 than r e a c t i o n ( i i )  state AH^<  E^AI-L^,  tribution.  i t i s possible that  Therefore,  a t i o n f o r the  we  i s .  However, s i n c e  ( i i ) imparts  a small  con-  can propose the f o l l o w i n g c o n f i g u r -  a c t i v a t e d complex: 0  i i•iitiIQ^O  1  1  ' 'CH, 5  11  The 3  pre-exponential factor -1'  -1  cm.molec. s e c .  by  was  assuming t h a t A  estimated  - Agjj  2  &  = 10  t o be -10  10  *^  3  -1  cm.molec.  -1  sec.  .  This value  decomposition  represents  r e a c t i o n s , and  certain rigidity  imparted  the  linearity  its  benzene segment.  Conclusion. radical the  a low  i t can  to the  be  of the r e a c t i o n s of the  the t r a n s f e r r a d i c a l  than  metathesis-dismutation a convenient  combination estimated  lead to  substrate i s thermally unstable,  the  d i o x i d e , and  i s , as- was  a  methyl  p r e d i c t e d , more  cyclohexadienyl radical.  s e q u e n c e o f r e a c t i o n s , 6 and  g e n e r a l m e t h o d o f p r e p a r i n g R*  The 9,  thus  radicals  COOR  ester the  has  ethyl  r e s u l t i n g from the a b s t r a c t i o n  This transfer r a d i c a l  thermally unstable  (b)  of -  conclusions:  decomposing t o give benzene, carbon  from the  both  .  study  o f a h y d r o g e n atom f r o m t h e  radical.  a  the p l a n a r i t y  with cyclohexa-1,4— diene-3-carboxylate  (a)  to  a c t i v a t e d complex by  •  This k i n e t i c  for unimolecular  attributed  o f i t s 0-^-C^-^-O s e g m e n t and  following  offers  limit  ratios  of the r a t e s of d i s p r o p o r t i o n a t i o n to  of the r a d i c a l p a i r s  as 1.4-6 + 0 . 2 5 ,  and  ( C H ~ ' , I " ) and (C H£,II') w e r e 2  0.24- + 0 . 0 6  2  respectively,  on  the  167 assumption that the rate and  I * was t w i c e  and  I I *.  F.  The U n s e n s i t i z e d  of disproportionation  the rate  between  o f d i s p r o p o r t i o n a t i o n between  Decomposition of A l l y l  C2^£>  Cyclohexa-1,4-  Diene-5-Carboxylate Unsensitized  decomposition of a l l y l  cyclohexa-1,4-diene-  3 - c a r b o x y l a t e was i n v e s t i g a t e d a s a p r e l i m i n a r y t o t h e k i n e tic  study of i t s reactions  w i t h the e t h y l r a d i c a l .  t i o n was i n d i c a t e d b y t h e f o r m a t i o n  Decomposi-  o f carbon d i o x i d e ;  i ti s  most l i k e l y t o p r o c e e d b y t h e f r e e r a d i c a l m e c h a n i s m  /""V  > C00CH CH=CH 2  + C0  the cyclohexadienyl  t h e mechanism o f t h i s  radical,  inves-  and t h e k i n e t i c s  r a d i c a l and t h e e s t e r .  TABLE X V I I s u m m a r i z e s t h e r e s u l t s o f n i n e  ments p e r f o r m e d between low  2  of i n t e r a c t i o n of the a l l y l  of m e t a t h e s i s between t h e a l l y l Results.  2  d e c o m p o s i t i o n , a n d t o make a q u a n t i t a t i v e  t i g a t i o n of both the pattern radical with  + CH -CH-CH  2  T h i s k i n e t i c s t u d y aims t o e l u c i d a t e unsensitized  2  130'  a n d 200°C.  experi-  The g a s e o u s a n d t h e  b . p . l i q u i d p r o d u c t s w e r e f o u n d t o be c a r b o n  dioxide,  p r o p y l e n e , b e n z e n e , hexadiene-1,5, c y c l o h e x a d i e n e - 1 , 4 , and cyclohexadiehe-1,3.  No h y d r o g e n , c a r b o n m o n o x i d e , a l l e n e ,  o r a c r o l e i n were d e t e c t e d .  The h i g h  b.p. f r a c t i o n o f t h e  l i q u i d p r o d u c t s was a n a l y z e d i n a t w o m e t r e g l y c o l c o l u m n a t 100°C a n d  12  psi.  polyethylene  Two unknown p e a k s  appeared  w i t h r e t e n t i o n t i m e s o f 4-5 a n d 50 m i n u t e s ; t h e s e , p e a k s w e r e r e s p e c t i v e l y assigned  to  TABLE X V I I :  time min,  T H E UNSENSITIZED DECOMPOSITION OP A L L Y L  .. ( C O ^  [B]  H  ( C H ) ( C H Q 1 , 4 ) (AC-2,4) 6  403  180  2.72  120  2.70  0.044  0.014  0.290 0.025  60  2.76  0.70 0.07  443  30  2.15  2.25 0.25  433  30  2.-15  6..60 1.-10  463  15  2.23  7.74 " 1.26  473  15  1.50  19.80 2.85*  t o TABLE  [B]  = cone.  (  = r a t e  )  —  A11  =  ( R  Q =R c  C3H  x  5  H 6  +  R  A C+ 2R  8 ^6 10 R  H  / R  AC  ;  C 6  H K  s e c .  -12  0.015 0.010  0.89 0-75  0.40 0.60  -  0.3 1.6 7.1 9.4 3.8 19.8 7.6 10.5 32.0 7.1 25 30 8.9 105 40 6.5 282 38 9.6 347 - 50" 12.7 1320 71  0.40 0.52 0.08 0.40 0.51 0.09 0.45 0.47 0..08 0.33 0.57 0.10 0.39 0.51 0.10 0.40 0.50 0.10 0.39 0.49 0.-12  - 3 - 1  m o l e c . c m . s e c .  CH-<2); A C = A C - 2 , 5 5  5  )/ C.0 ;  M  R  1 0  D  =  M, 'C - <P-95R o + 0 - ' 7 0 H -1 A  -  —  l O - ^ m o l e c c m ?  o f f o r m a t i o n x 1 0  6  0.030 0.023  —  3  XVII  AC-2,5 = C H -{2) ; AC-2,4 = M  C  1.02 1.12 1.03 0.090 1.01 0.010 0.093 1.01 0.071 0.015 1.04 1.08 0.19 .• 0 . 0 2 0.023 0.01 . 0 . 0 2 2 . 0.96 0.05 1.07 0.90 0.41 0.06 0.95 0.52 0.16 0.04 1.06 0.97 2.98 ' 0.98 0.92 0.52 0.20 0.23 2.25 ' 1.44 0.98 ,-3.12 1.00 0.35 1.33 0.43 0.33 / 2.50 1.46 0.99 6.66 0.94 0.70 3-07 1.88 0.53 5.34 1.16 0.76  (^-COOGjE^  5  0.005  0.042 0.005  0.103 0.010  2.75  Key  mm'  D  C  —  •-  —  -2 M A 1 1 R3a/Rx 10 Q M R3D/R3 k R3 /R MBz : • MA _  _  -  120  426  6  —  418  1q  _  0.006  1.86  180  408  (AC-23)  < 3 e? c  168  2  1  0 5  0  "  ?  H6  k  + 5  1  5  K  B  MA  =  Z  = (0.10R  6  8  + Rc H )/Ro H 6  8  6  6  10 3i- A | ( c m ? m o l e c 2 s e c ^ f 1  -^ 0 H ^CO. R  A C  +AC-2,4  169  •CEUCH=CH after  and  2  c o l l e c t i o n a n d s t u d y o f N.M.R. e v i d e n c e  a s now.des-  cribed. A prolonged performed  a t 180°C, a n d t h e h i g h b.p.  fractionated tions  thermal experiment,  d u r a t i o n 7 2 h o u r s , was l i q u i d products  i n the p o l y e t h y l e n e g l y c o l  column.  were  The f r a c -  c o r r e s p o n d i n g t o t h e two p e a k s u n d e r i n v e s t i g a t i o n  collected CDClj.  were  s e p a r a t e l y i n s e p a r a t e N.M.R. t u b e s c o n t a i n i n g  The y i e l d o f e a c h was s u b s t a n t i a l .  T h e i r N.M.R.  s p e c t r a were compared w i t h t h e s p e c t r a o f cyclohexadiene-1,4-, cyclohexadiene-1,3, (in  and hexadiene-1,5.  PPM) f o r t h e p e a k s o f e a c h o f t h e s e  on t h e . n e x t p a g e ;  t h eassignment  a , b , c , o r d was c o n f i r m e d , peaks,  expressed  corresponds was  ponding  fraction  area,  f o r the proton t o which i t  The m a i n d i f f e r e n c e b e t w e e n t h e s p e c t r a o f and a l l y l  c y c l o h e x a d i e n e - 2 , 5 was  contained a multiplet  peaks o f the  allyl  s p e c t r a showed a n y d e f i n i t e a, a n d e s p e c i a l l y  (S=2.6to2.7)  cyclohexadiene-2,4structure;  d u c t i o n o f the a l l y l  group i n t o  non-equivalent.  corres-  None-of t h e and - 2 , 5  the m u t i p l i c i t y o f t h e  o f the b and c protons  than i ncyclohexadiene-1,3  the r i n g  protons  o f the t o t a l peak  t o the proton b, b u t t h el a t t e r d i d not.  multiplet  given  s i n c e t h earea o f each o f t h e  as a percent  cyclohexadiene-2,4-  that the former  s p e c t r a are  shifts  o f each peak t o the  t o the value expected  assigned.  allyl  ved  The c h e m i c a l  i s much more i n v o l -  a n d -1,4-, b e c a u s e t h e i n t r o t h e r i n g makes t h e p r o t o n s o f  170 Sb Sc - °/o p e a k a r e a  Compound  H  a  m  2.6m  5.2-5.6 50<  Hb H H  a  50  s  5.2-5.6m 50<  2.0m  5.2-5.5m 20  2.0 40  50 m  s  6.0m 40  €  (  H  Sd  CE° -C&CE^  b  2  H -Y V-H H "l >-H H H . c a d HC CH-CH=CH2 a  ><  a  a  5.0-5.6 41 42  ra  a  f  ><  b  b  2 6-2o7 25 25  m  e  f  1.8-2.0 15 17  5.8-6.0 19 16  1.7-2.0 39 42  5.9-6.1 17 16  m  0  e  f  m  S  1  6  2  H -kJ-H H a  5.0-5.8m 44 42  a  1  m  f  S  m  e  f  e  a  m:- m u l t i p l e t ;  e:- e x p e c t e d ;  We w e r e u n a b l e  f : - found.  t o separate by gas chromatography and  i d e n t i f y b y N..M.R. a n y o t h e r h i g h b . p . l i q u i d p r o d u c t s . . Kinetic Analysis.  The n a t u r e  and d i s t r i b u t i o n o f t h e pro-  ducts i s consistent with the f o l l o w i n g reaction  +  C0 + C H* 2 25 o  C00C,H,25 2 [  C  35 ' H  +  S% \\  7  (1)  (2a)  C„H. 6 10 Xi  2C-H53  scheme:  +  C  3 4  A" 5 5 C  H  H  (2b) (3a)  171 (3b) C3H5  +  (3c) (C H ). 6  C  o  6 6 H  +  C  COOCJHL  5  53  35  6  ?  2  6  -> C K 6  6 7 6 6 H  C  H  3 5  G 0 0 C  H  8  .  +  6  The  6  5  5  2  (6a)  (6b)  52  p  6  (5)  3 6  35'  C H 6  Q  r  c  (C H G00C H )  5  (7a)  6  (7b)  -> C H + - C H COOC,H 6 8 / 6 5 35 -> C Rv- ' + C.H COOC-.H 6 o 6 7 0 5 r  C  H  6.7 6 6  53  (4b)  6 8  3  COOC^Hc (C H )  (4a)  ?  67  c  c  n  35  (7c)  [  65  (7d)  35  r a t e o f f o r m a t i o n o f c a r b o n d i o x i d e c a n be a d i r e c t  measure o f t h e r a t e o f d e c o m p o s i t i o n o f a l l y l diene-3-carboxylate  cyclohexa-1,4-  i n reaction 1 only i fthe sensitized  d e c o m p o s i t i o n does n o t t a k e p l a c e a t a s i g n i f i c a n t r a t e .  The  s e n s i t i z e d d e c o m p o s i t i o n c a n .occur o n l y t h r o u g h t h e agency o f the a l l y l  radical,  w h i c h may g e n e r a t e  allyl cyclohexadienyl—  c a r b o x y l a t e r a d i c a l s b y a b s t r a c t i o n o f a h y d r o g e n atom the e s t e r  ( r e a c t i o n 5)-  The t r a n s f e r r a d i c a l f o r m e d  from  can enter  i n t o t h e c o m b i n a t i o n r e a c t i o n s 6 a a n d 6 b , a n d may a l s o decompose i n t h e r e a c t i o n 6c  175  COOC^  ) ( ^ J ) + C0  2  + C H'  (6c)  5  The p r o d u c t s o f r e a c t i o n s 6a and 6b may decompose a t h i g h e r temperatures: i n t h e r e a c t i o n s ' 7b and 7 c . t i z e d decompositon  However, i f s e n s i -  o c c u r s , t h e n e t r a t e o f r e a c t i o n 1 c a n be  measured as' f o l l o w s : R  where thus  R  co  = 1 R  2  6c  =  R  +  6c  R  C H " 6  - R^n G0  •1 R  R  6  3c~' 4b~ R  0.10*R  +  2  Below  190°C,  ;  R  n p R C H G H ?  - S  R^R^Q  7c^ 7b  5  )  n "^ ' n C H C H  +  p  6  (where  ( R  r5  6  Q  ^+  R  Q  6  Q - C ^  t h i s means t h a t t h e s e n s i t i z e d decom-  2  |.  p o s i t i o n r e a c t i o n ( 6 c ) i s n e g l i g i b l e below: t h i s It  6  temperature.  would have, been most u n l i k e l y f o r t h e s e n s i t i z e d decompo-  s i t i o n t o be a p p r e c i a b l e below 160°C, where t h e r a t e o f f o r m a t i o n o f a l l y l r a d i c a l s was found t o be t o o slow t o e x p e c t r e a c t i o n 5'to p r o c e e d ^ a t s i g n i f i c a n t r a t e ; i t appears t h a t a 1  t e m p e r a t u r e o f 190°C i s needed b e f o r e t h e p r o d u c t i o n o f a l l y l r a d i c a l s i s s u f f i c i e n t f o r r e a c t i o n 5 t o be s i g n i f i c a n t . Below 190°C, t h e r a t e c o n s t a n t o f r e a c t i o n 1 c a n now be c a l c u l a t e d from  k^  The A r r h e n i u s p a r a m e t e r s 14 ± 1 -1 and A^ = 10  sec. .  =  RQQ^/ [B]  (F1) = 38 I 2: k c a l . / m o l e ,  o f k^ were  These a r e c o n s i s t e n t w i t h t h e f o r m -  a t i o n o f carbon d i o x i d e i n a u n i m o l e c u l a r r e a c t i o n .  The a c t i -  v a t i o n energy i s s u f f i c i e n t l y l o w f o r d e c o m p o s i t i o n t o o c c u r * The f a c t o r 0.10, w h i c h w i l l be d i s c u s s e d l a t e r , i s t h e average e x p e r i m e n t a l v a l u e o f 3 / ( 3 3tP K  C  R  a  +:  R  174 at temperatures Methyl  as low as 135°C.  cyclohexa-1,4-diene-3-carboxylate  (section E ) d i d  n o t decompose b e l o w 1 8 0 ° C , w h i c h may i m p l y t h a t tized  decomposition  i t s unsensi-  h a s a much h i g h e r a c t i v a t i o n  energy.  we compare t h e e n d o t h e r m i c i t i e s - o f t h e d e c o m p o s i t i o n o f t h e two e s t e r s , ester 20  i s less  we f i n d  endothermic  that  the decomposition  >  5  o-  of the a l l y l  t h a n .that .of t h e m e t h y l e s t e r b y  fT\  V C 0 .'+ CH* ; A H - 4 0 k c a l . / m o l e *  >  COOC^  o  + C0- + C^H*; AH.= 20 k c a l . / m o l e *  +  >  A H  'COgC^;'  \  of the hypothetical  »  ±  53 k c a L / m o l e *  A H ^ = 75 k c a V m o l e *  1  ;  Comparison o f t h e heats, o f these: h y p o t h e t i c a l  the  activated  ( E ^ = 38 k c a l . / m o l e ) >  Calculated f  (C H*) = 4 5 6  i t i slikely  from AHf(C02) = -94' 1 0 2  3  a n d A H . (7 %C00C H } = -34. =  7;  ted by t h e P a r t i a l  C  3  are i n kcal./mole* . *  , &H (CE') f  1 5  \ AH  The l a s t  by P a r t i a l  the nature of  the transition  f  = 34  1 0 2  state  ,  (Q-COOCH^)  = -55, '  two v a l u e s a r e c a l c u l a -  Bond C o n t r i b u t i o n s Method P  steps with the  suggests  that  l02  , AH (C H ) = 37.4 f  2  1; s i n c e A H ^ < E ^ < AH.^ < A H ^  complex o f r e a c t i o n  and E . - A H . a A H . - E . ,  1  2  •  COOC^H^ Ci- ) > (~^} COO + C ^ H * '  energy  1  2  OOOO-H^ ( i )  activation  1  2  R e a c t i o n 1 can take p l a c e by e i t h e r  AH  reactions  kcal./mole:  COOCH,  *  If  A l l values: 101 Bond C o n t r i b u t i o n Method  175 will  have t h e c o n f i g u r a t i o n  0 ,0-^-0 < i i . i i i i . i C H — C H — C H 2  2  where t h e c a r b o n - c a r b o n b o n d . a n d t h e c a r b o n — o x y g e n b o n d a r e 14 approximately equally  stretched.  pre-exponential factor proposed tion the  of reaction  t r a n s i t i o n state  i n the a l l y l O^Hr, g r o u p ;  a higher value  group,  there  1  indicates  that  i n this rota-  r e s t r i c t e d rocking i n  -  expected  %0  o f butane t o e t h y l  -17—1 i s 10 ' s e c .  i?^ J  have been r e p o r t e d  decomposition  r a d i c a l s , where no  i n the i n t e r n a l r o t a t i o n of the ethyl  groups on f o r m i n g t h e t r a n s i t i o n s t a t e ,  the  , of the  f o r A^:  change i s e x p e c t e d  -1 sec.  10  i f t h i s were n o t s o , we w o u l d h a v e  the decomposition  factor  1  i srestricted internal  and p o s s i b l y  —  For  The v a l u e ,  +  But v a l u e s  the pre-exponential  o f t h e magnitude  o f 10  14  for the pre-exponential factors of  of ethyl  benzene t o y i e l d  methyl and b e n z y l  135 radicals -  and t h e d e c o m p o s i t i o n  J  radicals' the  %  1 2 3  ,  of d i a l l y l  where i n b o t h r e a c t i o n s  t r a n s i t i o n state  to yield  allyl  the configuration of  shows r e s t r i c t e d i n t e r n a l m o t i o n :  176  Restricted  i n t e r n a l m o t i o n must  tion  f o r the decomposition  state  Restricted state of  also  be p r e s e n t . i n  of d i a l l y l  i n t e r n a l motions of t h i s type  oxalate  the t r a n s i ( s e c t i o n B)  i n the t r a n s i t i o n  appear t o lower the p r e - e x p o n e n t i a l f a c t o r by a  factor  the order of 1 0 . 5  The p r o p o s i t i o n cyclohexadienyl (reaction  that  carbon dioxide,  r a d i c a l s are y i e l d e d  1) o f t h e d e c o m p o s i t i o n  i n the primary  of a l l y l  diene-3-carboxylate  i s tested  ances f o r the a l l y l  and c y c l o h e x a d i e n y l  radical  allyl.radicals step  cyclohexa-1,4-  by examining t h e m a t e r i a l radicals.  c a n be consumed t o f o r m p r o p y l e n e ,  and  allene,  The  balallyl  hexadiene-1^,  a l l y l  cyclohexadiene-2,4,  (excluding  the products  and a l l y l  o f combination  cyclohexadienylcarboxylate formed the  only  H  A11  =  (  C  E  balance  5  H  This  2  R  0  ""  e x p r e s s i o n f o r M^-^  independent value the  + 4  ^ C J H J  (where  allyl.  H  6  that  + 1  0  E  0  H  6  3a,  C  7  H  3  HJ/  proposed rate to  benzene,  absence free  r a d i c a l  study  the r a t i o  130  between  s i t i o n . form not  mechanism,  a l l y l  o f the thermal  R 2  b  /  R  w 2  a  s  a  0  *  200°C.  and  ±  0.02,  (This  among  0  Q  8  ±  between was  (CgH^)  2  the rates  o f formation  an independent  a l l y l  the  according  o f  t o  d i a l l y l  may  form  cyclohexadiene-2,5 A l l these  o f the thermal  however,  also  be  consumed  which  dimers  com-  decompo-  we  i ti s possible  o f these study  since  small;  consumed  a n d CgH^OgHgCOOOjH^,  estimate  with the  °»°°3.  c a n be  the products  t o detect;  from  inconsistent  and cyclohexadiene-1,3.  t h e means  :  0.98  decomposition  The c y c l o h e x a d i e n y l r a d i c a l  v  value  to' be v e r y  cyclohexadiene-2,4-,  found  the dimers  t.  (F2)  2  i s understandable,  i s expected  have  R/-,  then  by  o f t h e reaction  although  cyclohexadienyl r a d i c a l  v/ere  a n d 5,  5  has t h e average  o f allene,  cyclohexadiene-1,4, pounds  3c  ;  the k i n e t i c  The  products a r e  i s given  C0  a l l y l  c y c l o h e x a d i e n y l c a r b o x y l a t er a d i c a l s  o f i t s formation  oxalate,  E  and  Q-C,H >  j u s t i f i e d . ) The  3b,  r a d i c a l  the exclusion  and a l l y l  I f these  2b,  O ^ V  o f temperature  indicates  2a,  f o rt h e a l l y l  0jH  R  + 6  o f a l l y l .  r a d i c a l s ) .  i n the reactions  material  cyclohexadiene-2,5  t o  d i d .-— t o  i n d i r e c t l y .  by. James- a n d S u a r t ,  we  178 know  t h a t  assuming R  4b.  c  R„  2.22,  /R,,,«  4a  4 b  t h a t  t h e CgHg  H C H COOC  combine  a s s u m p t i o n  H  b a l a n c e  i s o m e r s  V  YeT  :  3 5  w i t h  t h a t  n  n  H  C  6 7 6 6 a l l ,  R/ „ \ = 2 . 2 2 R „ •' C 6 7^2 °6 8  t h e r e f o r e ,  f  e  a r e produced a l l y l  w  C^HgCOOC^H^  t h i s  r a d i c a l  o n l y  r a d i c a l s ,  r a d i c a l s  c o m b i n a t i o n  f o r t h e a l l y l  H  i n  i f  a n y a t  ( b e c a u s e , . o n t h e  was n e g l i g i b l e ,  was  r e a c t i o n  0.98 1 0.02),  t h e m a t e r i a l a n dR~ „ .  6 7  >  n  Rn  u  nr\^n rr  O^u^OUUO^n,-  ;  t h e r e f o r e ,  we c a n  assume  t h a t  R  o a c  ^ 0.70  R  p  c  a n d  w r i t e  R  6a  =  R  C H C H C00C H 6  7  6  5  6  -.0.70 R  5  - 0 . 1 0 R .. o  cH  C  H  3 6 Thus,  be  t h e m a t e r i a l  b a l a n c e  g i v e n by  M  V.b.c," E  4a,b  :  E  since  R  c  \ H  „  c = 0  ?  ( E  H  3  = (0 H ) R  6  E  +  G  E  V  6  6  H  8  0  E  (C.H ).  +R  E  • t h e r e f o r e ,  M  T h i s  m a t e r i a l  (C  +  _  H  =  5 +  R  f i  r a d i c a l c a n  '''  - f \ H  2  7  3  8  *  S  0 H " 5  6  2  2  R  c  8  6 8 H  5  H,). . • b o i n 4b K  oji 6 8  0  H  "  R  6 6  C , H  between  t o . a c c o u n t  R c ^  t h i s  135  ,  5 . 4 ^ ^ ) / ^  v a l u e  0.95  ±  a n d180°C.  s e m i - q u a n t i t a t i v e l y  b y u s i n g  180°C,  '  R  6 8  h a st h e average  r a d i c a l s  Above  =  H  V^CO,,  +  0 H C H  O ^ Q R ^  o f t e m p e r a t u r e  a n d 6a.  5  C  6 7 3 5  a  m 3c  b a l a n c e  c y c l o h e x a d i e n y l 4a,b  y  6 H 7 0 5  p o s s i b l e  R  6 6 i n 3c  ).  H  6 6  K  0  independent t h e r e f o r e ,  ( C  (O.93R '  t h e n  c  =  R  4a,b  6  = R  C  2 R  -  6  = (0,H,),„ , „ 6 6 i n pc  6  +  > i n  G H - -°7  H  3 6 ,  Ja,b,c  2  3  - 0.07 8  c  i n t h e c y c l o h e x a d i e n y l  5  +  7  6a " 6  = 0.70 R  H  6 7 3 5  o n l y  0.10, I t i s , f o r t h e  t h e r e a c t i o n s  m a t e r i a l  3a,b,c,  b a l a n c e - i n c r e a s e d t o  ' 179 ;  t h e  value  1.46.  p o s i t i o n v/e  t h a t we  ( C ^ )  t h e r e a c t i o n s  t h a t  R ^  i n c r e a s e  o f t h e dimers  i n c l u d e  assume  T h i s  above  = R  a  7  i n t h e d e r i v a t i o n  t h e. d i m e r s  = R  a  7  + R  b  t o t h e decora-  C^E^C^E^GQOG^E^.  a n d  2  7a,b,c  180°C  a n dR g  a  v/asa t t r i b u t e d  decompose  ( i g n o r i n g  n&  Thus  i f  o f M ^ ,a n d  c o m p l e t e l y  r e a c t i o n  s o  7<3.) ,'  then  o b t a i n  '  M  and  C "  3a,b,c  ( R  s i n c e  and  R  3  c  at  + 2R  ' C ^ H  0  i  "  o f  1 8 0 , 190, 180°C,  + 2R  4 b  (  R  C  t h i s  6  H  C  7  C , E L - 2 , 5 ,  C  R  H  6  ?  = R  c  R  +  6  /  C0  R  2  balance  s e r i e s  ^ + R  C H )/ C0 . 6  R  8  a r e  r e s p e c t i v e l y ;  CgH,*,  V  +  „  n  •+ R  b  -  5  t h e r e a c t i o n  r a d i c a l s  ?  m a t e r i a l  a n d 200°C  b  7  GgHpOjhtj  H  3  R  „  n  + R  ? a  +  =• R  5a, b  v a l u e s  The  7a  2 R  ,  7  M  above  +  R „  t h e n  The  4b  2 R  +  1.03,0.98,  these  v a l u e s  7a,b,c./cannot  a n d C'^H^ i n t e r a c t  a n dbenzene  2  show  b e  3a,  t h a t  i g n o r e d .  t o y i e l d  i n it h e r e a c t i o n s  0.77  a n d  CgH.pCjH^-24, a n d 3c  3b,  6 7 3 5 r e s p e c t i v e l y :  R ,  ]  Q  =  R  n  H  oa. P  I f  we t e n t a t i v e l y  • >R *ts ^ 7b n  R„ 7c  U s i n g  ,  t h a t  t h e r a t i o s  were  independent  average R^  3c  / R , =  5  3b  values, 0.09  R  3c  K  =  R  assume  p  5""  I  R ^ / R ^ , o f  0.02.  • .  which  were  =  determined  d i r e c t l y  C H C H -2,5J 6  C  7  H  6  5  "  6  R  t h a t R C  p 6  e x p r e s s i o n s  were ±  3  f  -  R , 3c  t h e above  7  R  R  then  -a  n  6  R j  b  „ H  5  4 b "  R  e i t h e r 6  R  C  f o r R / R j ,  temperature  p  6  3  ~  R ^ +  TT H a  7a  9  R  a  > >  R  9  R  c  7  D  o  r  8  , R ^ ,  a n dR,-  a n dR ' ^ / R j between  R ^ / R ^ = 0 . 4 0 +  7c  R  (where  V/e n o w i n v e s t i g a t e  R  , we  5  b  /  R  5  found  R^ = R j  a n d 200°C;  135  0.05,  c  =  0.51  t h e v a l i d i t y  b  ^  t h e i r ± 0 . 0 4 , o f t h e  180 a s s u m p t i o n  t h a t  e i t h e r  R.,,,  +  R  14b examining I f  7c,  t h e v a l u e  benzene  M  t h e n  i s  = (R^  BZ  o f  7c'  t h e m a t e r i a l  + R^  b  i n  . L ,  0  y a  produced  c  »R  0  o r  b a l a n c e  i n  7 ) / c JJ R  R  a  +  3c  3a.  n  7c  t h e r e a c t i o n s  + Rr?  « E  R„  7b  ,  b y  benzene.  3 c , 4 b , must  c  ,  7b  be  7a,  a n d  e q u a l  t o  u n i t y .  R  = 0 . 1 0  3 c  I f  R  I f  R  4 b  R  +  c H C H  E  6  »R  ? a  5  ,R  7 b  t h e n  = R ,  ? b  ? c  ? c  T h e r e f o r e ,  i f  l a s t  average above the  o  E  m  ,  / ( R  R  t h e n  + R  e i t h e r  R,^  4 b  + R  ? &  + 7 K  b  = (0.1 OIL,  p  pr  R  +  > > R  a  7 a  = R  ? c  was independent  1 . 0 0 ±  assumptions  6  p r o d u c t s  a n d w i t h  + R  ? a  o  D  =R  7 b  r  R  o f  R ^  R  ,  6  6  temperature  w i t h  a n d h a d t h e  ,190°C.  arid  Thus,  R  3 c  /(R  + 3 a  R  3  o f  ^  D  =  ± 0 . 0 3 The  r a t i o  was d e t e r m i n e d  R^/R^  v a l u e  0 . 7 8 1  0 . 0 4 ; t h i s  v a l u e  0.77  0.17  -  agrees  r e p o r t e d  d i r e c t l y  c l o s e l y  f o r  t h e  w i t h  and h a d t h e  t h e  c o m b i n a t i o n  c o r r e s p o n d i n g r e a c t i o n s  103 the  t h e  t h e d i s t r i b u t i o n  t h e v a l u e  K  +  b  7b~ 7c'  C H  8  =R^  C 6 H 8  =  ? b  r  135  c o n s i s t e n t  R  +  ) / R n  TT  C H  5  0 . 0 4 between  were  R  C  q u a n t i t y  v a l u e  7 c  + R  4 b  + Rp  u  5  7  R  +  "  =  7 > 7  C H C H 6  V  +  Bz  r e l e v a n t  0.10  r  R^  M-  T h i s  f  3  7  e t h y l  a n d c y c l o h e x a d i e n y l  r a t e  o f  d i s p r o p o r t i o n a t i o n  t i o n  was 0 . 1 0 i  0 . 0 3 j p a i r  be  e n t r o p y  e x p l a i n e d  b y  t o  t h e  ^  was 0 . 3 8 ±  The r a t i o  combined  c o r r e s p o n d i n g  the  c y c l o h e x a d i e n y l  r a d i c a l s .  0 . 0 3 .  r a t e s  r a t i o T h i s  c o n s i d e r a t i o n s .  o f  .  o f  f o r  o f  c o m b i n a -  t h e  d i f f e r e n c e  U s i n g  t h e  H o l r o y d  e t h y l / c a n a n d  41 e q u a t i o n :  K l e i n ' s  7.63 •  l o g ^ /k (C H*,C H )}- 10B^k A (C H-,C H-)} d  S  °  (  C  2  H  6  c  )  "  2  6  7  d  S (C H C H ) 0  6  ?  2  5  -  c  3  S°(C H ) 3  6  +  6  =  S^CgR^CyL.)  181 An  e s t i m a t e  o f t h er e s p e c t i v e  e n t r o p i e s  w a s made  u s i n g t h e  101 P a r t i a l ( k  / k  d  c  T h i s  Bond  ( C  2  C o n t r i b u t i o n s  H - - , C  6  H - ) ) / ( K  e s t i m a t e  agrees:  0.38/0.10 = 3 . 8 , F u r t h e r o b t a i n e d  d  / k  c  ( C  Method 5  H * , C  6  H * ) )  r e a s o n a b l y  w h i c h  w e l l  t h ep r o d u c t s  the  r e a c t i o n s  a c t i v a t i o n ,  t h er a t e s .  C ^ H g , CgH^Q,  4 b , 2 a ,a n d  t h e n  independent  found  t h eq u a n t i t y  •145 k ^  a n d k  b  2  t u r e R  a  a  + k ^ )  independence  „  n  3  = R  0  0.013,  mechanism  R„  H  C  w h i c h  E i  n  6 8 H  C  /R  n  o, C .  I f  n  •  n  C  u  n  C  n  u  6 7 3 5 H  C  v a l u e  H  o n l y  n o energy  H  i n o f  must  H  o f Q was  o f temperature  between  w i t h  range. b  u  °6 7 3 5 H  6 10  o f Q i n d i c a t e s ; t h a t ' R ^  f o r 14-5 t o 190  a n d R_,  a r ef o r m e d  T h ea v e r a g e  temperature  c a nb e  H  Q c a n b e equated  f o rt h i s  ,  rj  6 10  r e q u i r e  independent  T h e r e f o r e  190°C".  / ( k  ±  ,  6 8  Q = Hi,  o f t e m p e r a t u r e .  t o b e 0.082  t h e v a l u e  a n d CgH^C^H^  3a,b,  t o b e< 2 . '  e x p e r i m e n t a l l y .  R~ „  C  be  w i t h  o f t h ea d o p t e d G  I f  was found  was measured  c o n f i r m a t i o n  b y examining  a n d t h e r a t i o  » R  T h e t e m p e r a -  7  a  + R  7  b  ,  a n d t h a t  we u s e t h e v a l u e  6 1 0 k  4 a ^ 4 b  -  The 5 a , b , c , t i o n  2 . 2 2  1  0  5  p r o p o s e d 4 a , b , 5,  ,  t h e n  mechanism a n d  o f t h er e a c t i o n s  200°C) pendent  k ^ k f  i s s u p p o r t e d  / ( k  a  5  +  a n d p o s s i b l y  b y t h ef o l l o w i n g  o f temperature  between  = 0 . 9 8 ± 0 . 0 2  (130  t o 200°C)  M  c  = 0 . 9 5 ±  (135  t o  M Q  B  z  =  1 . 0 3 ( a t  =  1 . 0 0 ±  180°C); 0 . 0 4  = 0 , 0 8 2 i 0.013  0 . 9 8 ( a t (135  t o  180°C,' w i t h 7d  v a l u e s ,  t h es t a t e d  A  0 . 1 0  t h er e a c t i o n s  130'-and  M  M£  k ^ ) ^ 0 . 1 2 .  ( c o m p r i s i n g  6 a , b between 7a,b,c  a  between w h i c h  l i m i t s :  ;  190°C)  ( 1 4 5 t o 190°C.)  0.77(at  2 a ,  t h e addi1 8 0  a n d  a r e i n d e -  180°C)  190°C);  1 ,  200°C)  • * Figure  25.  Metathesis- of the  allyl  radical  • with  cyclohexa-1,4-diene-3-carboxylate. ,  allyl  182.  Figure  26.  Patterns allyl  of i n t e r a c t i o n s  r a d i c a l and  between  the  the.cyclohexadienyl  radical.  1  1  r  184 The.mutual t i o n  was n o t confirmed  2b)  However, the  a  r e l a t i v e l y  presence  t h e s i s  d i s p r o p o r t i o n a t i o n  o f  between  which  f o r m a t i o n  R  R  C 2  5  H  q  5  +  R  = 0.008  b  Thus,  k  = R5  6  o f  C  2 a  R  &  H  t h e r a t e  / k ^  The  R  +  C  5  H  y  C  e  r  e  6  H  energy  =  C  R  6  H  ^ -  C  H  r  was  6  b y -  0.008  6  ^  R  H  8  meta-  The r a t e  o f  e x p r e s s i o n '  R  „  a  c y c l o h e x a - 1 , 4 -  5)-  ^  c a n b e  5  8  q u a n t i t y  C  R  R  t h e  found,  -  0.008  g i v e n  )/[B]R^  C g H ^  R  ^  .  b y  C g H ^  ( F I G . 25)  H  gave  t h e  5  /A| (cm?molec^sec^)^}=  7±1  a  i s  somewhat  b y  h i g h e r  t h e Evans  than  t h e  a n d P o l a n y i  v a l u e  e m p i r i c a l  i  ' f o r exothermic  :  Q  =  D ( C g H  p r e - e x p o n e n t i a l than  g i v e n  d e t e c t e d .  u n l e s s  ( r e a c t i o n  ( r e a c -  k c a l . / m o l e ;  ± 2  + log|A  6  t h i s  p r e d i c t e d  where  h i g h e r  3c  = R  5  • C  6  E  The  R  propylene  a n d t h e a l l y l  f o r r e a c t i o n  o f  E ^ = 11  k c a l . / m o l e  r a d i c a l  a n d R  p l o t  a c t i v a t i o n  130  e x p l a i n e d  R p TT + R p TT -  6  A r r h e n i u s  e q u a t i o n  n o t be  constant  15  8  c o u l d  c a n be  h  was n o t  o f  was c o n s i d e r e d  w  ^ ,  = ( R p p. -  parameters:  The  2b'  a l l e n e  r a d i c a l s  amount  propylene  3c  because  a l l y l  l a r g e  t h e a l l y l  d i e n e - 3 - c a r b o x y l a t e  o f  10^*'  -  = 11.5 — H )  7  f a c t o r , *  r e a c t i o n s  ~  -  0.25'Q  D ^ H ^ — H )  13  10  r e p o r t e d  k c a l . / m o l e  =.-15  7 + 1 = 1 0 ' " ,  A ^ / A ^  a l t h o u g h  f o r t h e m e t a t h e s i s  o f t h e  57 e t h y l a  r a d i c a l  m e t a t h e t i c a l  energy  w i t h  c y c l o h e x a d i e n e - 1 , 4 - "  r e a c t i o n .  These  a n d t h e p r e - e x p o n e n t i a l  p a r t i c i p a t i o n u n l i k e l y .  o f  r e a c t i o n  5  i n  v a l u e s f a c t o r  ,  i s  n o t u n l i k e l y  f o r t h e i n d i c a t e  t h e o v e r a l l  f o r  a c t i v a t i o n t h a t  mechanism "".  t h e  v  '  i s n o t  •185 addition to propylene, reaction 5 yields  In  hexadienylcarboxylate radicals. sumed i n t h e r e a c t i o n s 6a, The  r e a c t i o n s 7b,  ing  M^-j^ a n d  7c,  and  6b,  These r a d i c a l s 7b,  7c,  6c w e r e n o t  7d,  7c,'  c a n be  ^ ; s i n c e these m a t e r i a l b a l a n c e s were, 6 6  6c  and  C,' t h e  cannot'be s i g n i f i c a n t below t h i s  cyclohexadienylcarboxylate radical  of  6b,  7d;  and  these  reactions  cyclohexa-1,4—diene-3-carboxylate  (1)  study of the thermal  the primary step of the decomposition  a- u n i m o l e c u l a r p r o c e s s w i t h r a t e = 10^^  e  -(38±2)105/RT  Both i t s a c t i v a t i o n energy kinetically (2)  products  carbon d i o x i d e ,  react further.  have  /k  s e c  -1  and p r e - e x p o n e n t i a l f a c t o r  allyl  radicals,  A m e c h a n i s m was and  proposed  are  and c y c l o h e x a d i e n y l  and  2 a  < 0.01,  radicals  s u p p o r t e d by  the  cyclohexadienyl radicals. radicals  i n h a r m o n y w i t h t h e v a l u e 0.008 + 0.003 .  found f o r the thermal decomposition (4)  1)  constant  the p a t t e r n of mutual i n t e r a c t i o n of a l l y l 2 b  found  (reaction  i n t h e p r i m a r y s t e p , and t h e s e  material balances i n a l l y l (3)  we  decomposi-  acceptable.  r a d i c a l s are produced  gives k  allyl  reactions.  t i o n of a l l y l  ^  never-  temperature.  t h e r e i s no means o f d e t e c t i n g t h e  In this kinetic  is  6c.  i s consumed i n r e a c t i o n s  Conclusions.  that  con-  c o n s i d e r e d when d e r i v -  T h e r e f o r e , b e l o w 190°C", i t i s o n l y p o s s i b l e t h a t t h e  6a,  cyclo-  and p o s s i b l y  t h e l e s s , b o t h a p p r o x i m a t e l y u n i t y b e l o w 190 7b,  allyl  of d i a l l y l o x a l a t e .  the p a t t e r n of the i n t e r a c t i o n of a l l y l  and  cyclo-  hexadienyl r a d i c a l s gives reasonable values f o r k ^ / k ^ ,  186 . k ^ / k ^ , k ^ / k ^ , and k ^ / k ^ ; c  the. l a t t e r , v a l u e . ( 0 . 7 8 ± 0.04) 103  agrees for  closely with the corresponding value  the combination  ( 0 . 7 7 i 0.17)  .  o f ethyl radicals with cyclohexadienyl  radicals. (5)  metathesis  of the a l l y l  hexa-1,4-diene-3-carboxylate energy  t h e r e was no e v i d e n c e  t o have an a c t i v a t i o n '  t h a t t h e c y c l o h e x a d i e n y l and  c y c l o h e x a d i e n y l c a r b o x y l a t e r a d i c a l s decomposed u n d e r  the c o n d i t i o n s of the G.  was: f o u n d  cyclo- '  E ^ - 11 , i ' 2 k c a l . / m o l e .  (6) allyl  radical with a l l y l  Reactions  experiment.  of the E t h y l Radical with Allyl•Cyclohexa-1,4-  Diene-5-Carboxylate. The allyl  ethyl radical  s e n s i t i z e d decompositions  of both the  esters of cyclohexa-1,4-diene-3-carboxylic  and m e t h y l  a c i d have been s t u d i e d t o d e m o n s t r a t e and a p p l y t h e easy g e n e r a t i o n o f t h e f r e e r a d i c a l R* f r o m t h e c l a s s : o f s u b s t r a t e <  \~V ^C00R ^  sequence o f r e a c t i o n s m e t a t h e s i s - d i s m u t a t i o n .  >  When R* = a l l y l ,  g e n e r a t i o n o f r a d i c a l s s h o u l d be e v e n more  f a v o u r a b l e t h a n when R* = m e t h y l , ' b e c a u s e t h e a l l y l possesses  a stabilization  energy  radical  o f 13 k c a l . / m o l e ,  which  should increase the rate constant f o r the dismutation of the transfer radical. allyl  However, t h e t h e r m a l d e c o m p o s i t i o n  cyclohexa-1,4-diene-3-carboxylate  ( s e c t i o n E) i s ex-  p e c t e d t o c o m p l i c a t e t h e mechanism o f t h e s e n s i t i z e d To m i n i m i z e results,  this  complication, i n order to obtain  we l i m i t e d t h i s  study t o experiments  where t h e t h e r m a l d e c o m p o s i t i o n  i s still  of  reaction.  meaningful  below  150°C,  o f only minor  187 importance. R e s u l t s . . TABLE X V I I I s u m m a r i z e s t h e r e s u l t s o f s e v e n  120  ments between  and 150°C.  The  imposed by t h e low v o l a t i l i t y ing  low temperature  of the s u b s t r a t e .  experi-  limit The  was .  follow-  p r o d u c t s w e r e d e t e c t e d and t h e i r r a t e s o f f o r m a t i o n  determined:  carbon monoxide, carbon d i o x i d e , ethane,  ene, p r o p y l e n e , n - b u t a n e , 1-pentene, b e n z e n e , and  ethyl-  t r a c e s of  allene. The  r a t e o f f o r m a t i o n o f c a r b o n d i o x i d e was c o r r e c t e d  d i r e c t l y f o r the thermal decomposition of the s u b s t r a t e : 'net  = R^Q ~ 2  [B]; w h e r e k^  i s the rate constant f o r the  v  t h e r m a l d e c o m p o s i t i o n . • C o r r e c t i o n s f o r t h e b e n z e n e and pro-;, p y l e n e produced i n the t h e r m a l r e a c t i o n ; a r e based upon the the. maximum v a l u e s R^ ^ / C 0 i c H ^CO ^*30 6 6 2 3 6 2 observed f o r the thermal decomposition under corresponding R  conditions. exceed v y  6  The  a n <  R  =  These, c o r r e c t i o n s a r e a l w a y s , • =0.10 6thermal  ^  s m a l l and  never  = 0.30  k, [ B ]  [B] ; 3  6thermal  p r o c e d u r e s d e s c r i b e d i n s e c t i o n E were u s e d b o t h  separate the low v o l a t i l i t y  liquid  t o g r a p h y and t o ' o b t a i n t h e i r  p r o d u c t s by gas spectra.  N.M.R.  chroma-.  However,  this  a n a l y t i c a l technique d i d not permit the d e t e c t i o n e i t h e r any p r o d u c t s w i t h t h e s t r u c t u r e s C00C,H C00C H -.:-C H C0QC H,3 5 . / 3 5 2 x / 3 3 c  7  t  o  t  7  „  C00CJ3,3 5  ,  •  to  of  C00C-,H i 3 5  °2 5 H  or  o f t h e a l l y l ..analogues  of the e t h y l r a d i c a l  combination  ri  —  TABLE X V I I I REACTIONS OF THE ETHYL RADICAL WITH ALLYL time min.  [D] [B]  393  30  398  30  403  2d  408  20  414  20  420  20  423  ;  (C H )  (co )  (C H )  18.23 4.86 18.90  14..18 1.10 14.21 1.11 13.80  2  2  5.48 1.85 5.12 1.56 5.37 1.38 5.18 1.44 4.80 1.32 4.95 1.45 4.79 1.45  20  (CO)  2  6.05 17-91 6.44 17.74  ( .H ) ( C H ) Czj  6  ^ 5 10  (  4  13-64 0.92 12.93 0.88  6.50 17.52 7.90  15.09  0.89 16.22 0.98  18.55 8.88  C  H  )  6  5  ( C  E  5.06  3 4 H  6.50  0.36  D i e t h y l ketone; D -12 -3-1 ( ) = R a t e o f f o r m a t i o n x 10 molec.cm.sec.  Et  M  A 1 1  OfO^o = (Rc H 5  + 1 0  +  R  R  m  = 10 '3(k /k|) . k VJ  ) / R  +  5  A=  6  lo 3( 1  k ?  /k|)  —••— ( c m f m o l e c ^ s e c ) ^ — : — ' 1  1 0  ;  Bz  E t  0.107  0.84 0.89  0.107  0.115 0.130  0.51 0.97 0.69 0.96 0.77 1.08  0.94 0.88 0.70 0.92 0.77 0.97  0.150  k  M„ C 1.04  0.98 0.88 0.93 0.90 . 0.93  0.101  0.73 0.96 0.79 1.00 0.81  0.98  0.88  0.85  ME  k. •A  200 7.7 232 35 254  38  304  68 300 95 337 48  370  29  V E^ D 14.3  15.9 37.2 15.3 55.0  14.9  66.0 15.1 69.1 15.0 58.5 15.6 129  15.2  B = Substrate  M  R  R  / R  2  RC3H + R c H 4 2 R c H 6  6  1  6  1  k  R  M "Et. M , ., All  1 Q  0.094  C H 6 - C H 1 0 " C3H4 " < " A 1 1 ^ C 0 ~ 6 b ) 2  /k  t o TABLE X V I I I  -17 -3 [ ] = c o n c . x l O 'molec.cm.:  M  1 1 a  )  0.05 <0.01 5.83 0.49 0.05 <0.01 6.19 0.51 0.07 <0.01 7.28 0.57 0.10 0.06 6.38 0.58 0.06 0.02 8.00 0.60 0.09 0.10 0.85 8.50 0.10 0.15  3.84 Key  (0 H^ k  6  p6 10>  6.45 3.83 5.79 4.85 5.55 4.75 3.98 5.30 4.20 3.88 3.98 5.20  1.05  6.40 16.20  10  CYCLOHEXA-1,4-DIENE-3-CARB0XYLATE  C0 5 2  M  Bz  = R c  6 6 H  k = io-^(k k^/k D  9  / R  6bIt  C0  C0 ;  ;  R  M  2  6b = =  C  R  2  ° 2 0  " / R  1  +  (  1  2  ° -^*0.0*3  6  ) ; E = 4.575 x 10-5T(log.k - 16.00)  ^ (cm^molec.sec? )^**  D  /  D  kcal./mole  00 ro  189 products.  T h i s was p r o b a b l y b e c a u s e t h e s e compounds a r e v e r y  involatile,  and t h e r e f o r e have v e r y l o n g r e t e n t i o n t i m e s a t  column temperatures  a t which  they are stable.  The a n a l y t i c a l t e c h n i q u e o f s e c t i o n F was. u s e d  f o r the  d e t e c t i o n o f a n y medium v o l a t i l i t y p r o d u c t s w i t h t h e s t r u c tures  C  2 5 H  C  5 5 H  C  3 5 H  None o f .these compounds was d e t e c t e d , b u t t h r e e s m a l l o v e r l a p p i n g p e a k s were o b s e r v e d that of hexadiene-1,5. not  exceed  w i t h r e t e n t i o n times close t o  The t o t a l  area o f these peaks d i d  5$ o f t h e p e a k a r e a o f b e n z e n e .  I ti s probable  t h a t one o f t h e m c a n be a s c r i b e d t o h e x a d i e n e - 1 , 5 . t h e s e p e a k s c o u l d n o t be i d e n t i f i e d  conclusively,  Although a n d no  s e p a r a t e d e t e r m i n a t i o n o f t h e i r a r e a s c o u l d b e made, t h e r a t e of f o r m a t i o n o f hexadiene-1,5 third  oft h e i r total^area to this  Kinetic Analysis. 2 5  o  c  2 5  2C H*  -> C H 2  2  C H* 2  2  +  C H COC H 2  +  +  2  5  2  a  4  2  (2)  5  + C H  4  2  (3) •  6  -> C H C O C H  5  (4)  -> C H C O C H  5  (5)  2  5  C H COC H  (1)  2  H  •2C H* 2  > 2C H* + CO ~> ° 4 1 0  2  C H*  compound.  • '.  C^,Hr- C 0 C H  C H*  was e s t i m a t e d b y a s c r i b i n g one  4  4  2  9  C H 2  6  2  +  COOC^ 35  (61)•(6)  COOC,Hc•..5 1?  °2 6 H  +  OQC^H^  (en)  190 C  2 5 H  ^^>-COOC H 5  (eia^  5  l  C^H* -H <Q\-C00C H 3"  (61a)  7  '2"5  5  ^\  /  G  2 5 H  (61  J  COOC.H,5 5  x=x  C-H,-/ 2 5 C H2  +  (6a) (6.0^-,  XOOC-JI,3 5  G  (6Ha)  2 5 H  COOCjH^ (6Ha^COOC^H^  C^H* +  /TVcOOCjH^  (61b) COOC^Hr- + 0 H,. / 3 5 2 6 o  C H2  (6b) (6Hb) -  +  COOC-.H. 5 3  + C0  COOC,H 5 5  2  + C^H"  (9)  C  C  C,H; + CH*  (10)  5 10 H  -> C H  4  + CjHg  (11a)  "* C H  6  + C H  (11b)  2  0  3 5  '3"5  T  \ 3 ~  0  2 5  0  Q  C  *5  H  2  C  3 55 H  G  4  (12IaT  5 ^  +  5  C H C H 000C H . 5  5  6  6  isomers COOCUHc-  2 5  3  5  .  (12a) (12Ha)-  191 COOCH. 5 3  3 5  (12Ib)^| COOC-,H + C , H 3 5 3 6 c  o  5  \=/  (12Hb)> J COOC,H,5 3 *  5 3 The ide  (12 b)  C  C  6 C  H  (13)  1 0  3 4 H  +  C  (13a)  3 6 H  l a r g e r a t e s o f f o r m a t i o n o f ethane and carbon  indicate that the metathesis  r e a c t i o n 6and:the  diox-  dismuta-  t i o n r e a c t i o n 9 a r e t h e k e y r e a c t i o n s o f t h e g e n e r a l mechanism.  The r e a c t i o n s 6 1 a n d 6 1 1 b o t h y i e l d  addition, and  the a l l y l  ethane and, i n  cyclohexadienyl carboxylate radicals I "  I I * respectively:  ,  denoted I I *  denoted I * and  COO.CUHc-  3 5 The  5 5 r e a c t i o n s c a n be g i v e n b y  combined r a t e s o f these R  =  6  w h e r e R, = 0.136R„ „ 5 V 10  C  R  5  2  H  6  "  ; R  R  3  "  R  4  "" 6 b R  ~  R  11b  = k^/k|[D]R  ZL  A  S i n c e R g ^ c a n n o t be m e a s u r e d , a n e s t i m a t e may  p r o v e t o be s u f f i c i e n t ;  following considerations; c a l c u l a t e R^ f r o m t h e r a t i o e t h y l r a d i c a l w i t h methyl,  this R  6  c a n be o b t a i n e d f r o m t h e  ~ C0, R  1 2  > 6a R  +  R  ^ 6b*'  i  f  k^/k^ f o r t h e metathesis  w  e  of the  cyclohexa-1,4~diene-3-carboxylate  ( s e c t i o n E ) , we f i n d t h a t R g - R „ ^ 2.3x10  o f i t s magnitude  J2 v a r i e s from 6 . 1 x 1 0 to  2 m o l e c . c m ? s e c ? b e t w e e n 1 2 0 a n d 150°C, t h e s m a l l e r  values corresponding  roughly t o the higher temperatures.  I f  192 Figure  27.  M e t a t h e s i s of the e t h y l r a d i c a l allyl  with  cyclohexa-1,4-diene-3-carboxylate.  193 Figure  28.  Patterns  of decomposition  hexadienylcarboxylate'  of the a l l y l  radical.  cyclo-  194  v a l u e 0 . 5 2 f o r Rg^/R^a  we u s e t h e w e i g h t e d a v e r a g e we f i n d  that  (2.1  <  120 a n d 150°C.  t o 0 . 8 ) x 10  molec.cm.sec.  between  As a n a p p r o x i m a t i o n , we c a n u s e t h e a b o v e  v a l u e s t o d e f i n e an upper l i m i t f o r R ^ range  CsectionE),  i n the temperature  120-150°C: R  6b~  2  *  1  ( ^ 2 0 - t ° C ) x 0.04-5  +  at  t°C = 120°C:  at  t ° C = 150°C:  Thus a n a p p r o x i m a t e  6  b  «  6  b  ^  R  R  2.1x10  1 2  molec.cm sec? 3  0.8 x 1 0 m o l e c . c m ? s e c ?  etc.  1 2  estimate of the following  e x p r e s s i o n can  a l s o be made  The A r r h e n i u s p l o t  of this  e x p r e s s i o n was. l i n e a r ,  and t h e  p a r a m e t e r s were E g = 5 » 8 ± 0 . 7 k c a l . / m o l e and 5-5 15  + l o g J A ^ / A ^ C cm^molec^sec'] ) ^ .  cantly different radical  0.3 f o r  These .values a r e n o t s i g n i f i -  from those f o r the metathesis o f the e t h y l  w i t h methyl cyclohexa-1,4-diene-3-carboxylate:  E = 6 . 0 ± 0 . 5 k c a l . / m o l e ; 13 + l o g { A / A | ( c m ? m o l e c ? s e c ? ) ^  =  6  5.7 * 0.3 ( s e c t i o n E ) .  The r a t e d i f f e r e n c e R g - R  found  C Q  2  f r o m t h e e x p r e s s i o n G1 v a r i e s f r o m 4-.6 t o 1 . 6 x 1 0 1 2  -T  m o  ]_  e c  .  c m  ^sec  betv/een 120 a n d 150-°C, t h e s m a l l e r v a l u e s c o r r e s p o n d i n g r o u g h l y to  the higher temperatures. The r a t i o  ( 5 " Q Q )/ 6 R  r  R  0.25 f o r a temperature  d  e  c  r  e  a  s  G 0  since R 6 - R C o 2  s h a r p l y from. 0.4-9 t o  s  i n c r e a s e f r o m 120 t o 135°C\  f r o m 0 . 2 3 t o 0 . 1 5 f r o m 155 t o 150°G cate that R  e  (FIG. 28).  T h i s may  i n c r e a s e s , a t t h e e x p e n s e o f Rg-j- + ^  R 6  I  +  R  6 a I I  increase with temperature.  +  R  6 b I I '  a  n  d  s  i  n  c  e  E  6I  and s l o w l y  c  R  5 j j  + 6bH' R  a  a  n  o  n  indi-  l  y  I t can also lead t o the conclusion  195 *» 0.3  t h a t R g j 0 . 1 5 Rg, u n l i k e t h e v a l u e s R ^  ^VcOOCH,  °2 5 H  V COOCH^  Q  +  —  This the  may i n d i c a t e t h a t allyl  °2 6 H  / T V COOCH-, 5  611  the o p p o s i t i o n  i s more s h e l t e r e d i n  e s t e r than i n t h e methyl e s t e r o f cyclohexa-1,4—  diene-3-carboxylate. an u p p e r v a l u e 0.15 have  &  61  +  —  R for  From t h e g r a p h (FIG.  R g f o r Rg-j-y a n d s i n c e • Rg = Rg-j- + R g j j > The r a t i o R5kn/- 6 a ii f o r t h e R  = 0.85 R .  Rgj-j-  2 8 ) we c a n assume  Q  we  methyl  v  c y c l o h e x a - 1 , 4 ~ d i e n e - 3 - c a r b o x y l a t e s y s t e m ( s e c t i o n E ) was estimated write R  a s 0.24-. S i n c e  6 b I I  = (0.85R - R 6  R g j j + Rg^ix  c o  a  =  R  6 I I ~ C0  '  R  w  e  f o r Rg-^jjV'we c a n o b t a i n  c o n s t a n t k^ o f t h e d i s m u t a t i o n  t i o n 9:  - 5.16 R  5 b X I  Under comparable c o n d i t i o n s  c  0  2  R^ /(0.85 R o  -  Q  reac-  R ^ )  of temperature, i n t e n s i t y of  i l l u m i n a t i o n , and c o n c e n t r a t i o n the  n  a rough  estimate f o r the rate 9  a  )/5.16.  Using t h e upper l i m i t  k k^/k  c  v a l u e o f k^ f o r t h e a l l y l  of reactants,  we f i n d  that  e s t e r of cyclohexe-1,4—diene-  3 - c a r b o x y l i c a c i d e x c e e d s t h e v a l u e o f k^ f o r t h e m e t h y l e s t e r b y a f a c t o r o f 6 0 0 a t 135°C.  This  supports o u r con-  c l u s i o n s about t h e importance o f c o n t r i b u t i o n o f t h e s t a b i l i z a t i o n energy of t h e a l l y l of r e a c t i o n  r a d i c a l -to t h e t r a n s i t i o n  state  9. 1^  The (FIG.  Arrhenius  28),  p l o t o f o 2 ' 6 b I I Save a wide  which.frustrated  k  k  /  k  /  a direct evaluation  scatter  of i t s  196 parameters.  The a c t i v a t i o n e n e r g y ,  S^, was e s t i m a t e d  indirectly:  E ^ = 4.575 ( l o g C k ^ / k g ^ )  - 1 6 . 0 ) 1 0 ~ T , where 5  t h e v a l u e log^AgAg/A^-j.-j-Ccm^molec^sec^ ) ^ = 1 6 . 0 v/as a d o p t e d from t h e k i n e t i c carboxylate  system.  From t h i s  e x p r e s s i o n , t h e median v a l u e  E ^ was 15.2 ± 0 . 5 k c a l . / m o l e .  of  v a l u e s of. E ^ f o r t h e m e t h y l diene-3-carboxylic acid the d i f f e r e n c e values  cyclohexa-1,4-diene-3-  study o f t h e methyl  The d i f f e r e n c e b e t w e e n t h e  and a l l y l  5 kcal./mole,  i s about  •  ofAH ; Q  A H = -7 k c a l . / m o l e *  6 6 H  C 0 0 C H  5  > C  fi.H.COOC^H,, 6  parallelling  o f 17 k c a l . / m o l e b e t w e e n t h e c o r r e s p o n d i n g  y  C  cyclohexa-1,4-  esters of  '  6  In  6 6  »C  5 5 .  H  f  i  H  +  f  +  i  2.  C 0  6 6  +  CO. 2  C H  5  E = 20 + 1.5  5  + 'C,H";  A  H  5 5'  kcal./mole  ~ «/niole* E! = ,15 k c a l . / m o l e =  2  4  k c a l  t h e d e r i v a t i o n o f t h e r a t e s o f _ t h e r e a c t i o n s 6 and 9,  t h e p a r t i c i p a t i o n o f t h e r e a c t i o n 1 4 was i g n o r e d . C,H:  +  35  C-H^COOCH,67 35  T h i s v/as j u s t i f i e d the temperature R  If  14  =  R  C H 3  R  6  A  +  (141,11)  C H C00C,H c  c  (  66  35  by t h e s m a l l v a l u e o f R^/R^  range  11a"  >C'H 36  R  o f t h e experiment.  12b  v/e n e g l e c t R ^ b '  w  e  throughout  = R  C H $  °' ' b  C H  R  6  !:ain  2  a  n  u  + 4  PP  e r  ° '  1  5  6  % H  limit  " 12b R  1  0  f o rR^.  Using  t h a t R^^/Rg = 0.04 a t 150°C, a n d i s l o w e r a t  t h i s we f i n d  lower temperatures.  This result  implies that the rate of  production of a l l y l  cyclohexadienyl carboxylate radicals  c a n be a p p r o x i m a t e d  v e r y c l o s e l y b y R^ = R^  QQQQ JJ • 6 6 3 5 H  * A H f ( C 5 H 5 C O O C H 3 ) and A H f ( C 5 H 5 C O O C 3 H 5 ) were c a l c u l a t e d b y t h e P a r t i a l Bond C o n t r i b u t i o n s Method; o t h e r h e a t s o f f o r m a t i o n needed t o c a l c u l a t e t h e s e h e a t s o f r e a c t i o n were t a k e n from t a b l e s ' ^ . 1  197 The  material balance f o rthe a l l y l cyclohexadienylcar-  boxylate radicals M  C  =  ( R  C0  c a n be g i v e n b y •  2  +  R  6a  +  6b  R  +  12a  R  +  R  12b  +  2  R  x^  R  6 '  where R i s t h e r a t e o f f o r m a t i o n o f t h e d i m e r ( C H C 0 C H ) x. ^ 6 6 2 3 5 2 r  r  rates R^  The  A  ,  B  However, t h e i r of  R^Q  R  i 2 a b'  a  n  d  x  R  c  o  u  l^  n  o  ^ ^  e  m  o  2  c  n  easured.  t o t a l m a g n i t u d e c o u l d be i n f e r r e d  by the value  /Rg> w h i c h v a r i e d f r o m 0.51 t o 0.85 b e t w e e n 120 a n d  150°C. The  material balance f o rthe a l l y l  ved b y assuming t h a t t h i s  radical  rates o f a l l these r e a c t i o n s ,  The of  average  B  0 H 5  +  R  CV  value of t h i s  temperature,  restricted 2  3  6  The sum o f t h e  with theexception of R ^ a '  c a n be m e a s u r e d , a n d o n t h i s "  c a n be d e r i -  i s consumed o n l y i n t h e  10, 11a,b, 12a,b-, 13, 13a, a n d 1 4 .  reactions  "All  radical  V  b a s i s we o b t a i n  ) / E C 1 0  °2  (  G  3  )  i s 0.85 - 0 . 0 6 , i n d e p e n d e n t  ratio  i n d i c a t e s t h a t a p p r o x i m a t e l y 15$ o f t h e  which i  allyl  a r e c o n s u m e d i n r e a c t i o n 12a ( o r i n o t h e r r e a c -  radicals  t i o n s which  do n o t y i e l d  t h e substances  accounted  equation).  F o rthe thermal decomposition of a l l y l  f o ri n the cyclohexa-  1 , 4 - d i e n e - 3 - c a r b o x y l a t e ( s e c t i o n F ) , i t was shown t h a t R 12a^ 12V 12b C H - 1 1 a" 1 4 1  0  R  W  h  e  r  e  R  =  R  R  3  R  11a  10  1 5  " C K V °'^6 R  ^  R  2  (k  1 Z f  /k^)  = 10  7 : = 1  c  o  R  ;  6  and R ^  - ( k , ^ )  e x p ( 1 1 ± 1.3/RT)  '  (from s e c t i o n F ) —3  T h u s , i t was e s t i m a t e d t h a t and R  1 2 a  = ( 0 * 8 t o 1.2) x 1 0  ^  R  1  2  2  b  =  ° *  0  8  t  o  °.12 m o l e c . c m < s e c .  molec.cm?sec?  I f R  1 2 a  i s added  0  to  t h e numerator o f M  A  1  1  , then M  A 1 1  —1  = 1.10 ± 0.08.  This  198 indicates  that  our estimate f o r  e v e r , we c a n c o n c l u d e t h a t  ^  ed  n  The a l l y l tion  •  r v  4 a n d 6 one t r a n s f e r  radical  ( a ) by i n t e r a c t i o n w i t h an e t h y l  radical.  (b)  by i n t e r a c t i o n w i t h an a l l y l  radical.  (c)  by d i s m u t a t i o n . reac-  c a n be consumed b y i n t e r a c t i o n w i t h one o f t h e t h r e e ethyl, allyl,  tion of a l l y l  radicals  not possible  S ^ + V V ' W  radicals  radicals. " ^ H  where R  6 b  o f forma-  f o r every molecule o f ethane  a r e consumed:  +W ' W ? *  radicals  Since the rate  i s r e l a t i v e l y h i g h , f o r t h i s system i t  now a more r e a l i s t i c  tion of a l l y l  transfer.  t o assume t h a t  p r o d u c e d two e t h y l  Et  ;  F o r every molecule o f  r a d i c a l which i s produced i n t h e dismutation  radicals:  M  R~ = R „ n  f o r m e d , w h i c h c a n be c o n s u m e d i n one o f t h e f o l l o w i n g  t h r e e ways:  is  a n d 11b.  2  ethane produced i n t h e r e a c t i o n s  is  deriv-  r a d i c a l i s consumed o n l y i n t h e r e -  R , + R„ + • Rr- = R t r - R n rj - R 0 4 6 OpHg ^ 3 4  is  r a d i c a l c a n be  2, 3, 4, 5, 6, 6 a , 6 b , 10, 11a,  actions  accounts  radicals.  balance f o r the e t h y l  by assuming t h a t . t h i s  h i g h . How-  12a more t h a n  reaction  f o r t h e a p p a r e n t 15$ wastage i n a l l y l The m a t e r i a l  somewhat  s  2  V  +1 1  approximation;  0  the relationship  •"•'C-  (1 - M^.^)  i  M  A11  ) E  C0  the frac-  s  consumed b y c o m b i n a t i o n w i t h  transfer  Thus + 1  Q  E  G H 2  = 2.1  This material  6  E  C H 6  1 0  -  ^H^ - ' " W 1  1  1  H  C 0 . f  R 6  >  0  0  ~  + (120 - t ° C ) x 0 . 0 4 3  b a l a n c e h a s t h e a v e r a g e v a l u e 0.93 ± 0.06, i n d e -  p e n d e n t o f t e m p e r a t u r e b e t w e e n 120  and.130°C.  2  '  199 The  defect  of the value  s i g n i f i c a n t with the l i m i t s arise  7  6  H  of error s t a t e d .  +  6  C  H  2  t o be  I t could  C 0 0 C H 7  2  CHCH C H 2  2  (7)  C^COOCH^HCH^H,-  2  >C H CO.OCH CH(C H )CH C H  5  6  7  r e a c t i o n 7 were s i g n i f i c a n t ,  If  from u n i t y f a i l s  from a d d i t i o n of t h e e t h y l r a d i c a l t o the s u b s t r a t e :  CpH° + C H C 0 0 C H C H = C H °2 5  of M ^  2  2  5  a considerable  2  2  (?a)  5  proportion of  a d d u c t r a d i c a l s w o u l d be e x p e c t e d t o decompose t o 1-  the  pentene, carbon dioxide 67 This  and the c y c l o h e x a d i e n y l  j 5 2 5  67  radical:  5 10  2  d e c o m p o s i t i o n c o u l d be r e c o g n i z e d  by the p r o d u c t s o f  subsequent r e a c t i o n s o f t h e c y c l o h e x a d i e n y l  radical: (8a)  j>> Cf-EUCJEL i s o m e r s ^  7  C  6 6 H  °2 6  +  H  ,  1  ^  C^H^C-H,- i s o m e r s a r e s e n s i t i v e i n d i c a t o r s o f r e a c t i o n 8 , 6 7 2 5 . '  The  y  since they are e a s i l y detectable careful R  G h W  n  6  6  analysis failed  /R^p, G0  generation  i n trace  t o detect  them.  amounts; however Moreover, the r a t i o  = 0.98 ± 0.05 i s c o n s i s t e n t w i t h t h e e x c l u s i v e 2  o f benzene i n r e a c t i o n 9.  These f a c t s a r e s t r o n g  e v i d e n c e f o r b e l i e v i n g t h a t r e a c t i o n 8 i s n e g l i g i b l e , and by that r e a c t i o n 7 i s a l s o n e g l i g i b l e i n the tempera-  inference  (120 t o 150°C).  t u r e range o f our experiment  The v i e w  that  r e a c t i o n 7 i s n e g l i g i b l e c a n be f u r t h e r s u p p o r t e d , s i n c e t h e p l o t of k  Arrhenius coherent The  11a  =  R  A  = (1 - M )  2  E t  ^QQ/^^  ^  F  O  L  L  O  W  S  N  O  pattern. pattern  o f i n t e r a c t i o n between e t h y l and a l l y l f r o m t h e r e l a t i o n s h i p s R^Q ='RQ  c a l s v/as o b t a i n e d R  7  C V 2  0  -  1  5  6  \ H  1  0  '  a  n  d  R  11b  =  R  C H ' 3  4  ^  ,  radi-  200 ^Ha^lO 120  =  °*°7  a n d 150°C;  -  0.02,  R 1  1  b  /  independent o f temperature between ^ °-  R 1  0  b e t w e e n 120  0 2  and 150°C  v a l u e s a r e somewhat l o w e r t h a n t h o s e f o r a l l y l system ( s e c t i o n A ) : 0.03  1 0.01.  R 1  1  a  /  R  = 0 1  ,  1  -  0  0  a  n  d  R  3-butenoate  Hl/ 10 R  R  of  =  T h i s may be a t t r i b u t e d t o t h e l o w p r e c i s i o n  associated with the indirect determination of ^ ^ difference  These  o f much l a r g e r q u a n t i t i e s .  t h e r a t i o R« u /R  w  n  a  from t h e  A direct determination  gave, a v a l u e 0.11 t 0.03  between  °3 6 °5M10 120 a n d 135°G; t h i s v a l u e i s i n c l o s e a g r e e m e n t w i t h - t h e • v a l u e 0.10  xi  ± 0..03 f o u n d f o r t h e a l l y l  14-0°C, t h e r a t i o R~ TT /R w °3 6 °5 10  3-butenoate system.  Above  increases slowly with  n  tempera-  ture, which i n d i c a t e s that metathetical reactions of the a l l y l r a d i c a l a r e becoming  significant.  Conclusions.  The a l l y l  phase  120  between  i  r a d i c a l may be g e n e r a t e d i n t h e - g a s  a n d 150°C, b y a s e q u e n c e  o f m e t a t h e s i s and  dismutation: C H*" + C H C O O C H 2  6  7  5  C H C00C H 6  6  3  5  >C H  6  +  >C H  6  + C0  2  5  5  A- m e c h a n i s m h a s b e e n p r o p o s e d f o r t h i s p o r t e d by t h e f o l l o w i n g (1)  the ratio R  c  H  (2) reasonably (3)  /R  c o  + ^H*  system, which i s sup-  = 0.98 ± 0.05,  independent o f  2  a n d 150  C.  the material balance i n the a l l y l  radical i s  satisfactory-. t h e p a t t e r n o f i n t e r a c t i o n between a l l y l  r a d i c a l s conforms t o t h e r e s u l t s (4-)  2  observations:  6 6 t e m p e r a t u r e b e t w e e n 120  C^COOC^  t h e magnitudes  and e t h y l  o f p r e v i o u s work.  of t h e Arrhenius parameters f o r t h e  m e t a t h e s i s and d i s m u t a t i o n r e a c t i o n s a r e r e a s o n a b l e .  201 •H.  P h o t o c h e m i c a l R e a c t i o n s o f Acetophenone w i t h Cyclohexa1,4—Dienic In  Derivatives  s e c t i o n s E a n d P i t was shown t h a t t h e e t h y l  can s e n s i t i z e t h e d e c o m p o s i t i o n s  o f both methyl  radical  and a l l y l 10-5  cyclohexa-1,4—diene~3-carboxylate. h a v e shov/n t h a t a l k y l r a d i c a l s of  cyclohexadiene-1,4-.  A l s o , James a n d S u a r t  can induce the decomposition  I n a l l cases, metathesis of the a l k y l  r a d i c a l w i t h t h e s u b s t r a t e was f o u n d t o b e ' t h e step.  S i n c e t h e acetophenone t r i p l e t ,  74- k c a l . / m o l e , c a n a b s t r a c t a h y d r o g e n 80 s t r a t e s t o form a p i n a c o l it  '  sensitizing  w i t h an energy o f atom f r o m v a r i o u s , s u b -  (see below), i ti s possible  that  c a n a l s o be u s e d t o s e n s i t i z e t h e d e c o m p o s i t i o n o f c y c l o -  h e x a - 1 ,4— d i e n i c d e r i v a t i v e s .  B i n a r y , gas-phase m i x t u r e s o f  acetophenone w i t h each o f t h e s u b s t r a t e s cyclohexadiene-1,4-, methyl  c y c l o h e x a - 1 , 4 — d i e n e - 3 - c a r b o x y l a t e and a l l y l c y c l o h e x a -  1 , 4 — d i e n e - 3 - c a r b o x y l a t e v/ere e a c h i l l u m i n a t e d a t v a r i o u s temperatures  w i t h U..V. l i g h t  each s e r i e s o f experiments mechanisms w h i c h  o f A ^ 3000 A *•.  The r e s u l t s o f  a n d t h e p r e l i m i n a r y i n f o r m a t i o n on  c o u l d be o b t a i n e d f r o m t h e m a r e d i s c u s s e d  separately i n the following subsections. R e a c t i o n s o f Acetophenone w i t h Experiments to  were c o n d u c t e d  180°C u n d e r tv/o d i f f e r e n t  a dark thermal experiment  Cyclohexadiene-1,4i n the temperature  light  intensities.  was p e r f o r m e d  range  110  In addition,  a t 170°C w i t h a m i x -  t u r e o f acetophenone and cyclohexadiene-1,4-;  no p r o d u c t s  .were o b t a i n e d . T h r e e e x p e r i m e n t s w e r e p e r f o r m e d u n d e r f u l l I l l u m i n a t i o n s o u r c e a n d f i l t e r d e s c r i b e d o n p . 2 1 , E a n d B.  light  i n t e n s i t y , , and  1/20th  of f u l l * .  r i z e d -in.TABLE  The XIX.  s i x w i t h the l i g h t results  i n t e n s i t y reduced  o f these: e x p e r i m e n t s  Both the f u l l  s i t y experiments y i e l d e d benzene,  a r e summa- -  and r e d u c e d l i g h t pinacols,  inten- .  carbinols.and .  ^cyclohexadiene-1,3.  However, under  d i e n e - 1 , 3 v/as f o r m e d  o n l y a t t e m p e r a t u r e s up t o 160°C.  h e x e n e was  intensity. (Dg)  was  reduced l i g h t ,  a l s o y i e l d e d i n a l l experiments under  I n t e n s i t y and by t h e e x p e r i m e n t The  a t 180°C u n d e r  rate of disappearance of  appreciable; therefore  i t was  to  cyclohexaCyclo-  reduced  full  light  light  in  cyclohexadiene-1,4  directly  measurable.  N e i t h e r c a r b o n m o n o x i d e n o r m e t h a n e w e r e d e t e c t e d a t . a n y tern-' . p e r a t u r e under  either light  p o s i t i o n of t r i p l e t The  liquid  intensity;  acetophenone  therefore,  under  decom-  v/as e x c l u d e d .  residue a f t e r the removal  reactants v o l a t i l e  any  of a l lproducts  v a c u u m a t 120°C, was  and  investigated  -*•" The r e d u c t i o n o f l i g h t i n t e n s i t y was a c h i e v e d , b y a n e u t r a l density filter.. The d e g r e e o f r e d u c t i o n o f t h e i n t e n s i t y was e s t i m a t e d by p h o t o l y z i n g 5 . 8 x 1 0 molec.cm-r? s a m p l e s o f p u r e d i e t h y l k e t o n e , one w i t h a n d one w i t h o u t t h e f i l t e r , a n d b y measuring t h e y i e l d of c a r b o n monoxide i n each c a s e ; Full intensity : Rco = 1 . 5 x 1 0 3 V _3 _1 Reduced i n t e n s i t y : RCO 0.84x10l2jmolec.cm.sec. ..Both a c e t o p h e n o n e a n d d i e t h y l k e t o n e a b s o r b a t 3130 °, w i t h ^ A = 7 x 1 0 ~ 2 0 and = 7 x 1 0 - 2 1 cm^molecJcm^ r e s p e c t i v e l y . 8 0 The l i g h t i n t e n s i t y a b s o r b e d b y a c e t o p h e n o n e , l | t , c a n be 1  =  jA _ _ ^'o""^A A .)/(i _ I O ~ ^ ) a a s,rp where i s the c o n c e n t r a t i o n of acetophenone (C^ = 5 . 3 x 1 0 m o l e c . c r r ~ 3 ) , a n d Cj) a n d i g a r e , r e s p e c t i v e l y , t h e c o n c e n t r a t i o n ' o f and t h e l i g h t i n t e n s i t y a b s o r b e d by d i e t h y l k e t o n e : i-= l e n g t h o f c e l l ( 1 0 c m . ) . S i n c e ( P c O = 3» A 14 -3-1 Full intensity : I =10 q u a n t a cm.sec. ^ * p _3 —1 Reduced i n t e n s i t y : -I = 6x10 q u a n t a cm.sec. The a b o v e e s t i m a t e s a r e o n l y a p p r o x i m a t e , s i n c e t h e i n c i d e n t l i g h t was n o t s t r i c t l y m o n o c h r o m a t i c (3000 A t o 3200 A ) . estimated from  c  a  1  D C ] D 1  20J  for  the p r e s e n c e o f c a r b i n o l s and p i n a c o l s .  T h i s r e s i d u e was  d i s s o l v e d , i n d e u t e r a t e d c h l o r o f o r m a n d i t s N.M.R. s p e c t r u m obtained.  a t S = 7.3 t o 7.8, w h i c h  T h i s s p e c t r u m showed p e a k s  c o r r e s p o n d e d t o the p r o t o n s o f the benzene r i n g , at  £ = 1.5,  peaks likely  a d o u b l e t a t S = 1.7,  t h a t c o u l d n o t be i d e n t i f i e d  and a s i n g l e t  and a l s o a m u l t i t u d e of o t h e r clearly;  two o f t h e s e most  c o r r e s p o n d e d t o t h e p r o t o n s o f CO-CH^ a n d t o t h e  c  protons.  The s i n g l e t  (6=1.5)  i d e n t i f i e d by comparing  and the d o u b l e t  (S=1.7)  vinyl were  t h e N.M.R. s p e c t r a o f t h e r e s i d u e a n d  5/9 b y w e i g h t s o l u t i o n s i n CDCl-^ o f e a c h o f a c e t o p h e n o n e / c y c l o hexadiene-1,4, methyl p h e n y l c a r b i n o l , and methyl The  l a t t e r t w o were c h o s e n b e c a u s e  pinacol.  the c a r b i n o l and methyl  phenyl p i n a c o l are l i k e l y p r o d u c t s o f the system and are e x p e c t e d t o show p e a k s  s i m i l a r t o the two under  investigation;  m e t h y l p i n a c o l was u s e d a s t h e a v a i l a b l e p r o d u c t gous t o m e t h y l p h e n y l p i n a c o l . doublet group  (£ = 1.7)  Comparison  corresponds t o the protons o f the methyl,  o f the secondary a l c o h o l , methyl phenyl  p r o t o n s o f the methyl group  methyl phenyl p i n a c o l most l i k e l y  most a n a l o -  indicated that the  carbinol  (CgH(-) (CH^)CHOH, a n d t h a t t h e s i n g l e t '•(£= 1.5) the  ;  o f a t e r t i a r y a l c o h o l s u c h as.  (CgH^)(CHj)C(OH)  2  ; therefore i t i s  t h a t these a l c o h o l s are formed  t i o n o f acetophenone  corresponds' t o  b y cyclohexadiene-1,4-.  i n the  photo-reduc-  No q u a n t i t a t i v e  measurements o f t h e r a t e s o f f o r m a t i o n o f t h e s e a l c o h o l s  could  be o b t a i n e d . Kinetic Analysis. suggest a complex  The n a t u r e a n d d i s t r i b u t i o n o f t h e p r o d u c t s mechanism, w h i c h c a n n o t be d e s c r i b e d b y a  I  , TABLE X I X :  10 - l£££ 1  °K  2  REACTIONS OF THE TRIPLET-ACETOPHENONE WITH C Y C L O H E X A D I E N E - 1 , 4  W  [B]  Full light intensity 383 100 60 5.50 418 100 60 5.43 453 100 60 5.68 Reduced l i g h t i n t e n s i t y 393 6 600 5.68 203 6 600 5.71 418 6 600 5^37 435 6 600 5.68 443 6 600 5.68 453 6 600 5.68 ;  TABLE XX: °K  1 0  Full 572 384 394 406 416  light 110 110 110 110 110  1  2  I ^ ^  [D]  intensity 30 5-35 30 5.85 30 6..60 30 6.45 50 6..27 - / l  A = light a  6  6  [B] 2.66 2.33 2.45 2.53 2.33  g  (C0 ) 2  14.75 14.80 15.55 16.71 17.25  (CH„)  o f d i s a p p e a r a n c e o f B) x 10 6  6  B  MC^O-RO^O/DB;  M  ^ H /  13-93 14.85 15.61 15.82 17-30 m o  0.30 0.36 0.45 0.39 0.50  lec.cm?sec?;  -3 -1 m o l e c . c m . s e c . ; MQ = ( C 6 H 6 Q 6 H - i o R  C H 6  = RC H / B' M e D  8  6  8  M  \ « 8  0  0.02 , 0.05 0.05 0.07 0.19 0.25 0.27  0.83 0.78 0.96 0.80 0.87 0.88  ( C ^  O.05 0.06 0.04 0.05 0.06  ( ) = rate of formationx10-12  0.84 0.96 1.12  1  0.11 0.13 0.11 0.05 0.-06 0.06 0.03  CYCLOHEXA-1,4-DIENE-3-CARBOXYLATE  (CpHg)  4.42 5-32 6.91 6.46 8.78  " c ^V  0  0.95 1.08 1.24 . 0.93 0.89 1.09 0.99 1.13 1.14  x  —12  MC H = RC H /D ; 6  6  = ( R c H  4  +  + 2 R  R  C2H6  ) / R  1  * ^ <j>G0  0.94 1.00 1.00 0.95 1.00  2  '  0.13 0.14 0.14 0.15 0.16  /  B = substrate  - 3 - 1 i n t e n s i t y absorbed by acetophenone i n quanta c m . s e c ; D = d i e t h y l  Dg=(rate 6  2.83 2.83 2.85 2.85 2.70 2.84  •  B  REACTIONS OF TRIPLET-ACETOPHENONE WITH METHYL  [ ] = cone, x 10 7molec.cm5; I  1.68 1.74. 1.68'  «  (C iy (0 H^(0 H 13 • 10.6 8.9 1.2 11.0 10.5 1.4 10.2 11.4 0.2: 1.1 - •• 1.96 1-63 0.10 0.10 2..10 - 1 . 6 5 0.10 0.13 2.02 1.93 0.15 0.12 3.20 2.48 0.61 0.08 3.33 2.90 0,84 - -. 3.62 3.18 0.96 D  +  R  ketone  C6H )/^B 8  C0 5</>C02 2  = R  C0 /I 2  ro  o  205 s i m p l e r e a c t i o n scheme.  However, t h e ' . f o l l o w i n g d i r e c t  obser-  v a t i o n s c a n be made. I l l u m i n a t i o n v/ith U.V. l i g h t i s n e c e s s a r y f o r any p r o d u c t s t o be formed; t h u s , t h e k e y r e a c t i o n o f t h e system i s photochemical. acetophenone  A t t h e w a v e l e n g t h r a n g e used  only  (>3000A ), >  can absorb i r r a d i a t i o n t o give a t r i p l e t  excited  state. The f o r m a t i o n o f m e t h y l p h e n y l c a r b i n o l and a p i n a c o l s u c h a s m e t h y l p h e n y l p i n a c o l (N.M.R. e v i d e n c e ) i n d i c a t e s t h a t t h e acetophenone  triplet  a b s t r a c t s a hydrogen  c y c l o h e x a d i e n e - 1 , 4 - t o form a c y c l o h e x a d i e n y l  6  5  3  radical:  *  CgH^COCHj + h v  C H COCH  =>C H COCH 6  + <(_J>  5  (1)  5  > C H C'(0H)CH 6  5  + <^J>  5  (2)  2C H C(0H)CH 3  > ((C H )(CH )C(0H))  2C H C(0H)CH  3  > (C' H )(CH )CHOH + CgH^COCHj  6  6  5  5  atom f r o m  6  5  6  5  5  (3)  2  (4-)  5  The r a t i o M„ - (R + R + R „ )'/ D-Q i n c r e a s e s s l o w l y 6 6 6 8 6 10 f r o m 0 . 9 5 "to 1.24- between 110 and 180°C f o r t h e f u l l l i g h t 0  C  •  n u H  n  u H  C  .  n  C  H  B  ^  i n t e n s i t y e x p e r i m e n t s , and f r o m 0 . 9 0 t o 1.14- between 120 and 180°C f o r t h e r e d u c e d l i g h t e x p e r i m e n t s ( F I G . 2 9 ) . means t h a t c y c l o h e x a d i e n e - 1 , 4 - i s c o n v e r t e d a l m o s t m e t r i c a l l y t o benzene,  This stoichio-  c y c l o h e x e n e and c y c l o h e x a d i e n e - 1 , 3 .  These p r o d u c t s c a n be formed i n a r e a c t i o n sequence  depending  on t h e d e c o m p o s i t i o n o f t h e c y c l o h e x a d i e n y l r a d i c a l t o benzene and a h y d r o g e n atom ( r e a c t i o n 5), and p o s s i b l y b y t h e i n t e r a c t i o n of cyclohexadienyl radicals (reaction 6 ) .  These  206 F i g u r e : 29.  Reactions of the acetophenone cyclohexadiene-1,4-.  triplet  v/ith  207 plausible  r e a c t i o n sequences  At low l i g h t  H'  are given  intensity;  P r o d u c t i o n o f benzene f o l l o w e d by p r o d u c t i o n of cyclohexene  +  2°.  +  At b o t h l i g h t  J  intensities  (( • V—-—>  2  G  below:  6 7~ 6 7H  G  H  6a  '  > 6 6 C  H  1  isomers  C^-H^-C^Hn  Simultaneous and equimolar production of b e n z e n e a n d cyclohexadienes  ' +  C  ^6 8 E  XX  isomers  '  J  B o t h t h e 5-5a-5b a n d 6-6a r e a c t i o n s e q u e n c e s e r a t u r e dependent r e a c t i o n :  i n c l u d e a temp-  5 a n d 6a r e s p e c t i v e l y .  The  s e q u e n c e 5-5a-5b i s n o t c o n s i s t e n t w i t h t h e p r o d u c t s a t f u l l i n t e n s i t y b e c a u s e no c y c l o h e x e n e Since the values of K  perature The  occur i n s i g n i f i c a n t  unity,  a m o u n t s among  p r o d u c t s ; t h e r e f o r e , i f r e a c t i o n s e q u e n c e 6-6a d o e s  occur, E g (CgHr;)^  (except at 180°C).  are not s i g n i f i c a n t l y lower than  Q  i s o m e r s o f (CgH,-,^ c a n n o t the f i n a l  was f o r m e d  a  must be v e r y l o w , i f n o t z e r o , s o t h a t most o f t h e ,  isomers t h a t a r e formed  decompose t h r o u g h o u t  t h e tem-  range. r a t i o R~ „ /D,, i n c r e a s e s s l o w l y f r o m 0 . 8 5 t o 1.12 °6 6 and 180°C H  between 110°C  B  f o r the f u l l  light  intensity  experi-  ments, and f r o m 0.80 t o 0.90 between 120 and 180 C f o r t h e reduced l i g h t  intensity  experiments  (PIG. 29).  T h i s shows  208 t h a t cyclohexadiene-1,4 i s converted mainly t o benzene, pendently, of l i g h t ratio R  n  intensity.  inde-  The v e r y s m a l l i n c r e a s e o f t h e  w i t h t e m p e r a t u r e shows t h a t most b e n z e n e i s p r o -  Tr  °6 6 h  duced i n r e a c t i o n s w i t h a low a c t i v a t i o n energy; such t i o n s c o u l d be C H COCH  5  +  _^_ 0 H C(0H)CH  C H C(0H)CH  3  +  ^ ) _ Z ^ (C H )(CH )CHOH +  6  6  5  5  Cyclohexene experiments.  >  6  5  6  i s formed  5  3  <Q)  3  only i n the reduced l i g h t  intensity  T h i s may be e x p l a i n e d i n t e r m s o f - t h e r e a c t i o n  sequence 5-5a-5b, w h i c h i s f a v o u r e d a t r e d u c e d l i g h t sity.  reac-  inten-  The r a t i o R„. /2-n i s c o n s t a n t b e t w e e n 120 a n d 145°C, °6 10 u  H  B  v ; i t h a m e d i a n v a l u e 0 . 0 6 , a n d i n c r e a s e s f r o m 0 . 0 7 to 0.27 b e t w e e n 145 a n d 180°C ( F I G . 2 9 ) .  This'indicates that i n the  iow temperature range, cyclohexene i s produced i n a r e a c t i o n w i t h a l o w a c t i v a t i o n energy and i n t h e h i g h temperature r a n g e , i n a r e a c t i o n w i t h a h i g h a c t i v a t i o n energy. 5 has a h i g h a c t i v a t i o n energy  Reaction  = 31.2 - 4 . 7 k c a l . / m o l e s t  therefore cyclohexene can o r i g i n a t e  i n the reaction  5-5a-5b o n l y i n t h e h i g h t e m p e r a t u r e r a n g e .  sequence  I n t h e l o w tem-  p e r a t u r e range, i t i s p o s s i b l e t h a t _ c y c l o h e x e n e ^ i s formed i n a r e a c t i o n sequence i n v o l v i n g energy t r a n s f e r from t h e a c e t o pnenone t r i p l e t  t o the cyclohexadienyl radical.  The d e l o c a l -  i z e d and c o n j u g a t e d n a t u r e o f t h e bond system o f t h i s can r e n d e r such an energy t r a n s f e r p o s s i b l e E^=74 kcal./mole  8 0  radical  (Acetophenone,  ; cyclohexadiene-1,3, E^=54 kcal./mole  8 8  )  209 1 1 ^ C H COCH  C H^C0CH r  +  6  «•).  (triplet)  *  +  H*  o If  t h e energy  +•  o  +  o  H*  +  of the t r i p l e t  a c e t o p h e n o n e i s a b o u t 20 k c a l . mole h i g h e r than the energy o fthe t r i p l e t c y c l o h e x a d i e n y l r a d i c a l , t h e n r e a c t i o n s 5 * and 7 a r e m u t u a l l y e x c l u s i v e . A c o m p e t i t i o n between them w o u l d t a k e p l a c e o n l y i f t h e e n e r g i e s o f t h e i r triplet In  s t a t e s were a p p r o x i m a t e l y e q u a l . the f u l l  light  i n t e n s i t y experiments t h e approximate  quantum y i e l d f o r t h e d i s a p p e a r a n c e o f c y c l o h e x a d i e n e - 1 , 4 i s = 0.1*, whereas i n t h e reduced l i g h t  experiments i t  i n c r e a s e s f r o m 0.33*' t o 0.60* b e t w e e n 120 a n d 180°C. reduced l i g h t sumption initial  experiments, t h e h i g h e r e f f i c i e n c y i n t h e con-  o f c y c l o h e x a d i e n e - 1 , 4 i s ' p a r t l y , because a h i g h e r c o n c e n t r a t i o n o f c y c l o h e x a d i e n e - 1 , 4 was u s e d .  i n c r e a s e o f t h e quantum y i e l d light  In the  with temperature  The  i n t h e reduced  experiments i n d i c a t e s that i n these experiments  cyclo-  h e x a d i e n e - 1 ,4 i s c o n s u m e d n o t o n l y b y i n t e r a c t i n g w i t h t h e *  By s u b s t i t u t i n g t h e v a l u e s I - f u l l = 1 0 and I -reduced 1? —> 1 = 6x10 q u a n t a cm.sec. ( f r o m t h e p r e v i o u s f o o t n o t e ) i n a  7  the  relationship  <p  DB  =. DB/I^  ,  <^>D e  i s determined.  210 acetophenone 5b  that  depend  In t i  Rn  ments,  this  moved  more  source  This  declined suggests  e f f i c i e n t l y  Such  a reaction  duced 7-7a  l i g h t  0  The  R  „  n  producing  there  benzene  6  C H  +  6  experi120  between  i s  r e -  A .possible  8  a tf u l l  relative  °6 8 that  value  l i g h t  rather  .to/'the  sequence  isomers. R  rate  „  n  7  a r e reactions  C  Such  •  may-  6 6 H  o flow a c t i v a t i o n  but n o t cyclohexadienes. i,  than r e -  t h e reaction  o f cyclohexadiene  H  indicate  a n average  t o zero  I f E - ^ 0 ,  source  ratio  can be  favoured  can be another  the  cyclohexadiene-1,3  that  6  i s more  rate  0.05  - i UC H  intensities.  small  experiments, with  a s 5a a n d  r e a c t i o n (5).  I nt h e reduced  from  such  a t t h e low intensity.!.  o f cyclohexadienes  2  dependent  constant  11.0 a n d 180°C. ratio  170°C.  i n reactions  i n t e n s i t y  B  between  and  l i g h t  A */D-D i s v i r t u a l l y  8  0.12  h u t also  on a temperature  the f u l l  C H -1,3 6  t r i p l e t ,  energy  reactions  • •  •  can be ~"  (a)  2Q_* <^<:>  a /  (£)  Combxnation-Metathesis-Dismutation  _>0*  ;  0 H C- . Q ^ C g H j O - T Q - ^ O s H j C T ^ - ^ O g H j O 6  5  OH or  or  (Q  OH  ( b ) Combination-Energy  '  CH,  CH,  OH  OH  Transfer-Decomposition  CH  OH  ;• •  5  OH  CH  X  C.K-Q-+ C H C-^}A^ C 6 H 5 c i j - ^ 6  +  OH^  C H C. 6  5  OH  3  211 The  decomposition reactions  v e r y low  activation  e n e r g i e s , o t h e r w i s e the sequences  w i t h (R„ C  tion  Conclusions*  u  H  C  H  zene  T  H  A c e t o p h e n o n e when i l l u m i n a t e d  o f c y c l o h e x a d i e n e - 1 , 4 w i t h U.V. as t h e m a i n p r o d u c t .  Formation  i n the  of methyl phenyl  and m e t h y l p h e n y l p i n a c o l were i n d i c a t e d .  Evidence plete  of decomposition of t h i s  e l u c i d a t i o n o f t h e mechanism was  R e a c t i o n s o f Acetophenone w i t h M e t h y l  A mixture  at f u l l  gives the r e s u l t s  light of, f i v e  number o f p r o d u c t s was  found.  which  and  methyl  illuminated f o r  r u n s b e t w e e n 9 9 and  TABLE  143°C.  65$  methyl  A  of the t o t a l  mixture  analysis, residue.  area of a l l the  of secondary  chromato-  benzene,  and t e r t i a r y  corresponding to methyl phenyl c a r b i n o l  phenyl pinacol  cyclohexadiene-1,4  large  the f o l l o w i n g products,  c a r b o n d i o x i d e , methane, e t h a n e ,  an i n d i s t i n g u i s h a b l e  XX  i n d i c a t e d by t h e l a r g e , number o f  peaks observed i n a l l . the stages o f  contributed  hols possibly  com-  cyclohexa-1,4-  intensity, ( \ > 3 0 0 0 A).  only possible to i d e n t i f y  g r a p h i c peaks:  No  Cyclohexa-1,4-Diene-3-  and by t h e c o m p l e x i t y o f t h e N.M.R. s p e c t r a o f t h e was  mechanism  I ,  o f acetophenone  chromatographic  carbi-  achieved.  d i e n e - 3 - c a r b o x y l a t e i n t h e gas p h a s e was 30 m i n u t e s  The  ben-  as t h e m a i n i n t e r m e d i a t e  r a d i c a l was  Cafboxylate  presence  (A >3000 A*) gave  light  i n v o l v e d the c y c l o h e x a d i e n y l r a d i c a l  It  are  „ + R~ „ +. R~ )/D , >1. This condi6 6 6 10 °6 8 i s r e a s o n a b l e s i n c e t h e r e l e v a n t b o n d s a r e v e r y weak.  inconsistent  nol  v  o f t h e s e sequences, must have  and  alcoand  --•  ( b y t h e same N.M..R.evidence a s f o r t h e  system).  Carbon  monoxide was  not  found;  212 decomposition of the acetophenone Kinetic  Analysis.  suggest  a  simple can  complex  reaction  be  mechanism,  scheme;  and d i s t r i b u t i o n of which  however  cannot  certain  excluded.  the  products  be d e s c r i b e d  important  by  methyl  probable  phenyl  abstracts  reactions  formation  pinacol  a hydrogen  substituted  of  methyl  indicates from  that  phenyl  carbinol and  the acetophenone  the cyclohexadienic  cyclohexadienyl  t r i p l e t  substrate  to  radicals:  C H COCEL + h-o—>C.H COCH, 6 5 5 6 5 3 OgH^OOOHj +. CgH^COOCH^ — > C^CCOH) (CHj) + C^HgCOOCHj c  c  (1)  c;  (2)  ^( AC(OH)CH,) 2C -H C(0H)CH,. • o y ?f top P ^ C H COCH + 0 H Q'H(OH)CH  (3)  c  p  f  c;  6  Rn TT /Ron =0.98 °6 6 2 H  100  amounts  of  proportion  and  T43°C;  carbon of  the large  dioxide  be  6  5  (4)  5  of  temperature  the rates  involves  of  6  6  formation  energy  indicate  CgH-gCOOCHj  r a d i c a l  >C H  equal,  and approximately  and benzene  the transfer  approximately  which  5  0.02,independent  i  CgHgCOOOHj Because  5  C 0  between  are  a  recognized.  The  give  The nature  t r i p l e t was t h e r e f o r e  that i s  a  large  decomposing:.  + C 0 + OH"  (5)  2  of  carbon  the following  transfer  equal  to  dioxide  reaction  the substrate  and  benzene  sequence, molecule,  can  excluded,  CgHyjOCHj + C^COOCH^ C H C00CH 6  . since  carbon  absence  of  supported  dioxide  7  -^C^COCR^ + Cg^COOCHj > 6 7 C  5  H  +  C 0  but not benzene.is  cyclohexadienyl b y t h e .absence  of  radicals products  2  +  C H  3  produced.  i n this such  as  The  system  i s  CH^  also and  213 Q-CH . 5  The  quantum  increases carbon  tion  l e t  by  r a d i c a l  must  £ JJ QQQQJJ > 0 . 1 6 > cf>-Q 6 6 3 B a  hydrogen  CgRg-1,4-  CgHg^  ^  o f CgH^COOCH^  by  a  t h a t <^>£ ^  slow, i n c r e a s e much  atom  COOCH  of  greater  c  a  n  n  o  '  greater  than  size  much  t h a n c£>  suggest  c o  that  benzene  a r e formed  consumes E,.'it  most  was  2 0 . 5 . ± 1*5 f o r It  a  i n a  that  r a d i c a l s . 5  r e a c t i o n  kcal./mole;  small, f r a c t i o n  therefore,  C0  most  2  a  metathesis-energy  *  dioxide  decomposition  +  C H C00CH _5J!1> ( C H C 0 O C H ) *  ^C0 (see  R  2  C0  / 3 : 2  previous  6  6  a" »  5  w  h  e  r  e  footnotes  6  6  6  Z  i  =  6  1.5x10  i n this  and  process,  which  i n section  +  5  5  1  5  of  account formed.  i n an  CgH^COOCH^  CgH^CCOH^H^ +  (1-10-  section)  o f  sequence:  C ^ C O C H j  5  dioxide  i s 'p r o d u c e d  transfer-dismutation  7  6  The  COOCH  and benzene  C H C 0 0 C H —2-^ C H C 0 0 C H  5  cj>£ ^  5 can only  r e a c t i o n  +  6  0.16.  than  a c t i v a t i o n energy  5  C H COCH  f a c t o r  However,  and benzene  acetophenone-triplet-sensitized by  has an  o f the carbon  i s possible" that  •  the  concentration  of this  low a c t i v a t i o n energy  of the t r a n s f e r  found  the  t r i p -  greater  because  carbon  /  ;  acetophenone  greater  2  forma-  4> QQ  than  and the indication' that  CJ>QQ  of the  f o r the  i s p a r t l y  The  be  c  The  Since  CgH^COOCHj w i t h  i s greater  f  y i e l d  0.1.  w  This  o f 1.4.  f a c t o r  be  from .  dioxide  the decomposition  t h e quantum  {f>  concentration  not  only  of carbon  100 a n d 1 4 3 ° C * .  between  CgHgCOOCH^,  t r a n s f e r  abstracts  means  0.16  t o  e f f i c i e n c y than from  of  f o rthe formation  i s formed  r a d i c a l  of this  thus,  0.13  form  dioxide  transfer  y i e l d  C H C0CH 5  6  7  x  ^  1  )/0.09  H  °"  $  214-  (C H' C000H )*_^1> 6  The a n a l o g u e 1,4- s y s t e m  of this  6  + C0  6  reaction  d i d n o t appear  no a p p a r e n t  C H  5  6  sequence  r e a s o n why t h i s  i nthis  following  i n the cyclohexadiene-  t o be i m p o r t a n t , t h e r e f o r e sequence  of t h e c o n s i d e r a b l e q u a n t i t i e s produced  + CH*  2  system.  should account  o f carbon dioxide  f o r most  and benzene  T h e r e f o r e , i t seems l i k e l y  low a c t i v a t i o n  energy r e a c t i o n  logue i n t h e cyclohexadiene-1,4- system  sequence,  appeared  there i s  that the  whose  ana-  t o be i m p o r - .  tant,  a c c o u n t s f o r t h e p r o d u c t i o n o f much o f t h e c a r b o n d i -  oxide  and benzene: (a)  Gombination-Metathesis-Dismutation  2C H C00CH 6  6  >(C H C00CH ) -^>(C H GOOCH )(C H C0OCH )  5  5  6  5  2  6  5  5  6  6  5  > CHCOOCH-, + CH.,+ c o + CH: C C  C  o p (b) (i)  Combination-Energy  2C H C00CH 6  6  ,  5  3  6 6:  C H C(OH)CH .'+ 6  r5  5  6  6  6  2  5  6  5  6  6  C H C00GH —^C H C-C H C00CH —Al> 6  6  3  6  CH  CH  6  5  5  6  5  5;  + CgHg + C 0  2  + CH*  1 3  radical  produced  6  »C H C(OH)CH  The f o r m a t i o n o f methane  is  5  V  (CgH^C-C^HgCOOCHjJ  methyl  2  OH  OH  V  3  > (> CCHHC00CH ) — ^ (+ C^COOCH^ )* C00CH + C K C 0 + CH* . •  /  2  Transfer-Decomposition  • . If (ii)  0  and ethane  indicates  that the  i s a n i n t e r m e d i a t e i n t h e mechanism.  i n much l a r g e r  quantities  than ethane.  Methane This  means  t h a t t h e m e t h y l r a d i c a l i s consumed l a r g e l y b y m e t a t h e s i s w i t h CrH^COOCH.. a n d C H COCH,, and. b y o t h e r s e c o n d a r y p r o c e s s e s 6 7 3 6 5 5 c  such as  C  H  .  +  c  c^COOCH^ —  ^ CgHgCOOCHj + CH^  ;  .  215 Figure  30.  Reactions methyl  o f the acetophenone  triplet  with  cyclohexa-1,4-diene-3-carboxylate.  216 CH*. + CgH^COCH^ —2-> Ethane  can  o n l y be p r o d u c e d  radicals The  by mutual  2CH*  ratio  M ,  which  Me  f o r the methyl  The  >  C  CH^ .  combination  of  H  increases  methyl  f r o m 0.30  and  for  a r e p r o b a b l y consumed i n c o m b i n a t i o n r e a c t i o n s  C H C(OH)CH 6  The  large  large  5  rate  + CH*  3.  6 6  5  radicals  >  3 + CH*'  which  t o 0.50  100  CcHcCOOCH,.  between accounted such  as  c  > C H C(0H)(CH ) 6  of t r a n s f e r r a d i c a l s  (reaction  balance  CH,C HUCO0CH, 3 6 6 3 5  5  2  that  i s produced,  t h e n decompose t o g i v e c a r b o n d i o x i d e , radicals  are not  o f f o r m a t i o n o f methane i m p l i e s  quantity  methyl  2 6  roughly r e p r e s e n t s the m a t e r i a l  radical,  14-3°C.  CgH^COCHg •+  an  which  equally can  b e n z e n e , and m e t h y l  5)»  I  ;,. i'  -  Conclusion. sensitize  This kinetic  s t u d y showed t h a t  the decomposition of methyl  c a r b o x y l a t e much more e f f i c i e n t l y T h i s was: p a r t l y  attributed  large  (a)  acetophenone  (b)  methyl  (c)  than the e t h y l r a d i c a l  ;;  of  can.  energy  mechanism.  amounts o f c a r b o n d i o x i d e  c a n be produced i n t h e r e a c t i o n  can  cyclohexa-1,4~diene-3-  t o the p a r t i c i p a t i o n  t r a n s f e r p r o c e s s e s i n the o v e r a l l The  acetophenone  and b e n z e n e o b t a i n e d  sequences:  '  t r i p l e t metathesls-dismutation.  radical metathesis-dismutation.  .acetophenone  and  methyl  radical  metathesis-energy  transfer-dismutation. (d)  combination-metathesis-dismutation.  (e)  combination-energy  transfer-dismutation.  '  ' . . .• ' -'.  217, Reactions  of Acetophenone w i t h A l l y l  Cyclohexa-1,4— D i e n e - 3 -  Carboxylate 17 (5.8x10  Acetophenone 30 m i n u t e s  i n the presence  -3 molec.cm.) was  carboxylate in  (1.85x10  the vapour  —3  'molec.cm;) u n d e r  phase a t 130°C.  carbon dioxide R  C0  "  1 4  -52x 10  2  R  1 2  c  H  ,  -3  intensity,  of secondary  phenyl carbinol  and  propylene  R  1 2  c  »1.5x10  H  1 2  3 6  -1  J •  '  and t e r t i a r y methyl  :  p r o d u c t s were  molec.cm.sec.  a mixture  A- l a r g e  light  identified  • » 15.90 x 1 0  6 6  v  methyl  The  full  benzene  v  and  cyclohexa-1,4-diene-3-  of a l l y l  17  illuminated for  alcohols  assigned to  phenyl pinacol  number o f p r o d u c t s , c o n s t i t u t i n g  about  respectively.'  40$  of the  It o t a l , remained u n i d e n t i f i e d . Kinetic Analysis. The k i n e t i c f r o n t e d not  ' }/ s t u d y of,-''this s y s t e m /'  o n l y by t h e same m e c h a n i s t i c p r o b l e m s  o f t h e CgH^COOCHj-acetophenone system, technical tized  and m e c h a n i s t i c p r o b l e m s  d e c o m p o s i t i o n and Large  and  amounts o f b e n z e n e and  the r a t i o  R ^ TT /R^n C  ducts  involatility  are formed  6 6 H  = 1-1,  G 0  of the  from  study  additional  the u n s e n s i -  substrate.  carbon dioxide  which  con-  as t h e  but a l s o by  arising  was  means t h a t  were  formed  these pro-  2  i n reactions  s e n s i t i z e d decomposition  analogous  sequences  t o one  or a l l of the  d e s c r i b e d i n the  discussion  o f t h e acetophenone-CgH^COOCH^ s y s t e m . The  ^  f o r m a t i o n of propylene confirms the g e n e r a t i o n of  allyl  r a d i c a l s i n d e c o m p o s i t i o n r e a c t i o n s s u c h as C,H* + 0 H C 0 0 C , H - - T - - » C , H ' + C . H C 0 0 C H 3 5 6 7 3 5 3 6 6 6 5 M u t u a l d i s p r o p o r t i o n a t i o n o f a l l y l r a d i c a l s c a n be e x c l u d e d c  n  c  c  c  x  " 218 on t h e g r o u n d s t h a t no a l l e n e The dioxide  was f o u n d .  a p p r o x i m a t e quantum y i e l d  f o rthe formation of carbon  i s 0.15, w h i c h i s c o m p a r a b l e t o t h e v a l u e  i n the  C.^H^COOCH^-acetophenone s y s t e m . C o n c l u s i o n t o t h e Sfcudy o f t h e R e a c t i o n s Cyclohexadienic Acetophenone gives a t r i p l e t , hexadienic depend  when i r r a d i a t e d  substrate to give  6  C H C00C H 6  ?  There transfers  3  6  C E ^ C ^  C0 , C H  6  2  6  i s an i n d i c a t i o n  that  6  8  6  t h e acetophenone  extensive decomposition.  p o s i t i o n was most e v i d e n t ;  This type  i n the C^COOCH^ ... r  10  C ^ triplet  i t s energy t o c y c l o h e x a d i e n y l i c r a d i c a l s ,  then undergo  ..systems. '  L e s s e r p r o d u c t s ....  C0 , C H 6  \  used:  C H -1,3, C: H  2  5  which  6  6  5  of products,  C H  8  ?  o f X> 30002  a h y d r o g e n atom f r o m a c y c l o -  Main p r o d u c t s  C H -1,4 C H C00CH  w i t h U.V. l i g h t  a variety  on t h e t y p e o f s u b s t r a t e  6  with  Derivatives  which a b s t r a c t s  Substrate  of Acetophenone  '' •  which  o f decom-  and C ^ C O O C ^ R y •  219  GENERAL CONCLUSIONS M e t h o d s and K i n e t i c s Allyl,  of Generation of Free  cyclopropyl  and c y c l o h e x a d i e n y l  generated by t h e f o l l o w i n g general  radicals  were  m e t h o d s , w h i c h p r o m i s e t o be o f  application.  (a)  The s e n s i t i z e d d e c o m p o s i t i o n  of esters  C H = C H C H — ( - C 0 - > £ - R , where R = C H = C H - C H 2  Radicals  2  2  2  2  S e n s i t i z a t i o n was a c h i e v e d b y a d d i t i o n  o f the type  , and n = 1 o r 2  or O  o f an e t h y l r a d i c a l t o . \  the  double.bond o f the s u b s t r a t e . C H*'•+ CH =CHCH -{;C0 -^- R 2  2  2  >  2  ^5 io f 2^n" H  > C H  C ^ Q - ^ C O ^ R  5  TABLE X X I shows t h e r e a c t i o n s  CZXcoOR' achieved  C  H  3  o  r  v  =  /  2  (  + R"  7  )  (8)  Arrhenius  /  GH =CH-CH . 2  by metathesis  R  +' n C 0  1 Q  The s e n s i t i z e d d e c o m p o s i t i o n w n e r e= R  C0  7 a n d 8,/and t h e i r  parameters i n each system. (b)  _  2  of esters  of the type  S e n s i t i z a t i o n was  of the ethyl r a d i c a l with the substrate  COOR  —  > C H 6  6  + C0  2  COOR  (9)  + RV  COOR TABLE  X X I I shows t h e r e a c t i o n s  parameters i n each  6 and 9, and t h e i r A r r h e n i u s  system.  . The acetophenone t r i p l e t  was i n v e s t i g a t e d  a s an  TABLE X X I GENERATION OF F R E E RADICALS' BY AN ADDITION-DISMUTATION SEQUENCE E:.  Reactions •  C H* 2  5  2  .  •  +  1 Q  2  $  5  C ^ H ^ C O ^ C ^ -A » D  C  S 10~^ 2^2 3 5' H  C 0  G  2  2  3  [>C0 C H 2  C H* 2  5  5  1 0  + C H C0 <3 5  C H 5  2  5  1 Q  C0 <1  A - { C 0 9 - B c a n be 2  2  5  >C H R  H  C H*- + | > C 0 C H  c H  10  +CO^ + A l l y l -  -  1 5 . 4 ± 0.3 -12.2+ 0.2  1 0  + 2C0„ + A l l y l  0.0  '7.6  2  o  2  t 0.3  Units of k  A  and  D  e  =  estimated.  and  transfer  radical  35 ± 10 18 >  15 10  9  11 +  -12.1 1 0 . 2  6.9H 8 i  12.5 + 0 . 5 . 1  , v;here  + C^E^—^combination  6  8 . 5 ± 1.8  + 0.3  - 1 3  9  + 8  A, a r e m o l e c . c m . s e c • • A  k * ( c r a ? m o l e c . s e c . ) ^ = k^k^/k^, a n d A^^ ( c m ^ m o l e c . s e c . ) ^ = A^A^/A^ 20.-,^—C^H^Q  O  D  E  14.6  12.3i0.6  --5-> CCH^Q + C 0 + C y c l o p r o p y l  e i t h e r ACOgB o r B C 0 A .  5  -11.9 ± 0.2  1 6 . 0 ± 0.6  -A_>c H C0 <] 10  14  7.8+0.3  1 0  CCH^JQ + CO^ + C y c l o p r o p y l 5  10 k ,(135 C)  l o g Ap*  17.01 0.5 6.9 + 0.2  5  A  -10.8+ 0.3  f C O ^ O ^  2  17  0.4  1 ( r  -A - > [ > C 0 C H  10 k (l35°C)  A  \  8.7±  - ( C 0 ^ - C H --2-»C,-H  A  A  + C^H^CO^ C ^ C H  C H*  '  •'  "Ikcal. . E J J ^ mole:  ' ,  log  product-  6 .5' 2  TABLE GENERATION  OF F R E E RADICALS BY A METATHESIS-DISMUTATION  Reactions  E  COOCH-,  2 5, H  0  +  j  kcal./mole  SEQUENCE  log  A  log  A ,  M  D  10  i 6  k (135°C) M  10 k ,(135°C) 5  D  COOCH-,  XT G  XXII  M  >  C H 2  +  6  3  (fVjJ  6 » 0 i 0.7  -12.1 ± 0.4  4.0 1  1.5  COOCHj —  ^  CgH + C 0 £  COOC^Hf-  '  5 3  'C H2  +  [|  jj  _J->C H 2  6  +  2  + Methyl'  ^COOC,H  " X '  2 0 . 5 ± 1.5,  16.0 ± 0 . 7  5.8 ± 0 . 5  -12.0 ± 0 . 3  ^estimated  ^estimated  1.0 ± 0 . 8  3 5 c  (TO)  7.1  ±2.5  COOC^H^ JL>-C H + C 0 6  Units: k  k  and A  a£  = k k /k ,, /  D +  M  D  c  (  ,  M  6  2  molec2cm?sec^!; where 2 C H * 2  c  + Allyl*  6  6  Q  .  k * and A * ( c m ? m o l e c . s e c ? D  >C^H^Q  D  and  C H ' + transfer 2  c.' r a d i c a l —1-> c o m b i n a t i o n product  ^ ro  222 alternative  s e n s i t i z e r t o the e t h y l r a d i c a l .  Although  such  s e n s i t i z a t i o n was s u c c e s s f u l , no q u a n t i t a t i v e r e s u l t s were obtained. (•c) to  The u n s e n s i t i z e d  generate a l l y l  decomposition of d i a l l y l  k,, = 1 0 and  1  4  ±1  c  z  c  o  3  decomposition  of a l l y l  diene-3-carboxylate t o generate a l l y l i n equal  amounts  -> /n\ +  'COOC,H,5 P k ;« 1  10  1 Z f  1  1  only The  the desired  or unsensitized  tion  cyclohexadienyl  + C^H*  esters  1C~ sec7 6  described  decomposition  1  offers- t h e advantage amounts.  o f the D i s s o c i a t i o n Reaction. above i n v o l v e d  o f an a p p r o p r i a t e  o f cases the t r a n s i t i o n state  A l l  the sensitized ester.  In  f o r t h e decomposi-  r e a c t i o n was shown t o c o n f o r m t o a s i n g l e p a t t e r n : a l l  bonds b r o k e n t o form t h e f i n a l transition structure the  2  1  cyclohexa-1,4-  r a d i c a l s a r e formed i n major  Transition State  majority  C0  5  5  .methods o f g e n e r a t i o n  the  and  10" sec7"  e x p 1 0 ( - 3 8 ± 3)/RT; k^Cat 1 5 0 ° C ) » 2.5 x  .Thermal d e c o m p o s i t i o n o f t h e s e that  + 2CH* p p  e x p 1 0 ( - 3 7 ± 2 ) / R T ; k ^ a t 150°C) =  the unsensitized  radicals  :  radicals*  C H OOCOOOC H —>2C0 5 5 3 3 . 2 2  oxalate  are stretched  i n the  s t a t e , and a l l g r o u p s w h i c h have a d e - l o c a l i z e d i n the f i n a l  transition state.  products are p a r t i a l l y de-localized i n This  proposed t r a n s i t i o n s t a t e s of.allyl  products  3-butenoate  pattern  c a n be i l l u s t r a t e d  by the  f o r the s e n s i t i z e d decomposition  2 2 3  TABLE XXIII MODES OE DISSOCIATION AH  Reaction  E  kcal./mole  c H -eco ^-c H : 5  10  3  2  C  5 10  C  5 10  C  5 10  C  5 10  5  6 H C.OO ) C H : 5  10  2  2  3  5  0C0 0 H ; 2  5  1 0  H  H  H  H  + C0  2  5  10  2  C  CHCOCH; 6  6  2  5  + C0  6  6  2  3  5  2  2  C H (CO ) C H. 3  5  2 2  $  CgHr^COgG-jH  2  C0  2  + G^H^Q H  5  1 Q  + C^E^Q  5 10 + co <] 2  + C0 + CH^ + C0CH + C0 + C^H^ + C0 C H 5 10 + C0 + C' H^ 5 10 + C0 C H 2C0 + 2CH* P co + C^H^ + C0CH^ CH* + CO2 + C^H* CH- + 6O C H^ °66 66 66 66 H  C  2  H  2  3  H  C  2  H  2  H  C  C^H^QC0 C H^  5  + CpgCjH^  2  H  C  C H CO 0 H .  +  5  O  0- * C02 • t>co + C >•  3  + *(C0 ^-C H + 2C02 + Cp H* p  2  C H C0 <]  + C H*  2  5  2  2  #  H  C  5  2  2  2  5  2  -7.6  2  6  6  2  3  I  3  7  .  0  ±  0  .  5  0  .  6  0  .  6  2 7  - 7 0  - 2 5  14 27 14 28 -  } }  l  J  6  1  0  .  2  0  .  ±  3  ±  7  10 -24  2  }  0  .  5  1  1  .  5  ^estimated  7  -4 16  }  l  8  .  i  2  3 }  5  2  1  }  2  3  7  i  2  3  8  ±  3  3 9  20 }  5 3  .  6  224  C^B^Q ' ' • i i - 1 • t i • C ^ O i i i • t i i i C H - C H - C H 2  and  f o r the unsensitized Q  diene-3-carboxylate ~  v  These  / )  '  il.  i i i i i • i i i i  conclusions arise  energy  decomposition  of a l l y l  (TABIE  ,  0  from  t h e comparison  X X I I I ) , and from  pre-exponential factor  cyclohexa-1,4-  .  C ^ 0 » . •'»•• " C—*=0 ' ' " < •' • C i H -CH-CH  with the enthalpies of a l l possible  ciation  2  0  of the activation degrees  the interpretation  i n terms o f t h e treatment  of dissoofthe  g i v e n by  123 Benson each  .  decomposition  plete  dissociation  partial of  TABLE X X I I I  reaction  dissociation  and  f o r the decomposition  C^H^COOG^H^, C^Hj-COO^  methyl acid  and a l l y l  the  energy  of the transfer  of the transfer  of the p a r t i a l  following  transition  The  reactions  enthal-  pattern f o r the a n d CgH^COOC^H^,  radicals  d e r i v e d from  The a c t i v a t i o n radicals  derived  energies from t h e  the corresponding enthalpy  dissociation  G—0  i i i • i  R  than the other.  of the Free Radicals  of combination,  dif-  mode, w h i c h s u g g e s t s  state  where one bond i s more s t r e t c h e d Reactions  ;  of cyclohexa-1,4-diene-3-carboxylic:  i i i i i i i i i i i i i  Characteristic  isa  The c o m p a r i s o n  w i t h the' c a l c u l a t e d  and £>COOC^H^.  esters  i s a com-, .  and t h e l a t t e r  o f C^H^OOCCOOC^H^  have h i g h e r v a l u e s t h a n  ferences  products  confirms the proposed  decomposition  the decomposition  The f o r m e r  to intermediate species.  of decomposition  unsensitized  studied.  t o the f i n a l  t h e measured a c t i v a t i o n  pies  of  shows two modes o f d i s s o c i a t i o n f o r  disproportionation,  /  225 isomerization, cyclopropyl,  and m e t a t h e s i s were i n v e s t i g a t e d f o r t h e a l l y l ,  and c y c l o h e x a d i e n y l r a d i c a l s .  TABLE X X I V shows t h e p a t t e r n s o f c o m b i n a t i o n a n d d i s p r o p o r t i o n a t i o n f o r each allyl/allyl,  of the r a d i c a l pairs:  allyl/ethyl,  a l l y l / c y c l o h e x a d i e n y l , and c y c l o p r o p y l / e t h y l .  An i n s p e c t i o n o f t h i s t a b l e l e a d s t o t h e f o l l o w i n g g e n e r a l remarks. (1)  I n a l lr a d i c a l pairs containing  the rate  of formation of allene decreases  t i o n energy  > CyH^ +. C p H  2  D e r e a l i z a t i o n energy C K- + C H* 5  > C H  3  3  Delocalization C  3 5 H  (2)  +  4  3  of  6 8  ,  D e l o c a l i z a t i o n energy  of  >  C  3 4 H  +  C  H  °* = 24 k c a l . / m o l e  of formation of propylene  the nature o f the donor r a d i c a l C H 3  C  (3)  = 13 k c a l . / m o l e  I n the r a d i c a l pairs a l l y l / e t h y l , allyl/cyclohexa-  dienyl, the rate  .  0 kcal./mole  0.8*.  6  energy  O  increases:  3#  6  o f CgH^ =  + C H  radical,  as t h e d e l o c a l i z a - \  of the acceptor r a d i c a l species  , C j H J + C H*  ,  the'allyl  3 5 H  + C H*  3  O  +  The r a t e  species:  >C' H  2  5  >  C  5 6 H  i sinsensitive to  +  •• 9#  + C H^  6  2  C  6 6 H  9  *  ' .  . .  o f f o r m a t i o n o f benzene i n  (|7)  + R-  > RH + C H 6  I s a b o u t f o u r t i m e s l o w e r when R = a l l y l  6  t h a n when R = e t h y l . .  T h i s may be a t t r i b u t e d t o D ( C H = C H C H — H ) = 85 k c a l / m o l e 2  2  < D ( C H ^ — - H ) = 98 k c a l / m o l e 2  or t o a s u i t a b l e - d i f f e r e n c e i n the entropy of t h e respective  226 TABLE XXIV PATTERNS  OF I N T E R A C T I O N  Reactions  ^. +  C-7H*.  J  C  H  3  0  3  % 88 ± 4  A  10  >C H  C~H*.  2 3  ?  5  H  OF F R E E  6 +  C H 2  + C  4  C  Rate  90 ± 4 1  88 ± 4  D  10 + 3  9 ±3  4  H  2  ,  RADICALS  D 2  81 ± 4  8 ±3"  7 ± 2 2 ± 2  3±1  6  C  ^B  C H* + C 5 ; X  C  H :  X  5 5  C  99-2  6 10 H  3 6 H  +  3 4  0.8  + 2  51  I 4  H  C  * 3 5<I> C  40 ± 3  5 3 *  2  C  3 6 H  +  9 ± 2  6 6  C  H  * ^VG  +  C  2  H  H  +  ^  C H'  35 ±  +  6  C  2  sf  ( C H  C  3  )  2  (19/81 = 0.23)  H  6  4  2  H  6 2  5  W  5  CH- +  C H£  -> 5 8  2  C  H  C  3 6  +  17  2 4  C  H  CH^ * SOURCES:  H  +  C  C  2  H  (17/62 = 0 . 2 7 )  21  6  the decompositions  A:  C j H ^ f C O ^ C ^  (sensitized)  C:  C3H3(C02)2 3 5  (sensitized)  D :  C3H3C0 <]  :  3  D  19 ±  C H C  2  0  6 2  5  2  +  1  38 + 3  6  H  81 • +  t>C H t>  2  3  27" ± 3  - 0  5  °2 6  CH  F  H  C-zH*- +  C H*  a  C  2  a  H  (sensitized) (sensitized)  C O O C z Hn  3 5  B : CJHJJCCC^^CJ^ :  (thermal)  ^CC^C^j-(sensitized)'-  F : <^>^  JOOC3H5  (thermal)  227 products. (4) radical  The c y c l o p r o p y l r a d i c a l i n forming ^ ^ R C  R"  cyclopropane  H  2  .  5  + C H2  K  ^  RH + C H 2  Metathesis strates  /  like  =  [>•  R=sec-C H* 5  0.22 ± 0 . 0 3  C  4  of the a l l y l  the sec-propyl  i n the r e a c t i o n R =  K  A  behaves  radical  with  k,/k = d c  0.27  1 4  V  some o f t h e s u b -  was o b s e r v e d , b u t t h e A r r h e n i u s p a r a m e t e r s c o u l d be  measured  o n l y when t h e s u b s t r a t e  was a l l y l  c y c l o h e x a - 1 , 4 — . . . ••;  diene-3-carboxylate:  C H : ;  3*5  +  (  /==  Y  /fTY  ->C H. +  , K^JK  +  * 3*6 X  U  C00C-.H  +  ' 'C00C-,H  C  3 3  • .•  m  / k  c  Metathesis propyl  >C H  3  k  =  1  0  ~ ^  6  i  1  C;  5 3  2C H*  •  (m)  6  I  1 0  (c)  v  ^exp{l0 (-11,± 2)/RTJ cmfmolec^sec? 5  of the cyclopropyl  radical  with a l l y l  cyclo-  a n d c y c l o p r o p y l . 3-t>utenoate was o b s e r v e d ,  carboxylate  and t h e c o r r e s p o n d i n g A r r h e n i u s p a r a m e t e r s were d e t e r m i n e d . - Substrate:  [>-C00-All  ;  k k^/k , = 1 0 " * m c c Substrate: All-C00-<] ( 7  k Ak,, - 10- ' in c c £>• substrate ( 8  I  where  +  2  Isomerization allyl  radical  measured: "  2 : t 0  -  exp(l0 (-8.0±0.8)/RT) x <• • ) \ cmSmolec'.sec'. 5  6 )  exp{l0 (-7.5±0.8)/RT}  J  5  i.  J  > [> + ( s u b s t r a t e ) "  2C H-  >C^H  + [>.  > > C  2  C H*  7 ± 0 , 5 )  2  ;  1 0  H  (c) ; (c«)  5  of the cyclopropyl  (m)  radical  to give the  was o b s e r v e d a n d t h e A r r h e n i u s p a r a m e t e r s were  '228 Source: k  [>-C00-All  is c k  k  c'  10  =  1  7  ±  5  exp{l0 (-22±5)/RT)^ 5  A11-C00-<J •  Source: k  /  is c k  where  /  k  c'  ' °  =  1  [>.  cmT m o l e c f s e c ¥ 1  1 5 ± 2  exp  {l0 (-18± 5)/RT} '  ->CH -CH-CH 2  }  5  (is)'  2  The v a l u e f o r t h e a c t i v a t i o n e n e r g y  i s i n agreement  with  / 92 20 k c a l . / m o l e3 rr e e p o r t e d by Thynne. ( V a l u e now r e p o r t e d o f 22 k c a l . / m o l e  1 4 7  )  /  \  •• A / \  229  BIBLIOGRAPHY 1.  L . M. D o r f m a n a n d S- D. S h e l d o n , J . Chem. P h y s . , 511 (194-9).  2.  K. 0 . K u t s c h k e , M. H. J . Wijne.n a n d E-. W.. R. J . Am. Chem. S o c , 74, 71^ ( 1 9 5 2 ) .  3. 4. 5.  17,  Steacie, Chem., 33,  R. K. B r i n t o n a n d E.. W.. 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