UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Kinetic and equilibria studies in highly basic systems Kroeger, Dietrich Jacob 1966

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1966_A1 K75.pdf [ 8.63MB ]
Metadata
JSON: 831-1.0061994.json
JSON-LD: 831-1.0061994-ld.json
RDF/XML (Pretty): 831-1.0061994-rdf.xml
RDF/JSON: 831-1.0061994-rdf.json
Turtle: 831-1.0061994-turtle.txt
N-Triples: 831-1.0061994-rdf-ntriples.txt
Original Record: 831-1.0061994-source.json
Full Text
831-1.0061994-fulltext.txt
Citation
831-1.0061994.ris

Full Text

KINETIC AND EQUILIBRIA STUDIES  IN HIGHLY BASIC SYSTEMS by DIETRICH J . KROEGER M.A., U n i v e r s i t y o f Saskatchewan, 1963  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n t h e Department of Chemistry  We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e required standard  THE UNIVERSITY OF BRITISH COLUMBIA A u g u s t , 1966  In presenting for  this thesis  i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s  an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h Columbia, I agree  t h a t t h e L i b r a r y s h a l l , make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e study,  and  1 f u r t h e r agree t h a t permission., f o r e x t e n s i v e c o p y i n g o f t h i s  t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by t h e Head o f my Department o r by h i s r e p r e s e n t a t i v e s ,  I t i s understood that  copying  or p u b l i c a t i o n of" t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n  permission.  The U n i v e r s i t y o f B r i t i s h Vancouver 8, Canada  Columbia  The U n i v e r s i t y  of B r i t i s h Columbia  FACULTY OF GRADUATE STUDIES PROGRAMME OF THE FINAL ORAL EXAMINATION FOR THE DEGREE OF DOCTOR OF PHILOSOPHY r  of  DIETRICH J . KROEGER B.ED.,-The U n i v e r s i t y  o f Saskatchewan  B.A., The U n i v e r s i t y  o f Saskatchewan  M.A., The U n i v e r s i t y  of Saskatchewan  THURSDAY, SEPTEMBER 1, 1966 AT 3.30 P.M. IN ROOM 261, CHEMISTRY BUILDING COMMITTEE IN CHARGE Chairman:  C. A. B r o c k l e y  R. J . Bandoni  R. E . P i n c o c k  L. D. H a l l  R. Stewart  C. A. McDowell External  A. S t o r r  Examiner:  Department University  D. S. Noyce  of Chemistry, of C a l i f o r n i a ,  Berkeley, C a l i f o r n i a . Research S u p e r v i s o r :  R. Stewart  "EQUILIBRIUM AND KINETIC STUDIES IN STRONGLY BASIC SYSTEMS" • ABSTRACT Using 0 ( - c y a n o s t i l b e n e s as Lewis a c i d s ^ Lewis a c i d i t y s c a l e s have been e s t a b l i s h e d i n the systems DMSO-ethanol. and DMSO-methanol. c o n t a i n i n g the appropriate. 0.01M sodium a l k o x i d e and i n the system sodium methoxide-methanol, This s c a l e , designated HR_ d e s c r i b e s the a b i l i t y of the s o l v e n t to add an a l k o x i d e i o n to an a l k e n e . The Hg- v a l u e s range from 11.73 i n methanol, to 21.74 :> QS„.?? n^iu- ** DM50 i n e.r.ha:o.o'j.. s  The. most a c i d i c i n d i c a t o r used t o e s t a b l i s h the s c a l e was cX-cyano-2 4-din.i.trostilbene w i t h a pK of 12.73 i n DMSO-methanol. The. l e a s t a c i d i c was c K - c y a n o - 3 - t r i f l u o r o m e t h y l s t i l b e n e w i t h a pK o f 21.98 i n DMSO-ethanol. 3  The e f f e c t s of s u b s t i t u e n t s i n the two aromaticr i n g s of CX.-cyanost.il.ben.es on the. Lewis a c i d i t y of; these compounds has been measured. Using C7~ v a l u e s , an average P of 2.2 was o b t a i n e d f o r the '/3 -phenyl r i n g i n the v a r i o u s s o l v e n t systems s t u d i e d . Using 0"~ v a l u e s , the P f o r CX-cyanostil.benes w i t h s u b s t i t u e n t s i n the o(.-ring i s 4.77 i n DMSO-ethanol and 4.24 i n DMSO-methanol. In the CX-phenyl r i n g the 4 - n i t r o group e x h i b i t s a g r e a t l y e x a l t e d sigma v a l u e (1. .75) . In order to compare the H - and H_ s c a l e s i n one system, the H_ s c a l e has been e s t a b l i s h e d i n sodium methoxide-methanol u s i n g v a r i o u s carbon a c i d s as i n d i c a t o r s . The two s c a l e s are n e a r l y p a r a l l e l . R  The r a t e s of the base c a t a l y z e d i s o m e r i z a t i o n of C X - c y a n o - c i s - s t i l b e n e s were found to c o r r e l a t e w i t h the H -function„ P l o t s of t h e ' l o g a r i t h m s of the apparent f i r s t order r a t e c o n s t a n t s ( k i ) f o r the i s o m e r i z a t i o n a g a i n s t the HR- v a l u e s gave e x c e l l e n t s t r a i g h t l i n e s w i t h slopes ranging from 0.425 to 0.665 The s l o p e s of these l i n e s depend on the s u b s t i t u e n t p r e s e n t i n the 0(.-phenyl r i n g and on the s o l v e n t system. The slopes were shown t o be a measure of how c l o s e l y the t r a n s i t i o n s t a t e f o r the i s o m e r i z a t i o n r e a c t i o n resembles the c a r b a n i o n formed by the • e q u i l i b r i u m a d d i t i o n of a l k o x i d e i o n to an a l k e n e , R  The e f f e c t of s u b s t i t u e n t s on the r a t e o f isomerization of C X r c y a n o - c i s - s t i l b e n e s has been determined. Using Q~values the P f o r s u b s t i t u e n t s i n the CX-phenyl, r i n g i s 3=07 i n DMSO-ethanol and 2.82 i n DMSO-methanol., The a c t i v a t i o n parameters f o r the base c a t a l y z e d i s o m e r i z a t i o n r e a c t i o n have been determined i n DMSO-methanol, The e n t h a l p i e s o f a c t i v a t i o n range from 14,3 t o 16,7 k c a l . mole and,the e n t r o p i e s of a c t i v a t i o n range from -9.3 t o -13=7 e,u„ depending on the s u b s t i t u e n t . The base c a t a l y z e d i s o m e r i z a t i o n of CX - c y a n o - c i s s t i l b e n e s i s f i r s t order i n base and f i r s t order i n reactant. The mechanism o f t h i s r e a c t i o n i s d i s c u s s e d i n terms of the k i n e t i c - a c i d i t y f u n c t i o n c o r r e l a t i o n ^ the s u b s t i t u e n t e f f e c t s , and the a c t i v a t i o n parameters. The r e a c t i o n s o f 1 . 1 - b i s - ( 4 - n i t r o p h e n y l ) ethene and 4 , 4 ' - d i n i t r o b e n z o p h e n o n e w i t h h y d r o x i d e or a l k o x i d e ions i n DMSO are d e s c r i b e d . 3  GRADUATE STUDIES Field  of Study?  Ghemistry  Topics  i n P h y s i c a l Chemistry •  Topics  i n Organic C h e m i s t r y  Chemical K i n e t i c s  P h y s i c a l O r g a n i c Chemistry Recent S y n t h e t i c Methods i n Organic Chemistry  J.  A, R, Coope A, Bree  D, E. McGreer J , P. Kutney F. McCapra G. B; P o r t e r D. G. L. James R. Stewart  D. E. McGreer  The Chemistry o f Organometallic. Compounds  H. C. C l a r k  Programming and N u m e r i c a l Algorithms  H, Dempster  PUBLICATIONS Rearrangement S t u d i e s w i t h 'C XIX. The R e a c t i o n 2 - P h e n y l - l - C - E t h a n o l and T h i o n y l C h l o r i d e . C. C. Lee, D. J . Kroeger and D. P. T h o r n h i l l , Can. J . Chem., 42, 1130 (1964). iq  1 4  Rearrangement S t u d i e s w i t h C X V I I I . 2-Phenyl-2e t h y l c h l o r i d e from Gamma-irradiation of 2 - P h e n y l - l ethyl chloride. C. C. Lee and D. J . Kroeger, Can. Chem., 42, 976 (1964). 1 4  The P r e p a r a t i o n and I n f r a r e d and NMR S p e c t r a o f Monodeuterated P y r i d i n e and 3 - P i c o l i n e . R. A. Abramovitch, D. J . Kroeger and B. S t a s k i n , Can. J . Chem., 40, 2030 (1962).  1  i  ABSTRACT DIETRICH J . KROEGER.  Supervisor:  KINETIC AND  P r o f e s s o r R.  Using  EQUILIBRIA STUDIES IN HIGHLY BASIC SYSTEMS.  Stewart  (X-cyanostilbenes as Lewis a c i d s , Lewis  a c i d i t y s c a l e s have been e s t a b l i s h e d i n the systems DMSO-ethanol and DMSO-methanol c o n t a i n i n g the a p p r o p r i a t e 0.01M  sodium a l k o x i d e and i n the system sodium methoxide-  methanol.  T h i s s c a l e , d e s i g n a t e d HR-,  d e s c r i b e s the  a b i l i t y of the s o l v e n t to add an a l k o x i d e i o n to an alkene.  The HR- v a l u e s range from 1 1 . 7 3 i n methanol  to 21.7k  i n 9 3 . 2 7 mole % DMSO i n e t h a n o l . The most a c i d i c i n d i c a t o r used  the s c a l e was  to e s t a b l i s h  0^-cyano-2,>+-dinitrostilbene  1 2 . 7 3 i n DMSO-methanol.  w i t h a pK o f CX-  The l e a s t a c i d i c was  c y a n o - 3 - t r i f l u o r o m e t h y l s t i l b e n e w i t h a pK of  21.98  i n DMSO-ethanol. The e f f e c t s of s u b s t i t u e n t s i n the aromatic r i n g s of  two  (X-cyanostilbenes on the Lewis a c i d i t y  o f these compounds has been measured. v a l u e s , an average  p  of 2 . 2 was  Using  (re-  o b t a i n e d f o r the  p -phenyl r i n g i n the v a r i o u s s o l v e n t systems s t u d i e d . Using  Q~~ v a l u e s , the  s u b s t i t u e n t s i n the  p  f o r (X-cyanostilbenes w i t h  Q(-ring i s k.77  and ^ . 2 ^ i n DMSO-methanol.  In the  i n DMSO-ethanol CX-phenyl r i n g  the  ii  *+-nitro  group e x h i b i t s a g r e a t l y e x a l t e d  sigma value  (1.75). In order one  system, the H_  to compare the RRs c a l e has  two  s c a l e s are n e a r l y The  of  the H^-  carbon a c i d s as i n d i c a t o r s .  parallel.  r a t e s of the base c a t a l y z e d  0(-eyano-cis-stilbenes function.  isomerization  were found to c o r r e l a t e w i t h  P l o t s of the logarithms  of  apparent f i r s t order r a t e constants (k-j_) f o r isomerization against  the RR-  values  The  i n the  Ot-phenyl r i n g and  the  gave e x c e l l e n t 1  slopes of these l i n e s depend on the  present  the  from 0. +26 to 0.665.  s t r a i g h t l i n e s w i t h slopes ranging The  scales i n  been e s t a b l i s h e d i n sodium  methoxide-methanol u s i n g v a r i o u s The  and H_  on the  substituent solvent  slopes were shown to be a measure of how  system.  closely  the  t r a n s i t i o n s t a t e f o r the i s o m e r i z a t i o n r e a c t i o n resembles the c a r b a n i o n formed by the e q u i l i b r i u m a d d i t i o n of alkoxide  i o n to an a l k e n e . The  e f f e c t of s u b s t i t u e n t s  i s o m e r i z a t i o n of determined. i n the 2.82  on the r a t e of  0(-cyano-cis-stilbenes  U s i n g CT values  the  P  for  has  been  substituents  CX-phenyl r i n g i s 3«07 i n DMSO-ethanol and  i n DMSO-methanol. The  a c t i v a t i o n parameters f o r the  base  iii  c a t a l y z e d i s o m e r i z a t i o n r e a c t i o n have been d e t e r m i n e d i n DMSO-methanol. from. 1^.3  t o 16.7  The e n t h a l p i e s o f a c t i v a t i o n k c a l . mole  a c t i v a t i o n range from -9.3 the  1  and the e n t r o p i e s  t o -13.7  range of  e.u. depending  on  substituent. The base c a t a l y z e d i s o m e r i z a t i o n o f CX-cyano-  cis-stilbenes reactant.  i s f i r s t o r d e r i n base and f i r s t o r d e r i n  The mechanism o f t h i s r e a c t i o n i s d i s c u s s e d  i n terms o f the k i n e t i c - a c i d i t y f u n c t i o n  correlation,  the s u b s t i t u e n t e f f e c t s , and the a c t i v a t i o n  parameters.  The r e a c t i o n s o f l , l - b i s - ( + - n i t r o p h e n y l ) e t h e n e 1  and k,h -dinitrobenzophenone x  i o n s i n DMSO a r e  described.  w i t h h y d r o x i d e or a l k o x i d e  iv  TABLE OF CONTENTS  Page INTRODUCTION  1  A. B.  1  C.  A c i d s , Bases and A c i d i t y F u n c t i o n s .. The C o r r e l a t i o n o f K i n e t i c s w i t h A c i d i t y Functions .. .!. Base C a t a l y z e d c i s - t r a n s I s o m e r i z a t i o n s ..  21 2 5  OBJECT OF THE PRESENT RESEARCH  3^  METHODS OF APPROACH  36  EXPERIMENTAL  37  A. B. C. D. E. F. G.  P u r i f i c a t i o n o f S o l v e n t s and P r e p a r a t i o n of S o l u t i o n s E q u i l i b r i a Measurements .. Treatment o f the S p e c t r a l Data i n t h e E q u i l i b r i u m Measurements K i n e t i c Measurements Treatment o f the K i n e t i c Data '. P r e p a r a t i o n o f I n d i c a t o r s and R e a c t a n t s .. Reactions of l , l - B i s - ( + - n i t r o p h e n y l ) ethene .. .. 1  RESULTS A. B. C. D. E. F.  37 H-0 hi *+3 hh h7 6*+ 78  The H - F u n c t i o n .. E q u i l i b r i a S t u d i e s i n DMSO-Alcohol S o l u t i o n s .. E q u i l i b r i a Studies i n Concentrated Sodium Methoxide S o l u t i o n s .. .. I o n i z a t i o n B e h a v i o r o f Carbon A c i d s i n DMSO-Ethanol S o l u t i o n s Estimate of Error .. .. K i n e t i c s o f t h e Base C a t a l y z e d c i s - t r a n s I s o m e r i z a t i o n o f S u b s t i t u t e d C<-Cyanoc i s - s t i l b e n e s i n DMSO-Alcohol Solutions .. .. R  78 79 90 95 99  100  V  Page G. H. I.  The R e a c t i o n o f 0(-Cyano- OC' - m e t h o x y - c i s and t r a n s - s t i l b e n e s i n DMSO-Methanol Solutions The R e a c t i o n o f l , l - B i s - ( f - n i t r o p h e n y l ) ethene i n H i g h l y B a s i c Systems ... The R e a c t i o n o f k h -Dinitrobenzophenone i n H i g h l y B a s i c Systems  C. D. E. F. G. H. I. J. K. L.  11*+  1  f  115 117  DISCUSSION A. B.  llh  l  The V a l i d i t y o f t h e H R - F u n c t i o n .. .. I n t e r p r e t a t i o n o f t h e Lewis B a s i c i t y o f the S o l u t i o n s The V a l i d i t y o f t h e H_ S c a l e s The Comparison o f t h e H R - S c a l e s w i t h other Scales A Comparison o f pK V a l u e s .. .. C o r r e l a t i o n o f S t r u c t u r e w i t h Lewis Acidity The C o r r e l a t i o n o f R a t e s w i t h t h e H Function .. .. S u b s t i t u e n t E f f e c t s on t h e R e a c t i v i t y .. A c t i v a t i o n Parameters A Further D i s c u s s i o n of the I s o m e r i z a t i o n Mechanism The R e a c t i o n o f l , l - B i s - ( M - - n i t r o p h e n y l ) ethene i n H i g h l y B a s i c Systems The R e a c t i o n o f -Dinitrobenzophenone w i t h H y d r o x i d e i o n i n DMSO .. .. R  117 123 125 129 135 137 lM-8 156 160 163 171 17h  SUGGESTIONS FOR FURTHER WORK  176  BIBLIOGRAPHY  178  vi  LIST OF TABLES Page I  II III  IV  A b s o r p t i o n Maxima and Molar E x t i n c t i o n C o e f f i c i e n t s f o r OU.Cyanos t i l b e n e s i n DMSO-Ethanol .. ..  67  A b s o r p t i o n Maxima and Molar E x t i n c - _ t i o n C o e f f i c i e n t s f o r the A n i o n s AOR  68  A b s o r p t i o n Maxima and Molar E x t i n c t i o n C o e f f i c i e n t s f o r I n d i c a t o r Anions o f Carbon A c i d s i n Sodium MethoxideMethanol S o l u t i o n s  69  V a l u e s o f l o g [&0R~] / [ A ] f o r CX-Cyanos t i l b e n e s Used as I n d i c a t o r s t o E s t a b l i s h the H - S c a l e i n DMSOEthanol  70-71  V a l u e s o f l o g |AOR"!1/[A] f o r t h e Q ( - C y a n o s t i l b e n e s Used as I n d i c a t o r s t o E s t a b l i s h the H - S c a l e i n DMSO- Methanol .. .. .. .. ..  .72-73  R  V  R  VI  Values o f l o g [AOR~]/[A] f o r the C X - C y a n o s t i l b e n e s Used as I n d i c a t o r s to E s t a b l i s h the H - Scale i n Sodium Methoxide-Methanol S o l u t i o n s  7^  V a l u e s o f l o g [ A O R ~ ] / [ A ] f o r Lewis A c i d s Not Used t o Estab! i s h t h e H - S c a l e i n DMSO-Ethanol ..  75  V a l u e s o f l o g [ A ~ ] / |AH] f o r V a r i o u s Carbon A c i d s Used as I n d i c a t o r s t o E s t a b l i s h the H _ S c a l e i n Sodium Methoxide-Methanol S o l u t i o n s  76  V a l u e s o f l o g &."]/|AH] f o r V a r i o u s Carbon A c i d s S t u d i e d i n DMSO-Ethariol  77  R  VII  R  VIII  IX  vii  Page X  pK V a l u e s o f O C - C y a n o s t l l b e n e s Used as I n d i c a t o r s t o E s t a b l i s h the H - S c a l e s i n t h e DMSO-Ethanol, DMSO-Methanol and Sodium M e t h o x i d e Methanol Systems .. .. .. .. R  XI  XII  H - V a l u e s f o r the DMSO-Ethanol System a t 25° C o n t a i n i n g 0.01M Sodium E t h o x i d e  8M-  R  ..  85  H - V a l u e s f o r t h e DMSO-Methanol System a t 25° C o n t a i n i n g 0.01M Sodium Methoxide  86  pK V a l u e s o f I n d i c a t o r s i n DMSOE t h a n o l Not Used t o E s t a b l i s h the HR- Function  89  H - V a l u e s f o r t h e Sodium MethoxideMethano'l System a t 25°  92  P % A V a l u e s o f I n d i c a t o r s Used t o E s t a b l i s h t h e H_ S c a l e i n the Sodium Methoxide-Methanol System ....  9h  XVI  H__ V a l u e s f o r t h e Sodium M e t h o x i d e Methanol System a t 25°  96  XVII  I n d i c a t o r s Used i n an Attempt t o E s t a b l i s h a H_ S c a l e i n DMSO-Ethanol  99  XVIII  K i n e t i c s o f the Base C a t a l y z e d Isomerization of 0(-Cyano-cis-M— n i t r o s t i l b e n e i n Methanol a t 25°  XIII  XIV XV  XIX  XX  R  R  ••  103  Values of l o g k i Isomerization of cis-stilbenes i n i n g 0.01M Sodium  f o r the Base C a t a l y z e d S u b s t i t u t e d CX-CyanoDMSO-Ethanol C o n t a i n E t h o x i d e a t 25°  Values of l o g Isomerization or cis-stilbenes i n i n g 0.01M Sodium  f o r the Base C a t a l y z e d S u b s t i t u t e d CX-CyanoDMSO-Methanol C o n t a i n Methoxide a t 25° 1 0 6  105  viii  Page XXI  Correlation of log with HR- for the Base C a t a l y z e d I s o m e r i z a t i o n o f Substituted OC-Cyano-cis-stilbenes at 25°  109  XXII  R a t e - t e m p e r a t u r e Data f o r the Base Catalyzed Isomerization of Substituted O C - C y a n o - c i s - s t i l b e n e s i n DMSOMethanol I l l  XXIII  A c t i v a t i o n Parameters f o r the Base Catalyzed Isomerization of Substituted O C - C y a n o - c i s - s t i l b e n e s i n DMSOMethanol .. . . . . .. ,. ..  113  The Comparison o f the H R - and H_ S c a l e s i n C o n c e n t r a t e d Sodium Methoxide S o l u t i o n s ,. .. .. .. ..  13*+  XXIV  XXV  C a l c u l a t e d l o g k i Values f o r t h e I s o m e r i z a t i o n o f S u b s t i t u t e d OCC y a n o - c i s - s t i l b e n e s i n DMSO-Ethanol and DMSO-Methanol a t a H - V a l u e of 1 6 . 0 0 R  157  ix  L I S T OF FIGURES  Page 1.  2.  3. h.  5.  6.  7. .8. 9.  10.  11.  P l o t s o f l o g [AOR""] / [ A ] V e r s u s M o l e % DMSO f o r t h e Systems DMSO-EthanolS o d i u m E t h o x i d e (O.oiM) a t 25° ..  ..  80  P l o t s o f l o g [ A 0 R ~ ] / [ A ] V e r s u s Mole % DMSO f o r t h e S y s t e m : DMSO-MethanolSodium M e t h o x i d e (0.01M) a t 25° ..  ..  81  H - V a l u e s f o r DMSO-Ethanol S o l u t i o n s C o n t a i n i n g 0.01M S o d i u m E t h o x i d e ..  ..  87  H - V a l u e s f o r DMSO-Methanol S o l u t i o n s C o n t a i n i n g 0.01M S o d i u m M e t h o x i d e .. ..  88  R  R  |A0R~1/[A]  Plots of log Versus the C o n c e n t r a t i o n o f Sodium Methoxide i n Methanol  91  P l o t s o f l o g [A~]/(AH3 f o r Carbon A c i d s V e r s u s t h e C o n c e n t r a t i o n o f Sodium Methoxide i n Methanol  93  H R - and H _ Values f o r Concentrated Sodium M e t h o x i d e S o l u t i o n s  97  P l o t s o f l o g ( A ~ J V |AH] V e r s u s Mole % DMSO i n E t h a n o l f o r V a r i o u s C a r b o n A c i d s  98  K i n e t i c s o f t h e Base C a t a l y z e d I s o m e r i z a t i o n o f ( X - C y a n o - c i s - s t i l b e n e i n M+.05 Mole % DMSO i n M e t h a n o l C o n t a i n i n g 0.01M S o d i u m M e t h o x i d e a t 25° .. *  102  Plots o f l o g k i Versus H R - f o r the Isomerization o f Substituted 0(-Cyano-ciss t i l b e n e s i n DMSO-Ethanol C o n t a i n i n g 0.01M S o d i u m E t h o x i d e a t 25°  107  P l o t s o f l o g k]_ V e r s u s H R - f o r t h e I s o m e r i z a t i o n o f S u b s t i t u t e d CX-Cyano-ciss t i l b e n e s i n DMSO-Methanol C o n t a i n i n g 0.01M S o d i u m M e t h o x i d e a t 25° .. ..  108  X  Page 12.  13.  Ik. 15.  P l o t s o f l o g k V e r s u s 1/T K f o r t h e Base C a t a l y z e d I s o m e r i z a t i o n o f CX-Cyano-eiss t i l b e n e s i n DMSO-Methanol .. . . . .  112  A P l o t o f H V a l u e s V e r s u s Mole % .DMSO i n Methanol C o n t a i n i n g 0 . 0 1 M Sodium Methoxide for Various Indicators .. .. .. ..  131  Hammett C o r r e l a t i o n s o f t h e Lewis A c i d i t y o f O C - C y a n o s t i l b e n e s i n DMSO-Ethanol  139  Hammett C o r r e l a t i o n s o f t h e Lewis A c i d i t y o f 0 ( - C y a n o s t i l b e n e s i n DMSO-Methanol ..  l^-O  6  2  16.  Hammett C o r r e l a t i o n o f t h e Lewis A c i d i t y o f CX-Gyanostilbenes i n t h e Sodium M e t h o x i d e Methanol System .. .. 1>+1  17.  Hammett C o r r e l a t i o n s o f the Rates o f Isomerization o f Substituted 0(-Cyano-ciss t i l b e n e s i n DMSO-Ethanol and DMSOMethanol a t a H - V a l u e o f 1 6 . 0 0 a t 25° R  158  ACKNOWLEDGMENT  The  author wishes t o express h i s  sincere  a p p r e c i a t i o n t o P r o f e s s o r R. S t e w a r t f o r h i s guidance d u r i n g t h e course o f t h i s r e s e a r c h and f o r h i s suggestions during the preparation o f t h i s  thesis.  G r a t e f u l acknowledgment i s a l s o made t o the N a t i o n a l R e s e a r c h C o u n c i l f o r i t s generous f i n a n c i a l assistance.  1  INTRODUCTION  A.  A c i d s , Bases a n d A c i d i t y F u n c t i o n s A c i d s and bases have i n t r i g u e d c h e m i s t s f o r  centuries.  From as e a r l y a s 1663, when B o y l e  t h a t a c i d s gave a r e d c o l o r t o t h e b l u e  reported  vegetable  c o l o r i n g matter l i t m u s ( 1 ) , t h e s t u d y o f a c i d s and bases has l e d t o a f u l l e r u n d e r s t a n d i n g o f t h e fundamentals o f c h e m i s t r y . The  development o f a d e f i n i t i o n f o r a c i d s and  bases has p a r a l l e l e d t h e i n c r e a s e d u n d e r s t a n d i n g o f t h e i r nature.  L a v o i s i e r , i n t h e 1770's, n o t i c e d t h a t when  elements l i k e c a r b o n , n i t r o g e n and s u l f u r were burned i n oxygen, t h e p r o d u c t s y i e l d e d a c i d s i n w a t e r . led  This  him t o p o s t u l a t e t h a t oxygen was a n element common  to a l l acids (1).  W i t h t h e d i s c o v e r y by Davy t h a t hydrogen,  r a t h e r t h a n oxygen was t h e element common t o a c i d s , L i e b i g d e f i n e d a c i d s as those " . . . compounds c o n t a i n i n g h y d r o g e n i n w h i c h t h e hydrogen c a n be r e p l a c e d by m e t a l s " ( 1 ) . The  development o f t h e t h e o r y o f e l e c t r o l y t i c d i s s o c i a t i o n  by Ostwald and A r r h e n i u s led  i n t h e l880's (1) e v e n t u a l l y  t o t h e B r o n s t e d concept o f a c i d s and bases ( 2 ) .  According  to t h i s d e f i n i t i o n , an a c i d i s a proton  donor and a base i s a p r o t o n  acceptor.  2  Up u n t i l t h i s t i m e , d e f i n i t i o n s o f a c i d s and  bases were r e s t r i c t e d t o those systems w h i c h i n v o l v e d  the t r a n s f e r o f a p r o t o n .  The r e a l i z a t i o n t h a t some o f  the c h a r a c t e r i s t i c p r o p e r t i e s o f a c i d s and bases were p o s s e s s e d by s u b s t a n c e s n o t c o n t a i n i n g p r o t o n s l e d Lewis t o propose a b r o a d e r , more i n c l u s i v e d e f i n i t i o n o f a c i d s and b a s e s .  According  t o t h i s c o n c e p t , an a c i d i s a  s u b s t a n c e w h i c h can a c c e p t an e l e c t r o n p a i r and a base i s one a b l e t o donate a n e l e c t r o n p a i r  (3).  A l t h o u g h t h e Lewis d e f i n i t i o n i s q u i t e i n c l u s i v e and may i n c l u d e t h e B r o n s t e d  a c i d s as a s p e c i a l c a s e ,  G i l l e s p i e f e e l s that i t i s reasonable a c i d s as a s e p a r a t e I n the Bronsted  to regard  proton  c l a s s w i t h p a r t i c u l a r p r o p e r t i e s (*f).  sense, a c i d - b a s e  reactions involve only  the t r a n s f e r o f a p r o t o n , no m a t t e r what t h e a c i d may be. S i n c e these p r o t o n t r a n s f e r r e a c t i o n s a r e u s u a l l y v e r y f a s t , t h e y l e n d themselves r e a d i l y t o e q u i l i b r i u m measurements.  I n one s o l v e n t system t h e s t r e n g t h o f a n  a c i d i s dependent o n l y on the degree o f d i s s o c i a t i o n and independent o f the base w i t h w h i c h i t i s r e a c t i n g . such s i m p l e r e l a t i o n s h i p e x i s t s i n a c i d - b a s e when Lewis type a c i d s a r e i n v o l v e d . an a c i d - b a s e  No  reactions  In this latter  ease,  r e a c t i o n i n v o l v e s the complete m o l e c u l e and  i t s s t r e n g t h as an a c i d depends i t i s reacting.  on t h e base w i t h w h i c h  3  I n o r d e r t o measure t h e s t r e n g t h o f a c i d s , measurements on t h e e q u i l i b r i u m i n v o l v i n g a t l e a s t two acids are necessary  (5a).  AH  +  B ^  A  +  (The  charges have been o m i t t e d i n t h i s e q u a t i o n  i n o r d e r t o make i t more g e n e r a l .  BH  (1)  I n a l l cases t h e charge  on A w i l l be one l e s s t h a n t h a t on AH.)  The thermo-  dynamic e q u i l i b r i u m c o n s t a n t f o r t h i s r e a c t i o n i s t h e n g i v e n by t h e e x p r e s s i o n  *  (A) (BH) K  =  (2)  (AH)(B) S i n c e e q u i l i b r i u m c o n s t a n t s o f t e n v a r y by many powers o f t e n , i t i s customary t o u s e t h e d e f i n i t i o n pK  =  (3)  - log K  A l t h o u g h t h e above p e r t a i n s s p e c i f i c a l l y t o B r o n s t e d a c i d s , analogous e q u a t i o n s c a n be d e r i v e d f o r Lewis a c i d s . I n t h e case where water i s t h e s o l v e n t and a l s o the base i n e q u a t i o n ( 1 ) , t h e n t h e e q u i l i b r i u m c o n s t a n t i n e q u a t i o n ( 2 ) becomes  *  The symbols ( ) , [ ] and f w i l l be u s e d t o denote  the a c t i v i t y , c o n c e n t r a t i o n  and a c t i v i t y c o e f f i c i e n t on  t h e molar s c a l e r e s p e c t i v e l y .  where the s u b s c r i p t aq r e f e r s t o the s p e c i e s s o l v a t e d by water.  Since i n d i l u t e aqueous  s o l u t i o n , the a c t i v i t y o f  water i s e f f e c t i v e l y u n i t y when water i s taken as the standard s t a t e ( 6 ) , the term (R2O) i n e q u a t i o n been i n c l u d e d i n K.  When AH i s an uncharged  then the e q u i l i b r i u m constant i n e q u a t i o n as K  A H  (h) has  molecule,  (*+) i s denoted  and i s known as the a c i d d i s s o c i a t i o n constant Since equation  (7a).  (*+) i n v o l v e s the a c t i v i t i e s  o f i o n s , which cannot e a s i l y be measured, the u s u a l p r a c t i c e i s t o measure the d i s s o c i a t i o n  constant (5)  which i s the e q u i l i b r i u m constant u s i n g c o n c e n t r a t i o n s r a t h e r than a c t i v i t i e s .  The c o n c e n t r a t i o n measurements  a r e then made as a f u n c t i o n o f i o n i c s t r e n g t h and extrapolated to i n f i n i t e d i l u t i o n procedure  (8).  That  this  w i l l give the v a l u e f o r the thermodynamic  e q u i l i b r i u m constant i s e v i d e n t from the e x p r e s s i o n  (6)  (x) where X r e f e r s t o any s p e c i e s .  The a c t i v i t y  coefficient  5  term f ^ i s a measure o f how f a r the behavior o f X d e v i a t e s from i d e a l i t y and w i l l be equal t o u n i t y i n the standard state.  On a p p l y i n g e q u a t i o n (3) to e q u a t i o n (k), the  l a t t e r becomes (A) p  K  =  -log  (AH)  -  log (H.0 )  (7)  +  J  I n d i l u t e aqueous s o l u t i o n s , - l o g (H3O ) i s c l o s e l y approximated  by the pH, a l t h o u g h pH i s now d e f i n e d on an  operational basis ( 7 b ) . Equation  ( 7 ) a l l o w s one t o  measure the i o n i z a t i o n constants o f a c i d s and bases i n d i l u t e aqueous s o l u t i o n s o f low i o n i c s t r e n g t h . the i o n i c s t r e n g t h must remain low,  Since  the pK v a l u e s o f  a c i d s and bases measurable i n aqueous s o l u t i o n s a r e r e s t r i c t e d t o the pH range from 1 to 1 2 . Many weak a c i d s and bases have pK v a l u e s o u t s i d e the range o f 1 t o 1 2 and the measurement o f these has been a d i f f i c u l t problem.  One o f the most  popular methods o f overcoming t h i s d i f f i c u l t y was developed  by Hammett and Deyrup (9)»  F o r a c i d s which  i o n i z e a c c o r d i n g t o the e q u a t i o n BH  B  +  H  (8)  where the water o f s o l v a t i o n and i o n i c charges have been omitted, the pK i s g i v e n by the e x p r e s s i o n  6  pK  =  - log  (B)(H)  ' [B] (H)f - l o g =-r- log [BH] f  =  (BH)  B  B  (9)  H  For any two acids,. BH and C H , which i o n i z e to a measurable extent i n the same s o l v e n t , the A p K  ApK  =  pKBH  -pKcH  [B] [CH] - log  =  - log  r  M S i n c e the r a t i o s  i s g i v e n by  [ B ] / [BH]  and  i\ C  f  fBfGH  , , (16)  BH*C  can be o b t a i n e d  [c]/[CH]  e x p e r i m e n t a l l y , one can then o b t a i n , by t h i s stepwise p r o c e s s , A p K v a l u e s f o r a v a r i e t y o f a c i d s which according to equation equation  ionize  ( 8 ) , p r o v i d e d the l a s t term i n  (10) i s c l o s e to zero..  I f one a c i d i o n i z e s  i n the pH range, then a l l the other pK v a l u e s a r e based on water as the standard dynamic pK v a l u e s .  s t a t e and are thus t r u e thermo-  I n a d d i t i o n t o the pK v a l u e s , a  measure o f the a c i d i t y or b a s i c i t y o f the medium i s a l s o obtained.  This i s g i v e n by the a c i d i t y f u n c t i o n  d e f i n e d as [B]  H  =  l o g -p ^  (H)f - log — B  +  pK  B H  =  &HJ  The p o s t u l a t e t h a t H i s dependent  (11)  B H  o n l y on the s o l u t i o n  and independent o f the p a r t i c u l a r i n d i c a t o r used t o measure it  i s based on the fundamental assumption t h a t the r a t i o  o f the a c t i v i t y c o e f f i c i e n t s , fj^/f-Q^  i  s  t  h  e  same f o r  7  different  acids The  for  systems  a  highly  Since  the  H  where  Q  conjugate his  v  base  co-worker's  been  done  work  on  and  reported  various  A  amine  function which  then  hold  for  since  would  for  acids  been  ization  hold  which  behavior  determined  If  the  by  of a  ionization  should  give  -  an  H  a  the  i n i t i a l  of  i t  was  acid  plot  of  straight  of  That  log of  [B]/ the  l i n e  the  acid  work  The  Deno  based  does  largely  not  structure  or  not  H  function  Q  (12).  one  the  versus follows  unit  values  indicators  ideal i n  has  Paul  by  that  and  early  by  were  similar  (BH^  of  of  function  hoped  this  the  Hammett  published  Whether  follows  on  1957  substantially  shown.  an  a c i d s .  been  designated  of  amount  functions  Q  was  work  i n  (9).  uncharged  charge  a c i d i t y  variety  differ  i s  function  reviewed  H)>  behavior a  cases  to  recently early  developed (12)  acid  considerable  protonation.  conclusively  be  plot  the  equation  s u l f u r i c  concentrated  has  (9  by  the  bibliography  indicators  ionized  as  these  was  f i r s t  (12)  refers  functions  (11).  to  was  +  a c i d i t y  a  10),  Although on  i n  Since  (9,  using  since  base  H  such  subscript  a c i d i t y  Long  +  medium  (9).  function  according  appropriate  the  solution.  a c i d i t y  B  >  acidic  the  given  ionize  conjugate  molecule, as  a  Hammett  which  BH+  i n  i n  slope*  i o n can  HQ.  HQ,  this It  has  has  8  been shown t h a t f o r s e v e r a l c l a s s e s o f compounds, such (13),  as e t h e r s  pyrroles  (IMO, a z u l e n e s (15)> amides  (16 - 18), t e r t i a r y amines (19) and i n d o l e s above c r i t e r i o n was n o t f o l l o w e d . Hammett p o s t u l a t e  (20), the  This must mean t h a t t h e  o n l y h o l d s f o r a narrow range o f a c i d s  which d i f f e r only s l i g h t l y i n s t r u c t u r e . s e p a r a t e and s e l f - c o n s i s t e n t H  Q  e s t a b l i s h e d f o r the protonation  As a r e s u l t ,  f u n c t i o n s have been o f p r i m a r y (21, 22) and  t e r t i a r y ( 1 9 ) amines, amides (23 - 25) and i n d o l e s ( 2 0 ) . A l t h o u g h t h e above compounds a l l r e a c t , i n a c i d medium, a c c o r d i n g  t o simple protonation  o l s do n o t . I n s t e a d , according  equilibria,  carbin-  they react w i t h s u l f u r i c a c i d  t o the equation  ROH  +  H S0k.  R  2  +  +  H 0 2  +  HSOk."  F o r e q u i l i b r i a o f t h i s t y p e , G o l d and Hawes (26)  (13)  derived  an a c i d i t y f u n c t i o n c a l l e d J . F o r mathematical convenience, 0  t h e y f a c t o r e d e q u a t i o n (13) i n t o t h r e e a u x i l i a r y s t e p s H S0L,. ^ — -  HSO^"  2  ROH R0H  + 2  +  H  v  ^ R  +  H  +  (15)  H 0  (16)  R0H  +  +  +  (140  +  2  2  with e q u i l i b r i u m constants K  1 ?  K , and 2  respectively.  The o v e r a l l e q u i l i b r i u m c o n s t a n t K j , was t h e n  9  K  X  =  K KpK. * *  (R OCHSOj, )(H G) (R0H)(H SC^) P  =  n  (17)  2  By u s i n g the d e f i n i t i o n t h a t  (H ) f +  h  n  B  2-  (18)  =  •  (17)?  upon rearrangement, gave  equation  ROH  =  K  ;—  7~~  (ROH) Upon t a k i n g l o g a r i t h m s  h f 0  (19)  + R  O  H  9  and r e a r r a n g i n g , e q u a t i o n  then became  (19)  r n  POHJ' H  G  +  log(H 0)  =  2  - pK  +  R 0 H  log  F  + log  R0H2  (20) From the d e f i n i t i o n t h a t  [ROH] J  it  o  " P R0H  =  K  followed that H J  = O  H  0  + O  +  and J  L  Q  0  G  ~ ^ ~  (  2  1  )  were r e l a t e d by the e q u a t i o n  log(HoO)  +  log  (22) i  -P 1  R0H  + 2  +  10  By assuming t h a t % / % 0 H +  +  w  a  s  u n i  " y t  i  n  a l  l  solvents  c o n s i d e r e d , G o l d and Hawes (26) were a b l e t o c a l c u l a t e J  Q  v a l u e s f o r s u l f u r i c a c i d s o l u t i o n s u s i n g the known  H  D  v a l u e s and t h e measured a c t i v i t y o f water i n s u l f u r i c  acid solutions.  I n t e s t i n g t h i s r e l a t i o n s h i p they found  t h a t a p l o t o f l o g [R ] / [R0HJ +  against J  for  Q  hh  i n 80 t o 90% s u l f u r i c  trinitrotriphenylmethanol  l  9  acid  1.16.  y i e l d e d a s t r a i g h t l i n e o f slope  A l t h o u g h t h e above a s s u m p t i o n was a t f i r s t a c c e p t e d by Deno, J a r u z e l s k i and S c h r i e s h e i m (27), t h e y later established  a self-consistent acidity function i n (28)  s u l f u r i c a c i d f o r the e q u i l i b r i u m R  +  +  H 0 ^—-  ROH  2  +  H  (23)  +  The a c i d i t y f u n c t i o n , H , was d e f i n e d as R  [R ] +  %  =  pK  -  + R  l o  - log(H )  g  r  (2lf)  T  [ROHJ  . +  , ^ log(H 0) 2  . +  , log  f  f  where the d i f f e r e n c e  between HR and J f  H  R  -  J  D  =  R  Q  +  R0H  was shown t o be  +  (25)  l o g — f  R  R0H  + 2  11  By u s i n g of  (H  18 a r y l m e t h a n o l s , t h e y showed t h a t the v a l u e  - J)  R  Q  decreased g r a d u a l l y  to a value of -5  a t 82% s u l f u r i c a c i d , above w h i c h i t was  stationary.  T h i s e v i d e n c e i n d i c a t e d t h a t the a c t i v i t y c o e f f i c i e n t r a t i o , fp /fp.0H2 » ^  s  82% s u l f u r i c a c i d .  The f a c t t h a t G o l d and Hawes t e s t e d  +  +  n o  v  *  e  (  l  u  a  l  t o u n i t y below  i n 80 t o 30% s u l f u r i c a c i d and o b t a i n e d  their postulate  a s t r a i g h t l i n e o f near u n i t s l o p e when p l o t t i n g l o g \&f\ / [ROH] a g a i n s t  the c a l c u l a t e d J  0  values ( 2 6 ) , i s  i n accordance w i t h t h i s l a t e r evidence. By e v a l u a t i n g and  t h e Hp_ f u n c t i o n i n p e r c h l o r i c  n i t r i c a c i d s , Deno e t a l ( 2 9 ) were a b l e t o show t h a t  the pK + v a l u e s a r e l a r g e l y the same f o r a g i v e n a l c o h o l , R  even though measured i n d i f f e r e n t aqueous s o l u t i o n s .  This  showed t h a t f o r a r y l m e t h a n o l s , the v a l u e s o f t h e a c t i v i t y c o e f f i c i e n t r a t i o , f R / f R O H , a r e l a r g e l y independent +  of the arylmethyl  group.  C l o s e l y connected w i t h t h e H  R  a c i d i t y function  i s the a r y l o l e f i n - a r y l m e t h y l c a t i o n e q u i l i b r i u m .  This  was i n v e s t i g a t e d by Deno, Grover and S a i n e s (30) f o r s e v e r a l d i a r y l o l e f i n s f o r which the e q u i l i b r i u m protonation ol  can be w r i t t e n as +  H  +  R  +  where o l r e p r e s e n t s the o l e f i n and R  ( 2 6 )  +  the corresponding  12  methyl c a t i o n . equation  From t h e e q u i l i b r i u m c o n s t a n t f o r  (26), the expression +1  pK' +  =  R  - log(H )  & ] l o g7-T^p [ ]  +  ol  can be o b t a i n e d .  f + + llo go g— o l R  +  Combining e q u a t i o n  (27) w i t h  (2*+), w i t h t h e a s s u m p t i o n t h a t f + / f Q H R  (27)  f  a  n  R  d  fR  equation  + / / f  ol  a  r  e  e q u a l , r e s u l t e d i n the d e f i n i t i o n f o r H ' as g i v e n i n R  equation  (28). [ol]  H« R  The  =  Q  R  -  log(H 0)  =  2  pK' + R  data f o r t h e s i x d i a r y l o l e f i n s  f i t equation H  H  This evidence  g"^+J~  ( 2 8 )  studied s a t i s f a c t o r i l y  (28) r a t h e r t h a n e q u a t i o n  function (30).  +  l o  (24-) o r t h e  i n d i c a t e d that a separate  a c i d i t y f u n c t i o n H ' governs t h e p r o t o n a t i o n o f o l e f i n s . R  As c a n be seen from t h e above, t h e p r o t o n a t i o n o f n e u t r a l s p e c i e s has been t h o r o u g h l y contrast  studied.  In  t o t h i s , c o m p a r a t i v e l y l i t t l e work has been  done on s t u d y i n g t h e p r o t o n a t i o n o f n e g a t i v e l y charged species.  According  t o t h e p r o p o s a l o f Hammett ( 9 , 1 0 ) ,  the a c i d i t y f u n c t i o n d e s c r i b i n g the medium i n w h i c h t h e p r o t o n a t i o n o f a n e g a t i v e l y charged s p e c i e s t a k e s  place,  as d e s c r i b e d by the e q u i l i b r i u m HA  A~  +  H  +  (29)  13  would be t h e H_ f u n c t i o n .  H_  =  pK  T h i s i s t h e n d e f i n e d by  +  H A  (30)  log  l o g h. where (H ) f +  A  h_  f  (3D  AH  I n o r d e r t o s t u d y e q u i l i b r i a o f t h e type represented  by e q u a t i o n  (29) o u t s i d e t h e d i l u t e aqueous  r e g i o n , v e r y s t r o n g a c i d s i n s t r o n g l y a c i d medium (31> 3 2 ) , or c o n v e r s e l y , weak a c i d s and s t r o n g l y b a s i c systems (33) must be employed.  I n a c i d i c medium, P h i l l i p s  established  a H_ s c a l e f o r aqueous h y d r o c h l o r i c a c i d s o l u t i o n s u s i n g phosphate type i n d i c a t o r s (31) and Boyd e s t a b l i s h e d a H_ s c a l e f o r s u l f u r i c and p e r c h l o r i c a c i d s cyanocarbon a c i d s as i n d i c a t o r s ( 3 2 ) .  using  In highly basic  r e g i o n s , H_ s c a l e s have been e s t a b l i s h e d f o r a v a r i e t y o f systems employing a number o f d i f f e r e n t t y p e s o f i n d i c a t o r s (33)-  I t i s t h i s l a t t e r a r e a w h i c h w i l l be  summarized h e r e . S t r o n g l y b a s i c systems c a n be e s t a b l i s h e d i n any  one o f t h r e e ways.  One way i s t o i n c r e a s e t h e  c o n c e n t r a t i o n o f the s a l t o f the c o n j u g a t e base o f a  lep r o t i c solvent i n that solvent.  H_ s c a l e s f o r t h i s t y p e  o f system have been developed f o r p o t a s s i u m h y d r o x i d e - , water (3^)? sodium h y d r o x i d e - w a t e r (3*+> 35)  5  lithium  h y d r o x i d e - w a t e r ( 3 6 ) , benzyltrimethylammonium h y d r o x i d e water ( 3 6 ) , l i t h i u m ( 3 7 ) , p o t a s s i u m (37? 38) and sodium (37» 39 - ^1) methoxide-methanol  solutions.  I n d i l u t e s o l u t i o n s , f o r example 0.01 t o IM sodium h y d r o x i d e i n w a t e r , t h e e q u a t i o n H_  =  pK^  +  (32)  l o g [OH*"]  holds f a i r l y w e l l (35). But a t higher c o n c e n t r a t i o n s o f h y d r o x i d e i o n , t h e " e f f e c t i v e pH" i n c r e a s e s more r a p i d l y t h a n the v a l u e o f l o g |oH ~] would i n d i c a t e  (35> 3 6 ) ,  t h u s g i v i n g r i s e t o a H_ s c a l e . and S u l z b e r g e r (3^) were t h e  Schwarzenbach  f i r s t t o a t t e m p t t o s e t up a H_ s c a l e .  They u s e d  c o n c e n t r a t e d s o l u t i o n s o f aqueous sodium and p o t a s s i u m h y d r o x i d e s employing i n d i g o d e r i v a t i v e s  ( I ) and s u b s t i t u t e d  I  glutacondialdehyde d i a n i l s ( I I ) as i n d i c a t o r s . R-N=CH-CH=CH-CH=CH-NH-R  15  I n c e r t a i n c a s e s , some g l u t a c o n d i a l d e h y d e  dianils  showed anomalous i o n i z a t i o n b e h a v i o r w h i c h was a t t r i b u t e d to hydroxide i o n a d d i t i o n i n contrast to proton  removal.  R e c e n t l y , Edward and Wang (35) have r e i n v e s t i g a t e d t h e H _ s c a l e i n aqueous sodium h y d r o x i d e s o l u t i o n s u s i n g t h i o They c o n f i r m e d t h e H _ s c a l e o f  aeetamide a s a n i n d i c a t o r .  the e a r l i e r w o r k e r s and suggested  t h a t t h e anomalous  b e h a v i o r o f t h e g l u t a c o n d i a l d e h y d e d i a n i l s was due t o a d i f f e r e n c e i n h y d r a t i o n r a t h e r than a d i f f e r e n t  ionization  process. S e v e r a l w o r k e r s have r e c e n t l y attempted t o a p p l y t h e r a t i o n a l i z a t i o n o f Bascombe and B e l l  (4-2), who  showed t h a t the h i g h a c i d i t i e s i n c o n c e n t r a t e d a c i d s o l u t i o n s a r e m a i n l y due t o e x t e n s i v e d e s o l v a t i o n o f t h e p r o t o n , t o c o n c e n t r a t e d aqueous a l k a l i n e s o l u t i o n s (35, 4-3). For the e q u i l i b r i u m H A  +  G H ~ ^ = ^  where H A , O H and A  A "  +  (p  +  1)H 0 2  (33)  r e p r e s e n t t h e h y d r a t e d s p e c i e s and p  r e p r e s e n t s t h e d i f f e r e n c e i n h y d r a t i o n number between (HA +  0H~~) and A , Edward and Wang (35) d e r i v e d t h e  expression  -  [A  ]  —  —  [HAU  R  =  K TH TAA  K  H A  _-,  P § HH  J 1  L  J  (H 0) 2  (34-)  ~ ^  16  u s i n g the a p p r o x i m a t i o n t h a t  r log (Hp©) ^  fmf  E  f  A  plot (log  [A-]/[HA]  -  (35)  log °  A"  l o g [OH"]) versus l o g  (HpO)  f o r t h i o a c e t a m i d e i n aqueous sodium h y d r o x i d e  solutions  gave an a p p r o x i m a t e l y s t r a i g h t l i n e w i t h the s l o p e (r-p-1) being equal to 3.2.  Using t h i s v a l u e , they  c a l c u l a t e d the H_ v a l u e s u s i n g the e q u a t i o n H_  =  P*V  +  l o g E>H"]  +  (r-p-1) log(H 0)  and found t h a t the c a l c u l a t e d H_ v a l u e s a g r e e d w e l l w i t h the e x p e r i m e n t a l ones. and Anbar (*+3)  (36)  2  reasonably  More r e c e n t l y , Y a g i l  c a r r i e d out a s i m i l a r t r e a t m e n t f o r  aqueous sodium and p o t a s s i u m h y d r o x i d e  solutions.  W i t h the term ( r - p - 1 ) i n e q u a t i o n (36)  r e p l a c e d by  - ( n + 1)  and u s i n g the H_ v a l u e s o f Schwarzenbach and  S u l z b e r g e r G"*.), Y a g i l and Anbar found t h a t the  calculated  H_ v a l u e s agreed w i t h the e x p e r i m e n t a l ones o n l y when n was  equal to 3.  I n t h i s t r e a t m e n t , n was  number o f water m o l e c u l e s (*+3).  r e g a r d e d as the  s o l v a t i n g the h y d r o x i d e i o n  These two t r e a t m e n t s i n d i c a t e t h a t the i n c r e a s e d  b a s i c i t y of concentrated a l k a l i n e s o l u t i o n s i s p r i m a r i l y due t o a l e s s e n i n g o f the degree o f s o l v a t i o n o f the h y d r o x i d e i o n due t o i t s g r e a t e r c o n c e n t r a t i o n r e s u l t i n g i n an i o n w i t h a h i g h e r a c t i v i t y .  17  A s i m i l a r t r e a t m e n t has r e c e n t l y by R o c h e s t e r the  (kl) f o r  sodium methoxide  where  =  pK  [NaOMe]  M e 0  H  l o g [NaOMe]  +  was t h e  -  solutions.  Using  was a p p r o x i m a t e l y z e r o , various n were  p h e n o l s as fairly  5.6 f o r  to  knowledge about  values  —  of n u s i n g  The a v e r a g e v a l u e s  i n w h i c h one  N o t much s i g n i f i c a n c e  because  of a c t i v i t y  of  the  lack  other  concentration Using  of i t s e l f  in  diamine-water The  (k6)  such systems  system  comparatively  of water this  type  is of  decreased, system,  the  H_ scales  are  not  have  (kk, H-5), e t h y l e n e -  and 2-aminoethanol-water  protic-aprotic  As  basicity  (k?)  t h i r d method o f o b t a i n i n g h i g h l y  to use  systems  component u s u a l l y b e i n g w a t e r .  been developed f o r hydrazine-water  Since  of  coefficients  by u s i n g a two component  component i s  b a s i c and the  is  of  solutions.  c a n be e s t a b l i s h e d i s  systems  of  log(foMe ^AH^A"""^  A s e c o n d way i n w h i c h s t r o n g l y b a s i c  increases.  (37)  r a n g i n g f r o m 3*0 f o r p e n t a m e t h y l p h e n o l  these f i g u r e s the  concentration  calculated values  2,6-di-t-butylphenols.  was a t t a c h e d  methanolic  he  indicators.  large,  (n + l ) l o g ( M e O H )  stoichiometric  sodium methoxide and assuming t h a t  the  attempted  equation H_  to  been  polar  basic  component  inherently basic,  it  systems.  systems. is  18  necessary salt the  of  t o add  the  by  The  H_  keeping  increasing scales  basicity  increasing  commonly, by and  c e r t a i n amount o f  c o n j u g a t e base o f  system.  either  a  the  for  s u l f oxide-water  (36,  the  concentration  U-8),  a l l the  recent  k9).  was  values  studies  f o r the  r e v i e w by  S c h w a r z e n b a c h and have a l r e a d y have r e l i e d indicators  various  component.  (36  -  (36),  for  dimethyl-  other  systems.  (50)  highly  dimethyl-  H_  DMSO-water (>+9).  systems are  The and  listed  kk- -  in  50). (kO,  Edward and  fluorenes  have b e e n e m p l o y e d i n s e t t i n g up  arylamines  and H_  52).  In  (+8,  (35)  Wang  field  hindered  addition  polyarylmethanes scales  by  as  Recently, highly kl,  these  i n d i c a t o r s used  Other workers i n t h i s  substituted  been u s e d  substituted  been i n  mole %  n  39?  most  s y s t e m , a maximum  S u l z b e r g e r (3*+)  on  the  i n d i c a t o r s have b e e n u s e d i n  basic  heavily  constant  (33).  Bowden  been mentioned.  p h e n o l s have a l s o these,  base  0.011M t e t r a m e t h y l a m m o n i u m  i n 99  obtained  i n highly  more  systems.  f a r has  With t h i s  A v a r i e t y of  to  (51)  so  (36,  the  the  aprotic  systems s t u d i e d ,  hydroxide  H_  or,  increased  l  (DMSO) c o n t a i n i n g  The  be  to  • +9), d i m e t h y l s u l f o x i d e - m e t h a n o l  system e s t a b l i s h e d  o f 26  the  of  pyridine-water  s u l f oxide  value  systems can  base c o n c e n t r a t i o n ^  of  a  component,  the  dimethylsulfoxide-ethanol  basic  such as  s u c h s y s t e m s have b e e n e s t a b l i s h e d (36,  Of  protic  these  proportion  sulfolane-water  and  of  the  base,  51)•  19  (53»  A l t h o u g h S c h a a l and co-workers  54-) have  measured the a p p a r e n t pK v a l u e s o f some p o l y n i t r o b e n z e n e s ( I I I ) , t h e mode o f i o n i z a t i o n o f these compounds  cannot  be a s i m p l e p r o t o n l o s s as g i v e n by e q u a t i o n (29). an i o n i z a t i o n p r o c e s s such as  Instead,  . •0, p-  N0  2  +  OR"  N0  0 N 2  H  III  2  r  0N  (38)  2  OR  H  OR  IV •  was v i s u a l i z e d (53)• complex ( I V ) (55)  That such a Meisenheimer type  can be formed by p o l y n i t r o b e n z e n e s i n  b a s i c s o l u t i o n s has r e c e n t l y been shown w i t h t h e a i d o f NMR s p e c t r o s c o p y (56,  57).  S i n c e e q u i l i b r i a o f t h e type d e s c r i b e d i n e q u a t i o n (38)  do n o t f o l l o w a H_ f u n c t i o n , a f u n c t i o n  d e s i g n a t e d J _ has been suggested processes.  Rochester  (58)  (26,  58) f o r such  c o n s i d e r e d the a d d i t i o n o f  base t o a n i n d i c a t o r i n terms o f t h e two r e v e r s i b l e equilibria H  AH A  +  +  +  HoO u 2  A"  -^r  (39)  (%)  AHOH  (K ) 2  (H-0)  20  From t h e s e , by l e t t i n g . ' [AH0H"3 lo-g-r-p-rs:—  =  K  =  - pK  +  K-jK^, the  H__  expression  log  +  (H 0) P  +  |AHJ  fA"  l o g — fA H  OH  (to) was  With J _ defined  obtained.  J_  as  [ A H O H  =  pK  +  ]  log-p-r  (h2)  [AH]  the  r e l a t i o n s h i p between H _ and  J_  =  H_  log(H 0)  +  2  J__ was  +  g i v e n by the  log— f  The  r e l a t i o n s h i p between J _ and  t o t h a t between J Up established.  Q  to the  and  H  D  .  (^-3)  AH0H~  H__ i s t h e n a n a l o g o u s  (26).  p r e s e n t , o n l y one  J _ s c a l e has  Using 2, +-dinitroanisole,  p i c r i c a c i d and  equation  2, +-dinitroaniline,  1  2,^,6-trinitroanisole,  been  l  Rochester attempted  to e s t a b l i s h a J _ scale  f o r sodium methoxide i n methanol  (59)•  or t h r e e p o s s i b l e  However, the  involved  two  equilibria  i n each case would t e n d to c a s t some doubt  the v a l i d i t y o f  a s c a l e u s i n g such i n d i c a t o r s .  on.  21  B.  The C o r r e l a t i o n o f K i n e t i c s w i t h A c i d i t y F u n c t i o n s The c o r r e l a t i o n o f t h e k i n e t i c s o f a c i d  catalyzed  r e a c t i o n s w i t h a c i d i t y f u n c t i o n s has been w e l l documented (60).  I n c o n t r a s t t o t h e work i n a c i d r e g i o n s , few  c o r r e l a t i o n s o f base c a t a l y z e d r e a c t i o n s w i t h t h e appropr i a t e a c i d i t y f u n c t i o n have been made. The r e l a t i o n s h i p between k i n e t i c s and a c i d i t y f u n c t i o n s i n aqueous a l k a l i n e s o l u t i o n s f o r v a r i o u s  by Anbar e t a l ( 6 l ) .  o f mechanisms has been d i s c u s s e d  They showed t h a t the l o g a r i t h m o f t h e r a t e c o n s t a n t correlates with  or w i t h  H _  i s the c o n c e n t r a t i o n  H__  types  +  l o g C - ^ O J where  either CJJ^G  o f water n o t bound by s o l v a t i o n .  The case where a r a p i d p r e - e q u i l i b r i u m i s s e t up f o l l o w e d by a slow u n i m o l e c u l a r  r e a c t i o n was  represent-  ed by t h e e q u a t i o n s SH  +  _ S  0H~ ^  S ~  +  H  (4-4-)  +  slow .  >  With the assumption that and A  ^  (4-5)  products  fs^/f^  =  ^AH^A""'  where  A H  r e f e r t o the i n d i c a t o r s used t o e s t a b l i s h the H _  s c a l e and f * i s t h e a c t i v i t y c o e f f i c i e n t f o r t h e t r a n s i t i o n s t a t e i n t h e r e a c t i o n , i t was shown t h a t t h e r e l a t i o n between k, t h e r a t e c o n s t a n t ,  and H _ i s g i v e n  by the e x p r e s s i o n ( 6 l ) log k  =  H _  +  constant  (4-6)  22  An example o f t h i s type was (62,  63).  f i r s t r e p o r t e d by R i d d e t a l  They s t u d i e d the d e c o m p o s i t i o n o f c h l o r o f o r m  i n sodium methoxide-methanol s o l u t i o n s .  The  slow s t e p  i n t h i s r e a c t i o n had p r e v i o u s l y been shown t o be decomposition carbene.  the  o f the c o n j u g a t e base, C C l ^ , t o form  the  -  U s i n g the H_  e s t a b l i s h e d (39),  s c a l e w h i c h they had p r e v i o u s l y  O ' F e r r a l l and R i d d (63)  reported that  a p l o t o f l o g k v e r s u s H_  gave a r e a s o n a b l y s t r a i g h t  w i t h a s l o p e o f about 0 . 8 .  Another example o f t h i s  line type  i s the c o r r e l a t i o n between the r a t e o f the base c a t a l y z e d r a c e m i z a t i o n o f ( + ) - 2 - m e t h y l - 3 - p h e n y l p r o p i o n i t r i l e and the b a s i c i t y o f the medium, as measured by a H_ DMSO-methanol system methoxide as base (50). l o g k and H_,  s c a l e f o r the  c o n t a i n i n g 0.025 molar sodium The  e x c e l l e n t c o r r e l a t i o n between  as e v i d e n c e d by a s t r a i g h t l i n e f o r a  b a s i c i t y change o f seven powers o f t e n w i t h a s l o p e o f O.87,  was.used t o argue i n f a v o r o f a r a p i d  equilibrium  f o r m a t i o n o f an " a s y m m e t r i c a l l y s o l v a t e d c a r b a n i o n " f o l l o w e d by a slow r a t e d e t e r m i n i n g r a c e m i z i n g s t e p . When the s u b s t r a t e SH i s i n r a p i d p r e - e q u i l i b r i u m w i t h i t s c o n j u g a t e base S , as g i v e n i n e q u a t i o n  (kk),  w h i c h i s f o l l o w e d by a b i m o l e c u l a r r a t e d e t e r m i n i n g r e a c t i o n of S S  „  w i t h a n o t h e r r e a c t a n t Y t o form the +  Y  slow >  products  products (k7)  23  t h e n the r e l a t i o n between the r a t e c o n s t a n t and H__ i s still f  Y Sr/ f  g i v e n by e q u a t i o n (H-6) i f t h e a s s u m p t i o n t h a t f = , =  =  f  AB/ A~ f  ;  l s  t  r  u  (6l).  e  An example o f t h i s  was r e p o r t e d t o be the r e a c t i o n o f ammonia w i t h i n concentrated a l k a l i n e hydroxide  chloramine  s o l u t i o n s (61).  The  k i n e t i c s o f t h i s r e a c t i o n was found t o c o r r e l a t e w i t h H_ g i v i n g a s l o p e o f 0.90 (6H-). I n the case where t h e r a t e d e t e r m i n i n g i s the n u c l e o p h i l i c a t t a c k o f t h e h y d r o x i d e  step  ion, either  i n the p r o t o n r e m o v a l o r t h e s u b s t i t u t i o n s t e p , i t was shown t h a t the k i n e t i c s s h o u l d c o r r e l a t e w i t h H_ (6l).  +  logCjj^O  I n the base c a t a l y z e d e l i m i n a t i o n r e a c t i o n o f  d l - s e r i n e phosphate ( V ) , H P0 -0-CH CH(NH )C0 H 2  3  2  2  2  Vw h i c h was shown by d e u t e r i u m  isotope e f f e c t to react  by a slow r a t e d e t e r m i n i n g p r o t o n r e m o v a l s t e p f o l l o w e d by a r a p i d d e c o m p o s i t i o n l o g k v e r s u s H_  +  t o products  (65), t h e p l o t o f  l o g G ^ o gave a s t r a i g h t l i n e w i t h a  s l o p e o f O.98 ( 6 l , 65).  F o r the a l k a l i n e h y d r o l y s i s o f  e t h y l i o d i d e , w h i c h goes by t h e S 2 mechanism, i t was shown N  t h a t a p l o t o f l o g k v e r s u s H_ l i n e w i t h a s l o p e o f 1.03  (6l).  +  logCjj Q gave a s t r a i g h t S i m i l a r l y i n the  h y d r o l y s i s o f c h l o r a m i n e , w h i c h i s thought  to involve a  2h  slow n u c l e o p h i l i c a t t a c k of hydroxide the p l o t o f l o g k v e r s u s H_ l i n e o f s l o p e 1.00  ( 6 l ) .  +  i o n on chloramine  (66),  logCjj^Q gave a s t r a i g h t  These examples s u p p o r t t h e  p r o p o s a l s by Anbar e t a l ( 6 l ) . S e v e r a l l e s s v a l i d c o r r e l a t i o n s o f H_ w i t h r a t e d a t a have a l s o been r e p o r t e d . of ^-dinitrobenzene  (67),  chloronitrobenzenes  These i n c l u d e the d e g r a d a t i o n  2-dinitrobenzene  (69) i n m e t h a n o l i c  (68), and 2- and  alkoxide solutions  and the h y d r o l y s i s o f c a r b o n d i s u l f i d e i n c o n c e n t r a t e d a l k a l i n e hydroxide  s o l u t i o n s (70).  These s t u d i e s have t h e  common f e a t u r e t h a t i t i s u n l i k e l y t h a t the mechanisms i n v o l v e a f a s t e q u i l i b r i u m i o n i z a t i o n by the l o s s o f a p r o t o n t o form an a n i o n f o l l o w e d by a r a t e - d e t e r m i n i n g decomposition  o f the a n i o n .  Instead, these r e a c t i o n s  l i k e l y p r o c e e d e i t h e r by a f a s t e q u i l i b r i u m a d d i t i o n o f a base m o l e c u l e f o l l o w e d by a r a t e - d e t e r m i n i n g o f t h e base a d d u c t , ' o r  decomposition  by a slow r a t e - d e t e r m i n i n g a d d i t i o n  o f base t o the u n s a t u r a t e d  system.  Because these r a t e s were  c o r r e l a t e d w i t h a c i d i t y s c a l e s d e r i v e d by u s i n g i n d i c a t o r s i o n i z i n g by a p r o t o n l o s s , t h e r e i s doubt a s . t o t h e meani n g o f such c o r r e l a t i o n s . Such r e a c t i o n s as above s h o u l d be c o r r e l a t e d w i t h a J _ type a c i d i t y f u n c t i o n .  One such k i n e t i c  c o r r e l a t i o n w i t h a J _ s c a l e has been a t t e m p t e d . equation  (V3)  w i t h the a s s u m p t i o n t h a t  Using  log(f _/fATTDH") A  25  was  z e r o and employing  the H_ v a l u e s o f Schwarzenbach  and S u l z b e r g e r (3*4-.) c o u p l e d w i t h the a c t i v i t y o f w a t e r i n aqueous sodium h y d r o x i d e , R o c h e s t e r f o r the d i s a p p e a r a n c e I t was  correlated log k  of 2 , M — d i n i t r o a n i s o l e w i t h J _  found t h a t a p l o t o f l o g k v e r s u s H_  +  logCR^O),  1.11.  o r . J _ , gave a s t r a i g h t l i n e w i t h a s l o p e o f  C.  (71)»  Base C a t a l y z e d c i s - t r a n s I s o m e r i z a t i o n s In order f o r n u c l e o p h i l i c reagents to r e a c t w i t h  carbon-carbon  double bonds, the u n s a t u r a t e d system must  be a c t i v a t e d by s t r o n g l y e l e c t r o n w i t h d r a w i n g a c t i v a t e d carbon-carbon  groups.  Such  double bonds can r e a c t w i t h a  v a r i e t y of n u c l e o p h i l i c reagents to give a v a r i e t y of products.  A common c h a r a c t e r i s t i c o f a l l t h e s e r e a c t i o n s  i s t h a t the f i r s t s t e p i s the a t t a c k o f the  nucleophilic  r e a g e n t on the p o s i t i v e l y p o l a r i z e d carbon r e s u l t i n g i n an u n s t a b l e c a r b a n i o n (72,  73)'  The  f a t e o f the  i s dependent on the n a t u r e o f the a t t a c h e d groups, n a t u r e o f the s o l v e n t and o t h e r m o l e c u l e s s o l u t i o n w h i c h may stages  (72).  carbanion the  p r e s e n t i n the  p a r t i c i p a t e i n the r e a c t i o n i n subsequent  The v a r i o u s types o f n u c l e o p h i l i c a t t a c k s  and the r e s u l t i n g p r o d u c t s have r e c e n t l y been r e v i e w e d by P a t a i and Rappoport i n a book e d i t e d by P a t a i Of the r e a c t i o n s w h i c h a c t i v a t e d double  (73).  carbon-carbon  bonds can undergo w i t h n u c l e o p h i l i c r e a g e n t s ,  the  26  simplest  i s the c i s - t r a n s i s o m e r i z a t i o n .  case, the n u c l e o p h i l e  In t h i s  adds t o the double bond forming the  c a r b a n i b n which i s then f r e e t o r o t a t e or i n v e r t , by  simple  followed  the e l i m i n a t i o n o f the n u c l e o p h i l e . One o f t h e e a r l i e s t  cis-trans isomerizations  s t u d i e s o f base  catalyzed  was t h a t o f the t r a n s f o r m a t i o n  o f methyl maleate t o methyl fumarate.  3 2  K  >  3  H  3  H  *  X  (4-8)  H  CO2CH3  Clemo and Graham (74-) found t h a t t h i s t r a n s f o r m a t i o n catalyzed,by  was  primary and secondary amines but not by  t e r t i a r y amines.  In a l a t e r  study, Nozaki (75) found t h a t  the r e a c t i o n was f i r s t . o r d e r i n the u n s a t u r a t e d e s t e r and second order i n amine.  I t was a l s o found t h a t the r a t e s  c o r r e l a t e d w i t h the base s t r e n g t h The  ( p K ^ - O o f the amine.  r a t e determining step was then p o s t u l a t e d  ROpC \  COpR / C=C . / \ H H  +  H 2R NR 1  .  1  . NR'o I . RO-C-OH > I H-C  OR I C=0 I • C-H  .I  NR«  t o be  (4-9)  I  H  2  VI where ( V I ) , i s the c o r r e c t e d  s t r u c t u r e f o r the " a c t i v a t e d  27  complex" g i v e n by D a v i s and Evans ( 7 6 ) . I n s t e a d  of structure  V I , D a v i s and Evans p r e f e r r e d s t r u c t u r e V I I ,  y  (HHNR  H-C=cf  1 P  OR .O^NHR'p H-C=C' X  0R  VII where the t r a n s i t i o n complex i n v o l v e s two a c t u a l o r i n c i p i e n t " d a t i v e " bonds ( 7 6 ) . On t h e o t h e r R a p p o p o r t , Degani and P a t a i (77) p o s t u l a t e d  hand, that a four-  c e n t e r O i ^ - a d d i t i o n was p o s s i b l e w i t h p r i m a r y a n d s e c o n d a r y amines, a s shown i n e q u a t i o n ( 5 0 ) , t o form t h e amine adduct V I I I  R'?N + CHCOpR  Y A\ * H CHC0 R 4  >  2  R'pNCH-COoR  ^ I HCHC0 R 2  R'oNH ^ ^  R0 C-CH P  II HCC0 R  +  2HNR'  (50)  rai  Due  t o t h e p r e s e n c e o f f r e e amine m o l e c u l e s , a base-  c a t a l y z e d removal o f amine was thought t o be p o s s i b l e to give fumarate.  This explained  the o v e r a l l  third-  o r d e r k i n e t i c s and a l s o t h e c o r r e l a t i o n between t h e r e a c t i v i t y o f t h e amines and t h e i r r e s p e c t i v e basicity.  P  2  proton  28  W i t h more h i g h l y a c t i v a t e d  carbon-carbon  double bonds, such as i n I X , the amine c a t a l y z e d c i s -  Ar /COpCpHV >=cr H  X  CN  IX t r a n s i s o m e r i z a t i o n r e v e r t s from t h i r d t o second-order k i n e t i c s , and t e r t i a r y as w e l l as p r i m a r y and secondary amines c a t a l y z e t h e r e a c t i o n ( 7 7 ) • Not o n l y amines but a l s o other nucleophiles isomerization.  were found t o enhance the r a t e o f  H y d r o x i d e i o n and the c a r b a n i o n s o f a c t i v e  methylene compounds such as e t h y l c y a n o a c e t a t e and m a l o n o n i t r i l e were s t r o n g  c a t a l y s t s whereas water and  e t h a n o l were much weaker ( 7 8 ) . The p o s t u l a t e d  mechanism f o r i s o m e r i z a t i o n s ,  using a v a r i e t y of nucleophiles  Y as c a t a l y s t s , i s  shown i n t h e f o l l o w i n g scheme ( 7 7 , 7 8 ) *•  29  Scheme I  Y NCL  H  .C02C2H^  NC  X X ~ "  IX  C  2  H  5  ^ X ciJ  c=c H  2  Ar  H  • ^Ar  C O  + x  y  3 ^ H ^ C p O  C02C2Hc^  "^k -3  ?  G  —  --  CN  Ar  H "  X trans In the case where the a t t a c k i n g n u c l e o p h i l e Y was an amine, a z w i t t e r i o n i c intermediate t h i s case, u s i n g  was thought to be formed.  In  the steady s t a t e approximation, i t was  r a t i o n a l i z e d that the experimental f i r s t order  rate  constant w i l l be g i v e n by  k  k exp  l 2  k  k  (5D  -1  where. k_2.!!>k (77). I f the same mechanism were t o be 2  f o l l o w e d when n u c l e o p h i l e s  such as hydroxide, ethoxide  or methoxide ions were a c t i n g as c a t a l y s t s , then i t may be expected that the r a t e o f i s o m e r i z a t i o n might be  30  c o r r e l a t e d w i t h an a p p r o p r i a t e a c i d i t y f u n c t i o n . I n the case o f the amine c a t a l y z e d i s o m e r i z a t i o n o f I X , Rappoport, Degani and P a t a i (77)  found t h a t the  e n e r g i e s o f a c t i v a t i o n were i n the range f r o m 2.7 -1 k c a l . mole -4-3  to  5'0  and the e n t r o p i e s o f a c t i v a t i o n ranged from  t o -66  e.u.,  as c a t a l y s t .  depending on the p a r t i c u l a r amine u s e d  The low e n e r g i e s o f a c t i v a t i o n were r a t i o n a l -  i z e d by a p p l y i n g the E  exp  equation  =  E  l  +  E  2  -  E  -  <52)  l  where the s u b s c r i p t s r e f e r t o the i n d i v i d u a l s t e p s i n r e a c t i o n Scheme I . for  By t a k i n g v a l u e s from the  literature  as b e i n g i n the o r d e r o f 13 k c a l . mole  assuming t h a t E_-j_ was  by  l e s s t h a n 30 k c a l . mole "'', w h i c h -  i s the normal v a l u e f o r base c a t a l y z e d e l i m i n a t i o n r e a c t i o n s , and by assuming t h a t E  2  was  higher than 2 to 6  k c a l . . mole""^", .which i s the v a l u e f o r s t e r i c a l l y r o t a t i o n s , an energy o f a c t i v a t i o n was  hindered  c a l c u l a t e d which  a g r e e d r e a s o n a b l y w e l l w i t h the e x p e r i m e n t a l v a l u e s . I n a manner analogous t o the above, the o f a c t i v a t i o n was  A  s  ?xp  =  entropy  g i v e n by  A  s  i  +  A  S  2*  -  A s  «3)  -1  The l a r g e n e g a t i v e e n t r o p y o f a c t i v a t i o n was  thought  to  31  be due  t o the r e l a t i v e l y s m a l l v a l u e f o r A S  the l a r g e p o s i t i v e v a l u e f o r A s ^ , due  2  compared w i t h  t o two  neutral  m o l e c u l e s b e i n g formed from a z w i t t e r i o n , and a l a r g e n e g a t i v e v a l u e f o r A s * , as a r e s u l t o f a z w i t t e r i o n b e i n g formed from two n e u t r a l s p e c i e s The  (77)•  a s s u m p t i o n t h a t k_-jj>k , 2  or t h a t  the  e l i m i n a t i o n i s f a s t e r t h a n the r o t a t i o n , i s i n agreement w i t h the f i n d i n g t h a t i n c e r t a i n c a s e s , v i n y l i c s u b s t i t u t i o n s o c c u r w i t h r e t e n t i o n of c o n f i g u r a t i o n ( 7 9 ,  80).  Jones e t a l (80) found t h a t the r e a c t i o n o f e t h y l - ^ c h l o r o - c i s - and t r a n s - c r o t o n a t e s w i t h n u c l e o p h i l e s  such  as t h i o e t h o x i d e i n e t h a n o l , gave m a i n l y p r o d u c t s w i t h r e t e n t i o n of c o n f i g u r a t i o n a l t h o u g h took p l a c e .  some i s o m e r i z a t i o n  S i m i l a r l y , M i l l e r and Yonan ( 7 9 ) found t h a t  the e a r l y stages o f the r e a c t i o n of p-?nitro-^/'-bromostyrene w i t h i o d i d e proceeded l a r g e l y w i t h r e t e n t i o n o f c o n f i g u r ation.  The  r e s u l t s of such r e a c t i o n s have been e x p l a i n e d  on the b a s i s of r o t a t i o n a l energy b a r r i e r s ( 8 0 ) . incoming n u c l e o p h i l e a t t a c k s perpendicular o f the double bond and  I f the  t o the p l a n e  the e l i m i n a t e d group l e a v e s  s i m i l a r l y , t h e n the group X can be e l i m i n a t e d f r o m e i t h e r the c a r b a n i o n i c intermediate X I I r e s u l t s from a 60°  X I I or X I I I . The  r o t a t i o n i n the p r i m a r y  conformer intermediate  X I whereas the conformer X I I I r e s u l t s from a 120°  rotation.  32  Scheme I I  R:  Ri X  Y  X  Y  R  -C  V  XII  R  •R  x  X  2  X X X  R3-j^:-R R Y  ^R  T  X I f the e l i m i n a t i o n  i s f a s t e r t h a n the r o t a t i o n , t h e n the  v i n y l i c s u b s t i t u t i o n s h o u l d go v i a X I I , due t o a l e s s e r amount o f r o t a t i o n r e s u l t i n g i n l e s s e c l i p s e d w i t h an o v e r a l l r e t e n t i o n  of configuration  forms,  (73)'  I n cases .where a carbon-carbon double bond system has one -CHB^  group a t t a c h e d t o i t , base  cis-trans isomerizations c a r b a n i o n (81,  82).  can take p l a c e v i a an  catalyzed allylic  But t h i s p r o c e s s depends upon the  a c i d i t y o f the p r o t o n r a t h e r a t t a c k on the a l k e n e bond.  t h a n the ease o f  nucleophilic  33  I n one c a s e , t h e mechanism o f a base  catalyzed  i s o m e r i z a t i o n was p o s t u l a t e d t o go t h r o u g h a v i n y l carbanion ( 8 l ) .  Cram and Hunter s t u d i e d t h e t - b u t o x i d e  c a t a l y z e d i s o m e r i z a t i o n o f c i s - s t i l b e n e , w h i c h was shown, by d e u t e r i u m exchange s t u d i e s , t o go t h r o u g h a carbanion of s t r u c t u r e XIV.  vinyl  T h i s r e a c t i o n i s much s l o w e r  Pti  Ph  XIV  t h a n p r e v i o u s l y s t u d i e d i s o m e r i z a t i o n s as shown by the f a c t t h a t when c i s - s t i l b e n e potassium t-butoxide  ( 0 . 6 7 M )  was h e a t e d w i t h  (0.255M) i n t - b u t a n o l a t 14-6° f o r  36.7 hours o n l y 1% t r a n s - s t i l b e n e was p r o d u c e d .  This i s  much s l o w e r t h a n the r e a c t i o n s s t u d i e d by P a t a i and c o w o r k e r s (73, 77, 7 8 ) .  3H-  OBJECT OF THE PRESENT RESEARCH  T h i s work was u n d e r t a k e n t o d e v e l o p a s e t o f i n d i c a t o r s o f a p p r o p r i a t e Lewis a c i d i t y i n o r d e r t o s t u d y the Lewis b a s i c i t y o f some h i g h l y b a s i c workers (53?  58,  59,  systems.  Several  83) have a t t e m p t e d t o s t u d y t h e Lewis  a c i d i t y o f p o l y n i t r a t e d benzenes and s u b s t i t u t e d  benzenes  as w e l l as t h e Lewis b a s i c i t y o f such bases as h y d r o x i d e (53,  58) and methoxide  (59,  83) i o n s .  Polynitrated  benzenes a r e n o t the i d e a l c h o i c e f o r such a s t u d y because o f : the p o s s i b i l i t y o f more t h a n one p l a c e o f a t t a c k , the p o s s i b i l i t y o f s u b s t i t u t i o n g i v i n g n i t r i t e i o n (67,  68,  840 and the p o s s i b i l i t y o f more t h a n one type o f i o n i z a t i o n , e s p e c i a l l y when p o l y n i t r a t e d a n i l i n e s a r e u s e d (58,  59).  As a r e s u l t , i n d i c a t o r s were d e s i r e d w h i c h d i d n o t have t h e s e d i s a d v a n t a g e s and y e t i n v o l v e d  a system i n w h i c h the  Lewis a c i d i t y c o u l d be changed s u b s t a n t i a l l y by a l t e r i n g the  substituents  i n a phenyl r i n g .  The system o f i n d i c a t o r s  w h i c h was f i n a l l y chosen were s u b s t i t u t e d w i t h the numbering  c<-cyanostilbenes  system as i n d i c a t e d i n XV. 3  a NC XV  3  35 I n order  t o change the Lewis a c i d i t y o f t h e s e i n d i c a t o r s  v a r i o u s t y p e s of e l e c t r o n w i t h d r a w i n g and c o u l d be p l a c e d i n the p h e n y l r i n g s .  d o n a t i n g groups  Thus a s t u d y o f  the r e l a t i o n s h i p between the s u b s t i t u e n t s and constants  was  possible.  S i n c e R_ DMSO-alcohol (50, methanol (37?  s c a l e s had a l r e a d y been e s t a b l i s h e d i n 51)  and c o n c e n t r a t e d  sodium methoxide-  39 - M-l) s o l u t i o n s , these systems were  thought t o be the most p r o m i s i n g a Lewis b a s i c i t y s c a l e . systems was  the i o n i z a t i o n  The  i n which' t o e s t a b l i s h  Lewis b a s i c i t y o f aqueous  a l s o d e s i r a b l e ; b u t , s i n c e the type o f compounds  u s e d as i n d i c a t o r s a r e s u b j e c t t o r a p i d h y d r o l y s i s i n b a s i c aqueous s o l u t i o n s (73? One  85?  86)  t h i s was  of the i d e a s u n d e r l y i n g  the  unattainable.  establishment  of a c i d i t y scales i s t h e i r bearing  on the mechanism o f  a c i d or base c a t a l y z e d r e a c t i o n s .  One  possible reaction  w h i c h might be dependent on the Lewis b a s i c i t y of  the  medium i s the base c a t a l y z e d c i s - t r a n s i s o m e r i z a t i o n o f substituted  ot-eyano-cis-stilbenes.  A study of  r e a c t i o n was  u n d e r t a k e n i n an attempt t o c o r r e l a t e the  k i n e t i c s w i t h the Lewis b a s i c i t y of the system.  this  In  c o n j u n c t i o n w i t h t h i s , the e f f e c t s of s u b s t i t u e n t s and e f f e c t of a change i n the temperature on the r a t e s were a l s o s t u d i e d i n order  t o g a i n f u r t h e r i n s i g h t i n t o the  mechanism o f t h i s r e a c t i o n .  the  36  METHODS OF APPROACH  The i n d i c a t o r s u s e d t o d e v e l o p t h e Lewis a c i d i t y s c a l e a l l absorbed energy i n t h e u l t r a v i o l e t o r v i s i b l e r e g i o n o f t h e spectrum.  I n a d d i t i o n , the wavelength o f  maximum a b s o r p t i o n o f a n i o n d i f f e r e d c o n s i d e r a b l y from that f o r the corresponding  m o l e c u l e so t h a t UV  spectroscopy  c o u l d be u s e d t o measure t h e c o n c e n t r a t i o n o f t h e s p e c i e s . S i n c e the m o l e c u l e ' s a b s o r p t i o n was s m a l l o r z e r o a t t h e w a v e l e n g t h o f maximum a b s o r p t i o n o f t h e i o n t h i s  latter  a b s o r p t i o n was u s e d i n a l l cases t o measure t h e e x t e n t of i o n i z a t i o n of the i n d i c a t o r s . S i n c e the w a v e l e n g t h o f maximum a b s o r p t i o n and the e x t i n c t i o n c o e f f i c i e n t o f t h e e l e c t r o n i c s p e c t r a o f the t r a n s - c y - c y a n o s t i l b e n e s d i f f e r e d s u b s t a n t i a l l y from t h a t of the c i s - o(-cyanostilbenes, the wavelength of the maximum a b s o r p t i o n o f t h e t r a n s - i s o m e r  afforded a  convenient  means o f f o l l o w i n g t h e k i n e t i c s o f t h e base c a t a l y z e d • cis-trans isomerization.  T h i s method o f a n a l y s i s ' w a s  used i n a l l the k i n e t i c s t u d i e s .  37  EXPERIMENTAL  A.  P u r i f i c a t i o n o f S o l v e n t s and P r e p a r a t i o n o f S o l u t i o n s 1.  P u r i f i c a t i o n o f d i m e t h y l s u l f o x i d e (DMSO) ( 4 - 9 ) Baker a n a l y z e d grade DMSO was s t i r r e d over  night  over c a l c i u m h y d r i d e and t h e n d i s t i l l e d from i t under n i t r o g e n a t reduced p r e s s u r e u s i n g a 34- cm V i g r e u x  column.  Only t h e c e n t e r f r a c t i o n s were u s e d i n subsequent work. The  p u r i f i e d DMSO was s t o r e d i n g l a s s - s t o p p e r e d  flasks  i n a d r y box.  2.  Preparation of dry ethanol Dry e t h a n o l was p r e p a r e d a c c o r d i n g t o V o g e l  (87a).  To one l i t r e o f a b s o l u t e a l c o h o l i n a 2 1 f l a s k  equipped w i t h a r e f l u x condenser and d r y i n g tube was added 7 g o f c l e a n sodium.  When t h i s had r e a c t e d , 2 7 . 5 g  o f e t h y l p h t h a l a t e was i n t r o d u c e d and t h e m i x t u r e f o r two h o u r s .  The p u r i f i e d e t h a n o l was t h e n  refluxed  distilled  under n i t r o g e n u s i n g a 21 cm V i g r e u x column and t h e c e n t e r f r a c t i o n c o l l e c t e d i n f l a s k s each f i t t e d a s h o r t s i d e a r m and a n a p p r o p r i a t e rubber e t h a n o l was s t o r e d under n i t r o g e n u n t i l  3.  with  stopple.  The  used.  P r e p a r a t i o n o f d r y methanol Dry methanol was p r e p a r e d a c c o r d i n g t o t h e  38  method o f V o g e l  (87b).  To 5 g o f magnesium and 0.5  g  o f i o d i n e i n a 2 1 round bottom f l a s k equipped w i t h a added 50 t o 75  w a t e r condenser and d r y i n g tube was o f methanol. r e a c t i o n had t h i s was minutes.  T h i s was  warmed s l i g h t l y and a f t e r  s t a r t e d , i t was  ml  the  c o n t r o l l e d by c o o l i n g .  To  added 900 ml o f methanol and r e f l u x e d f o r 4-5 T h i s was  t h e n d i s t i l l e d under n i t r o g e n u s i n g  a 21 cm V i g r e u x column, and the c e n t e r f r a c t i o n  collected  and s t o r e d as i n the case o f e t h a n o l .  4-.  P r e p a r a t i o n o f a s o l u t i o n o f sodium e t h o x i d e in  ethanol  To 4-5 ml o f d r y e t h a n o l was 0.6  g o f sodium.  added  approximately  P r i o r t o the a d d i t i o n , the sodium.was  c l e a n e d and a l l o w e d t o r e a c t w i t h c l e a n e t h a n o l f o r a short time.  A f t e r the r e a c t i o n was  complete, a l i q u o t s o f  the s t o c k s o l u t i o n were t i t r a t e d w i t h s t a n d a r d  acid.  The  stored  s t o c k s o l u t i o n was  i n the r e f r i g e r a t o r .  k e p t under n i t r o g e n and I n t h i s way  no  decomposition  o c c u r r e d over l o n g p e r i o d s of t i m e .  5.  P r e p a r a t i o n o f a s o l u t i o n o f sodium methoxide i n methanol T h i s was  prepared  i n the same way  f o r the sodium e t h o x i d e s o l u t i o n . methoxide s o l u t i o n was  as d e s c r i b e d  I n t h i s case,  the  not s t o r e d i n a r e f r i g e r a t o r .  39 6.  P r e p a r a t i o n o f DMSO-alcohol s t o c k s o l u t i o n s The  DMSO-alcohol s t o c k s o l u t i o n s were made up  according t o weight f o r approximately  e v e r y 5 mole  per cent DMSO from 0 t o 100 p e r cent DMSO.  Dry b o t t l e s ,  w h i c h had been f l u s h e d w i t h d r y n i t r o g e n and equipped with w e l l f i t t i n g  rubber s t o p p l e s , were weighed.  Into  each o f these was s y r i n g e d the r e q u i r e d volume o f p u r i f i e d DMSO under a n atmosphere o f n i t r o g e n i n a d r y box.  The s t o p p e r e d  b o t t l e s c o n t a i n i n g t h e DMSO were  weighed a g a i n t o g i v e t h e w e i g h t o f DMSO.  To t h i s was  t h e n added t h e a p p r o p r i a t e amount o f a l c o h o l .  T h i s was  done v i a s y r i n g e t h r o u g h t h e rubber s t o p p l e s , thus m i n i m i z i n g t h e c o n t a c t w i t h a i r and m o i s t u r e . The  b o t t l e s containing the stock s o l u t i o n s  were weighed f o r t h e f i n a l time g i v i n g the w e i g h t o f added a l c o h o l .  These s t o c k s o l u t i o n s were k e p t under  n i t r o g e n and s t o r e d i n a d e s i c c a t o r over s i l i c a g e l . The  DMSO-ethanol and t h e DMSO-methanol s o l u t i o n s were  made up i n t h e above manner.  7•  Preparation of stock s o l u t i o n s o f i n d i c a t o r s or r e a c t a n t s An a c c u r a t e l y weighed q u a n t i t y o f t h e i n d i c a t o r ,  or r e a c t a n t , was p l a c e d i n a 10 ml v o l u m e t r i c f l a s k .  In  a d r y box, under n i t r o g e n , a n a p p r o p r i a t e amount o f DMSO,  1+0  o r o t h e r s o l v e n t , was a d d e d t o t h e s a m p l e w h i c h was transferred a rubber  then  t o a s m a l l b r o w n b o t t l e w h i c h was f i t t e d w i t h  stopple.  T h i s a f f o r d e d a n e a s y means o f w i t h -  d r a w i n g 30 |*1 o f s t o c k s o l u t i o n v i a s y r i n g e w i t h o u t exposing i t t o the a i r or moisture.  B.  E q u i l i b r i a Measurements All  e q u i l i b r i a m e a s u r e m e n t s w e r e made u s i n g a  B a u s c h a n d Lomb s p e c t r o p h o t o m e t e r , M o d e l No. 502 w i t h t h e c e l l s t h e r m o s t a t e d a t 25° ± 0 . 1 °  by means o f w a t e r  through a metal block from a constant temperature The  general procedure  was a s f o l l o w s .  passing bath.  i n making t h e measurements  The q u a r t z UV c e l l was f i t t e d w i t h a  N e o p r e n e s t o p p e r w h i c h was e a s i l y p u n c t u r e d b y s y r i n g e needles. and  Two n e e d l e s , one c o n n e c t e d  to a nitrogen cylinder  t h e o t h e r s e r v i n g a s a n o u t l e t , were b o t h  inserted  through the stopper a short d i s t a n c e i n t o the c e l l .  The  c e l l was t h e n f l u s h e d w i t h d r y n i t r o g e n f o r a s h o r t t i m e ; a f t e r w h i c h 2.4-7 m l o f t h e d e s i r e d D M S O - a l c o h o l  solution  was a d d e d t h r o u g h t h e s t o p p e r v i a a n e e d l e a n d 5 m l s y r i n g e equipped w i t h a channey a d a p t o r .  Dry n i t r o g e n  was t h e n b u b b l e d t h r o u g h t h e D M S O - a l c o h o l s o l u t i o n f o r about ul  10 m i n u t e s .  of the i n d i c a t o r  To t h i s was a d d e d , i n t h e same way, 30 s t o c k s o l u t i o n u s i n g a 50 u l H a m i l t o n  s y r i n g e w i t h a f i x e d n e e d l e and channey a d a p t o r .  The  s o l u t i o n was t h e n a l l o w e d t o e q u i l i b r a t e f o r a s h o r t t i m e  i n the c e l l block o f the spectrophotometer. The  c e l l s c o n t a i n i n g t h e i n d i c a t o r and t h e  r e f e r e n c e c e l l were h a n d l e d i d e n t i c a l l y e x c e p t t h a t t h e r e f e r e n c e c e l l d i d n o t c o n t a i n t h e 30 p l o f DMSO i n d i c a t o r stock s o l u t i o n .  The spectrum o f t h e m o l e c u l e was r e c o r d e d  and t h e z e r o a b s o r p t i o n l i n e a d j u s t e d i n t h e r e g i o n o f maximum a b s o r p t i o n o f t h e i o n . w i t h a f i x e d needle,  U s i n g a 50 u l s y r i n g e  t h e a p p r o p r i a t e amount o f a l k o x i d e  s o l u t i o n (35 |*1 o f sodium methoxide s o l u t i o n o r 36^1 o f sodium e t h o x i d e  s o l u t i o n ) was added by i n s e r t i n g t h e  needle a short d i s t a n c e through the stopper. was  The spectrum  t h e n r e c o r d e d a t l e a s t a t two d i f f e r e n t times t o  ensure t h a t t h e i o n was s t a b l e .  I f t h e i o n were not  s t a b l e , t h e absorbance was measured as a f u n c t i o n o f time and e x t r a p o l a t e d back t o z e r o t i m e .  T h i s , t h e n , gave  the absorbance o f t h e i o n a t t h e w a v e l e n g t h o f i t s maximum a b s o r p t i o n . • The s p e c t r a l d a t a f o r the v a r i o u s compounds a r e g i v e n i n Tables  I - I I I . The w a v e l e n g t h s o f maximum  a b s o r p t i o n and t h e molar e x t i n c t i o n c o e f f i c i e n t s a r e l i s t e d f o r many o f t h e m o l e c u l a r  and i o n i c forms o f t h e  i n d i c a t o r s and r e a c t a n t s .  C.  Treatment o f the S p e c t r a l Data i n t h e E q u i l i b r i u m Measurements The a b s o r p t i o n data f o r i n d i c a t o r s w h i c h i o n i z e  4-2  according  to the equation A  +  c a n be t r e a t e d ionized,  HOR  i n t h e u s u a l manner.  and i f the s o l u t i o n s  B e e r ' s Law i s f o l l o w e d  £  -(540  +  I f cx i s t h e f r a c t i o n  a r e d i l u t e enough so t h a t  d i "  w a v e l e n g t h o f t h e measurement which the i n d i c a t o r  (55)  e,A O R -  i s t h e molar e x t i n c t i o n  £^  H  (88), then  " i.  [A]  where:  +  A O R "  X  V  coefficient a t the i n a solution i n  i s partially  i s the molar e x t i n c t i o n  ionized;  coefficient  of the  u n i o n i z e d molecule; and G A 0 R ~  m  ° l  a  r  extinction  c o e f f i c i e n t of the  ion. Since  i n many c a s e s t h e a b s o r b a n c e  negligible  a t t h e w a v e l e n g t h a t w h i c h t h e measurements  w e r e t a k e n , 6 A c o u l d be n e g l e c t e d . simpler  This resulted  i n the  expression  ^ Since  o f t h e m o l e c u l e was  °A0R"  t  t h e same c o n c e n t r a t i o n s o f i n d i c a t o r s  e a c h measurement, t h e m o l a r e x t i n c t i o n r e p l a c e d by t h e a b s o r b a n c e A .  were u s e d f o r  coefficient 6  was  The i o n i z a t i o n d a t a f o r the v a r i o u s i n d i c a t o r s have been r e c o r d e d i n T a b l e s IV - V I I .  These d a t a have  been r e c o r d e d i n the form o f l o g I v a l u e s f o r .the v a r i o u s s o l v e n t c o m p o s i t i o n s .where I  =  [AOR]/[A]  o f t h e carbon a c i d s , the data f o r I  =  .  I n the case  |A ] / [AR]  have  been r e c o r d e d i n the T a b l e s V I I I and I X .  D.  K i n e t i c Measurements I n measuring  the k i n e t i c s o f the base c a t a l y z e d  c i s - t r a n s i s o m e r i z a t i o n of o ( - c y a n o - c i s - s t i l b e n e s , the procedure i n making up the s o l u t i o n s i n the q u a r t z UV c e l l s was-the same as t h a t a l r e a d y d e s c r i b e d i n the case f o r e q u i l i b r i a measurements.  The o n l y d i f f e r e n c e was i n t h e  l e n g t h o f time a l l o w e d f o r the s o l u t i o n s t o come t o thermal e q u i l i b r i u m .  I n the k i n e t i c measurements, b e f o r e  t h e a d d i t i o n o f the a l k o x i d e s o l u t i o n , the s o l u t i o n i n the UV c e l l s was a l l o w e d t o come t o t h e r m a l e q u i l i b r i u m f o r a p p r o x i m a t e l y 30  minutes.  Many o f the k i n e t i c measurements were made u s i n g • a Beckman DU Spectrophotometer. Model  21+00  with  A f t e r t h e r m a l e q u i l i b r i u m had been a t t a i n e d the o f the c i s - i s o m e r a t the wavelength  thermospacers. absorbance  o f the maximum  a b s o r p t i o n o f t h e t r a n s - i s o m e r was measured.  A f t e r the  a d d i t i o n o f the a l k o x i d e s o l u t i o n t o t h e r e f e r e n c e c e l l , the r e f e r e n c e energy was b a l a n c e d .  Then t h e same amount o f  kk  a l k o x i d e s o l u t i o n was added t o t h e sample c e l l and t h e absorbance r e c o r d e d as a f u n c t i o n o f t i m e . In  s t u d y i n g the e f f e c t o f a change i n t e m p e r a t u r e  on t h e r a t e o f i s o m e r i z a t i o n , a Bausch and Lomb Model No. 502 s p e c t r o p h o t o m e t e r was u s e d because o f b e t t e r t h e r m a l c o n t a c t between t h e c o n s t a n t temperature b l o c k and t h e cells.  The procedure was s i m i l a r t o t h a t u s e d w i t h t h e  Beckman DU S p e c t r o p h o t o m e t e r .  The temperature o f t h e c e l l  b l o c k was measured by means o f a c o p p e r - i r o n c o n s t a n t a n thermocouple p l a c e d i n a b r a s s probe i n the c o n s t a n t temperature b l o c k , w i t h the r e f e r e n c e thermocouple i n an ice  b a t h , u s i n g a H o n e y w e l l Model No 2732 P o t e n t i o m e t e r .  The thermocouple had p r e v i o u s l y been c a l i b r a t e d a g a i n s t a mercury thermometer u s i n g a c o n s t a n t temperature water bath.  The a v e r a g i n g o f s e v e r a l emf r e a d i n g s as measured  by the p o t e n t i o m e t e r d u r i n g the course o f the r e a c t i o n and t h e subsequent i n t e r p o l a t i o n from t h e a p p r o p r i a t e c a l i b r a t i o n curve gave the average temperature a t w h i c h the  r e a c t i o n took p l a c e .  E.  Treatment o f the K i n e t i c Data For  a bimolecular r e a c t i o n of the type  X  +  C  > Y  +  C  (57)  where C i s a t r u e c a t a l y s t and i s r e g e n e r a t e d , the r a t e e x p r e s s i o n i s g i v e n by  4-5 dY  =  dt  where k  2  (58)  kp(.X)(C)  i s t h e second o r d e r r a t e c o n s t a n t .  I f the  concentration of the c a t a l y s t i s i n l a r g e excess, equation (58)  s i m p l i f i e s t o an apparent  f i r s t order r e a c t i o n w i t h  the r a t e expression dck  >  *1  J l  r  (59)  ( * [  -  dt t h e r e l a t i v e p r o p o r t i o n o f Y p r e s e n t and  where Ckls  kj_ i s t h e apparent i n t e g r a t i o n of t h i s  f i r s t order r a t e constant.  The  yields  1 In  = 1  k.t  -OC  (60)  1  I f X and Y a r e the o n l y s p e c i e s a b s o r b i n g a t a p a r t i c u l a r wavelength,  t h e n i t can e a s i l y be shown t h a t  oC  and  =  —  — bx  (61)  h6  wheres Gx i s the molar e x t i n c t i o n c o e f f i c i e n t of. t h e r e a c t a n t X; Gy i s the molar e x t i n c t i o n c o e f f i c i e n t o f t h e p r o d u c t Y; and Cf i s t h e molar e x t i n c t i o n c o e f f i c i e n t o f the s o l u t i o n at  a time t , a l l t a k e n a t one p a r t i c u l a r  wavelength.  I f t h e s o l u t i o n s a r e s u f f i c i e n t l y d i l u t e .so t h a t  Beer's  Law h o l d s , t h e n t h e molar e x t i n c t i o n c o e f f i c i e n t s can be r e p l a c e d by a b s o r b a n c e s .  S i n c e the absorbance  of the  r e a c t a n t w i l l be g i v e n by t h a t a t time z e r o , i t f o l l o w s t h a t Cx can be r e p l a c e d by cf  A , and s i n c e the absorbance 0  the p r o d u c t w i l l be g i v e n by t h a t a t the c o m p l e t i o n o f  t h e r e a c t i o n , t h e n Gy can be r e p l a c e d by  AQO>  then the  r a t e e x p r e s s i o n i s g i v e n by the e q u a t i o n AQO  ln  — ^ Aoo  In  -  A 0  — -  A  =  (63)  k j t•  t  t h i s c a s e , a p l o t o f log(Aoc< -  A )/(AQO 0  -  Al-^.) v e r s u s  time w i l l g i v e a s t r a i g h t l i n e w i t h t h e a p p a r e n t  first  o r d e r r a t e c o n s t a n t k]_ b e i n g e q u a l t o 2.3026 times t h e slope. manner.  A l l t h e k i n e t i c d a t a were t r e a t e d i n t h e above When the second o r d e r r a t e c o n s t a n t s were  d e s i r e d , as i n the temperature  s t u d y , k^ was d i v i d e d  by the c o n c e n t r a t i o n o f t h e base.  k7  F.  P r e p a r a t i o n o f I n d i c a t o r s and R e a c t a n t s 1.  1 , 1 - B i s - (M--nitrophenyl )ethene 1 , 1 - D i p h e n y l e t h a n e was p r e p a r e d  and  from benzene  s t r y e n e a c c o r d i n g t o t h e method o f Szmant and Y o n c o s k i e  (89).  T h i s was t h e n n i t r a t e d w i t h fuming n i t r i c a c i d  below 10° t o g i v e l , I - b i s - ( M — n i t r o p h e n y l ) e t h a n e ( 9 0 ) , w h i c h i n t u r n was b r o m i n a t e d w i t h N-bromosuccinimide i n c a r b o n t e t r a c h l o r i d e u s i n g b e n z o y l p e r o x i d e as c a t a l y s t . The  crude bromide was t h e n d e h y d r o h a l o g e n a t e d a c c o r d i n g  t o Szmant and D e f f n e r  (90) by r e f l u x i n g i n p y r i d i n e t o  give l,l-bis-(4—nitrophenyl)ethene.  T h i s was t h e n  r e c r y s t a l l i z e d from methanol and from e t h y l a c e t a t e t o g i v e yellow-orange 1.75. - 1 7 6 . 5 ° 2.  p l a t e l e t s m e l t i n g a t 17"+ - 5° (90)  (lit.  value:  ).  Q(-Cyano-2,M—dinitrostilbene . To a s o l u t i o n o f 0 . 7 g o f 2 , M — d i n i t r o b e n z y l  cyanide, prepared and  a c c o r d i n g t o F a i r b o u r n e and Fawson ( 9 1 ) 5  0.,k g o f benzaldehyde i n 20 ml o f e t h a n o l was added k  drops o f p i p e r i d i n e and t h e m i x t u r e was r e f l u x e d f o r 16 hours.  The s o l u t i o n was c o o l e d , some o f t h e e t h a n o l was  evaporated 0.6  and t h e dark c o l o r e d s o l i d f i l t e r e d t o y i e l d  g o f crude m a t e r i a l f o r a 60% y i e l d .  T h i s was r e c r y s t a l -  l i z e d f r o m a c e t i c a c i d t o a c o n s t a n t m e l t i n g p o i n t o f 160 - 1 6 1 ° . Analysis:  calculated found  carbon 61.02 60.93  hydrogen 3.07 3.24-  nitrogen 14-.23 lk, 17  4-8  3.  p(-Cyano-4-,4-' - d i n i t r o s t i l b e n e o(-Cyano-4-,4-'-dinitrostilbene  condensing  4—nitrobenzyl  cyanide w i t h  was p r e p a r e d  by  4—nitrobenzaldehyde  i n ethanol using piperidine  as the c a t a l y s t a c c o r d i n g t o  t h e m e t h o d o f M e r c k x (92).  The p r o d u c t  was r e c r y s t a l l i z e d  f r o m a c e t i c a c i d t o a c o n s t a n t m e l t i n g p o i n t o f 214- (lit.  value:  4-.  211-212°  (92) ) .  Q(-Cyano-3 ' - c h l o r o - 4 — n i t r o s t i l b e n e To a s o l u t i o n o f 1.6  and  g 4—nitrobenzyl  solution.  After  15  t o 20 m i n u t e s ,  ethoxide-ethanol t h e s o l u t i o n was c o o l e d  t h e r e s u l t i n g c r y s t a l s were f i l t e r e d and washed w i t h  e t h a n o l t o g i v e 1.8  g o f m a t e r i a l f o r a y i e l d o f 63$.  T h i s was r e c r y s t a l l i z e d f r o m e t h a n o l a n d f r o m a c i d t o a c o n s t a n t m e l t i n g p o i n t o f 168 ( l i t . value:  5.  -  1.25  l 6 l . 5 ° (93) ) .  Q(-Cyano-4— n i t r o s t i l b e n e cyanide  m l o f b e n z a l d e h y d e i n e t h a n o l was a d d e d a s m a l l  amount o f a I N s o d i u m e t h o x i d e f o r a b o u t 10 m i n u t e s . was  acetic  168.5°.  To a s o l u t i o n o f 2 g 4— n i t r o b e n z y l and  cyanide  1.4- g 3 - c h l o r o b e n z a l d e h y d e i n 50 m l o f e t h a n o l a t  50° was a d d e d 10 d r o p s o f I N s o d i u m  and  215°.  filtered  s o l u t i o n and heated  Upon c o o l i n g ,  c o l l e c t i n g 1.0  the s o l i d  g o f product  a t 50°  product  for a yield  4-9  o f 31%>  T h i s was  r e c r y s t a l l i z e d from e t h a n o l t o a  m e l t i n g p o i n t o f 176  - 176.5°.  ( l i t . valuet 175.6°  constant (94-)  ).  .oC -Cyano-4- - m e t h y l - 4 — n i t r o s t i l b e n e  6.  1  The  condensation  of 4 — n i t r o b e n z y l cyanide  4—methylbenzaldehyde i n e t h a n o l i c sodium e t h o x i d e ,  and accord-  i n g t o the method o f Schonne, Braye and B r u y l a n t s (9*+), gave the c o r r e s p o n d i n g was  oC-cyanostilbene i n 8 4 $ y i e l d .  This  r e c r y s t a l l i z e d once from e t h a n o l and t w i c e from  petroleum  ( f r a c t i o n b o i l i n g a t 64- - 110°)  ether  to give  s l i g h t l y y e l l o w c r y s t a l s m e l t i n g a t 14-6 -• 14-7°. ( l i t . values  14-6 - 14-7°  7•  (95)  ).  '  oC~Cyano-4-' - m e t h o x y - 4 — n i t r o s t i l b e n e The  p-anisaldehyde  condensation  of 4 — n i t r o b e n z y l cyanide  i n e t h a n o l i c sodium e t h o x i d e ,  and  according  t o the method o f Schonne, Braye and B r u y l a n t s (94-), gave s u b s t i t u t e d oC-cyanostilbene  the corresponding yield.  T h i s was  r e c r y s t a l l i z e d from a c e t i c a c i d t o a  c o n s t a n t m e l t i n g p o i n t o f 162 165°  (95)  8.  i n 85$  - 163°.  (lit.  values  ).  oC-Cyano-4-'-dime t h y l a m i n o - 4 — n i t r o s t i l b e n e T h i s was  prepared  by condensing 4 — n i t r o b e n z y l  c y a n i d e w i t h 4—dimethylaminobenzaldehyde i n e t h a n o l u s i n g  50  piperidine  as t h e c a t a l y s t a c c o r d i n g t o t h e method o f  Merckx (92).  The p r o d u c t was r e c r y s t a l l i z e d t o a c o n s t a n t  melting point of (92)  2*44-.  5  -  24-5.5°.  ( l i t . value:  24-4- - 24-6°  ).  9«  01,4—Dicyano-4-' - n i t r o s t i l b e n e 4—Cyanobenzyl  c y a n i d e was p r e p a r e d i n l o w y i e l d  from 4 — c y a n o b e n z y l bromide and p o t a s s i u m c y a n i d e i n e t h a n o l and water a c c o r d i n g t o t h e method o f G a b r i e l  and Otto  (96).  The 4 — c y a n o b e n z y l c y a n i d e was r e c r y s t a l l i z e d from water t o g i v e s l i g h t l y p i n k c r y s t a l s m e l t i n g a t 99 - 100°. ( l i t . v a l u e : 100° (97)  )•  The p u r i f i e d 4 — c y a n o b e n z y l c y a n i d e was condensed w i t h 4—nitrobenzaldehyde i n e t h a n o l u s i n g p i p e r i d i n e as c a t a l y s t , a c c o r d i n g t o t h e method o f Merckx (92), t o g i v e a  y i e l d o f . 0 ( , 4 - d icyano-4- - n i t r o s t i l b e n e . 1  T h i s was  r e c r y s t a l l i z e d from a c e t i c a c i d t o g i v e f i n e y e l l o w n e e d l e s m e l t i n g , a t 212 Analysis:  10.  212.5°. carbon 69.81 69.58  calculated found :  hydrogen 3-30 3.98  nitrogen 15-27 15.14-  0(, 4— D i c y a n o - 3 - c h l o r o s t i l b e n e 1  4— Cyanobenzyl  c y a n i d e , p r e p a r e d as d e s c r i b e d  above, was condensed w i t h 3 - c h l o r o b e n z a l d e h y d e  i n ethanolic  sodium e t h o x i d e a t 4-0° a c c o r d i n g t o the method o f Schonne,  51  (94-).  Braye and B r u y l a n t s y i e l d , was  The  11.  collected i n  r e c r y s t a l l i z e d from e t h a n o l and a c e t i c a c i d t o  a c o n s t a n t m e l t i n g p o i n t o f 195 Analysis:  product,  -  195.5°•  carbon 72.60 72.76  calculated found  hydrogen 3.4-3 3.55  nitrogen 10.58 10.62  Q( , 4 — D i c y a n o s t i l b e n e The  prepared  condensation  o f 4—cyanobenzyl  cyanide,  as d e s c r i b e d above, and benzaldehyde i n e t h a n o l i c  sodium e t h o x i d e a t 50°,  (94-), gave the  Braye and B r u y l a n t s i n 89% y i e l d .  a c c o r d i n g t o the method o f Schonne,  T h i s was  OC,4—dicyanostilbene  r e c r y s t a l l i z e d from e t h a n o l t o  g i v e c o l o r l e s s c r y s t a l s m e l t i n g a t 14-4-.5 - 14-5• 5° • ( l i t . value:  14-5°  12.  (98)  ).  oC,3-Dicyanostilbene The  condensation  w h i c h was p r e p a r e d e t a l (99),  of 3-cyanobenzyl  cyanide,  i n the manner d e s c r i b e d by I p a t i e f f  w i t h benzaldehyde i n e t h a n o l i c sodium  y i e l d e d the Oi.,3-dicyanostilbene p r o d u c t was  i n 95%  yield.  r e c r y s t a l l i z e d from e t h a n o l t o g i v e  ethoxide  The colorless  c r y s t a l s m e l t i n g a t 14-8 - 14-9° • Analysis:  calculated found  carbon 83.4-6 83.72  hydrogen 4-. 38 4-.22  nitrogen 12.17 12.04-  52  13.  Ql-Cyano-2-nitrostilbene The  w h i c h was  condensation  prepared  of 2 - n i t r o b e n z y l cyanide,  i n the manner d e s c r i b e d by  Pschorr  and Hoppe (100), w i t h benzaldhyde i n e t h a n o l w i t h CX,-cyano-2-nitrostilbene  p i p e r i d i n e as the c a t a l y s t gave the i n $k% y i e l d .  The  p r o d u c t was  r e c r y s t a l l i z e d from e t h a n o l  to a constant melting point of I l k - I l k . 5 ° . ( l i t . value  :  Ik.  115°  (101)  ).  oC 3-Dicyano-H— c h l o r o s t i l b e n e y  3-Cyano-M— c h l o r o t o l u e n e was  prepared  3-amino-H— c h l o r o t o l u e n e by the Sandmeyer  reaction  a c c o r d i n g t o the method d e s c r i b e d by V o g e l 3-cyano-U—chlorobenzyl 6.k  bromide was  from  prepared  (87c). by  The  brominating  g o f 3 - c y a n o - M — c h l o r o t o l u e n e w i t h 9 g o f N-bromo-  s u c c i n i m i d e i n 125  ml carbon t e t r a c h l o r i d e u s i n g  p e r o x i d e as the c a t a l y s t by r e f l u x i n g f o r 3.5  benzoyl  hours.  A f t e r removing the c a r b o n t e t r a c h l o r i d e , the crude was  product  d i s s o l v e d i n 100 ml o f e t h a n o l and r e a c t e d w i t h 2.6  of potassium  cyanide  i n 20 ml o f w a t e r .  f o r "+5 m i n u t e s , the e t h a n o l was r e s u l t i n g o i l was  evaporated  extracted with ether.  the e t h e r , the o i l s o l i d i f i e d and was w a t e r ; 0.3 w i t h 0.1  g o f m a t e r i a l was  After  obtained.  g  refluxing  and  After  the evaporating  r e c r y s t a l l i z e d from T h i s was  condensed  g o f benzaldehyde i n 5 ml of e t h a n o l and a  few  53  drops o f a I N e t h a n o l i c sodium e t h o x i d e  a t 4-0°.  solution  T h i s gave a 78% y i e l d o f 0 ( , 3 - d i c y a n o - 4 — c h l o r o s t i l b e n e w h i c h was r e c r y s t a l l i z e d from e t h a n o l t o a c o n s t a n t m e l t i n g p o i n t o f 156 - 1 5 7 ° . Analysis:  15*  calculated found  carbon  72.60 73-83  hydrogen 3A3 4-.06  nitrogen 10.58 10.30  cX-Cyano-2-chloro-4—nitrostilbene T h i s i n d i c a t o r was p r e p a r e d a c c o r d i n g t o t h e  method o f Meerwein, the f i l t e r e d  Buchner and v a n Emster  (102).  To  s o l u t i o n o f the diazonium s a l t o f 2 - c h l o r o -  4 — n i t r o a n i l i n e , p r e p a r e d a c c o r d i n g t o t h e method d e s c r i b e d by V o g e l (87d), was added 3«5 g o f sodium a c e t a t e , 2.1 g o f c i n n a m o n i t r i l e i n 19 ml o f acetone and 0.68 g o f c u p r i c c h l o r i d e i n 2 ml o f w a t e r .  The aqueous s o l u t i o n  i n t h e d i s t i l l a t i o n f l a s k was decanted and the r e s i d u e t a k e n up i n acetone and passed t h r o u g h a n a l u m i n a column u s i n g benzene as t h e e l u t e n t .  The r e s u l t i n g dark c o l o r e d  p r o d u c t , l e f t a f t e r e v a p o r a t i n g t h e benzene, was r e c r y s t a l lized to  from a c e t i c a c i d , u s i n g c h a r c o a l to d e c o l o r i z e i t ,  g i v e a s m a l l amount o f y e l l o w c r y s t a l s m e l t i n g a t  174- - 1 7 5 ° .  Analysis:  calculated found  carbon  63.28 63.61  hydrogen 3.19 3.65  nitrogen 9.8410.01  5*  16.  O^-Cyano-3-trifluoromethylstilbene 3-Trifluoromethylbenzyl  cyanide was p r e p a r e d  i n 78% y i e l d f r o m 3 - t r i f l u o r o m e t h y l b e n z y l c h l o r i d e and p o t a s s i u m cyanide  i n an ethanol-water  s o l u t i o n according  t o t h e method o f R o s e n k r a n t z e t a l (103). methylbenzyl  The 3 - t r i f l u o r o -  cyanide was condensed w i t h benzaldehyde i n  e t h a n o l i c sodium e t h o x i d e  s o l u t i o n a t 55° a c c o r d i n g t o  the method d e s c r i b e d by Schonne, Braye and B r u y l a n t s (9*+) t o g i v e a 70% y i e l d o f t h e c o r r e s p o n d i n g The  OC-cyanostilbene.  product was r e c r y s t a l l i z e d once from e t h a n o l and  t w i c e from methanol t o g i v e c o l o r l e s s c r y s t a l s  at  melting  80-81°.  Analysis:  17.  carbon 70.33 70. 54-  calculated found  hydrogen 3.69 3-68  nitrogen 5.13 5.02  CX-Cyano-3-nitrostilbene 3-Nitrobenzyl  cyanide was prepared  i n 60% y i e l d  f r o m t h e r e a c t i o n o f 3 - n i t r o b e n z y l c h l o r i d e w i t h sodium cyanide  i n an ethanol-water  s o l u t i o n according t o the  method d e s c r i b e d by Bent e t a l (104-). d i s t i l l e d a t 14-4- - 14-5° a t 0.7mm  The p r o d u c t  ( l i t . v a l u e : 160 - 165°  a t 3mm (104-) ) and m e l t e d a t 55 - 56°.  The 3 - n i t r o b e n z y l  cyanide was condensed w i t h benzaldehyde i n a n e t h a n o l i c sodium e t h o x i d e  s o l u t i o n a c c o r d i n g t o t h e method d e s c r i b e d  by Schonne, Braye and B r u y l a n t s  (94-) t o g i v e t h e Q(-cyano-  55  3-nitrostilbene.  The p r o d u c t was r e c r y s t a l l i z e d  from  e t h a n o l t o a c o n s t a n t m e l t i n g p o i n t o f 165 - 166° ( l i t . 165°  value:  (9*0  ).  Q^-Cyano~3-chlorostilbene  18.  T h i s was p r e p a r e d  by condensing  3-chlorobenzyl  c y a n i d e w i t h benzaldehyde i n a n e t h a n o l i c sodium e t h o x i d e s o l u t i o n a c c o r d i n g t o the method d e s c r i b e d by Schonne, Braye and B r u y l a n t s (9*+).  The p r o d u c t was  recrystallized  e t h a n o l t o a c o n s t a n t m e l t i n g p o i n t o f 95 -  from  ( l i t . v a l u e : 9h - 95°  (105)  96°  ).  Q(-Cyano-H— c h l o r o s t i l b e n e  19.  o f k-chlorobenzyl  The c o n d e n s a t i o n  benzaldehyde i n a n e t h a n o l i c sodium e t h o x i d e  cyanide  with  solution,  a c c o r d i n g t o the method d e s c r i b e d by Schonne, Braye and B r u y l a n t s (9*0, 80% y i e l d .  gave the oC-cyano-M—chlorostilbene i n  The p r o d u c t was r e c r y s t a l l i z e d f r o m e t h a n o l  t o a c o n s t a n t m e l t i n g p o i n t o f 112 value:  110  20.  - 112°  (105)  - 113°. ( l i t .  ).  o( - C y a n o - c i s - s t i l b e n e CX-Phenyl-trans-cinnamic  a c i d was p r e p a r e d  by  condensing p h e n y l a c e t i c a c i d w i t h benzaldehyde i n t r i ethylamine  and a c e t i c a n h y d r i d e  a c c o r d i n g t o the method  56  of B u c k l e s and Bremer  f r o m e t h a n o l and w a t e r , a melting at  169-5  -  A f t e r one  (106). 5*+$  y i e l d o f p r o d u c t was  ( l i t . value:  170.5°.  C X - C y a n o - c i s - s t i l b e n e was to  recrystallization  172  -  obtained  173°  (106)  prepared according  the method o f C o d i n g t o n and M o s e t t i g  A  (107).  solution  of 1 0 g o f 0 ( - p h e n y l - t r a n s - c i n n a m i c a c i d i n 1 5 ml t h i o n y l c h l o r i d e was  h e a t e d t o s o l u t i o n and t h e n r e f l u x e d f o r "+0  m i n u t e s , f o l l o w e d by the e v a p o r a t i o n o f the t h i o n y l chloride. dry  The r e s u l t i n g o i l was  benzene and ammonia was  d i s s o l v e d i n 1 0 0 ml o f  passed t h r o u g h the  solution.  A f t e r f i l t e r i n g the ammonium c h l o r i d e , the benzene e v a p o r a t e d and the r e s u l t i n g o i l s o l i d i f i e d and  was  was  r e c r y s t a l l i z e d from acetone g i v i n g 5 g o f m a t e r i a l m e l t i n g at  112 - 122°.  A m i x t u r e o f 5 g o f the crude amide, 1 0 g  of phosphorus p e n t o x i d e and 2 5 ml o f x y l e n e was for  one hour w i t h s t i r r i n g .  d e c a n t e d and the r e s i d u e was of hot x y l e n e .  refluxed  The hot x y l e n e s o l u t i o n  was  f u r t h e r e x t r a c t e d w i t h 1 0 ml  The x y l e n e was  t h e n d i s t i l l e d and  the  r e s i d u e d i s t i l l e d under r e d u c e d p r e s s u r e ; 1 . 6 g o f y e l l o w material boiling at l l h ( l i t . value: redistilled  90  -  100°  -  at  115°  at  0.05mm  0.15mm (107)  was  ).  collected  This  was  and t h e n f u r t h e r p u r i f i e d by vapor phase  chromotography u s i n g a 1 0 f o o t s i l i c o n column w i t h the column temperature a t  220°.  ).  57  21.  o(-Cyano-cis-4~  chlorostilbene  4 — C h l o r o p h e n y l a c e t i c a c i d was l y z i n g 4— c h l o r o b e n z y l c y a n i d e (87e).  d e s c r i b e d by V o g e l  The  from h i g h b o i l i n g petroleum  prepared  i n s u l f u r i c a c i d i n the manner p r o d u c t was r e c r y s t a l l i z e d  ether.  0( -(4— C h l o r o p h e n y l ) - t r a n s - c i n n a m i c prepared,  by h y d r o -  acid  was  as d e s c r i b e d by C o d i n g t o n and M o s e t t i g (107),  by  c o n d e n s i n g the sodium s a l t o f 4— c h l o r o p h e n y l a c e t i c a c i d w i t h p u r i f i e d benzaldehyde i n r e d i s t i l l e d a c e t i c a n h y d r i d e . p r o d u c t was  r e c r y s t a l l i z e d from e t h a n o l t o g i v e a 51$  o f p r o d u c t m e l t i n g a t 173 (107)  ).  The amide was  - 178°  prepared  ( l i t . v a l u e : 180 by r e a c t i n g  -  The yield  181°  the a c i d  chloride,  prepared  f r o m the r e a c t i o n o f cX-(4— c h l o r o p h e n y l ) - t r a n s -  cinnamic  a c i d w i t h t h i o n y l c h l o r i d e , w i t h ammonia i n  benzene (107).  The  phosphorus p e n t o x i d e  d e h y d r a t i o n o f the amide w i t h i n x y l e n e , as d e s c r i b e d by C o d i n g t o n  and M o s e t t i g (107), r e s u l t e d i n the stilbene.  T h i s was  b o i l i n g petroleum 55.5  - 57.5°.  22.  1*35  r e c r y s t a l l i z e d from methanol and  low  ether to a constant melting p o i n t of  ( l i t . v a l u e : 56 - 57-5° (107)  ).  (X-Cyano-cis-3-chlorostllbene The  prepared  o(,-cyano-cis-4~chloro-  sodium s a l t o f 3 - c h l o r o p h e n y l a c e t i c a c i d ,  by r e a c t i n g 10 g o f 3 - c h l o r o p h e n y l a c e t i c a c i d w i t h  g o f sodium i n methanol and  then evaporating  the  58  methanol, was condensed w i t h 6.2g o f p u r i f i e d  benzaldehyde  i n 39 ml o f . d i s t i l l e d a c e t i c a n h y d r i d e by h e a t i n g a t 100° for  17 hours (107).  T h i s s o l u t i o n was poured i n t o 100 ml  of water and h e a t e d t o b o i l i n g w i t h v i g o r o u s s t i r r i n g . A f t e r c o o l i n g , the s o l i d was f i l t e r e d and r e c r y s t a l l i z e d f r o m e t h a n o l t o g i v e 9.2 g o f p r o d u c t f o r a Gl% y i e l d . To t h e o ( - ( 3 - c h l o r o p h e n y l ) - t r a n s - c i n n a m i c a c i d , from above, was added 15 ml o f t h i o n y l c h l o r i d e ; t h e m i x t u r e was h e a t e d t o e f f e c t s o l u t i o n and t h e n was r e f l u x e d f o r "4-0 m i n u t e s .  The excess t h i o n y l c h l o r i d e was d i s t i l l e d  and t h e r e s u l t i n g o i l d i s s o l v e d i n benzene w h i c h was t h e n s a t u r a t e d w i t h ammonia. the  The benzene was e v a p o r a t e d and  r e s u l t i n g o i l r e c r y s t a l l i z e d from p e t r o l e u m e t h e r -  e t h a n o l t o g i v e the d e s i r e d amide.  A m i x t u r e o f 3«7 g o f  t h i s amide, 6.5 g o f phosphorus p e n t o x i d e and 25 ml o f x y l e n e was r e f l u x e d w i t h s t i r r i n g f o r one h o u r .  The x y l e n e  was decanted and t h e r e s i d u e was e x t r a c t e d w i t h a f u r t h e r 10 ml o f h o t x y l e n e .  The x y l e n e was t h e n d i s t i l l e d  g i v i n g the crude C X . - c y a n o - c i s - 3 - c h l o r o s t i l b e n e as an o i l . T h i s was p u r i f i e d by m i c r o d i s t i l l a t i o n f o l l o w e d by passage t h r o u g h a s h o r t c a r b o n - c e l i t e column and, f i n a l l y , by vapor phase chromotography u s i n g a 10 f o o t column w i t h the column temperature a t 220°. spectrum, a peak a t 2200 cm the  cyano  group.  silicon I n the i n f r a r e d  i n d i c a t e d the presence o f  59  Analysis.:  23.  carbon  75.16  calculated found  7H-.85  hydrogen H-.20 H-.20  Q(-Cyano-cis-H—methoxystilbene CX-(H—Methoxyphenyl)-trans-cinnamic a c i d  was  p r e p a r e d by condensing 25 g o f H-methoxyphenylacetic a c i d . w i t h 16 g o f p u r i f i e d benzaldehyde i n 15 g o f t r i e t h y l a m i n e and 71 ml o f d i s t i l l e d a c e t i c a n h y d r i d e by r e f l u x i n g f o r H-8 hours a c c o r d i n g t o the method o f Cadogan, D u e l l and Inward (108).  The p r o d u c t was r e c r y s t a l l i z e d once f r o m  an e t h a n o l - w a t e r m i x t u r e . The crude c i n n a m i c a c i d (27.7  g) from above was  d i s s o l v e d i n 70 ml o f t h i o n y l c h l o r i d e by h e a t i n g and t h e n r e f l u x e d f o r a f u r t h e r 35 m i n u t e s .  The excess t h i o n y l  c h l o r i d e was d i s t i l l e d and the r e s u l t i n g o i l d i s s o l v e d i n benzene w h i c h was t h e n s a t u r a t e d w i t h ammonia. ammonium c h l o r i d e was f i l t e r e d  and the benzene f i l t r a t e  was e v a p o r a t e d l e a v i n g an o i l w h i c h c r y s t a l l i z e d standing.  The  on  T h i s was r e c r y s t a l l i z e d from carbon t e t r a c h l o r i d e  to  g i v e 5»7  of  phosphorus  g o f the amide.  with stirring  A m i x t u r e o f t h i s amide, 10 g  p e n t o x i d e and 35 ml o f x y l e n e was f o r 1.25  hours.  refluxed  The hot x y l e n e s o l u t i o n was  decanted and the r e s i d u e was f u r t h e r e x t r a c t e d x ^ i t h 20 of hot x y l e n e .  The x y l e n e was d i s t i l l e d under  ml  reduced  p r e s s u r e l e a v i n g the crude o ( - c y a n o ~ c i s - H — m e t h o x y s t i l b e n e  60  as an o i l . followed  T h i s was  f u r t h e r p u r i f i e d by a m i c r o  by passage t h r o u g h a s h o r t c a r b o n - c e l i t e  220°.  column  using a 7  and f i n a l l y by vapor phase chromotography silicon  distillation  foot  gum rubber column w i t h the column temperature a t I n the i n f r a r e d spectrum, a peak a t 2200  i n d i c a t e d the presence o f t h e cyano Analysis:  1  group.  carbon 81.68 81.2k  calculated found  cm"  hydrogen 5-57 5.9+  Q(-Cyano-cis-3~nitrostilbene  2k.  3-Nitrophenylacetic hydrolyzing  3-nitrobenzyl  a c i d (13*3 cyanide  g)  ?  p r e p a r e d by (87e),  i n sulfuric acid  was  condensed w i t h 7.8  g o f p u r i f i e d benzaldehyde i n  9.7  g of triethylamine  and k5 ml o f d i s t i l l e d  acetic  a n h y d r i d e by r e f l u x i n g f o r k8 hours a c c o r d i n g t o the method o f Cadogan, D u e l l and Inward ( 1 0 8 ) . was r e c r y s t a l l i z e d from e t h a n o l g i v i n g 5.8  The p r o d u c t g of f a i r l y  crude cx - ( 3 - n i t r o p h e n y l ) - t r a n s - c i n n a m i c a c i d . The 5>8  g o f a c i d from above was  dissolved  i n 10 ml o f t h i o n y l c h l o r i d e by h e a t i n g and the s o l u t i o n r e f l u x e d f o r a f u r t h e r kO m i n u t e s .  The excess t h i o n y l  c h l o r i d e was d i s t i l l e d and t h e r e s u l t a n t  solid  i n 75 ml o f benzene w h i c h was t h e n s a t u r a t e d The r e s u l t i n g s o l i d was  filtered  dissolved  w i t h ammonia.  and the benzene f i l t r a t e  e v a p o r a t e d t o dryness g i v i n g v e r y l i t t l e p r o d u c t .  The  61  s o l i d m a t e r i a l was t h e n h e a t e d w i t h e t h a n o l , f i l t e r e d and the e t h a n o l f i l t r a t e e v a p o r a t e d  g i v i n g a s o l i d w h i c h was  r e c r y s t a l l i z e d from benzene t o g i v e 4-.0 g o f t h e amide m e l t i n g a t 151 - 155° • A m i x t u r e 7.0 g o f phosphorus p e n t o x i d e  o f 4-.0 g o f t h i s amide,  and 30 ml o f x y l e n e was  r e f l u x e d w i t h s t i r r i n g f o r 1.25 h o u r s .  The h o t x y l e n e  s o l u t i o n was decanted and t h e r e s i d u e was f u r t h e r w i t h 15 ml o f h o t x y l e n e .  The x y l e n e s o l u t i o n was d i s t i l l e d  under r e d u c e d p r e s s u r e l e a v i n g 2.9 g o f s t i l b e n e as a s o l i d .  extracted  c\-cyano-cis-3-nitro-  T h i s was r e c r y s t a l l i z e d from e t h a n o l  t o a c o n s t a n t m e l t i n g p o i n t o f 121 - 1 2 2 ° . spectrum had a sharp band a t 2200 cm  The i n f r a r e d  i n d i c a t i n g the  presence o f t h e cyano group. Analysis:  calculated found  25.  carbon 71.99 71-95  hydrogen "+.03 M-.39  nitrogen 11.20 10.88  CX-Cyano-cis-4—nitrostilbene o ^ - ( " 4 — n i t r o p h e n y l ) - t r a n s - c i n n a m i c a c i d was  prepared  by condensing t h e sodium s a l t o f 4— n i t r o p h e n y l a c e t i c  a c i d w i t h p u r i f i e d benzaldehyde i n d i s t i l l e d anhydride  acetic  a c c o r d i n g t o t h e method o f Sehmid (109). The  crude p r o d u c t was r e c r y s t a l l i z e d once from a c e t i c g i v i n g y e l l o w c r y s t a l s m e l t i n g a t 221 - 2 2 3 ° . 227  - 228°  (109)  acid  (lit.  value:  ).  CX-(4— N i t r o p h e n y l ) - t r a n s - c i n n a m i c a c i d  (14-.9 g)  62  was  d i s s o l v e d i n 50 ml o f t h i o n y l c h l o r i d e by  and  t h e n r e f l u x e d f o r a f u r t h e r 4-5 m i n u t e s .  t h i o n y l c h l o r i d e was  w h i c h was was  t h e n s a t u r a t e d w i t h ammonia.  melting at approximately  and  210°  g o f t h i s amide, 11.5  70 ml o f x y l e n e was  hours.  The  hot x y l e n e  was  The  6.6  T h i s was  pressure  resulting  g of yellow  collected.  g o f phosphorus  A  s o l u t i o n was  crystals  pentoxide  f i l t e r e d and  1.25  the  pressure  c X - c y a n o - c i s - 4 ~ n i t r o s t i l b e n e as a y e l l o w  r e c r y s t a l l i z e d from e t h a n o l t o a  m e l t i n g p o i n t o f 135  - 136°.  solid  mixture  refluxed with s t i r r i n g for  r e s u l t a n t f i l t r a t e d i s t i l l e d under r e d u c e d l e a v i n g the  excess  d i s s o l v e d i n 190 ml o f benzene  r e c r y s t a l l i z e d from e t h a n o l and  o f 6.6  The  d i s t i l l e d under r e d u c e d  l e a v i n g a s o l i d w h i c h was  heating  solid.  constant  I n the i n f r a r e d spectrum, a  peak a t 2200 cm"""" i n d i c a t e d the p r e s e n c e o f the 1  cyano  group. Analysis;  26.  calculated found  carbon 71-99 72.10  hydrogen 4-. 03 5.04-  nitrogen 11.20 10.93  o(-Cyano- Q('-methoxy-cis- and t r a n s - s t i l b e n e s CX.-Cyanodesoxybenzoin was  p r e p a r e d by r e a c t i n g  b e n z y l cyanide w i t h e t h y l benzoate  i n benzene  and  p o t a s s i u m a c c o r d i n g t o the method d e s c r i b e d by W i s l i c e n u s , B u t t e r f a s s and Koken (110).  T h i s was  r e c r y s t a l l i z e d from  c a r b o n t e t r a c h l o r i d e t o g i v e the p u r i f i e d  (X-cyanodesoxy-  63  benzoin. The were p r e p a r e d  two  i s o m e r s o f CX-cyano-o(' - m e t h o x y s t i l b e n e  by the r e a c t i o n o f 0 ( - c y a n o d e s o x y b e n z o i n  w i t h a l k a l i n e d i m e t h y l s u l f a t e a c c o r d i n g t o the method o f M a t t i and Reynaud ( 1 1 1 ) .  The  two  g e o m e t r i c a l isomers  were s e p a r a t e d by f r a c t i o n a l r e c r y s t a l l i z a t i o n as by M a t t i and Reynaud ( 1 1 1 ) . m e l t e d a t 8*4 - 8 5 ° v a l u e s : 8*4.5 and  27.  The  lower m e l t i n g isomer  and the o t h e r a t 1 0 5  106°  - 106°. ( l i t .  (111) ) .  4,*4' - D i n i t r o t r i p h e n y l m e thane " 4 , 4 ' - D i n i t r o d i p h e n y l m e t h y l bromide was  by b r o m i n a t i n g  with  ml o f carbon t e t r a c h l o r i d e u s i n g  g o f b e n z o y l p e r o x i d e as c a t a l y s t a c c o r d i n g to the  method o f Wragg, Stevens and O s t l e ( 1 1 2 ) .  A f t e r evaporating  the s o l v e n t and r e c r y s t a l l i z i n g the p r o d u c t t e t r a c h l o r i d e , 7 . 7 g o f m a t e r i a l was o f 59%*  To 7 « 7  d i s s o l v e d i n 100 6.1  prepared  1 0 g of 4,4'-dinitrodiphenylmethane  2 m l o f bromine i n 1 6 0 0.6  described  from c a r b o n  obtained f o r a y i e l d  g o f 4 , 4 ' - d i n i t r o d i p h e n y l m e t h y l bromide ml d r y t h i o p h e n e  f r e e benzene was  g of aluminum c h l o r i d e and the m i x t u r e was  added  then  r e f l u x e d w i t h s t i r r i n g f o r two hours d u r i n g w h i c h a t h i c k black t a r separated. d e c a n t e d and e v a p o r a t e d  The  benzene s o l u t i o n  to dryness.  The  was  s m a l l amount  o f 4 , 4 ' - d i n i t r o t r i p h e n y l m e t h a n e ( 1 . 8 g) was  recrystallized  r e p e a t e d l y from t o l u e n e t o a c o n s t a n t m e l t i n g p o i n t o f  64-  175  -  176°.  Analysis:  G,  carbon 68.26 68.52  calculated found  hydrogen 4-.22 4-.51  nitrogen 8.38 8.31  Reactions o f l,l-Bis-(4--nitrophenyl)ethene l t  With hydroxide i o n i n DMSO P u r i f i e d l , l - b i s - ( 4 — nitrophenyl)ethene  (1 g) was  d i s s o l v e d i n 300 ml o f p u r i f i e d DMSO i n a short-necked f l a s k f i t t e d w i t h a rubber  stopple.  through the s o l u t i o n f o r one hour, methylammonium hydroxide-water  A f t e r passing nitrogen  6.5 ml o f a 10$ t e t r a -  s o l u t i o n was added v i a  a s y r i n g e , thus n o t exposing the system about  t o the a i r .  After  one minute, the r e a c t i o n was quenched by the a d d i t i o n  of 6 ml o f a c e t i c a c i d .  The r e s u l t i n g  s o l u t i o n was poured  onto 1 . 5 1 o f i c e water whereupon a f i n e suspension formed. Sodium c h l o r i d e was added t o a i d i n b r e a k i n g up the s u s p e n s i o n and the y e l l o w s o l i d which separated was f i l t e r e d and washed w e l l w i t h water.  The r e s u l t i n g s o l i d was  r e c r y s t a l l i z e d from benzene-acetone t o y i e l d  0.4-3 g o f  product w i t h a m e l t i n g p o i n t o f 188 - 189°. Analysis: calculated found The  hydrogen 3«98 4-.07  carbon nitrogen 60.21 10.03 60.23 10.04-  mol. weight 555 5¥i-  c a l c u l a t e d v a l u e s are f o r d i - l , l - b i s - ( 4 ~ n i t r o p h e n y l ) -  e t h y l e t h e r (XVI),  and the molecular weight was determined  65  0 N^  ^>j-CH-CH -0-CH2-CH-.(<f  2  2  \)NO;  XVI by t h e R a s t method.  2.  W i t h sodium methoxide  in  D M S O  To 0.5 g o f l , l - b i s - ( H — n i t r o p h e n y l ) e t h e n e i n a s h o r t - n e c k e d f l a s k f i t t e d w i t h a r u b b e r s t o p p l e was added 200 ml o f p u r i f i e d  D M S O .  N i t r o g e n was b u b b l e d t h r o u g h t h e  s o l u t i o n f o r one hour and t h e n 6 ml o f a p p r o x i m a t e l y I N sodium methoxide needle.  s o l u t i o n was added v i a a s y r i n g e and  A f t e r 10 m i n u t e s , t h e r e a c t i o n was quenched by  t h e a d d i t i o n o f 6 ml o f g l a c i a l a c e t i c a c i d . was  poured onto i c e and t h e b r e a k i n g up o f t h e e m u l s i o n  was a i d e d by t h e a d d i t i o n o f sodium c h l o r i d e . was  The s o l u t i o n  The s o l i d  f i l t e r e d , washed w e l l w i t h water a n d r e c r y s t a l l i z e d  f r o m e t h a n o l and a p e t r o l e u m e t h e r - e t h a n o l m i x t u r e t o a c o n s t a n t m e l t i n g p o i n t o f 118 - 119°. Analysis:  calculated found  carbon 59-60 59.77  hydrogen k.67 h.62  nitrogen 9.27 8.58  The c a l c u l a t e d v a l u e s i n t h e a n a l y s i s a r e f o r 1,1-bis(4—nitrophenyl)-2-methoxyethane  °2 \ N  (XVII).  7)-CH-CH -0CH3 2  XVII  66  The NMR spectrum  o f t h i s compound d i s s o l v e d i n  hot t e t r a c h l o r o e t h y l e n e was o b t a i n e d .  T h i s shows a s i n g l e t  a t 6.56^ a doublet a t 6.06^T and 5 . 9 5 t w i t h a c o u p l i n g constant o f 6 cps, and an obscure 5A8t  triplet  centered a t  w i t h an approximate c o u p l i n g constant o f 6 c p s .  The areas o f the s i n g l e t : d o u b l e t : t r i p l e t a r e i n the r a t i o o f 3*2:1.  The aromatic p o r t i o n o f the spectrum  has two  d o u b l e t s , one a t 2.4-87"* and 2.63T** and the other a t 1.7l"t  and 1.84?, each w i t h a c o u p l i n g constant o f 9 c p s .  67 TABLE I A b s o r p t i o n Maxima and M o l a r E x t i n c t i o n C o e f f i c i e n t s f o r ( X - C y a n o s t i l b e n e s i n DMSO-Ethanol Substituent  Observed V a l u e s  G  Reported Values  Amax^  -Cyano--trans' - s t i l b e n e s -Cyano32,500 4-,4-'-dinitro 336 3 -chloro-M—nitro 332 28,000 27,600 4—nitro 336 28,600 4- -me t h y l - 4 — n i t r o 350 4-'-methoxy-M—nitro 372 29,800 30,100 4—cyano-4- - n i t r o 336 38,4-00 4- -dime thy lamino-4--n i t r o 4-56 29,500 4—cyano-3 -chloro 321 4—cyano 326 30,000 3-cyano-4—chloro 318 26,000 3-cyano 23,000 22,4-00 316 3-1r i f l u o r ome thy1 25,200^ 3-nitro 311 23,4-00^ 3-chloro 315 25,800° 4— c h l o r o 318 21,800 hydrogen 318 4-methoxy. 333 24-,800  £  ref.  336  30,000  a  95  33434-8 370  26,500 l8,200 26,500  a  4-4-5  H-l,700  316 312  27,500 25,700  107 107  295 295  15,800 16,600  107 107  1  1  a  a  95 95 95  1  1  b  92  1  c  c  0(-Cyano-cis-stilbenes 309 12,200 277 17,200 290 13,100 296 14-, 700 291 13,100 313 10,700  4-nitro 3-nitro 3- chloro 4 - chloro hydrogen 4-methoxy  a b c d  a  I n 0.002M m e t h a n o l i c H C l In alcohol From i s o m e r i z a t i o n o f the c i s - i s o m e r I n methanol  68  TABLE I I  A b s o r p t i o n Maxima and Molar E x t i n c t i o n C o e f f i c i e n t s f o r t h e A n i o n s AOR*" Substituent  I n DMSO-Ethanol  /\m x°T a  G  I n DMSO-Methanol  Xmxf  £  d\-Cyanostilbenes 2,4-dinitro 4-, 4 - ' - d i n i t r o . 553 3 -chloro-4--nitro 9+1 4--nitro 5^-7 "H-'-methyl-H-nitro 9+7 4-'-methoxy-4~nitro 54-7 4-'-cyano-4-'-nitro 393 4-' - d i m e t h y l a m i n o - 4 - n i t r o 552 4--cyano-3'-chloro 4-02 4--cyano 4-02 2- n i t r o 603 3 - cyano-4--chloro 3743-cyano 363 3-trifluoromethyl 353 2-chloro-4--nitro 550 1  4-2,100 4-3,700 4-2,600 4-2,800 4-2 , 500 4-4-, 000 4-3,300 47,200 4-7,4-00 7,630 33,600 28,500 23,700 4-0,500  Others l,l-bis-(4~nitrophenyl) ethene  710  25,700  4-80 553 54-7 9+8 54-8 9+9 395 552  27,100 4-1,100 4-2 , 600 4-2,700 4-2,4-00 4-2,300 4-4-, 200 4-3,4-00  4-02  4-7,700  69  TABLE I I I  A b s o r p t i o n Maxima and Molar E x t i n c t i o n C o e f f i c i e n t s f o r I n d i c a t o r A n i o n s o f Carbon A c i d s i n Sodium Methoxide-Methanol  Indicator  Solutions  Observed V a l u e s  Reported  Values  methyl f l u o r e n e 9-carboxylate  387  "+,220  389  4-,690  •+,"+',V-trlnitrotriphenylmethane  530  25,600  650 707  20,OOo£ 19,300  •+,4'-dinitrodipheny Ime thane  534-  28,000  570 704-  4-5,700]? kk4-0,600° 51  4--nitrobenzyl cyanide  530  30,700  528  28,700  2-nitrobenzyl cyanide  54-6  10,200  •+,"+' - d i n i t r o triphenylmethane  a b c  506  20,900  In ethanol I n aqueous h y d r a z i n e s o l u t i o n s I n DMSO-methanol s o l u t i o n s  a  51 kk 51  39  70 TABLE I V V a l u e s o f l o g |i.0R~] / [ A ] f o r t h e oC-Cyanostilbenes Used a s I n d i c a t o r s t o E s t a b l i s h the HR- S c a l e i n DMSO-Ethanol o  fH  o •p •H  Mole % DMSO i n Ethanol  •H  Xi I  -+ O.98 1.99 3.51 5.63 10.82 15.5420.09 25.09 30.09 35.07 4-0.16 4-5.22 50.27 55.03 59.62 64-. 59 69.26  -.4-17 -.366 -.209 -.04-2 + .364+ .724-  I  I  oo uu O  H  rH O O  - P - H  0  1  fn 4-> •H  I J  nO  -.983 -.810 -.4-12 -.080 + .24-3 + .589 + .959  -  Ci I  >>fH  xi-p  - P ' H Q)  S  1  1  Ci I  !>>  Xo O fH X i - P -P - H  o  d  a i  Ci Ci cd 1 >»O J "  - H  !>» 1  xiJ•P  0>  1 o  a d •H - H a  J-  J-  -.827 -.500 -.169 + .182 + .528 + .878  o fH 1 -P O - H  -p  H Ci  -.84-4-  -.516 -.180 + .185 + .517 + .886  -.959 -.611 -.276 + .115 + .4-73 + .865  -.869 -.532 -.196 + .173 + .54-3 + .907  -.860 -.504-.153 + .207 +.611 + .938  71  TABLE IV  (Continued)  o  Mole % DMSO i n Ethanol  1 a  o H  o si >>O  o i  PO  1  _+  50.27  55.93  59.62 64.59 69.26  7k.15 79.11 84.12 89.17 93.29  -.662 -.305 + .045 + .H-59 + .89H-  o  O  U  o  o  ce  -P •H  a  >>  o i  c!  I  CM  -.883 -.523 -.152 + .281 + .841  M  o  3 H  1O O <H  o  r3  t>»  ctf  O  oi  •H  -P  >>  O J  1 "  o  40  s  oo  00  1  nO  -1.035 -.599 -.815 - . 1 0 8 -.3 +0 +.422 +.188 + .7"+3  1  f4  l  O  !  -.936 -.297 + .274  -.85*+ -.218  72  TABLE V V a l u e s o f l o g (AOR"3 / [A] f o r t h e d>-Cyanostliberies Used as I n d i c a t o r s t o E s t a b l i s h the H - S c a l e i n DMSO-Methanol B  o in -P  •H  £ •H  Mole % DMSO i n Methanol 0.68 2.32 5.39 8.75 15.30 20.60 25-5H30.4-7 35.1439.88 H-H-.05 4-9.95 54-.79 59.61 6^.32 69.63  T3  o  fn -P •H  •H  T5  1  1i  -  CM CM  -+  I  1  o o u u  O H  -P - H  .c a O 1i o1 -+  *•  r o ro  -.898 -.695 -.362 -.005 +.618 -1.011 -.560 - . 1 3 8 -.767 +.308 -.358 + . 7 1 5 +.04-0 +.4-4-4+.809  I  o U -P •H  -H |  J-  >»  HO !>» m X! -P -P -H  MO OU .3 -P -P -H  j -  j -  ai  s i  o M  1-P O -H £ £  >>j -  - . 7 0 6 -1.04-2 -.274- - . 6 3 1 +.088 -.279-.706 +.594+.231 - . 1 8 1 - . 9 8 1 + . 9 9 1 +.64-4- +.24-4-.565 +1.029 +.676 -.14-4+.275 +.724-  73  TABLE V  (Continued)  o u  -P  H  l-H  U  Mole • -+I irrlrx fo - £P DMSO I n oo Methanol . -  ° SH ox! g ? 1  1 J -  59.61  -.736  -.882  69.63 +.188 74-.26 +.626 78.52 +1.081 83.52 88.2493.98 97.61  +.011 +.4-58 +.954-  64-.32  I  O  C t>> I  O  o g 1 J -  o 5  O  I fO OH g •§  ?H  C2 S, H H ^ £  1  O g  1 CM  r o  -.990 -.4-29 +.178 +1.022  -.609 -.007 +.74-7  r o  I  I  r o  -.312 -.4-64-.932 -.4-95 -.056 +.526  -1.120 - .195 -.687 + .724- +'.332  74TABLE V I Values o f l o g  [AOR~]/  f o r t h e o(.-Cyanostilbenes  [A]  Used a s I n d i c a t o r s t o E s t a b l i s h the H - S c a l e i n Sodium Methoxide-Methanol S o l u t i o n s K  o fH  -p  o  fH  S o d i u m  Methoxide cone._ (mole l - l ) 0.010 0.056 0.115 0.229 0.4-640 . 6 9 7  0.952 1.19 1.4-8 1.78 2.07 2.36 2.65 2.93 3.24-  3.51 3.82  4-.08 4-.73  -P •H d •H TJ '1  H  i ~ OJ  CM  -.84-2  -.087 + .253 + .616  O fn  1  -P •H d •H TJ  1  —^  _+  -• J" J -  -.813 -.370 -.075 + .219 + .4-82 + .836  O  fH  o  fH  O -P H -H H  xi O'  d  1  H  —  V I m  -.978 -.686 -.4-08 -.153 + .164+ .4-76 + .809  rH O >>  O ^ •H d  i 'd i J-  'd  43  ^  "d  d  !>> I  W O O fn X! -P  fn  Xl-P  fn  +J  H  I >»  !  XIJ-PI  0)0  s  c  ?1  ?A  " ? §  J -  J-  J -  -.808 -.504-  -.858 -.568 -.979 + .091 -.289 -.686 + .4-02 + .016 -.385 + .722 + .332 -.094+ .652 + .220 -.214-  + .582  +1.000  -.917 -.680 -.4-25 -.160 + .116 + .613  75  TABLE V I I  Values o f l o g  [AOR~~]/[A]  f o r Lewis A c i d s  Not Used t o E s t a b l i s h t h e H - S c a l e i n D M S O - E t h a n o l R  Mole % DMSO i n Ethanol  o(-cyano-2-chloro4—nitrostilbene  15.54-  -1.025  20.09  -.607  25.09  -.250  30.09  + .135  35.07  + .500  4-0.16  + .913  l,l-bis-(4—nitrophenyl)ethene  59.62  -.798  64-. 59  -.4-04-  69.26  + .020  74-.15  + .4-98  79.11  +1.037  76  TABLE V I I I o f l o g j/f] / |AH]  Values  f o r Various  Carbon A c i d s  Used as I n d i c a t o r s t o E s t a b l i s h the H_  Scale  i n Sodium Methoxide-Methanol S o l u t i o n s  i © id - p CD cd fn O  O  Sodium Methoxide cone. , (moles l " ) 1  0.01 0.0240.056 0.115 0.229 0.4-60 0.4-6"+ 0.697 0.952 0.977 1.19 1.78 2.07 2.10 2.36 2.4-0 2.65 2.66 2.93 2.97 3.243.51  X*  m  H cd xi »  - p ON CD  a -.582 -.174+ .184+ .538 + .988  CD id  i  f-i  -p -p •H CD sd S •H H  H  >» N  a  f- id>? 1  ©  CD  -p  O  -H id  CD =1ja  fn  -p •H sd  cd  t>»  o  -  ©  cd .C  o  fH - P  1  fd  cd  i  id  - P  ©  O -p  >H jd  •H  •H  >>  -  cd o  c\j  -.782 -.4-15 + .14-1 + .4-21 + .74-8  •H  CD  id  xi  - P  0 © u a H  >5  id a 1  ©  ft >H  J-  -1.034-.681+  -.214+ .094+ .3H-3 + .706  -1.04-9 -.591 -.271 + .052 + .308 + .902  -1.070 -.74-4-.702 -.4-23 -.363 -.122 -.036 + .199 + .284+ .567 + .814-  77  T A B L E  Values of l o g  | A ] / [ A H ]  I X  f o r V a r i o u s Carbon A c i d s  S t u d i e d i n DMSO-Ethanol ©  ©  cd  © sd  ! O  -p  ^d  -p sd  a  0 ©  •H sd  -P rH •H >>  •H  •H  sd  i sd o cd fn ^d  H  >» N  © ©  Mole % DMSO i n Ethanol 0.97 1.81 3.4-1 5.88 10.72 15.77 21.11 25.4-5 30.63 35.56 H-0.20 H-5.27. 4-9.9454-.86 59.98 64-.98  fH  sd  a  fn  >»  •H rH  sd O  xi  •P -P •H ©  id  -H «  •P cd •H >» sd O  !  CM  -.354+ .052 + .4-05 + .780  -p sd 1 © = .sd  Jr ft ~  fH  <±-P UN  -.569 -.508 -.4-06 -.218 + .094+.376 +.654+.871  i ©  o  SH r-l •P t>>  sd © jd  ~  ft  I -H  (H  J " -P  -.752 -.4-27 -.180 +.116 +.363 +.612  cd  p  fn  a  sd sd  -  ©  1 ft -H  fH  ©  •H cd sd xi i -p  J-  1  ©  r-i  CO t>» •H sd  -Q ©  I Xi  H  ft  -.663 -.24-8  + .1+6 +.594+1.009  -.4-85 -.1+6  + .304-  + .760  78 RESULTS  A.  The H - F u n c t i o n R  The i o n i z a t i o n behavior o f i n d i c a t o r s which i o n i z e i n h i g h l y basic  systems by the a d d i t i o n o f base  to the u n s a t u r a t e d system, r a t h e r  than by an a b s t r a c t i o n  o f a p r o t o n by the base, w i l l not f o l l o w a H_ f u n c t i o n . Such i n d i c a t o r s w i l l  generate a separate a c i d i t y s c a l e ,  termed H ~ i n t h i s t h e s i s .  I f A i s an u n s a t u r a t e d Lewis  R  a c i d , then the a d d i t i o n e q u i l i b r i a between A and a Lewis base such as the methoxide or ethoxide i o n (OR ) can be formulated as i n e q u a t i o n equation  (5*+).  For analysis  sake,  (540 can be f a c t o r e d i n t o the two e q u i l i b r i a : A  +  0 R ~ ^ = ^ AOR~  HOR  H  +  +  (64-)  (65)  OR""  where K  (AOR"")  ,  _  =  (66)  (A)(OR )  and (H )(OR~) +  T?OH  K  Then i f K  .=  (67)  =  (HOR)  K U i l  K'K  R 0 H  ,  then IAOR"3  (AOR") ( H ) +  K  =  = (A) (HOR)  L  fAOR"  <  H +  >  (68)  A U K r l  [_Aj  f  (HOR)  79  From t h i s H - can be d e f i n e d as rl  HR-  (H =  )f  A 0 R  -log  *  =  ( H O R )  pK  +  f  & 0 R ] log-p^ |_Aj  (69)  where (H ) +  h R  B.  =  f/VOR-  (70) (H0R)f  A  E q u i l i b r i a S t u d i e s i n DMSO-Alcohol S o l u t i o n s In D M S O - a l c o h o l s o l u t i o n s containing 0 . 0 1 M  sodium a l k o x i d e , t h e r a t i o o f t h e i o n i z e d t o u n i o n i z e d indicator concentrations ( I =  [ 1 O R J / [ A ] ) was  measured as d e s c r i b e d i n the p r e v i o u s s e c t i o n .  After  p l o t t i n g l o g I , f o r each i n d i c a t o r , a s a f u n c t i o n o f t h e s o l v e n t c o m p o s i t i o n i n mole % drawn through -1.  D M S O ,  a smooth curve was  the p o i n t s f o r which l o g I was between 1 and  T h i s corresponded  t o u s i n g only that part o f the  i o n i z a t i o n curve f o r w h i c h t h e i n d i c a t o r was between 1 0 and 90$ i o n i z e d .  The p l o t s o f l o g I f o r the v a r i o u s  i n d i c a t o r s u s e d v e r s u s the s o l v e n t c o m p o s i t i o n i n mole %  D M S O  are given f o r D M S O - e t h a n o l i n Figure  DMSO-methanol i n Figure 2 . to  1,  and f o r  The numbers on the p l o t s r e f e r  those o f the i n d i c a t o r s l i s t e d i n Table X.  Using  Hammett's method ( 1 0 ) , pK v a l u e s were t h e n o b t a i n e d by a g r a p h i c a l technique.  F o r any two i n d i c a t o r s , i and j ,  F I G U R E  1.  P L O T S  O F  L O G  [AOR  J /  [A]  D M S O - E T H A N O L - S O D I U M  ' N U M B E R S  0  10  2 0  3 0  V E R S U S  E T H O X I D E  R E F E R  TO  M O L E  T H O S E  4 0  I N  5 0 M O L E  %  %  (O.OIM)  D M S O  D M S O A T  T A B L E S  X  6 0 I N  F O R  T H E  S Y S T E M :  25°  A N D  7 0 E T H A N O L  X I I I  8 0  9 0  82  w h i c h i o n i z e t o an a p p r e c i a b l e e x t e n t i n a g i v e n s o l v e n t , t h e A p K v a l u e i s g i v e n by the e x p r e s s i o n ApK  =  log I i  -  log I.  (71)  where 1^ and I j r e f e r t o the i o n i z a t i o n r a t i o s o f the two i n d i c a t o r s i n a s o l v e n t o f one p a r t i c u l a r  composition.  By i n t e r p o l a t i n g l o g I v a l u e s f o r i n d i c a t o r s i and j from F i g u r e s 1 and 2 a t r e g u l a r i n t e r v a l s o f s o l v e n t c o m p o s i t i o n , a number o f A p K v a l u e s were o b t a i n e d by u s i n g e q u a t i o n ( 7 1 ) .  These were t h e n averaged t o o b t a i n  the A p K v a l u e between i n d i c a t o r s i and j . S i n c e (X-cyanostilbenes a r e r e a d i l y h y d r o l y z e d i n b a s i c aqueous s o l u t i o n s , t h e pK o f no i n d i c a t o r be d e t e r m i n e d i n aqueous b u f f e r s o l u t i o n s .  Due t o t h i s  d i f f i c u l t y , an a r b i t r a r y pK v a l u e o f lk.k2 was t o the i n d i c a t o r  could  given  OC-cyano-M-jM-'-dinitrostilbene which  was t h e n u s e d as a s t a n d a r d t o w h i c h a l l o t h e r pK v a l u e s were r e f e r r e d .  The v a l u e o f 1.H-.M-2 was a r r i v e d a t by  assuming a H - v a l u e o f 1M-.00 f o r a 0.01M R  sodium e t h o x i d e  s o l u t i o n i n e t h a n o l , w h i c h i s the same as t h e H_ v a l u e r e p o r t e d by Bowden and S t e w a r t (51) were u s e d as i n d i c a t o r s .  when c a r b o n a c i d s  I t was reasoned t h a t the r i b -  and H_ v a l u e s s h o u l d be n e a r l y i d e n t i c a l i n d i l u t e b a s i c solutions.  Then by i n s e r t i n g the e x p e r i m e n t a l v a l u e o f  -0.M-2 f o r l o g I f o r C X - c y a n o - M - , ^ ' - d i n i t r o s t i l b e n e i n the above s o l u t i o n i n t o e q u a t i o n ( 6 9 ) ,  t h e pK v a l u e o f  1  8 3  14.4-2 was o b t a i n e d . The pK v a l u e s o f a number o f s u b s t i t u t e d  OC-cyano-  s t i l b e n e s were measured r e l a t i v e t o t h e a r b i t r a r y s t a n d a r d . The v a l u e s o b t a i n e d i n DMSO-ethanol and  DMSO-methanol  a r e l i s t e d i n Table X. By s u b s t i t u t i n g the pK v a l u e s from Table X and the experimental l o g I v a l u e s i n t o equation ( 6 9 ) , H j > - values were c a l c u l a t e d f o r the v a r i o u s DMSO-ethanol and DMSOmethanol s o l u t i o n s .  Due t o the o v e r l a p p i n g o f the  i o n i z a t i o n curves o f i n d i c a t o r s , s e v e r a l H R - v a l u e s were o f t e n obtained f o r a solvent of a p a r t i c u l a r  composition.  The averaged H R - v a l u e s f o r the DMSO-ethanol s o l v e n t system c o n t a i n i n g 0.01M sodium e t h o x i d e a r e l i s t e d i n Table XI and those f o r the DMSO-methanol  s o l v e n t system  c o n t a i n i n g 0.01M sodium methoxide a r e l i s t e d i n Table X I I . The g r a p h i c a l r e p r e s e n t a t i o n s o f how the H p _ - v a l u e s v a r y w i t h the s o l v e n t c o m p o s i t i o n s a r e g i v e n i n F i g u r e s 3 and 4- f o r DMSO-ethanol and DMSO-methanol  respectively.  The pK v a l u e s o f two i n d i c a t o r s , w h i c h were not u s e d t o e s t a b l i s h the H R - s c a l e , were measured i n t h e DMSO-ethanol system.  The pK v a l u e s were e s t i m a t e d t o be  e q u a l t o the v a l u e s o f H R - f o r t h e s o l u t i o n s i n w h i c h the i n d i c a t o r s were h a l f i o n i z e d . log  I versus H R - f o r the i n d i c a t o r  Because a p l o t o f o(-cyano-2-chloro-  4 — n i t r o s t i l b e n e d i d not g i v e a l i n e o f u n i t s l o p e , t h i s i n d i c a t o r was not u s e d t o e s t a b l i s h t h e H r > - s c a l e .  TABLE X pK V a l u e s o f o V - C y a n o s t i l b e n e s Used As I n d i c a t o r s t o E s t a b l i s h the E - S c a l e s i n the DMSO-Ethanol, DMSO-Methanol and R  Sodium Methoxide-Methanol Indicator  Substituent  Number  1 2 3 *+  5 6 7 8 9 10 11 12 13 14-  2,4—dinitro 4-, 4- ' d i n i t r o 3'-chloro-4— n i t r o 4—nitro 4- -me t h y l - 4 — n i t r o 4-' -methoxy-4— n i t r o 4— cyano-4- - n i t r o 4- -dimethylamino-4— n i t r o 4—eyano-3 -chloro 4—cyano 2-nitro 3-cyano-4— c h l o r o 3-cyano 3-trifluoromethyl 1  1  1  1  Systems  pK i n  pK i n  pK i n Sodium  DMSO-  DMSO-  Methoxide-  Ethanol  Methanol  Methanol  12.73 14- .4-2 15.08 15.81 16.17 16.59 17.38 17.97 18.13 19.08  12.96 14-. 4- 2 15.06 15.73 16.10 16.52  14-. 4-2  15.20 15.95 16.31 16.7k  17.38 18.07 18.23 19.20 20.11 20.34-  21.kh 21.98  20.02 20.23  21.20  21.54-  17.76  85  TABLE X I  H - V a l u e s f o r the DMSO-Ethanol System a t 2 5 ° R  C o n t a i n i n g 0.01M Sodium E t h o x i d e  Mole % DMSO  H «  0.98 1.99 3.51 5.63  14.00  R  14.05  14.21 14.38 14.78  10.82 15.54 20.09  15.13 15.45  25.09  15.79  16.14  30.09  16.48 16.84  35.07  40.16  17.20  45.22 50.27  17.57 17.92 18.29  55.03 59.62 64.59  18.68 19.06  69.26 74.15  19-50  20.01  79.11 84.12  20.52  21.12  89.17  21.74  93.27  a  Ave. Dev. from t h e Mean —  0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.01 0.03  0,01 0.02 0.01 0.05 0.03 0.03  0.02 0.04 0.03  Numbers r e f e r t o those i n TABLE X  Indicators  2 2 2, 3 2, 3 2 3 3 3 4 4  -4 - 5 - 6 - 6 -7 - 7  5 - 8 6 - 9  7 - 9  7-10 8-10 8-11 10 - 12 10 - 12 11 - 1 3 12 - 14 13, 14  a  86  TABLE X I I  H - V a l u e s f o r t h e DMSO-Methanol System a t 25° R  C o n t a i n i n g 0.01M Sodium Methoxide  .e % DMSO  0.00 0.68 2.32 5.39 8.75 15.30 20.60 25.5430.47 35.14 39.88 44.05 49.95 54.79 59.61 64.32 69.63 74.26 78.52 83.52 88.24 93.98 97.61  n  11.73 11.83 12.03 12.37 12.72 13.38 13.87 14.29 14.72 15.12 15.53 15.89 16.40 16.82 17.25 17.63 18.14 18.59 19.05 19.61 20.17 21.14 21.65  a  Ave. Dev. f r o m the Mean  0.03  0.01 0.02 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.05 0.03 0.01 0.03 0.02 0.09 0.17 0.27  Numbers r e f e r t o those i n TABLE X  Indicators  3 -  by e x t r a p o l a t i o n 1 1 1 1 1, 2 1, 2 2 , 3, 2 - 4 2 - 5 3 - ? 3 - 6 4 - 7 4 - 7 6 - 9 7 - 9 7 - 9 8-10 8-11 10 - 12 11 - 13 12 - 14 12 - 14  FIGURE 3.  H - VALUES FOR DMSO-ETHANOL SOLUTIONS CONTAINING R  O.OIM SODIUM ETHOXIDE  0  10  20  30  40  50  60  'MOLE % DMSO IN.ETHANOL  70  80  90  FIGURE >+.  H - VALUES FOR DMSO-METHANOL SOLUTIONS CONTAINING R  O.OIM SODIUM METHOXIDE  0  10  20  30  40  50  60  MOLE % DMSO IN METHANOL  70  80  90  100  89  I n t h e case o f l , l - b i s - ( 4 — n i t r o p h e n y l ) e t h e n e  ?  a plot of  l o g I v e r s u s H - gave a f a i r l y good s t r a i g h t l i n e o f near R  u n i t slope.  T h i s i n d i c a t o r was n o t u s e d t o e s t a b l i s h t h e  Hp_- s c a l e because i t was d e s i r a b l e  t o keep t h e i n d i c a t o r s  u s e d t o s e t up t h e s c a l e as s t r u c t u r a l l y s i m i l a r as p o s s i b l e . The pK v a l u e s f o r these two i n d i c a t o r s a r e l i s t e d i n Table X I I I .  TABLE X I I I pK V a l u e s o f I n d i c a t o r s  i n DMSO-Ethanol  Not Used t o E s t a b l i s h t h e H - F u n c t i o n R  Indicator Number  Indicator  Mole % DMSO-EtOH i n which half-ionized  pK i n DMSOEthanol  15  o(-cyano-2-chloro-Hnitrostilbene  28,4-0  16.06  16  l,l-bis~(H--nitrophenyl)ethene  69.05  19-08  90 C.  E q u i l i b r i a S t u d i e s i n Concentrated  Sodium Methoxide  Solutions Using the pK v a l u e of 14-.4-2 f o r cX-cyano- ^-, l- ,  L  ,  d i n i t r o s t i l b e n e as the standard, pK v a l u e s f o r a number of  s u b s t i t u t e d c X - c y a n o s t i l b e n e s were determined, as  d e s c r i b e d p r e v i o u s l y , i n concentrated sodium methoxide solutions.  The p l o t s of l o g I as a f u n c t i o n of the  methoxide i o n c o n c e n t r a t i o n f o r the v a r i o u s i n d i c a t o r s are g i v e n i n F i g u r e 5»  The pK v a l u e s f o r the  used to e s t a b l i s h the H -  s c a l e have been i n c l u d e d i n  R  Table  X. Using e q u a t i o n (69),  from the pK v a l u e s l i s t e d log  indicators  I values.  HR  v a l u e s were c a l c u l a t e d  i n Table X and  The averaged H R  the  experimental  v a l u e s f o r the v a r i o u s  c o n c e n t r a t i o n s of sodium methoxide i n methanol are listed  i n Table  XIV.  In order to compare the H R  scale with a  H_  s c a l e i n the same s o l v e n t system, the l a t t e r was u s i n g carbon a c i d s as i n d i c a t o r s . the pKjjAvalues was of  developed  The method of determining  the same as d e s c r i b e d above.  The  plots  l o g I as a f u n c t i o n of the methoxide i o n c o n c e n t r a t i o n s  are given i n Figure  6.  By u s i n g a p % ^  v a l u e of 12.88  f o r methyl  f l u o r e n e - 9 - c a r b o x y l a t e , as r e p o r t e d p r e v i o u s l y by Bowden and Stewart indicators  (51)  5  the p % £  were determined  v a l u e s of the other  by the g r a p h i c a l method and  F I G U R E  5.  P L O T S  S O D I U M  O F  LOG(AOR]/[A]  M E T H O X I D E  N U M B E R S  0  0.5  1.0  \5 S O D I U M  I N  V E R S U S  T H E  C O N C E N T R A T I O N  O F  M E T H A N O L  R E F E R  ZD M E T H O X I D E  TO  T H O S E  2.5 C O N C .  I N  3.0  T A B L E  X  3.5  ( M O L E S / L I T R E )  4.0  4.5  5-0  92  TABLE X I V  H - Values f o r the R  Sodium Methoxide-Methanol System a t 2 5 ° Sodium Methoxide -1 Cone, (moles 1~ )  0.01 0.0562 0.115 0.229 0.4-640.697 0.952 1.19 1.4-8 1.78 2.07 2.36 2.65 2.93 3.243.51 3.82 ^.08 "+.73  A v e . Dev. ^R"  12.12 12.87 13.23 13.59 14-. 06 14-.36 14-. 6414-. 91 15.23 15.53 15.83 16.13 16.4-416.75 17.12 17A3 17.60 17.88 18.37  a  f r o m t h e Mean  —  0.02 0.01 0.02 0.01 0.01 0.01 0.02 0.01 0.03 0.01 0.01 0.01 0.05 0.10 —  0.  Indicators  1 1 1, 1, 2, 2, 2,  2 2 3 3 3  2-4-  2 3 3 3  -5 - 6 - 6 - 6 4- - 6 5, 65, 6, 8 6, 8 8 8 8  Numbers r e f e r t o those i n TABLE X, page 84-  F I G U R E  6.  P L O T S T H E  O F  L O G  (A""] /  C O N C E N T R A T I O N  [AH) O F  F O R  C A R B O N  S O D I U M  A C I D S  M E T H O X I D E  V E R S U S I N  M E T H A N O L  0  0.5  1.0  1.5 S O D I U M  £0 M E T H O X I D E  2.5 C O N C .  3.0  3.5  ( M O L E S / L I T R E )  4.0  9h  a r e g i v e n i n Table XV. reported p%A  This table a l s o includes previously  v a l u e s where found i n the  literature.  TABLE XV P HA K  V a  -lu  e s  of I n d i c a t o r s  Used t o E s t a b l i s h the H_  Scale  i n the Sodium Methoxide-Methanol System  Indicator Number  L i t . value P%A  Indicator  P%A  1  methyl f l u o r e n e 9-carboxylate  12.88  2  4-nitrobenzyl cyanide  14-.24-  3  4-,4-> , 4 - " - t r i n i t r o - •  a  14-.56  12.88  (5D  4-8)  13-4-5 (4-5,  14-.32 ( 5 D  triphenylmethane 4-  2-nitrobenzyl cyanide  14-. 94-  5  4-,4-'-dinitrodiphenyImethane  16.89  a  15.85  (5D  S t a r t i n g v a l u e t a k e n from r e f e r e n c e  U s i n g the pK-^  v a l u e s l i s t e d i n T a b l e XV  (51)  and  t h e e x p e r i m e n t a l l o g I v a l u e s , H__ v a l u e s were c a l c u l a t e d , u s i n g e q u a t i o n ( 3 0 ) , f o r the v a r i o u s c o n c e n t r a t i o n s o f sodium methoxide i n methanol.  The average H__ v a l u e s  95  are g i v e n i n Table XVI.  For e a s i e r comparison,  g r a p h i c a l r e p r e s e n t a t i o n s of the Hp_- and H_  s c a l e s are  both p l o t t e d i n F i g u r e 7 as a f u n c t i o n of the of  ^*  the  concentration  sodium methoxide i n methanol.  I o n i z a t i o n Behavior  of Carbon A c i d s i n DMSO-Ethanol  Solutions Because of some l a r g e d i s c r e p a n c i e s i n the determined p K ^ found  v a l u e s l i s t e d i n Table XV w i t h  i n the l i t e r a t u r e , a check on the pKj-j^ and  v a l u e s i n DMSO-ethanol s o l u t i o n s c o n t a i n i n g sodium ethoxide was for  those  attempted.  The  H_  0.01M  i n d i c a t o r s used  t h i s study are l i s t e d i n Table XVII  -  While the  i o n i z a t i o n data f o r the i n d i c a t o r s , r e p o r t e d as l o g I v a l u e s f o r the v a r i o u s DMSO-ethanol s o l v e n t  compositions,  are l i s t e d i n Table IX, the g r a p h i c a l r e p r e s e n t a t i o n i s shown i n F i g u r e 8.  Because of the n o n - p a r a i l e d slopes of  the i o n i z a t i o n curves f o r the v a r i o u s i n d i c a t o r s , n e i t h e r the p % £  v a l u e s f o r the i n d i c a t o r s nor the H__ values  the medium c o u l d be c a l c u l a t e d w i t h any degree of certainty.  of  96  TABLE X V I  H_ V a l u e s f o r t h e Sodium Methoxide-Methanol System a t 2 5 °  Sodium Methoxide T Cone, (moles 1 " ' )  H_  A v e . Dev. from t h e Mean  Indicators  0.01 0.0240.0562 0.115 0.229  12.26 12.71 13.06 13.44 13.86  0.02 0.04-  0.4-60 0.4-64-  14-.35 14-.36  0.02  3 2,  0.01 0.0 0.01 0.01 -  2 - 4 2, 4 3 3, 4 4, 5 5 5 5 5 5 5 5 5 5 5 5  14.66 14-.99 14-.9 0 15.26 15.83 16.15 16.19 16.47 16.53 16.77 16.85 17.09 17.17 17.46 17.70 18.18  0.697 0.952 0.977 1 . 1 9  1.78 2.07 2.x0 2.36 2 . 4 0  2.65 2.66 2.93 2.97 3 . 2 4  3.51 4.01  a  1 1 1 1 ,  Numbers r e f e r t o those i n TABLE XV  2 1 - 4 4  FIGURE 7 .  0.5  H - AND H_ VALUES FOR CONCENTRATED SODIUM METHOXIDE SOLUTIONS R  1.0  1.5  2.0  2.5  3.0  3.5  SODIUM METHOXIDE CONC. (MOLES/LITRE)  4J0  4.5  5J0  9 9  TABLE X V I I I n d i c a t o r s Used i n a n Attempt To E s t a b l i s h a H_ S c a l e i n DMSO-Ethanol  Indicator Number 1 2  Indicator 2 - n i t r o b e n z y l cyanide 4-,4-',4-""trinitrotriphenylmethane  3  4-,4-'  4-  4 - , 4 - - d i n i t r o d i p h e n y l m e thane  5  E.  -dinitrotriphenylmethane  5  1,1-bis-(4—nitrophenyl)ethane  Estimate of E r r o r I n any d e t e r m i n a t i o n o f pK and H v a l u e s by t h e  Hammett o v e r l a p method ( 1 0 ) , e s t i m a t e the a b s o l u t e e r r o r .  i t i s very d i f f i c u l t to E r r o r s i n pK v a l u e s f o r  two o v e r l a p p i n g i n d i c a t o r s a r e u s u a l l y i n the o r d e r o f +0.02 t o + 0 . 0 5 .  But s i n c e these e r r o r s may accumulate  on going from t h e most' a c i d i c t o the l e a s t a c i d i c  indicators,  i t i s d i f f i c u l t t o e s t i m a t e t h e e r r o r i n pK f o r t h e l e s s acidic indicators.  F o r these i t i s e s t i m a t e d t h a t t h e ...  e r r o r i n pK i s i n the o r d e r o f +0.2 t o +0.3•  Thus,  a l t h o u g h the p'K v a l u e s a r e l i s t e d t o two f i g u r e s , t h e second s i g n i f i c a n t f i g u r e i s meaningless  u n l e s s the  100  pK v a l u e s o f two o v e r l a p p i n g i n d i c a t o r s a r e compared. accumulation  The  o f e r r o r s i n pK and H v a l u e s c a n be m i n i m i z e d  by u s i n g a l a r g e number o f i n d i c a t o r s so t h a t a l a r g e number o f p o i n t s o f o v e r l a p may be o b t a i n e d .  This  r e d u c e s t h e dependence o f t h e v a l u e o f H on any one indicator.  As can be seen from Tables X I , X I I , and  XIV, H - v a l u e s f o r one s o l u t i o n have been c a l c u l a t e d R  f r o m as many as f o u r i n d i c a t o r s .  The s i t u a t i o n was n o t  as f o r t u n a t e i n t h e c a l c u l a t i o n o f t h e H_ v a l u e s .  Thus  the e r r o r i n t h e H__ v a l u e s i s l i k e l y g r e a t e r t h a n t h a t i n t h e HR- v a l u e s .  F.  K i n e t i c s o f t h e Base C a t a l y z e d C i s - t r a n s I s o m e r i z a t i o n o f S u b s t i t u t e d Q ( - C y a n o - c i s ~ s t i l b e n e s i n DMSO-Alcohol Solutions The k i n e t i c s o f t h e base c a t a l y z e d i s o m e r i z a t i o n  o f a number o f s u b s t i t u t e d 0 ( . - c y a n o - c i s - s t i l b e n e s was s t u d i e d i n t h e DMSO-ethanol and DMSO-methanol s o l v e n t systems.  S i n c e i n a l l cases t h e O C - e y a n o - t r a n s - s t i l b e n e s  a b s o r b a t a h i g h e r w a v e l e n g t h and have a l a r g e r molar e x t i n c t i o n c o e f f i c i e n t t h a n the c i s - i s o m e r s , f o l l o w i n g t h e change i n absorbance a t the w a v e l e n g t h o f maximum a b s o r p t i o n o f t h e t r a n s - i s o m e r was a c o n v e n i e n t way o f f o l l o w i n g t h e kinetics.  Because a p p r o x i m a t e l y  1000 f o l d excess  was u s e d , f i r s t o r d e r p l o t s o f l o g (AQO -  base  A ) / ( A o o - A-)-) Q  101  versus first  t h e t i m e gave good s t r a i g h t l i n e s w i t h t h e a p p a r e n t order  rate constant  being  equal  t o 2.3026 t i m e s t h e  slope.  A r e p r e s e n t a t i v e p l o t i s shown i n F i g u r e  clearly  shows t h a t t h e r e a c t i o n i s f i r s t  order  9»  This  i n the  (X-cyano-cis-stilbene. In order with respect  t o e s t a b l i s h the order  of the reaction  t o t h e base, t h e i s o m e r i z a t i o n o f CX-cyano-  e i s - 4 - ~ n i t r o s t i l b e n e was s t u d i e d i n m e t h a n o l u s i n g amounts o f b a s e . order The  Table XVIII  rate constants  second order  dividing  the apparent f i r s t  c o n c e n t r a t i o n o f t h e base. rate constants  order  i n base. The  k  2  order  first  concentration.  was c a l c u l a t e d b y rate constant  by t h e  The c o n s t a n c y o f t h e s e  second  indicates that the r e a c t i o n i s f i r s t  extent  goes t o c o m p l e t i o n  theapparent  as a f u n c t i o n o f t h e base  rate constant  order  gives  various  t o which the c i s t o trans  isomerization  was c h e c k e d b y means o f t h e UV s p e c t r a .  I n t h e case o f c ^ - c y a n o - H — n i t r o s t i l b e n e ,  the trans-isomer  a m o l a r e x t i n c t i o n c o e f f i c i e n t o f 2 . 7 H - x 10"* a t  has  335 ma.  Using  a s o l u t i o n i n which the concentration  -5 c i s - i s o m e r was 2.97 x 10  of the  -1 moles 1  , t h e absorbance a t  335 mu. a t t h e e n d o f t h e r e a c t i o n was 0.805 r e s u l t i n g i n an  extinction coefficient  k i n e t i c run,  end  x 10  J  I n another  t h e c o n c e n t r a t i o n o f t h e c i s - i s o m e r was  -5 2.91  o f 2 . 7 1 x 10 .  1 moles 1  .  The a b s o r b a n c e a t 335 m ^ a t t h e  o f t h e r e a c t i o n was 0.792 r e s u l t i n g  i n an extinction  .102 FIGURE 9.  K I N E T I C S OF THE BASE CATALYZED ISOMERIZATION OF CX-CYANO-  TIME  (MIN.)  103  TABLE X V I I I K i n e t i c s o f the Base C a t a l y z e d  Isomerization  0 C - c y a n o - c i s - 4 — n i t r o s t i l b e n e i n Methanol a t 2 5  of  Sodium Methoxide Cone, (moles 1~ ) -  k  kjmin  2  1 moles  0.00548  0.138  25.2  0.0107  0.263  24.5  0.0212  0.504  23.8  0.0412  0.962  23.3  c o e f f i c i e n t o f 2.72 x 10^.  p  min  I n these c a s e s , a comparison o f  the two e x t i n c t i o n c o e f f i c i e n t s a t the end o f the r e a c t i o n s 4  (2.71 for  x 10  and 2.72 x 104) w i t h the e x t i n c t i o n c o e f f i c i e n t  0(-cyano-trans-4-nitrostilbene  (2.74 x 10^) i n d i c a t e s  t h a t t h e s e i s o m e r i z a t i o n r e a c t i o n s went e s s e n t i a l l y t o completion. . When the changes i n UV s p e c t r a o f t h e r e a c t i o n s were f o l l o w e d as a f u n c t i o n o f t i m e , v e r y good i s o b e s t i e p o i n t s were o b s e r v e d .  T h i s shows t h a t no s u b s t a n t i a l  s i d e r e a c t i o n s o c c u r i n these i s o m e r i z a t i o n r e a c t i o n s . S i n c e the k i n e t i c s t u d y was u n d e r t a k e n t o determine the r e l a t i o n s h i p between the r a t e s and t h e E-o-  f u n c t i o n , the r a t e s o f the base c a t a l y z e d  isomerization  1 0 4  of various a t 25°  substituted 0(-cyano-cis-stilbenes  i n the D M S O - e t h a n o l and  DMSO-methanol  systems c o n t a i n i n g the a p p r o p r i a t e as base.  Table XIX  contains  were  0.01M  solvent  sodium a l k o x i d e  the l o g a r i t h m s  apparent f i r s t order r a t e constants,  studied  of  the  l o g k-j_, f o r  the  i s o m e r i z a t i o n i n the D M S O - e t h a n o l s o l v e n t system.  DMSO-methanol  a n a l o g o u s r a t e data f o r the i s o m e r i z a t i o n i n the solvent  system a r e c o n t a i n e d  representations  i n Table XX.  f o r the D M S O - e t h a n o l and  1 1  systems r e s p e c t i v e l y . versus H -  The  i n the  are g i v e n i n F i g u r e s  R  and  graphical  o f the d a t a i n T a b l e s XIX and XX  f o r m of p l o t s of l o g k-^ v e r s u s H 1 0  The  The  DMSO-methanol  solvent  s l o p e s of the p l o t s o f l o g k]_  were d e t e r m i n e d by a l e a s t square a n a l y s i s .  R  These s l o p e s , as w e l l as the c o r r e l a t i o n c o e f f i c i e n t r and  the  s t a n d a r d d e v i a t i o n of the s l o p e S p are  i n Table XXI  f o r the two  solvent  contained  systems.  I n an a t t e m p t t o g a i n f u r t h e r i n s i g h t i n t o  the  i s o m e r i z a t i o n mechanism, a s t u d y of the e f f e c t o f a change i n temperature on the r a t e was c i s - s t i l b e n e and  c a r r i e d out.  cX-cyano-cis-3-chlorostilbene,  of i s o m e r i z a t i o n i n  4 1 . 1 2  mole %  D M S O  45°.  mole %  D M S O  rates containing  temperatures  Using CX-cyano-cis-stilbene  cis-4-methoxystilbene,  the  i n methanol  0 . 0 1 M sodium methoxide were s t u d i e d a t f i v e between 1 0 and  U s i n g CX-cyano-  and  the r a t e of i s o m e r i z a t i o n i n  i n methanol c o n t a i n i n g  0 . 0 1 M  oC-cyano64.21  sodium methoxide  105  TABLE X I X  V a l u e s o f l o g k-^ f o r t h e Base Isomerization of Substituted i n DMSO-Ethanol C o n t a i n i n g  %  0.98 1.99 3.51 5.63 10.82 15.9+  20.09 25.09 30.09 35.07 4-0.16 4-5.22 50.27 55.03 59.62. 6i+. 59 69.26 7+-.15 79.11 84-. 12 89.17  cX-Cyano-cis-stilbenes  0.01M Sodium E t h o x i d e  a t 25°  Substituent  Mole DMSO-EtOH  Catalyzed  ER 14-. 00 14-.05 14-.21 14-.38 14-.78 15.13 15.+5 15.79 16.1416.1+8  16.84I7.2.O 17.57 17.92 18.29 1.8.68 19.06 19.50 20.01 20.52 21.12  4 ~ N 0  2  0.029 0.14-1 0.212 0.395  3-NO;  -0.914-0.852 -0.810 -0.724-0.501 -0.330 -0.198  3-ci  -1.878 -1.783 -1.560 -1.377 -1.169 -O.986 -O.718  -O.1+86  -O.307  4-ci  -2.115 -1.924-1.730 -1.538 -1.339 -1.126 -0,875 -0.686 -0.4-4-2 -O.236  H  -2.182 -1.963 -1.739 -1.507 -1.286 -1.030 -0.771 -0.608 -0.307  4--OCR3  -2.063 -1.800 -1.612 -1.398 -1.100 -0.853 -0.551 -0.226 +0..114+0.558  106  TABLE XX  V a l u e s o f l o g k]_ f o r the Base C a t a l y z e d Isomerization of Substituted  CX-Cyano-cis-stilbenes  I n DMSO-Methanol C o n t a i n i n g 0.01M Sodium Methoxide a t 25°  Mole  %  DMSO-Me OH  0.68 2.32 5.39 8.75 15.30 20.60 25.5+ 30.H-7 35.1M39-88 44.05 49.95 54.79 59.61 64.32 69.63 74.26 78.52 83.52 88.24  Substituent H R  11.83 12.03 12.37 12.72 13.38 13.87 14.29 14.72 15.12 15.53 15.89 16.40 16.82 17.25 17.63 18.14 18.59 19.05 19.61 20.17  4~N0  3~N0  -0.551 -0.492 -O.343 -0.202 +0.076 +0.318  -1.495 -1.422 -1.266 -1.147 -0.835 -0.591 -0.380 -0.093  2  2  3-C1  -1.981 -1.726 -1.430 -1.197 -0.957 -0.724 -0.490 -0.279  4-C1  -1.818 -1.591 -1.3+7 -1.158 -O.898 -0.682 -0.394 -O.117  H  -1.913 -1.662 -I.486 -1.136 -O.918 -0.673 -0.402 -0.121  H-OCH3  -1.993 -I.742 -1.490 -1.227 -O.906 -O.63O -0.37+ +0.035 +0.427  107 FIGURE 1 0 .  PLOTS OF LOG k  ±  VERSUS H R  FOR  THE ISOMERIZATION OF SUBSTITUTED CX-CYANO-CIS-STILBENES IN DMSOETHANOL CONTAINING 0 . 0 1 M SODIUM ETHOXIDE AT 25° 4-0 C H 0.6 0.4 0.2  0 -0.2 -0.4 -0.6  LOG  kj  -0.8 -1.0 -1.2 -1.4 -1.6 -1.8 -2.0 -2.2  4-N0  2  3  108  FIGURE 1 1 .  PLOTS OF LOG k  ±  VERSUS H R - FOR  THE ISOMERIZATION OF SUBSTITUTED CX-CYANO-CIS-STILBENES IN DMSOMETHANOL CONTAINING 0.01M SODIUM METHOXIDE AT 2 5 ° 4-0CH  LOG  k,  3  —  109  TABLE X X I  Correlation  of l o g  with H R  f o r t h e Base C a t a l y z e d I s o m e r i z a t i o n o f Substituted  Substituent  Slope =  CX-Cyano-cis-stilbenes a t 2 5 ° d(log k ) a  d(H -) R  S t a n d a r d Dev. o f the Slope  Correlation Coefficient r  DMSO-Ethanol 4~nitro 3-nitro 3- chloro 4~ c h l o r o hydrogen 4 - methoxy  0.464 0.494 0.607 0.602  0.646 0.665  0.058 0.013 0.011 0.008 0.008 0.006  0.9954 0.9984 0.9989 0.9992 0.9994 0.9999  0.009  O.9989 0.9972 0.9986 0.9994 0.9994 0.9994  DMSO-Methanol 4-nitro 3-nitro 3- chloro 4- c h I o r o hydrogen 4-methoxy  0.426 0.475 0.549 0.574 0.595 O.638  0.0140.012 0.008 0.007 0.007  110  were s t u d i e d a t f i v e t e m p e r a t u r e s between 10 and k5°. (113)  By employing t h e d e n s i t y measurements o f L i n d b e r g a t v a r i o u s temperatures,  t h e c o n c e n t r a t i o n o f the  methoxide i o n was c o r r e c t e d f o r t h e e x p a n s i o n t i o n of the s o l u t i o n .  or contrac-  U s i n g these temperature c o r r e c t e d  c o n c e n t r a t i o n s o f methoxide i o n , second o r d e r r a t e c o n s t a n t s were c a l c u l a t e d .  The a p p r o p r i a t e r a t e data  a r e c o n t a i n e d i n Table X X I I and t h e p l o t s o f l o g k  2  v e r s u s 1/T°K a r e shown i n F i g u r e 1 2 . A l e a s t square a n a l y s i s of the p l o t s of l o g k slopes.  2  v e r s u s 1/T°K gave t h e  With these, the energies o f a c t i v a t i o n E  were c a l c u l a t e d u s i n g t h e r e l a t i o n E  "+.576  =  a  x  a  (11H-)  slope  (72)  The e n t h a l p i e s o f a c t i v a t i o n A H * were t h e n d e t e r m i n e d u s i n g the  e q u a t i o n (UH-) A  =  H *  E  a  -  (73)  RT  where R i s t h e gas c o n s t a n t and T i s t h e a b s o l u t e temperature. equation  Then by u s i n g t h e t r a n s i t i o n s t a t e t h e o r y  (11M-) (  k  =  KT h  e  A H * )  RT  A S *  e  R  (7H-)  Ill TABLE XXII Rate-temperature Data for the  Base-Catalyzed  Isomerization of Substituted CX-Cyano-cisStilbenes i n DMSO-Methanol  Substituent Mole % DMSO  Temp.°K k ( l moles" 2  1  secT ) log k 1  2  3-chloro  4-1.12  284.26 291.59 298.10 308.34 317.39  0.158 0.308 0.540 1.226 2.522  -0.800 -0.511 -0.268 +0.088 +0.402  hydrogen  41.12  284.34 291.56 298.21 308.37 317.42  0.00924 0.0201 0.0358 0.0894 0.204  -2.034 -I.696 -1.447 -1.048 -0.691  hydrogen  64.21  284.26 291.58 298.10 308.34 317.41  0.164 0.323 0.571 1.310 2.770  -0.784 -0.491 -0.244+0.117 +0.4-42  4-methoxy  64.21  284.34 291.60 298.19 308.36 317.41  0.0208 0.0454 0.0861 0.220 0.511  -1.682 -1.353 -1.065 -0.657 -0.291  FIGURE 1 2 .  PLOTS OF LOG k  2  VERSUS 1/T°K FOR THE BASE CATALYZED  ISOMERIZATION OF CX-CYANO-CIS-STILBENES IN  3.14  3.18  3.22  3.26  3.30 . 10  3-3 4 3  x 1/T°K  3.38  3.42  3-46  3.50  113  where:  K i s t h e Boltzmann  constant,  h i s P l a n c k ' s c o n s t a n t , and T i s the absolute temperature, the e n t r o p i e s o f a c t i v a t i o n A s * were c a l c u l a t e d , f o r T e q u a l t o 298°K.  The a c t i v a t i o n parameters a r e summarized  i n Table X X I I I .  TABLE X X I I I A c t i v a t i o n Parameters f o r t h e Base Isomerization of Substituted  Catalyzed  <X-Cyano-cis-stilbenes  i n DMSO-Methanol  Substituent  Mole % DMSO  E  A  AH*  (kcal. —1  moles" )  (kcal.  As*  —1  moles" ) (e.u.)  3-chloro  1+1.12  1H-.93 + 0.05  1+.3+  -13.7  hydrogen  1+1,12  16.59 + 0.25  16.00  -13.5  hydrogen  6"+.21  15.21 + 0.0H-  l*+.6l  -12.6  l+-methoxy  6+.21  17.32 + 0.09  16.72  - 9.3  114  G.  The R e a c t i o n o f o(-Cyano- C<' - m e t h o x y - c i s - and t r a n s s t i l b e n e s i n DMSO-Methanol S o l u t i o n s I n o r d e r t o e s t a b l i s h t h a t t h e base c a t a l y z e d  i s o m e r i z a t i o n o f the o ( - c y a n o - e i s - s t i l b e n e s d i d not take p l a c e by p r o t o n r e m o v a l , t h e two i s o m e r s o f Q^-cyano- CX'methoxy-stilbene was  were p r e p a r e d .  A preliminary  study  c a r r i e d o u t on t h e i s o m e r i z a t i o n o f t h e lower m e l t i n g  i s o m e r , t a k e n t o be t h e c i s - s t i l b e n e .  I n 7 4 . 2 6 mole %  DMSO i n methanol, t h e l o w e r m e l t i n g isomer had a maximum a b s o r p t i o n a t 2 9 0 mp.  When sodium methoxide was added  t o the s o l u t i o n , t h e w a v e l e n g t h o f maximum a b s o r p t i o n changed g r a d u a l l y t o 2 8 7 m^ and t h e absorbance i n c r e a s e d somewhat.  On the o t h e r hand, i n 7 4 . 2 6 mole % DMSO i n  methanol, t h e h i g h e r m e l t i n g isomer had a maximum a b s o r p t i o n a t 2 8 6 ima..  When sodium methoxide was added t o  t h i s , t h e w a v e l e n g t h o f maximum a b s o r p t i o n s h i f t e d t o 2 8 7 m|A. and t h e absorbance dropped somewhat.  H.  The R e a c t i o n o f l , l - b i s - ( 4 - n i t r o p h e n y l ) e t h e n e i n H i g h l y B a s i c Systems The  e l e c t r o n i c spectra o f 1 , 1 - b i s - ( 4 - n i t r o p h e n y l ) -  ethene i n DMSO-methanol has a n a b s o r p t i o n maximum a t 3 0 6 m|m.  When enough sodium methoxide s o l u t i o n was added  t o make a 0 . 0 1 M s o l u t i o n , t h e absorbance a t 3 0 6 mjA d e c r e a s e d and a peak w i t h a maximum a b s o r p t i o n a t 7 1 0 mU  115  was  formed.  On making t h e s o l u t i o n a c i d i c by t h e a d d i t i o n  o f a c e t i c a c i d , t h e a b s o r p t i o n a t 710 mjoi d i s a p p e a r e d  with  the peak i n the r e g i o n o f 282 t o 306 mjU r e a p p e a r i n g , t h e e x a c t l o c a t i o n o f t h e l a t t e r depended on t h e mole % DMSO used.  As t h e c o n c e n t r a t i o n o f DMSO was i n c r e a s e d f r o m 60  t o 90 mole %, t h e w a v e l e n g t h o f maximum a b s o r p t i o n o f t h e s p e c i e s formed when t h e r e a c t i o n was quenched w i t h a c e t i c a c i d d e c r e a s e d from 299 m^w. t o 282 m^u. w i t h a f a i r l y good i s o b e s t i c p o i n t a t 294- rn^u.  I.  The R e a c t i o n o f U-,4-'-Dinitrobenzophenone i n H i g h l y B a s i c Systems When tetramethylammonium h y d r o x i d e was added  t o a s o l u t i o n o f 4-,4- - d i n i t r o b e n z o p h e n o n e  i n DMSO, a n  1  a b s o r p t i o n peak w i t h a maximum a t 4-34- nyx d e v e l o p e d v e r y quickly.  When a c e t i c a c i d was added, t h i s peak  virtually  instantaneously.  disappeared  I t was a l s o found t h a t t h e a n i o n o f 4 — n i t r o p h e n o l had a maximum a b s o r p t i o n a t 4-34- m|t i n DMSO w i t h a molar 4e x t i n c t i o n c o e f f i c i e n t o f 3»3°> x 10 . S i n c e t h e c o n c e n t r a t i o n o f 4-,4-'-dinitrobenzophenone was 2 . 8 8 x 1 0 " ^ moles l ™ , 1  i f one mole o f p - n i t r o p h e n o l a t e  i o n was produced per' mole  o f 4 - , 4 - ' - d i n i t r o b e n z o p h e n o n e , t h e n the expected a t 4-34- mjuiwould be 0 . 9 7 3 '  absorbance  S i n c e t h e o b s e r v e d absorbance  a t 4-34- m^t was 0 . 9 0 0 , t h e r a t i o o f the o b s e r v e d t o t h e c a l c u l a t e d absorbances was 0 . 9 0 0 / 0 . 9 7 3  =  O.925.  116  I t was  a l s o n o t e d t h a t a t lower c o n c e n t r a t i o n s  i n w a t e r , the r a t e of i n c r e a s e  of DMSO  i n the absorbance a t  mu o c c u r r e d a t a measurable r a t e .  H-3H-  11?  DISCUSSION  A.  The V a l i d i t y o f the H R  The Hp_- f u n c t i o n  Function has been d e v e l o p e d to. d e s c r i b e  the b a s i c i t y o f a s o l u t i o n i n w h i c h the base adds t o a n u n s a t u r a t e d system t o form the n e g a t i v e l y  charged  The c x > c y a n o s t i l b e n e system o f i n d i c a t o r s was an a p p r o p r i a t e  species.  chosen as  system t o s t u d y such an e q u i l i b r i u m  a d d i t i o n o f base.  This e q u i l i b r i u m i s described  i n the  equation  (75)  That the e q u i l i b r i u m s t u d i e d was t h a t i n e q u a t i o n (75)  is fairly  certain.  described  There a r e s e v e r a l  o t h e r p o s s i b l e methods o f i o n i z a t i o n w h i c h w i l l now  be  discussed. Instead  o f i o n i z i n g by an e q u i l i b r i u m a d d i t i o n  o f the Lewis base a p r o t o n might be a b s t r a c t e d base.  NC  by the  Then the e q u i l i b r i u m  \=/  HOR  NC  (76)  XVIII would g i v e r i s e t o a H_ f u n c t i o n .  That such an i o n i z a t i o n  118  i s p o s s i b l e i n the case o f s t i l b e n e s was and Cram (81)  shown by Hunter  by d e u t e r i u m exchange s t u d i e s .  By u s i n g  p o t a s s i u m t - b u t o x i d e i n t - b u t a n o l they showed the h a l f l i f e f o r the d e u t e r i u m exchange a t 116° 100 h o u r s .  t o be a p p r o x i m a t e l y  T h i s , shows t h a t the d e u t e r i u m exchange i s v e r y  slow and t h a t the e q u i l i b r i u m , as e x p r e s s e d i n e q u a t i o n (76), must be f a r t o the l e f t .  In a d d i t i o n , Z i n n et a l  (115)  were a b l e t o show t h a t w h i l e e t h y l  ethyl  ^3-phenyleinnamate,  c h a l c o n e and  cinnamate,  trans-cinnamonitrile  underwent d e u t e r i u m exchange a t the 0( - p o s i t i o n i n d e u t e r i o e t h a n o l w i t h c a t a l y t i c amounts o f sodium e t h o x i d e , e t h y l CX-phenylcinnamate exchange a t a l l .  d i d not undergo any  deuterium  These two p i e c e s o f e v i d e n c e  strongly  suggest t h a t the i o n i z a t i o n does not i n v o l v e the removal o f the p r o t o n from the ^ - c a r b o n t o a s i g n i f i c a n t e x t e n t . S p e c t r a l e v i d e n c e i s a l s o i n s u p p o r t of the i o n i z a t i o n by e q u a t i o n (75)  r a t h e r t h a n by e q u a t i o n  (76).  I t would be e x p e c t e d t h a t the e l e c t r o n i c s p e c t r a o f the a n i o n s XIX and XX would be v e r y s i m i l a r .  XIX  I n f a c t the  XX  e l e c t r o n i c s p e c t r a o f XIX has a maximum a t 5+8 m u i n DMSO-  119  methanol and XX has  a maximum a t 540 mjj. i n 95 mole %  s u l f o l a n e i n water (116) w i t h the g e n e r a l s p e c t r a b e i n g s i m i l a r as w e l l .  shape of  Such a c l o s e  similarity  would not be e x p e c t e d f o r the e l e c t r o n i c s p e c t r a s t r u c t u r e s X V I I I and The  the  of  XX.  e f f e c t of s u b s t i t u e n t s on the  equilibrium  (vide i n f r a ) a l s o s t r o n g l y supports alkoxide  addition  r a t h e r than proton removal. Another e q u i l i b r i u m w h i c h i s p o s s i b l e i n b a s i c s o l u t i o n s i s the p r o t o n removal from the a l c o h o l a d d i t i o n product.  CytAV^ ^-^NC  •  H  OK  J4--2M NC  H\=/  +  HOR  ( 7 7  ,  T h i s e q u i l i b r i u m i s always p o s s i b l e f o r a l l the i n d i c a t o r s u s e d t o e s t a b l i s h the H R  s c a l e ; b u t , whether i t i s  i m p o r t a n t or not depends on the r e l a t i v e pK v a l u e s f o r equilibria  (75) and  (77)•  I f 4—nitrobenzyl  cyanide-can  be t a k e n as a model compound f o r the r e a c t i o n shown i n e q u a t i o n (77)?  t h e n we  can o b t a i n some i d e a as t o  r e l a t i v e pK v a l u e s f o r the two  processes.  the  The pKjj^  v a l u e most o f t e n quoted f o r 4 — n i t r o b e n z y l c y a n i d e i s 13.4-5 ( 4 5  5  48).  T h i s v a l u e can be t a k e n as a rough  e s t i m a t e even i f the i o n i z a t i o n b e h a v i o r of 4 - n i t r o b e n z y l  120  c y a n i d e I s i n doubt (116).  The e s t i m a t e d pK v a l u e  f o r the  a d d i t i o n of ethoxide i o n to oC-cyano~ +-nitrostilbene i s !  15.95  i n DMSO-ethanol.  A t a H R - v a l u e o f 1H-.95, the r a t i o  o f the i o n i z e d t o u n i o n i z e d forms o f O C - c y a n o - H — n i t r o s t i l b e n e w o u l d be 0.10.  T h i s i s a p p r o x i m a t e l y the lower l i m i t o f  p o s s i b l e measurements.  I f the H R - and H_ v a l u e s a r e  a p p r o x i m a t e l y e q u i v a l e n t i n t h i s r e g i o n , M— n i t r o b e n z y l c y a n i d e w o u l d be 97%° i o n i z e d .  This i n d i c a t e s that only  a s m a l l amount o f the a l c o h o l adduct was p r e s e n t a t any t i m e and t h a t the e q u i l i b r i u m measured was r e a l l y t h a t i n equation  (75). S p e c t r a l e v i d e n c e a l s o s u p p o r t s the above  argument.  The a l c o h o l adduct does not a b s o r b t o a n  a p p r e c i a b l e e x t e n t i n the r e g i o n where the oC-cyanos t i l b e n e absorbs.  Thus i f e q u a t i o n (77) made a n a p p r e c i -  a b l e c o n t r i b u t i o n t o the o v e r a l l e q u i l i b r i u m , no i s o b e s t i c p o i n t would be o b s e r v a b l e .  The f a c t t h a t a r e a s o n a b l e  i s o b e s t i c p o i n t was o b t a i n e d a g a i n i n d i c a t e s t h a t the r e a c t i o n shown i n e q u a t i o n (77) a b l e c o n t r i b u t i o n t o the o v e r a l l  does not make an a p p r e c i equilibrium.  The use o f the Hammett p o s t u l a t e (9» 10) t o e s t a b l i s h an a c i d i t y s c a l e H ~ u s i n g a s e r i e s o f R  s t r u c t u r a l l y s i m i l a r i n d i c a t o r s seems t o be  justified.  The Hammett p o s t u l a t e (9? 10) s t i p u l a t e s t h a t the v a l u e o f ( l o g Ij_ - l o g Is)  be c o n s t a n t f o r two o v e r l a p p i n g  121  I n d i c a t o r s when measured i n the same s o l u t i o n .  This  i m p l i e s t h a t the a c t i v i t y c o e f f i c i e n t r a t i o i n e q u a t i o n (10)  i s close to u n i t y .  lines  f o r overlapping  against  solvent  2 and 5«  The c l o s e p a r a l l e l i s m between i n d i c a t o r s when l o g I was  plotted  c o m p o s i t i o n can be seen f r o m F i g u r e s  1,  This conforms t o the b a s i c Hammett p o s t u l a t e .  T h i s i s a l s o shown, i n a d i f f e r e n t way, i n the s m a l l r e l a t i v e e r r o r i n the v a l u e s of Hp_- c a l c u l a t e d f o r one s o l u t i o n from the i o n i z a t i o n d a t a f o r s e v e r a l i n d i c a t o r s (see Tables X I , X I I and X I V ) . The Hammett p o s t u l a t e  a l s o i m p l i e s t h a t the  pK v a l u e s s h o u l d be independent o f the s o l v e n t  system.  I n cases where a Lewis base i s i n v o l v e d , t h i s must be r e s t r i c t e d t o the same base i n d i f f e r e n t s o l v e n t (4).  systems  That t h i s h o l d s f a i r l y w e l l f o r DMSO-methanol and  sodium methoxide-methanol s o l u t i o n s can be seen from Table X.  On c l o s e r i n s p e c t i o n o f the pK v a l u e s i n DMSO-  methanol and sodium methoxide-methanol, i t can be seen t h a t a p a r t from i n d i c a t o r s 1 and 8, d i f f e r , a t the most, by 0 . 0 8 systems.  the o t h e r i n d i c a t o r s  pK u n i t s i n the two  solvent  T h i s i s a good i n d i c a t i o n t h a t the pK v a l u e s  f o r the e q u i l i b r i u m a d d i t i o n of methoxide i o n t o C(-cyanostilbenes  i s independent of the s o l v e n t i n w h i c h  measured. The d i f f e r e n c e i n the measured pK v a l u e s f o r  122  0^cyano-4- -dimethylamino-4—nitrostilbene  i n DMSO-methanol  !  and  sodium methoxide-methanol i s 0 . 2 0 u n i t s .  was  the l a s t one u s e d i n the sodium methoxide-methanol  system. Indicator  Because o f t h i s t h e r e was was  s o l u t i o n used.  This  indicator  doubt as t o whether the  c o m p l e t e l y i o n i z e d i n the most b a s i c As a r e s u l t , the d i f f e r e n c e i n the  pK  v a l u e s f o r t h i s i n d i c a t o r i n the two s o l v e n t systems i s l i k e l y an e x p e r i m e n t a l The  error. oC-cyano-  d i f f e r e n c e i n the pK v a l u e s f o r  2 , 4 — d i n i t r o s t i l b e n e o f 0 . 2 3 u n i t s i n the two systems i s more s e r i o u s . d i n i t r o s t i l b e n e was  solvent  S i n c e the pK o f OC-cyano-4-,4- 1  t a k e n as an a r b i t r a r y s t a r t i n g p o i n t  I n a l l ' s o l u t i o n s , the d i f f e r e n c e i n A p K  between the  two i n d i c a t o r s due  t o s o l v e n t change i s a d i r e c t  on the r e l i a b i l i t y  o f the e x p e r i m e n t a l measurements.  It  s h o u l d f i r s t of a l l be noted t h a t the A p K  between the two i n d i c a t o r s was DMSO-methanol. overlap.  found  t o be 1 . 6 9  value in  T h i s i s n e a r i n g the l i m i t f o r e f f e c t i v e  As the amount o f o v e r l a p p i n g i n the  curves o f two  reflection  i n d i c a t o r s decreases,  ionization  the e r r o r i n the  A p K v a l u e s i n c r e a s e s because, i n the f i r s t p l a c e , o f a s m a l l e r number of e x p e r i m e n t a l p o i n t s over w h i c h the v a l u e s can be a v e r a g e d .  The  ApK  increased error also arises  from the f a c t t h a t the most a c c u r a t e s p e c t r a l measurements a r e p o s s i b l e when the i n d i c a t o r i s between  1 0 and  90%  123  ionized.  As these l i m i t s a r e r e a c h e d , e r r o r s i n i n d i v i d u a l  s p e c t r a l measurements i n c r e a s e and a r e r e f l e c t e d i n t h e e r r o r o f the A p K measurements.  A s s o c i a t e d w i t h these  two causes i s the r a p i d r i s e i n H^- a t l o w c o n c e n t r a t i o n s o f sodium methoxide i n methanol.  I t was f e l t t h a t t h e s e  causes o f e r r o r were enough t o e x p l a i n the d i f f e r e n c e o f 0.23 u n i t s i n the pK v a l u e s f o r i n d i c a t o r number 1 i n t h e two s o l v e n t systems.  B.  I n t e r p r e t a t i o n o f the Lewis B a s i c i t y o f t h e S o l u t i o n s The a d d i t i o n o f DMSO t o e t h a n o l o r methanol  c o n t a i n i n g 0.01M sodium a l k o x i d e was found t o have a p r o f o u n d e f f e c t on the a b i l i t y o f the a l k o x i d e i o n t o a c t as a Lewis base.  The H^- v a l u e s were found t o  i n c r e a s e from Ik.00 i n O.98 mole % DMSO i n e t h a n o l t o 21.7k i n 93.27 mole % DMSO i n e t h a n o l and from 11.73 i n methanol t o 21.65 i n 97.61 mole % DMSO i n methanol. I n the f i r s t c a s e , the Lewis b a s i c i t y o f t h e e t h o x i d e i o n i n c r e a s e s by a p p r o x i m a t e l y 7 powers o f 10 and i n t h e second c a s e , the Lewis b a s i c i t y o f the methoxide i o n i n c r e a s e s by about 10 powers o f 10.  T h i s shows t h a t DMSO  has a s u b s t a n t i a l e f f e c t on the Lewis b a s i c i t y o f t h e alkoxide ions. From e q u a t i o n (69), w i t h the a i d o f e q u a t i o n (65)?' the e x p r e s s i o n  1 2 4  H -  +  R  log K  H 0 R  =  l o g (OR")  +  l o g - A f  can be o b t a i n e d .  A0R"  From t h i s , i t can be seen t h a t t h e v a l u e  o f R R - i s dependent on two terms:  the logarithm o f the  a c t i v i t y o f the a l k o x i d e i o n and t h e l o g a r i t h m activity coefficient ratio.  a f i r s t approximation,  to the H » value. R  of the  Because l i t t l e i s known about  a c t i v i t y c o e f f i c i e n t behavior  term i n equation  (77)  i n alcohol solutions, to  i t can be assumed t h a t t h e l a s t  (77) makes o n l y a s m a l l c o n t r i b u t i o n I f t h i s i s so, then the increase i n  the H - v a l u e must be due t o a n i n c r e a s e i n t h e a c t i v i t y R  o f the a l k o x i d e i o n . The a c t i v i t y o f t h e a l k o x i d e i o n c o u l d be i n c r e a s e d by d e s o l v a t i o n .  I f the a l k o x i d e i o n i s somewhat  l i k e t h e h y d r o x i d e i o n (35, 4 3 ) t h e n i t i s l i k e l y t h a t t h e a l k o x i d e i o n has around i t a sheath o f s o l v a t i n g p r o t i c solvent molecules.  The number o f methanol m o l e c u l e s  s o l v a t i n g t h e methoxide i o n have been e s t i m a t e d f r o m 3 t o 5°6 f o r v a r i o u s h i n d e r e d  phenols ( 4 l ) .  t o range Thus,  as t h e p r o p o r t i o n o f DMSO i s i n c r e a s e d , t h e amount o f a l c o h o l a v a i l a b l e t o s o l v a t e t h e a l k o x i d e i o n w i l l be decreased.  T h i s may a c c o u n t f o r t h e r i s e i n the R e -  v a l u e as the amount o f a l c o h o l p r e s e n t  becomes s m a l l .  I t has a l s o r e c e n t l y been proposed t h a t t h e i n c r e a s e i n a c t i v i t y o f t h e methoxide i o n as DMSO i s added c o u l d be t h e r e s u l t o f a breakdown o f t h e methanol  125  s o l v e n t s t r u c t u r e (117).  The s t r u c t u r e o f methanol has  been c o n s i d e r e d t o be psuedo p o l y m e r i c (118).  That t h e  a d d i t i o n o f DMSO t o methanol has a d i s r u p t i v e e f f e c t on the s o l v e n t s t r u c t u r e o f methanol can be seen from the NMR spectrum (119).  On a d d i n g DMSO t o methanol, the p r o t o n  resonance i s s h i f t e d t o a h i g h e r f i e l d .  T h i s was r e g a r d e d  as meaning t h a t the hydrogen bond between two methanol m o l e c u l e s i s s t r o n g e r t h a n t h a t between a methanol and a DMSO m o l e c u l e .  The d i s r u p t i v e e f f e c t o f DMSO on the  s t r u c t u r e o f methanol i s a l s o e v i d e n t from v i s c o s i t y measurements.  The v i s c o s i t y o f DMSO-methanol m i x t u r e s  was r e p o r t e d t o show n e g a t i v e d e v i a t i o n s , a l t h o u g h s m a l l , from what would be e x p e c t e d from a d d i t i v e (113).  A  considerations  g r e a t e r f l u i d i t y t h a n e x p e c t e d on the  a d d i t i o n o f DMSO i s i n agreement w i t h a breakdown o f the s t r u c t u r e o f methanol.  C.  The V a l i d i t y o f the H_ S c a l e s There appears t o be some doubt as t o t h e  v a l i d i t y o f the H_ s c a l e i n sodium solutions.  methoxide-methanol  Some e v i d e n c e p o i n t s towards i t b e i n g a v a l i d  s e l f - c o n s i s t e n t s c a l e whereas o t h e r e v i d e n c e i s not as favorable. On l o o k i n g c l o s e l y a t the i o n i z a t i o n b e h a v i o r o f the i n d i c a t o r s u s e d , i t can be n o t e d from F i g u r e 5 t h a t the p l o t s o f l o g I v e r s u s the c o n c e n t r a t i o n o f  126  sodium methoxide a r e q u i t e c l o s e l y p a r a l l e l .  This,  then,  p o i n t s towards t h e Hammett p o s t u l a t e a p p l y i n g i n t h i s case.  The s m a l l r e l a t i v e e r r o r i n t h e H_ v a l u e c a l c u l a t e d  f o r one s o l u t i o n from the i o n i z a t i o n data f o r s e v e r a l overlapping  i n d i c a t o r s (see T a b l e XIV") i s a l s o i n  agreement w i t h the above Hammett p o s t u l a t e . On the o t h e r hand, the d i s c r e p a n c i e s  between  the d e t e r m i n e d pKjj^ v a l u e s and those found i n t h e l i t e r a t u r e a r e , t o say t h e l e a s t , d i s t u r b i n g . discrepancy for  4-  e x i s t s between the d e t e r m i n e d P % [ A . v a l u e  n i t r o b e n z y l cyanide  i n the l i t e r a t u r e misleading  ( 1 3 . 4 5 )  ( 1 4 . 2 4 )  and that  ( 4 5 , 4 8 ) .  reported  But t h i s may be  s i n c e i t was found t h a t 4 - n i t r o b e n z y l c y a n i d e  was h a l f i o n i z e d i n O.38M sodium methoxide O.67 mole % DMSO whereas O ' F e r r a l l and R i d d i t "to be h a l f i o n i z e d a t a p p r o x i m a t e l y methoxide.  A large  containing (39)  reported  0 . 5 M sodium  S i n c e t h e s m a l l amount o f DMSO would t e n d t o  i n c r e a s e t h e H_ v a l u e by a p p r o x i m a t e l y  0.1 u n i t , the  two r e s u l t s a r e f a i r l y c l o s e c o n s i d e r i n g t h a t t h e d i f f e r e n c e i n H_ v a l u e s  between O.38M and 0.50M sodium  methoxide i s 0 . 2 u n i t s . An even l a r g e r d i s c r e p a n c y of 4,4'-dinitrodiphenylmethane. methanol s o l u t i o n s , t h e  ApK-g^  e x i s t s i n t h e case  I n sodium methoxidev a l u e between m e t h y l  f l u o r e n e - 9 - c a r b o x y l a t e and 4 , 4 ' - d i n i t r o d i p h e n y l m e t h a n e was found t o be 4 . 0 1  pKr™  u n i t s whereas Bowden and S t e w a r t  127  (5D  r e p o r t e d a v a l u e o f 2,97 i n t h e DMSO-ethanol s o l v e n t  system.  T h i s amounts t o a d i f f e r e n c e o f over a u n i t i n  t h e ^ P % £ v a l u e s on g o i n g from methanol t o DMSO-ethanol. These d i f f e r e n c e s may be due t o a s o l v e n t e f f e c t .  In  the majority, o f cases, the d i f f e r e n c e s i n the A p K values on g o i n g from one s o l v e n t t o a n o t h e r , f o r example on g o i n g from water t o methanol t o e t h a n o l , a r e n o t l a r g e but d i f f e r e n c e s as g r e a t as 1 pK u n i t a r e n o t uncommon (120a).  F o r example, t h e ApKgg+ v a l u e between 4 - n i t r o -  and 4 - f l u o r o a n i l i n e s i n methanol was r e p o r t e d t o be 4.199  and i n e t h a n o l t o be 4.759 (12.1).  This r e s u l t s  i n a d i f f e r e n c e o f 0.56 pK u n i t s i n t h e A pKgjj+ v a l u e s determined  i n methanol and e t h a n o l . I n o r d e r t o f u r t h e r check t h e d i f f e r e n c e s i n t h e  A p K g ^ v a l u e s as measured i n methanol and e t h a n o l , t h e p r e v i o u s work i n DMSO-ethanol was r e p e a t e d .  The i o n i z a t i o n  behavior of the v a r i o u s i n d i c a t o r s I s i l l u s t r a t e d i n F i g u r e 8.  This f i g u r e c l e a r l y i l l u s t r a t e s  of l o g I versus solvent composition f o r triphenylmethane  t h a t the p l o t s  4,4',4"-trinitro-  and 4 , 4 ' - d i n i t r o d i p h e n y l m e t h a n e a r e  n e i t h e r p a r a l l e l nor do t h e y o v e r l a p t o any e x t e n t . B o t h p a r a l l e l i s m and good o v e r l a p p i n g a r e o f paramount importance  i n the e s t a b l i s h m e n t o f a H_ s c a l e .  I n order  to achieve the o v e r l a p , 4 , 4 ' - d i n i t r o t r i p h e n y . l m e t h a n e was  prepared.  Although a p l o t of l o g I versus solvent  128  composition  f o r 4-,4-' - d i n i t r o t r i p h e n y l m e t h a n e  overlapped  w i t h t h a t f o r 4-,4-' , 4 - " - t r i n i t r o t r i p h e n y l m e t h a n e and 4-,4-'dinitrodiphenylmethane, dinitrodiphenylmethane  the i o n i z a t i o n b e h a v i o r  o f 4^4-'-  was n o t p a r a l l e l t o t h a t o f the  o t h e r two, w h i c h were p a r a l l e l between t h e m s e l v e s . F u r t h e r m o r e , t h e maximum a b s o r p t i o n o f the e l e c t r o n i c s p e c t r a o f t h e a n i o n s o f b o t h 4-,4-' , 4 - " - t r i n i t r o t r i p h e n y l methane and 4 - , 4 - ' - d i n i t r o t r i p h e n y l m e t h a n e  underwent such  d r a s t i c s h i f t s i n w a v e l e n g t h as the DMSO content increased —  was  s h i f t s o f around 100 mjl t o h i g h e r wavelengths  were o b s e r v e d —  t h a t a t t e m p t s t o c o r r e c t f o r these  were i m p o s s i b l e .  shifts  W i t h such l a r g e s h i f t s , t h e r e was no  a s s u r a n c e t h a t the e x t i n c t i o n c o e f f i c i e n t s d i d not change as w e l l as the w a v e l e n g t h o f maximum a b s o r p t i o n w i t h a change i n s o l v e n t .  This c l e a r l y i n d i c a t e s that i n d i c a t o r s  l i k e 4-,4-' , 4 - " - t r i n i t r o t r i p h e n y l m e t h a n e and 4 - , 4 - ' - d i n i t r o t r i p h e n y l m e t h a n e cannot be u s e d t o e s t a b l i s h a H_ s c a l e i n DMSO-ethanol s o l u t i o n s .  T h i s o f course a l s o p o i n t s t o  the n e c e s s i t y o f r e d e t e r m i n i n g  the H_ s c a l e f o r carbon  a c i d s i n DMSO-ethanol s o l u t i o n s . The d i f f i c u l t i e s e n c o u n t e r e d i n t h e e q u i l i b r i a measurements u s i n g c a r b o n a c i d s i n DMSO-ethanol were n o t e n c o u n t e r e d i n sodium methoxide-methanol s o l u t i o n s . i t i s reasonable  t o e x p e c t t h a t t h e H_ s c a l e f o r  c a r b o n a c i d s i n t h e sodium methoxide-methanol system i s a s e l f - c o n s i s t e n t one w i t h some v a l i d i t y .  Thus  129  D.  The Comparison o f the H - S c a l e s w i t h o t h e r S c a l e s R  B e f o r e comparing the H - s c a l e s w i t h o t h e r s c a l e s , R  i t i s n e c e s s a r y t o e x p l a i n the c h o i c e o f H - a s a symbol R  f o r the a c i d i t y f u n c t i o n d e s c r i b i n g the e q u i l i b r i u m a d d i t i o n o f base t o a n u n s a t u r a t e d system.  R o c h e s t e r has  a l r e a d y u s e d the symbol J _ f o r such a n a c i d i t y f u n c t i o n ( 5 8 ) i n w h i c h the r e l a t i o n s h i p between J _ and H_ was by e q u a t i o n (4-3). between J  0  given  T h i s r e l a t i o n s h i p i s the same a s t h a t  and H , w h i c h was g i v e n by e q u a t i o n ( 2 2 ) . I n 0  b o t h c a s e s , the a c t i v i t y c o e f f i c i e n t term was assumed t o be u n i t y .  I n the a c i d r e g i o n , Deno, J a r u z e l s k i and  S c h r i e s h e i m ( 2 8 ) were a b l e t o show t h a t the  activity  c o e f f i c i e n t r a t i o was not u n i t y and thus e s t a b l i s h e d the a c i d i t y f u n c t i o n H R g i v e n by e q u a t i o n (2k).  S i n c e h _ was  g i v e n b y e q u a t i o n (31) and h^- by e q u a t i o n (?0)> t h e n  F  h  AOR  (HOR)  *AH (78)  f.f  and F  H_  By u s i n g e q u a t i o n s  =  log(HOR)  log  AOR  F  AH  (79)  (4-3) a n d ( 7 9 ) ? the r e l a t i o n s h i p between  130  HR-  and  J__ i s  given  by  the  expression  f  H -  -  R  J_  =  f I  From  this and  H^-  i t  can  J_ i s  be  seen  i d e n t i c a l  Therefore  the  symbol  symbolism  developed  that to  HRby  A"  l o g —  was  Deno  A0R  the  that  relationship  between  chosen et  (80)  —  a l  i n  (29)  between  and  H^  J  Q  .  keeping  with  and  i n  now  the general  use. If, coefficient for  acids  ments,  for  the  f  A  to the  the  / f  ,  rise  would  or  i s  a c t i v i t y  the  f^oR"  ratio  o r  scale  "^ne  term  may  D  must  be  solvation than  as  s  e  i n  from  for  the  f^~  for  due  to  not  as the  so basic  13.  to  assume  species,  the  DMSO  H R  content  scale i n  a c t i v i t y  adduct  decrease  one  highly  neutral  the  require-  Figure  for  then  HR-  is  reasonable  that a  the  this  far  Then,  suggests ^  so  a c t i v i t y  neglected,  That  is  unity.  systems  This  same  seen  i t  the  be  faster  be  (79)j  H_  coefficient  acids.  can  to  increased  term  rise  coefficient  than  the  established  DMSO  close  can  (79)  decreases.  equation  unsaturated  oxygen  should  scales  be  faster  coefficient  the  equation  alcohol  to  approximation,  approximately  a c t i v i t y  system  carbon  f i r s t  containing  referring the  i n  scale  H_  a c i d i t y  that A H  term  of  solutions In  the  having  the  a c t i v i t y  i n  for  more  anions  carbonrapidly  from  carbanions  than  nitrogen  having  FIGURE 13.  A PLOT OF H VALUES VERSUS MOLE % DMSO IN METHANOL CONTAINING O.OIM SODIUM METHOXIDE FOR VARIOUS INDICATORS  MOLE % DMSO IN METHANOL  132  greater  s o l v a t i o n requirements than nitrogen  o r oxygen  anions. I n t h e DMSO-ethanol s o l v e n t and  H_ s c a l e s  since  R  ( 5 1 ) c a n n o t be compared  f o r carbon acids  i t was p o i n t e d  system, t h e H -  out previously  that  the v a l i d i t y  o f t h e H_ s c a l e f o r c a r b o n a c i d s was i n d o u b t . The the  H^- a n d H_ s c a l e s were b o t h d e t e r m i n e d i n  sodium methoxide-methanol s o l v e n t  ease o f comparison,  these  one  7.  graph i n F i g u r e  two s c a l e s  scale;  two  scales are almost  Hp_-  a n d H_ s c a l e s , by u s i n g  that  used. and  By i n s e r t i n g  have s l i g h t l y  values  i n the l a s t  i t c a n be s e e n t h a t  ^AOR-Z^A"  ^  extent  f o r these  s e  different  H__) were  adjusted  to unity  two s c a l e s .  f o r H - , H_ R  a  n  d A0R"^ A"* f  f  T  n  e  s  e  two columns o f T a b l e XXIV.  From t h i s ,  l°  i n Table  (79), i t i s possible to  o f l o g f&QR-/f£  c  (H^- -  the experimental values  calculate values  s  i s given  recently  a t t h e lowest methoxide i o n c o n c e n t r a t i o n  log(CH^OH) i n t o e q u a t i o n  are given  (122),  the d i f f e r e n c e s  i t i s zero  values f o r  solutions reported  B e c a u s e t h e two s c a l e s points,  The c o m p a r i s o n o f t h e  the a c t i v i t y  F r e e g u a r d , Moodie a n d S m i t h  starting so  more q u i c k l y t h a n t h e  parallel.  methanol i n sodium methoxide  XXIV.  o f sodium  but. f r o m 0.8 t o 4-.0M s o d i u m m e t h o x i d e , t h e  H -  by  F o r greater  have b e e n p l o t t e d o n  A t low c o n c e n t r a t i o n s  m e t h o x i d e , t h e H_ s c a l e r i s e s R  system.  the assumption  that  i s obeyed t o a r e a s o n a b l e This  i s i n contrast  to; t h e  133  r e l a t i o n s h i p between the HR and  J  scales i n s u l f u r i c a c i d  0  s o l u t i o n s where the d i f f e r e n c e between the two (HR 82%  -  J ) was 0  scales  found t o decrease t o a v a l u e o f -5  at  (28).  sulfuric acid  I n comparing the H  R  and  J  0  functions,  the  a c t i v i t y c o e f f i c i e n t fR+ r e f e r s t o a carbonium i o n whereas the a c t i v i t y c o e f f i c i e n t % 0 H 2  +  r  e  ^  e  r  to  s  a  s p e c i e s w i t h the p o s i t i v e charge r e s i d i n g on the oxygen. The  two  species R  +  and R0H2  +  t h e n l i k e l y have d i f f e r e n t  s o l v a t i o n r e q u i r e m e n t s r e s u l t i n g i n the r a t i o o f  the  a c t i v i t y c o e f f i c i e n t s being d i f f e r e n t from u n i t y . However, i n comparing the HRnegative  and  J _ functions,  charge i n the c a r b a n i o n s AOR  a c a r b o n atom i n each c a s e .  and A  resides  I n t h i s c a s e , the  n e g a t i v e l y charged s p e c i e s are q u i t e s i m i l a r and the r a t i o of the a c t i v i t y c o e f f i c i e n t s would be  on  two therefore  likely  close to u n i t y . According  t o the above e v i d e n c e , i t i s l i k e l y  t h a t R o c h e s t e r ' s J__ v a l u e s (71)  the  i n sodium h y d r o x i d e s o l u t i o n s  are r e a s o n a b l y c l o s e t o the H^-  c o u l d be d e t e r m i n e d  v a l u e s , i f these  i n the aqueous system.  One  doubtful  p o i n t r e m a i n i n g i s t h a t the H_ v a l u e s u s e d by R o c h e s t e r were based on n i t r o g e n i n d i c a t o r s and  t h i s s c a l e may  be e n t i r e l y a p p l i c a b l e t o carbon a c i d s .  not  (71)  13+  TABLE XXIV  The Comparison o f the H R - and H _ S c a l e s i n Concentrated Sodium Methoxide S o l u t i o n s  ^  OH  I  -di  •H H  K  o n  Si CD -PrH  JXJ  JO S a a "  cd  W O OO  pj . •HO  ffi O  ^3 £  O O COO  ^  0.01 0.0562 0.115 0.229  0.1+6"+ .  0.697 0.952 1.19 1.78 2.07 2.36 2.65 2.93 3.2+ 3.51  0.999 0.997 0.991 0.981 0.960 0.939 0.913 0.886 0.801+ O.767 0.722 0.680 0.639 0.598 0.563  o  w  |  o  o n  o o  B txO O H  I (  W  0 -0.05 -0.07 -0.13 -0.16 -0.16 -0.21 -0.21 -0.16 -0.18 -0.20 -0.19 -0.20 -0.20 -0.13  I I  «ai  I  B p ? ' -  I  •  —'  w  0.000 -0.001 -0.00+ -0.008 -0.018 -0.027 -0.0+0 -0.053 -0.095 -0.115 -0.1+2 -0.168 -0.19*+ -0.223 -0.250  ffi  £  0tuO rH  hO 0  H  0 +0.01+9 +0.066 +0.122 +0.1+2 +0.133 +0.170 +0.157 +0.065 +0.065 +0.058 +0.022 +0.006 -0.023 -0.12  N  I p£ O <J  «H  1 1.12 1.16 1.32 1.39 1.36 1.1+8 1.H-+  1.16 1.16 1.1+ 1.05 1.01 0.95 O.76  (122)  a  Taken from Reference  b  Taken from Tables XIV and XVI and c o r r e c t e d f o r the d i f f e r e n c e a t 0.01M Sodium Methoxide  135  E.  A Comparison o f pK Values A comparison o f the pK v a l u e s f o r the v a r i o u s  i n d i c a t o r s i n Table X, shows t h a t the pK v a l u e s  determined  i n the DMSO-ethanol system a r e , w i t h one e x c e p t i o n , a l l l a r g e r than those determined  i n the DMSO-methanol system.  T h i s may r e f l e c t a s o l v e n t e f f e c t on the pK-values.  I t has  a l r e a d y been mentioned t h a t d i f f e r e n c e s as great as 1. pK u n i t i n the A p K v a l u e s between two i n d i c a t o r s on going from one s o l v e n t t o another a r e not uncommon  (120a).  A s o l v e n t e f f e c t on the pK v a l u e s , however, does not give the complete p i c t u r e .  When s t u d y i n g the  e q u i l i b r i u m a d d i t i o n of alkoxide ions to unsaturated systems, the complete base molecule carbanion. expected,  i s i n v o l v e d i n the  I t i s t h e r e f o r e not necessary, and h a r d l y t h a t the pK v a l u e s f o r one i n d i c a t o r u s i n g two  d i f f e r e n t bases should be i d e n t i c a l . The  pK v a l u e s f o r the e q u i l i b r i u m a d d i t i o n o f  ethoxide i o n to two u n s a t u r a t e d compounds were measured but were not used i n the c a l c u l a t i o n o f the H R  The  indicator  scale..  C X l - c y a n o - 2 - c h l o r o - 4 - n i t r o s t i l b e n e was not  used t o c a l c u l a t e the H - s c a l e because the p l o t o f R  l o g I v e r s u s the s o l v e n t composition i s not p a r a l l e l to t h a t o f the other i n d i c a t o r s .  T h i s may be due t o  impure m a t e r i a l s i n c e i n s u f f i c i e n t m a t e r i a l was o b t a i n e d f o r complete p u r i f i c a t i o n .  I n any case, i t i s i n t e r e s t i n g  136  t h a t the pK v a l u e , d e t e r m i n e d from the H - v a l u e o f t h e R  s o l u t i o n i n w h i c h the i n d i c a t o r was h a l f i o n i z e d , i s higher than that f o r 0(-cyano-4-n i t r o s t i l b e n e .  T h i s may  r e f l e c t a s t e r i c e f f e c t o f the o r t h o - c h l o r o group. I n t h i s r e g a r d i t c a n be noted t h a t 0 ( - c y a n o - 2 - n i t r o s t i l b e n e was  found t o have a n a b n o r m a l l y  h i g h pK v a l u e o f 20.11  when compared t o a pK v a l u e o f 15*95 f o r CX-cyano-4n i t r o s t i l b e n e i n DMSO-ethanol s o l u t i o n s .  These r e s u l t s  cannot be e x p l a i n e d on the b a s i s o f e l e c t r o n i c s i n c e these would be expected  effects  t o be n e a r l y the same f o r  the n i t r o group i n the two p o s i t i o n s . Here a g a i n , a s t e r i c e f f e c t o f the o r t h o group may e x p l a i n the r e s u l t s . The  s u b s t i t u e n t s i n the o r t h o p o s i t i o n may be c a u s i n g t h e  p h e n y l r i n g t o t w i s t t o some degree.  T h i s would cause  the amount o f resonance i n t e r a c t i o n between the group and the  nitro  0 ( - c a r b a n i o n c e n t e r t o be r e d u c e d .  Since  the n i t r o group s t r o n g l y s t a b i l i z e s a n (X-carbanion by resonance i n t e r a c t i o n , any r e d u c t i o n i n t h i s resonance i n t e r a c t i o n w i l l i n c r e a s e t h e pK v a l u e o f the  indicator.  Other cases where a n o r t h o - n i t r o group e x h i b i t s a weaker a c i d s t r e n g t h e n i n g e f f e c t than the p a r a - n i t r o group are known.  F o r example, the p K ^ f o r 2 - n i t r o -  d i p h e n y l a m i n e (17.91) i s g r e a t e r by 2.24 u n i t s t h a n t h a t f o r 4-nitrodiphenylamine ]p]%A  for 2-nitrophenol  that f o r 4-nitrophenol  (15.67) (49).  S i m i l a r i l y , the  (7.22) i s 0.07 u n i t s g r e a t e r (7.15) (8).  than  The g r e a t e r vK-EA. v a l u e s  137  f o r the o r t h o - n i t r o a c i d s i n these two  cases can  a t t r i b u t e d t o a hydrogen bonding e f f e c t .  be  However, t h i s  argument cannot be u s e d t o e x p l a i n the h i g h e r pK for cX~ y °-2-nitrostilbene c  a n  OC~cyano-4-nitrostilbene.  as  value  compared t o t h a t f o r  I n the e q u i l i b r i u m a d d i t i o n o f  e t h o x i d e i o n t o an a l k e n e , no hydrogen bonding e f f e c t i s possible. A l t h o u g h the i o n i z a t i o n curve f o r nitrophenyl)ethene  l,l-bis-(4  i s p a r a l l e l t o t h a t f o r the  other  i n d i c a t o r s , the s t r u c t u r e of t h i s i n d i c a t o r i s q u i t e d i f f e r e n t from t h a t of the o t h e r i n d i c a t o r s u s e d t o e s t a b l i s h the Hp_-  scales.  None the l e s s , t h i s ethene  appeared t o be a good i n d i c a t o r and b a s i c systems w i l l be d i s c u s s e d  F.  i t s reactions  in  later.  C o r r e l a t i o n of S t r u c t u r e w i t h Lewis A c i d i t y . An  i n s p e c t i o n o f Table X shows t h a t the  a c i d i t i e s of s u b s t i t u t e d 0(-cyano-stilbenes  are  s e n s i t i v e t o the type of group p r e s e n t i n the rings.  One  of the most w i d e l y u s e d methods o f  t i v e l y estimating  very  phenyl quantita-  t h i s s e n s i t i v i t y i s the Hammett  c o r r e l a t i o n (120b).  T h i s c o r r e l a t i o n was  a number of s u b s t i t u e n t s These are  Lewis  i n two  shown i n F i g u r e s  14,  or t h r e e 15 and  16.  0~~D  c a r r i e d out solvent  for  systems.  A l l the  slopes  were d e t e r m i n e d by the method of l e a s t square a n a l y s i s  (123)  138  and  these a r e recorded  i n the f i g u r e s a l o n g w i t h the'  correlation coefficients r  (123).  When s u b s t i t u e n t s w e r e p l a c e d i n t h e CX-cyano-H—nitrostilbene  ^5-ring o f  ( X X I ) , t h e pK v a l u e s  XXI  were found  t o c o r r e l a t e w i t h t h e r e s p e c t i v e CT v a l u e s .  A p l o t o f t h e pK v a l u e s , when Z was " 4 - ' - n i t r o ,  3'-chloro,  h y d r o g e n , 4-'-me t h y l , V - m e t h o x y a n d "H-'-dimethylamino, a g a i n s t t h e r e s p e c t i v e cr- v a l u e s straight lines with p b e i n g e q u a l t o 2.27  (120c) gave r e a s o n a b l y  and the c o r r e l a t i o n c o e f f i c i e n t r  a n d 0.996 i n D M S O - e t h a n o l , 2.21  and  0.992 i n DMSO-methanol a n d 2.09 a n d 0.993 i n s o d i u m methoxide-methanol  respectively.  The f a c t t h a t t h e pK v a l u e s f o r ' X X I c o r r e l a t e w i t h t h e r e s p e c t i v e 0~ v a l u e s shows t h a t t h e r e i s l i t t l e resonance  i n t e r a c t i o n between the s u b s t i t u e n t i n the  (3-ring and the a n i o n formed i n t h e e q u i l i b r i u m of a l k o x i d e i o n . Cr Values are determined  addition  by m e a s u r i n g  the i o n i z a t i o n c o n s t a n t s o f s u b s t i t u t e d benzoic a c i d s and  i n the a n i o n o f b e n z o i c a c i d , r e p r e s e n t e d by  structure XXII,  t h e r e i s no way o f d r a w i n g  a  resonance  139 FIGURE 14.  HAMMETT CORRELATIONS OF THE LEWIS ACIDITY OF CX-CYANOSTILBENES IN DMSO-ETHANOL  G~  or  Cr~~  iko  FIGURE 15.  HAMMETT CORRELATIONS OF THE LEWIS A C I D I T Y OF CX-CYANOSTILBENES I N DMSO-METHANOL  2 2 h —  NC  2lh-  \=/  CN J3 3-C N-4-C I  20hNC  SLOPE = - V . 2 H r = 0.985  P=CH  4-CN  9h-  K >4'-N(CH )  SLOPE = - 2 , 1 7  3  r = 0.996  ^-NOz  • 4-N02  SLOPE = - 2 . 2 1 r = 0.992 -0.8  -0.4  0  4-N0  0.4 cr  or  0.8 cr~  2  1.2  FIGURE 1 6  0  HAMMETT CORRELATION  OF THE LEWIS ACIDITY OF  OC-CYANOSTILBENES IN THE SODIUM METHOXIDEMETHANOL SYSTEM  4-N(CH ) 3  17  K  SLOPE = - 2 . 0 9 r  =  0 . 9 9 3  14  -0.8  -0.6  -0.4  -0.2  0  0.2  0.4  0.6  0.8  142  • s t r u c t u r e w i t h the n e g a t i v e charge r e s i d i n g i n the r i n g .  XXII T h e r e f o r e , Q~ v a l u e s e s s e n t i a l l y measure the e f f e c t of s u b s t i t u e n t s  (5b).  That the  v a l u e f o r the 4 ' - n i t r o group i n XXI v a l u e o f 1.27  r a t h e r t h a n the  appropriate  i s O.78  (5b),  formed f r o m t h e . a l k o x i d e  (120c),  clearly indicates  t h a t o n l y as much resonance i n t e r a c t i o n i s between the s u b s t i t u e n t  inductive  occurring  i n the a d d i t i o n t o XXI  as therms' i s i n  the case of the a n i o n s of s u b s t i t u t e d b e n z o i c a c i d s . The. above e v i d e n c e a l s o sheds f u r t h e r on the mode o f i o n i z a t i o n o f the  light  oC-cyanostilbenes.  If  the i o n i z a t i o n took p l a c e by a p r o t o n r e m o v a l , as i n d i c a t e d i n e q u a t i o n (76)'. t h e n the n i t r o group i n the 4'  p o s i t i o n would undergo a s t r o n g resonance i n t e r a c t i o n  w i t h the r e s u l t a n t a n i o n as shown below. N0 N0 2  2  N0  2  NC  XXIII  143  I n o t h e r words, s t r u c t u r e X X I I I would be e x p e c t e d t o make a l a r g e c o n t r i b u t i o n t o the o v e r a l l resonance h y b r i d . I f t h i s were the c a s e , the a p p r o p r i a t e sigma v a l u e f o r the 4 ' - n i t r o  group s h o u l d be t h e  0~~ v a l u e o f 1.27.  The  G~~ v a l u e r e f e r s t o the i n t e r a c t i o n between a s u b s t i t u e n t and an a n i o n where resonance i n t e r a c t i o n i s p o s s i b l e as i n the case of the i o n i z a t i o n o f p h e n o l s .  That t h e  a p p r o p r i a t e sigma v a l u e f o r the 4 ' - n i t r o group i s r a t h e r t h a n 1.27  s t r o n g l y suggests  d e s c r i b e d by e q u a t i o n (76)  t h a t the  O.78  ionization  i s unimportant.  The magnitude o f p  f o r the i o n i z a t i o n o f XXI  g i v e s a q u a n t i t a t i v e e s t i m a t e o f the s e n s i t i v i t y o f the Lewis a c i d i t y on the e l e c t r o n i c e f f e c t s o f groups i n the  ^3-ring.  A p  v a l u e o f about 2.1  for this  equilibrium,  the e x a c t v a l u e o f w h i c h i s dependent on the  particular  s o l v e n t system u s e d ,  values of  1.00,  2.11  and 2.77  can be compared w i t h p  f o r the i o n i z a t i o n o f b e n z o i c a c i d s ,  phenols and a n i l i n i u m i o n s r e s p e c t i v e l y i n water a t (120d), a v a l u e o f 4.07  f o r the i o n i z a t i o n o f d i p h e n y l -  amines i n DMSO-water (49),  and a v a l u e o f 1.88  f o r the  i o n i z a t i o n o f 2 , 4 , 6 - t r i n i t r o d i p h e n y l a m i n e s (XXIV)  N0  25°  2  XXIV  i n aqueous s o l u t i o n s ( 5 2 ) .  T h i s comparison shows t h a t  the Lewis a c i d i t i e s o f ( X - e y a n o - + - n i t r o s t i l b e n e s a r e 1  about as dependent on the e l e c t r o n i c nature u e n t s i n the  |3-ring  of s u b s t i t -  as are the a c i d i t i e s o f phenol and  anilinium ions. A p l o t o f the pK v a l u e s f o r C X , 4 - d i c y a n o s t i l b e n e s (XXV), where Z was h - n i t r o , . 3 ' - c h l o r o and hydrogen, 1  a g a i n s t the r e s p e c t i v e c r v a l u e s y i e l d e d p  and r v a l u e s  CN  N C  \ = /  XXV o f 2.33 and 0.999 i n DMSO-ethanol and 2.17 DMSO-methanol r e s p e c t i v e l y .  Since o n l y three p o i n t s were  used i n each case, the r e l i a b i l i t y i s not g r e a t .  o f these p  But they do show t h a t the p  i o n i z a t i o n o f XXV i s v e r y  and O.996 i n  values  value  f o r the  s i m i l a r t o t h a t f o r the  i o n i z a t i o n o f XXI. In the i o n i z a t i o n o f  Z-  06-cyanostilbenes  ^ ^  >  C  H  /  N C  XXVI  /  \  X  (XXVI)  w i t h s u b s t i t u e n t s i n t h e o ( - r i n g , a p l o t o f t h e pK v a l u e s v e r s u s the r e s p e c t i v e 0""~ v a l u e s (5b) f o r t h e s u b s t i t u e n t s 4-cyano, 3 - c y a n o - 4 - c h l o r o ,  3-cyano and 3 - t r i f l u o r o m e t h y l  and r v a l u e s o f 4.77 and 0.994 r e s p e c t i v e l y i n  gave p  DMSO-ethanol and 4.24 and 0.985 r e s p e c t i v e l y i n DMSOmethanol. the p  Because o n l y f o u r p o i n t s were u s e d t o determine  v a l u e s , the e r r o r i n p  i t appears t h a t t h i s p  may be h i g h . N e v e r t h e l e s s ,  value i s s l i g h t l y higher  than  the v a l u e o f 4.07 f o r t h e i o n i z a t i o n o f d i p h e n y l a m i n e s (49).  The h i g h p o s i t i v e p  v a l u e and the f a c t t h a t t h e  a p p r o p r i a t e sigma v a l u e f o r t h e 4-cyano group i s t h e Cr~ v a l u e o f 1.00 i n d i c a t e s t h a t s t r u c t u r e s such as X X V I I I make a c o n s i d e r a b l e c o n t r i b u t i o n t o t h e s t r u c t u r e o f t h e base adduct X X V I I .  C  N  XXVII  XXVIII  C o n s i d e r i n g t h e p v a l u e s o f 2.11 f o r the i o n i z a t i o n o f phenols diphenylamines higher p ions to  (120d) and 4.07 f o r the i o n i z a t i o n o f  ( 4 9 ) , one might have a n t i c i p a t e d a much  v a l u e f o r the e q u i l i b r i u m a d d i t i o n o f a l k o x i d e CX-cyanostilbenes.  A p v a l u e as h i g h as t e n  has been e s t i m a t e d f o r t h e i o n i z a t i o n o f t o l u e n e s ( 4 9 ) .  lH-6  However, the a b i l i t y o f the-(X-cyano group t o e f f e c t i v e l y s t a b i l i z e the n e g a t i v e charge would t e n d t o have a "swamping" e f f e c t .  p  T h i s r e c a l l s the reduced  value  observed f o r the i o n i z a t i o n o f 2 , h , 6 - t r i n i t r o d i p h e n y l amines ( X X I V ) , 1.88,  compared to t h a t f o r the  i o n i z a t i o n of diphenylamines, From F i g u r e 14-,  4-.07.  i t can be seen t h a t the  p  v a l u e f o r the e q u i l i b r i u m a d d i t i o n of e t h o x i d e i o n t o . XXI or XXV averages the a d d i t i o n t o i n the o6-ring  out t o 2.30,  whereas the p  OC-cyanostilbenes i s k.77»  value for  w i t h the s u b s t i t u e n t s  T h i s means t h a t the  p  value  f o r the ^ - r i n g , where the s u b s t i t u t e d p h e n y l r i n g i s removed by one carbon atom from the s i t e of the c a r b a n i o n , i s 0.4-8  o f the  p  v a l u e f o r the  C X - r i n g where the  s u b s t i t u t e d p h e n y l r i n g i s a d j a c e n t t o the c a r b a n i o n . T h i s compares c l o s e l y w i t h the r a t i o o f the p  values f o r  the i o n i z a t i o n of s u b s t i t u t e d b e n z o i c and p h e n y l a c e t i c acids.  The  P  v a l u e f o r the i o n i z a t i o n o f b e n z o i c  a c i d s i s 1.00  and t h a t f o r the i o n i z a t i o n o f p h e n y l a c e t i c  a c i d s i s 0.4-9  (5b).  I n p h e n y l a c e t i c a c i d , the  phenyl  r i n g i s one carbon atom f a r t h e r away from the c a r b o x y l group t h a n i n b e n z o i c a c i d . I t i s a l s o e v i d e n t from F i g u r e s Ik and 15  that  the 4 — n i t r o group i s e x c e p t i o n a l l y good i n s t a b i l i z i n g  the  n e g a t i v e charge of the a n i o n formed from the e q u i l i b r i u m a d d i t i o n of a l k o x i d e i o n t o Q ( - - c y a n o - 4 — n i t r o s t i l b e n e .  147.  I n these p l o t s o f pK v e r s u s Ch o f 1.70  i n DMSO-ethanol and  t o be a t t r i b u t e d  , e f f e c t i v e sigma  1.81  values  i n DMSO-methanol had  t o the 4 - n i t r o group i n o r d e r t o b r i n g  i t onto the s t r a i g h t l i n e j o i n i n g the o t h e r f o u r p o i n t s . W h i l e t h i s a n a l y s i s u s e d o n l y a s m a l l number of s u b s t i t u e n t s , i t i s c l e a r t h a t an e x a l t e d 0~ v a l u e the p a r a - n i t r o group. e x a l t e d C~  v a l u e has  i s required for  There are o t h e r been r e p o r t e d  cases inhere  f o r a p a r a - n i t r o group.  I n the i o n i z a t i o n o f d i p h e n y l a m i n e s , Dolman found e f f e c t i v e Q~  value  of 1.65  f o r t h e ' 4 - n i t r o group  F i s h e r , R i d d o l s and Vaughan (124) have values  of 1.70  and  1.81  an (49).  reported  f o r the 4 - n i t r o group i n the  i o n i z a t i o n o f s u b s t i t u t e d 1-naphthols and a t i o n o f 1-naphthoxide i o n s r e s p e c t i v e l y .  i n the m e t h y l A  of these e x a l t e d 0~ v a l u e s w i t h those o f 1.27 i o n i z a t i o n o f phenols and  O.78  comparison f o r the  f o r the i o n i z a t i o n o f  b e n z o i c a c i d s i m p l i e s t h a t s t r u c t u r e s such as XXX make a g r e a t e r  an  must  c o n t r i b u t i o n t o the c a r b a n i o n XXIX t h a n  s t r u c t u r e s such as XXXII do t o the a n i o n XXXI formed from the i o n i z a t i o n of  N0  4-nitrophenol.  2  XXIX  XXX  148  0  N0  o  2  XXXI G.  The  o_  XXXII  C o r r e l a t i o n o f R a t e s w i t h the H -  Function  R  One  of the u n d e r l y i n g  purposes o f  establishing  an a c i d i t y f u n c t i o n i s t o a i d i n the e l u c i d a t i o n of mechanisms o f a c i d or base c a t a l y z e d  the  (60).  reactions  However, the p r o s p e c t t h a t d i f f e r e n t a c i d i t y s c a l e s e x i s t f o r each narrow c l a s s o f s t r u c t u r a l l y s i m i l a r compounds i n the h i g h l y a c i d r e g i o n s (125) wave of u n c e r t a i n t y  g r e a t care must be e x e r c i s e d i n cases  k i n e t i c s t u d y are  cast  a  on the i n t e r p r e t a t i o n s o f k i n e t i c  correlations with a c i d i t y functions.  correlations  has  Because of  this,  i n i n t e r p r e t i n g such  where the r e a c t a n t s  u s e d i n the  s t r u c t u r a l l y q u i t e d i f f e r e n t from  the  i n d i c a t o r s u s e d to e s t a b l i s h the a c i d i t y s c a l e . I n the  case where the r e a c t a n t s  used i n  k i n e t i c s t u d y and  the i n d i c a t o r s u s e d t o set up  a c i d i t y s c a l e are  s t r u c t u r a l l y very s i m i l a r  the  the  the  i n t e r p r e t a t i o n of the k i n e t i c s - a c i d i t y f u n c t i o n c o r r e l a t i o n s h o u l d be on f i r m e r  ground.  Such a case  1+9  e x i s t s here.  The  s u b s t i t u t e d cX-cyano~trans-stilbenes  u s e d t o e s t a b l i s h the HRt o the s u b s t i t u t e d  scale are n e a r l y  identical  C X - c y a n o - c i s - s t i l b e n e s u s e d i n the  k i n e t i c s t u d y o f the base c a t a l y z e d i s o m e r i z a t i o n .  The  o n l y d i f f e r e n c e s are the s u b s t i t u e n t s i n the p h e n y l r i n g s and  the g e o m e t r i c a l  arrangement.  i n the same s o l u t i o n s h o u l d The  existence  Solvation differences  be reduced t o a minimum.  of a good l i n e a r r e l a t i o n between  the l o g a r i t h m of the a p p a r e n t f i r s t o r d e r r a t e log k  1 ?  and  10 and 11.  the a c i d i t y s c a l e HR- i s e v i d e n t The  closeness  The  correlation coefficient  good a s t r a i g h t l i n e i s produced  by the e x p e r i m e n t a l p o i n t s . b e t t e r the s t r a i g h t l i n e  from F i g u r e s  t o l i n e a r i t y of t h i s c o r r e l a t i o n  i s a l s o r e f l e c t e d i n Table X X I . r g i v e s a measure of how  The  (126).  be seen t h a t a l l the v a l u e s  c l o s e r r i s t o one, From Table X X I ,  H R  values  the  i t can  of r are g r e a t e r t h a n 0.995'  T h i s shows t h a t v e r y good s t r a i g h t l i n e s are when v a l u e s  constant,  of l o g k-j_ were p l o t t e d a g a i n s t the i n b o t h DMSO-ethanol and  obtained respective  DMSO-methanol.  A l t h o u g h the l i n e s are s t r a i g h t , , the s l o p e s are f a r from unity. I n the a c i d r e g i o n t h e r e a r e cases when a l o g k - a c i d i t y f u n c t i o n c o r r e l a t i o n r e s u l t s i n slopes  of  l e s s t h a n u n i t y f o r r e a c t i o n s i n v o l v i n g a slow p r o t o n transfer step.  Kresge and  Chiang (127)  found t h a t f o r  the l o s s of t r i t i u m i o n from 1 , 3 ? 5 - t r i m e t h o x y - [ . 2 - 3 ] H  150  benzene i n aqueous p e r c h l o r i c a c i d , a p l o t of l o g ^exchange But  versus H  0  the p r o t o n a t i o n  f o l l o w the H '  gave a s t r a i g h t l i n e o f s l o p e 1.07'. of 1 , 3 ? 5 - t r i m e t h o x y b e n z e n e  f u n c t i o n and  R  i n the r e g i o n i n w h i c h  k i n e t i c s were measured, the 2H  =  0  %•  e x c  j  i a n  g  '  versus H *  e  the  expression  h o l d s a p p r o x i m a t e l y (127). log k  should  R  (81) The  s l o p e of the p l o t of  would t h e n be 0«53»  I t was  also  shown t h a t the hydrogen exchange i n 1 , 3 ? 5 - t r i m e t h o x y benzene f o l l o w e d the B r o n s t e d c a t a l y s i s r e l a t i o n w i t h C X b e i n g e q u a l t o 0.518  w i t h a s t a n d a r d d e v i a t i o n o f 0.007  (128). Noyce and  co-workers have s t u d i e d the a c i d  c a t a l y z e d i s o m e r i z a t i o n of c i s - b e n z a l a c e t o p h e n o n e (129), c i s - c i n n a m i c a c i d (130  - 132)  c i s - s t i l b e n e s (133)•  and  They found t h a t the k i n e t i c s of the i s o m e r i z a t i o n o f cis-cinnamic  a c i d s p a r a l l e l e d the a c i d i t y f u n c t i o n  w i t h n e a r l y u n i t slope log k versus H  (133).  large negative  the H  Q  and  0  that a p l o t of  I n b o t h c a s e s , a slow p r o t o n  proposed as the f i r s t s t e p on the b a s i s  a s u b s t a n t i a l solvent isotope  t h a t the H^'  131)  H  f o r the i s o m e r i z a t i o n of c i s - s t i l b e n e  0  gave a s l o p e of 1.2-5 a d d i t i o n was  (130,  the  p  value  (131,  f u n c t i o n should  f u n c t i o n and  e f f e c t (132, 133)•  I f one  133)  and  a  considers  be a p p l i c a b l e r a t h e r  t h a t e q u a t i o n (81)  of  than  h o l d s , t h e n the  151  s l o p e s o f the l o g k-H ' c o r r e l a t i o n would be a p p r o x i m a t e l y R  the same as t h a t found by Kresge and Chiang  (127).  The r e s u l t s o f Kresge and Chiang (127, 128) and those o f Noyce and co-workers (130 - 133) suggest t h a t when the p r o t o n i s t r a n s f e r r e d i n the r a t e  determining  stage, a p l o t of l o g k versus the appropriate f u n c t i o n gives a slope of l e s s than u n i t y .  acidity  The same may  a p p l y t o base c a t a l y z e d r e a c t i o n s . When a n a l k o x i d e i o n a c t s as a n u c l e o p h i l e and adds t o a n u n s a t u r a t e d system i n the r a t e  determining  s t e p , the a p p r o p r i a t e c o r r e l a t i o n o f t h e k i n e t i c s i s w i t h the % -  function.  The mechanism f o r the base  catalyzed isomerization of CX-cyano-cis-stilbenes can be r e p r e s e n t e d by t h e e q u a t i o n  C  +  0R"^=^  where C, T, and O R  C0R"^==^  T  +  OR"  (82)  r e p r e s e n t t h e c i s and t r a n s  isomers  and t h e base r e s p e c t i v e l y . The r a t e o f t h e r e a c t i o n c a n t h e n be g i v e n by t h e e x p r e s s i o n  (83)  where v i s the r a t e o f t h e r e a c t i o n , -d|_CJ/dt, k-j_ i s the apparent f i r s t order r a t e constant, k  9  i s t h e second  152  o r d e r r a t e c o n s t a n t and f  i s the a c t i v i t y c o e f f i c i e n t  f o r the t r a n s i t i o n s t a t e .  I f the t r a n s i t i o n state f o r the  c i s - t r a n s i s o m e r i z a t i o n has a s t r u c t u r e  intermediate  between t h a t o f t h e s t r u c t u r e s o f C  OR  +  and COR ,  then the a c t i v i t y c o e f f i c i e n t o f the t r a n s i t i o n  state  can be w r i t t e n i n terms o f t h e a c t i v i t y c o e f f i c i e n t s o f (13+).  the two l i m i t i n g forms  i-a f+  =  (f  C OR~ f  )  (f  cx  COR-  W  }  Here C X i s a measure o f t h e degree t o w h i c h t h e t r a n s i t i o n s t a t e resembles the intermediate have a v a l u e between 0 and 1.  COR , and as such s h o u l d  By u s i n g e q u a t i o n (84-),  e q u a t i o n (83) becomes  k. [0R-]f °R fcf  k  l  f  (85)  C0R  The a c t i v i t y c o e f f i c i e n t term i n e q u a t i o n (85) c a n be e x p r e s s e d i n terms o f a n a c i d i t y f u n c t i o n .  For the  equilibrium  TOR  T  +  OR  a n a c i d i t y f u n c t i o n b_ c a n be d e f i n e d a s  (86)  153  )  fm(OR  [TORl  = f  K  -VT^  (87)  T0R  where K i s the e q u i l i b r i u m constant f o r e q u a t i o n From e q u a t i o n (87)  i ' - S f  T  0  R  one  (86).  can o b t a i n the e x p r e s s i o n  -  -  (88)  -  b  &R ]  S i n c e T and C d i f f e r o n l y i n geometric arrangement, the corresponding a c t i v i t y c o e f f i c i e n t be almost  i d e n t i c a l ; and,  terms fjOR"  a  n  d  f  C0R°"  T e  ^  e T  terms f j and f  s i n c e the a c t i v i t y '  to  virtually  i n t e r m e d i a t e s , the a c t i v i t y c o e f f i c i e n t  c  must  coefficient  identical term i n  equation  (85)  can be r e p l a c e d by a measurable q u a n t i t y .  Equation  (85)  then becomes  *1  By u s i n g equations  (89)  (70)  K HOR h _ R  and  (87),  the e x p r e s s i o n  (90)  154-  can be o b t a i n e d where K the s o l v e n t .  H 0 R  i s the i o n i z a t i o n c o n s t a n t  Using t h i s expression,  for  equation.(89) then  becomes  l  k  (91)  [OR"]  Upon t a k i n g l o g a r i t h m s  l o g k-L  i s obtained  =  since k  2  and  s i m p l i f y i n g , the  OfHR-  and %QR  +  a r e  equation  (92)  constant  constants  and  i n the  s o l u t i o n s i n w h i c h the e q u i l i b r i a ' a n d k i n e t i c s were s t u d i e d , the c o n c e n t r a t i o n  o f the a l k o x i d e i o n was  kept  constant.  T h i s a n a l y s i s shows t h a t the s l o p e of a p l o t of l o g k v e r s u s the a p p r o p r i a t e o f how  a c i d i t y f u n c t i o n g i v e s an i n d i c a t i o n  c l o s e l y the t r a n s i t i o n s t a t e resembles the  inter-  mediate a n i o n i n cases where the base c o n c e n t r a t i o n kept  is  constant. On i n s p e c t i o n of Table X X I ,  i t can be  seen  t h a t the k i n e t i c s of the base c a t a l y z e d i s o m e r i z a t i o n of OC-cyano-cis-stilbenes acidity function H R  O.665.  c o r r e l a t e very w e l l with  the  w i t h s l o p e s of between 0.4-26 and  T h i s i m p l i e s t h a t the t r a n s i t i o n s t a t e f o r  i s o m e r i z a t i o n has a s t r u c t u r e a p p r o x i m a t e l y h a l f between t h a t f o r the s t a r t i n g m a t e r i a l (C  +  the  way OR  )  155  and t h e i n t e r m e d i a t e a n i o n ( C O R ) . I t i s a l s o e v i d e n t from Table XXI t h a t as t h e s u b s t i t u e n t s become more e l e c t r o n w i t h d r a w i n g , t h e s l o p e decreases  i n value.  displacement  T h i s suggests t h a t t h e f r a c t i o n a l  of the t r a n s i t i o n state along the r e a c t i o n  c o o r d i n a t e i s l e s s e n e d as e l e c t r o n w i t h d r a w i n g s u b s t i t u e n t s a r e p l a c e d i n the r i n g . I n a d d i t i o n t o t h i s , t h e s l o p e s o f the k i n e t i c H R - c o r r e l a t i o n were found t o be g r e a t e r f o r each r e a c t a n t when e t h o x i d e i o n was t h e base t h a n when methoxide i o n was t h e c a t a l y s t .  I f these s l o p e s can be t a k e n as a n  i n d i c a t i o n o f t h e e x t e n t o f t h e bond f o r m a t i o n i n t h e t r a n s i t i o n s t a t e between t h e r e a c t a n t and t h e a l k o x i d e , as proposed  above, t h e n t h e e x t e n t o f the bond f o r m a t i o n i n  the t r a n s i t i o n s t a t e when e t h o x i d e i s the base must be g r e a t e r t h a n i n t h e case when methoxide i o n i s t h e base. Due t o a n a d d i t i o n a l methylene group, t h e e t h o x i d e i o n i s l a r g e r s t e r i c a l l y t h a n the methoxide i o n .  The g r e a t e r  s i z e o f t h e . e t h o x i d e i o n may n e c e s s i t a t e a g r e a t e r d e c o u p l i n g o f t h e 77"-electrons i n t h e  carbon-carbon  double bond b e f o r e the i s o m e r i z a t i o n can take p l a c e . The k i n e t i c s o f c e r t a i n a r o m a t i c displacements  nucleophilic  i n c o n c e n t r a t e d sodium methoxide s o l u t i o n s  were found t o c o r r e l a t e w i t h t h e a p p r o p r i a t e H R - f u n c t i o n . S c h a a l and Peure (67)  studied the a l k a l i n e  degradation  o f "H—dinitrobenzene i n sodium methoxide-methanol s o l u t i o n s  156  and  the  s l o p e of the l o g k v e r s u s H  The  Hj^ s c a l e had  previously  and  Lambert. (37)  and  p l o t was  M  been d e t e r m i n e d by  i s based on methanol as  standard state u s i n g mainly s u b s t i t u t e d and  d i p h e n y l a m i n e s as i n d i c a t o r s .  d a t a of. S c h a a l and HR-  near u n i t y .  Peure (67),  Schaal  the  anilines  U s i n g the  kinetic  a p l o t of l o g k versus  g i v e s a good s t r a i g h t l i n e of s l o p e 0.80.  r e c e n t l y , S c h a a l and  Latour studied  More  the a l k a l i n e decomposi  t i o n o f 2 - d i n l t r o b e n z e n e i n sodium methoxide-methanol solutions.  Here a g a i n a p l o t of l o g k v e r s u s H ^ gave a  s t r a i g h t l i n e o f near u n i t s l o p e (68) l o g k v e r s u s HR-  while a plot  g i v e s a s l o p e o f 0.81.  On l o o k i n g  the i n d i c a t o r s u s e d t o e s t a b l i s h the Hj^ and HRone  would e x p e c t t h a t a r o m a t i c n u c l e o p h i l i c  s h o u l d c o r r e l a t e b e t t e r w i t h the HRscale. l o g k-HR-  The  This i s i n favor followed  H  O  by the  Substituent  be due  substitutions  t h a n w i t h the  slow r a t e d e t e r m i n i n g  the  pre-equilibrium step.  Reactivity  I n o r d e r t o determine the e f f e c t o f on the r a t e s of i s o m e r i z a t i o n , the r a t e s a t one composition.  HR-  substituents  i t i s n e c e s s a r y t o compare  v a l u e or i n a s o l v e n t  From F i g u r e s 10 and  t h i s comparison was  H^  to experimental e r r o r s ,  o f a mechanism w i t h a  E f f e c t s on the  at  scales,  s l i g h t l y l e s s than u n i t slopes f o r  c o r r e l a t i o n s may  of  11,  oniv possible with  of  fixed  i t can be  seen t h a t  extrapolation  157  i n some c a s e s .  By u s i n g t h e s l o p e s c a l c u l a t e d by t h e  method o f l e a s t square a n a l y s i s and r e c o r d e d i n Table X X I , it  i s p o s s i b l e t o c a l c u l a t e l o g k, v a l u e s f o r t h e v a r i o u s  s u b s t i t u t e d CX-cyano-eis-stilbenes a t a H - value o f R  ,16.00 i n DMSO-ethanol and DMSO-methanol  solutions.  The  r e s u l t s o f these c a l c u l a t i o n s a r e r e c o r d e d i n Table XXV. U s i n g t h e l o g k]_ v a l u e s r e c o r d e d i n Table XXV, a p l o t o f t h e l o g k]_ v a l u e s f o r t h e base c a t a l y z e d i s o m e r i z a t i o n of s u b s t i t u t e d ( X - c y a n o - c i s - s t i l b e n e s versus the r e s p e c t i v e XT' v a l u e s gave r e a s o n a b l y s t r a i g h t  lines.  These p l o t s a r e r e c o r d e d i n F i g u r e 17.  TABLE XXV C a l c u l a t e d l o g k^' V a l u e s f o r t h e I s o m e r i z a t i o n o f S u b s t i t u t e d CX-Cyano-cis-stilbenes i n DMSO-Ethanol and DMSO-Methanol a t a H - V a l u e o f 16.00 R  Substituent  l o g k-, i n DMSO-Ethanol  l o g k-, i n DMSO-Methanol  4-nitro  +O.963  +1.208  3-nitro  +O.O87  +0.4-50  3-chloro  -0.817  0.24-2  4— c h l o r o  -1.187  -0.616  hjrdrogen  -2.049  -1.394  4-methoxy  -2.882  -2.271  FIGURE 1 7 .  HAMMETT CORRELATIONS OF THE RATES OF ISOMERIZATIONS OF SUBSTITUTED O 6 - C Y A N 0 - C I S - S T I L B E N E S I N DMSO-ETHANOL AND DMSO-METHANOL AT A H VALUE OF 1 6 . 0 0 AT 2 5 ° R  1.6 1.2 0.8 0.4  DMSO-METHANOL  0  SLOPE = + 2 . 8 2 p = 0.995  -0.4 H  -0.8 LOG  CO  k.  - 1.2  DMSO-ETHANOL SLOPE = + 3 . 0 7  - 1.6  r  -2.0  =  0.999  -2.4 -2.8 -0.4  -0.2  0.2  0.4  cr  0.6  0.8  1.0  159  as d e t e r m i n e d by the method o f l e a s t square a n a l y s i s , a r e 3.07 and 2.82 i n DMSO-ethanol and DMSO-methanol r e s p e c t i v e l y . T h i s shows t h a t  c o n s i d e r a b l e n e g a t i v e charge i s d e v e l o p e d These p  i n the t r a n s i t i o n s t a t e .  v a l u e s c a n be compared  w i t h a v a l u e o f 2.54 f o r the s a p o n i f i c a t i o n o f e t h y l benzoates i n 85$ e t h a n o l a t 25° 3.3 f o r t h e n u c l e o p h i l i c  (120d) and a v a l u e o f  s u b s t i t u t i o n by e t h o x i d e i o n o f  4—substituted-2-nitrophenyl fluorides i n ethanol a t  4-9.6°  (135).  Although the  P value  f o r the  i s not as h i g h as t h a t f o r the a r o m a t i c  isomerization  nucleophilic  s u b s t i t u t i o n , i t i s h i g h e r t h a n t h a t f o r the s a p o n i f i c a t i o n of e t h y l benzoates. The p  v a l u e f o r the i s o m e r i z a t i o n  c i s - s t i l b e n e s can a l s o be compared \ ^ i t h the e q u i l i b r i u m a d d i t i o n of a l k o x i d e  ions to  I n DMSO-ethanol, the r a t i o o f the p  o f CX-cyanop v a l u e f o r the  cX-cyanostiiben.es.  v a l u e f o r the i s o m e r -  i z a t i o n t o t h a t f o r the e q u i l i b r i u m a d d i t i o n o f e t h o x i d e ion i s  0.64-, and i n DMSO-methanol, the c o r r e s p o n d i n g  r a t i o i s 0.66. the  The v a l u e s o f these r a t i o s i n d i c a t e  that  i o n i z a t i o n c o n s t a n t s a r e much more s e n s i t i v e t o  substituent  e f f e c t s t h a n a r e the r a t e s  of  isomerization.  I t i s a l s o i n t e r e s t i n g ' t o note t h a t the v a l u e s o f t h e s e r a t i o s a r e i n a p p r o x i m a t e agreement w i t h the s l o p e s o f the k i n e t i c - a c i d i t y f u n c t i o n  correlation.  F i g u r e 17 shows t h a t the p o i n t f o r t h e 4 — n i t r o  160  s u b s t i t u e n t f a l l s o f f the l i n e j o i n i n g the other  five  p o i n t s r e g a r d l e s s o f whether t h e CT o r G~~ v a l u e i s u s e d . The average e f f e c t i v e 0"" v a l u e f o r t h e 4— n i t r o s u b s t i t u e n t was c a l c u l a t e d t o be  0.95*  T h i s suggests  t h a t the r e s o n -  ance i n t e r a c t i o n o f t h e . 4 — n i t r o group i s reduced  but n o t  completely e l i m i n a t e d . T r a n s - s t i l b e n e has a c o p l a n a r s t r u c t u r e whereas c i s - s t i l b e n e cannot assume such a s t r u c t u r e because t h e ortho-hydrogens  would o v e r l a p .  As a r e s u l t , one o f t h e  phenyl r i n g s i s f o r c e d t o r o t a t e out of the plane of the r e s t o f the m o l e c u l e  (136).  I t i s very l i k e l y that the  same s i t u a t i o n e x i s t s i n t h e case o f O C - c y a n o - c i s - s t i l b e n e s . I t i s thus p o s s i b l e t h a t t h e resonance i n t e r a c t i o n o f t h e 4— n i t r o s u b s t i t u e n t w i t h t h e r e a c t i o n s i t e i s reduced because o f t h e t w i s t i n g o f one o f the p h e n y l r i n g s o u t o f the plane o f t h e r e s t o f t h e m o l e c u l e .  T h i s would  e x p l a i n the e f f e c t i v e CT" v a l u e o f 0 . 9 5 f o r t h e 4 — n i t r o group i n t h e i s o m e r i z a t i o n o f C X - c y a n o - c i s - s t i l b e n e s .  I.  A c t i v a t i o n Parameters I n any k i n e t i c s t u d y , i t i s d e s i r a b l e t o have  an e s t i m a t e o f the a c t i v a t i o n parameters.  By comparing  the e x p e r i m e n t a l v a l u e s w i t h t h e v a l u e s - f o u n d i n t h e l i t e r a t u r e , some mechanisms may be f a v o r e d w h i l e o t h e r s may he d i s c o u n t e d .  l6l The a c t i v a t i o n parameters i n Table X X I I I show t h a t the r a t e i n c r e a s e f o r the i s o m e r i z a t i o n o f CX-eyanoc i s - s t i l b e n e on going from 41.12 t o 64.21 mole % DMSO i n methanol i s due l a r g e l y t o a d e c r e a s e i n the of a c t i v a t i o n A H *  enthalpy  a i d e d s l i g h t l y by a n i n c r e a s e i n the  e n t r o p y o f a c t i v a t i o n As*.  The dependence o f t h e  r a t e i n c r e a s e , on going t o h i g h e r DMSO c o n c e n t r a t i o n s , on the decrease i n A H * i s i n agreement w i t h the r e s u l t s o f Cram e t a l (137) f o r the base c a t a l y z e d r a c e m i z a t i o n o f (+)~2-methyl-3-phenylpropionitrile  i n DMSO-methanol  s o l u t i o n s and the r e s u l t s o f K i n g s b u r y  (117) f o r t h e  r e a c t i o n o f CgH^CH S K " w i t h 4 - f l u o r o n i t r o b e n z e n e i n 4  2  DMSO-methanol s o l u t i o n s . Kingsbury  Both Cram e t a l (137) and  (117), however, r e p o r t e d d e c r e a s e s i n A.S*as R o b e r t s (138),  the c o n c e n t r a t i o n o f DMSO was i n c r e a s e d .  on the o t h e r hand, r e p o r t e d t h a t i n the h y d r o l y s i s o f v a r i o u s e s t e r s i n aqueous DMSO s o l u t i o n s , t h e A s * tended t o i n c r e a s e as the p r o p o r t i o n o f DMSO i n c r e a s e d . r e s u l t s suggest t h a t no g e n e r a l t r e n d i n e x p e c t e d as the DMSO c o n t e n t  These  A s * can be  i s increased.  I n g e n e r a l , the e n t r o p y and e n t h a l p y o f a c t i v a t i o n s l i s t e d i n Table X X I I I a r e a p p r o x i m a t e l y i n l i n e w i t h those f o r a b i m o l e c u l a r r e a c t i o n between a charged i o n and a n e u t r a l m o l e c u l e .  F o r example, i n the  n u c l e o p h i l i c s u b s t i t u t i o n o f m e t h y l bromide by e t h o x i d e  162  i o n a t 55°,  the e n t r o p y o f a c t i v a t i o n i s -13*9  energy o f a c t i v a t i o n i s 20.0 k c a l . m o l e " . 1  e.u. and the  I n the  a n a l o g o u s r e a c t i o n o f e t h y l bromide, the e n t r o p y o f a c t i v a t i o n i s -11.6 i s 21.0  e.u. and the energy o f a c t i v a t i o n  k c a l . mole"  1  (139).  These v a l u e s a r e f a i r l y c l o s e  t o the e n t r o p y o f a c t i v a t i o n o f -13.5 o f a c t i v a t i o n o f 16.6  k c a l . mole"  1  e.u. and the energy  f o r the methoxide i o n  catalyzed i s o m e r i z a t i o n of CX-cyano-cis-stilbene i n 41.12  mole % DMSO i n methanol a t 2 5 ° . On the o t h e r hand, the a c t i v a t i o n  parameters  l i s t e d i n Table X X I I I a r e q u i t e d i f f e r e n t from those r e p o r t e d by Rappoport, Degani and P a t a i c a t a l y z e d i s o m e r i z a t i o n of e t h y l phenylacrylate (XXXIII).  (77)  f o r the amine  CX-cyano-|3 -2-methoxy-  These w o r k e r s r e p o r t e d e n e r g i e s  ^COpCpHr-  XXXIII o f a c t i v a t i o n (Ea) i n the range o f 5«06 t o 2.71  k c a l . mole"  w i t h the e x a c t v a l u e depending on the p a r t i c u l a r amine u s e d as c a t a l y s t .  Accompanying  were v e r y n e g a t i v e v a l u e s f o r A s -66 e.u.  these low v a l u e s f o r Ea , r a n g i n g f r o m -43 t o  These low v a l u e s f o r Ea and h i g h n e g a t i v e  v a l u e s f o r A s * were e x p l a i n e d i n terms o f a z w i t t e r i o n i c  163  intermediate  or t r a n s i t i o n s t a t e .  r e p l a c e m e n t o f the n e g a t i v e  T h i s shows t h a t t h e  methoxide i o n as a base by  a n e u t r a l amine has an e x t r e m e l y l a r g e e f f e c t on the a c t i v a t i o n parameters even though the two mechanisms be s i m i l a r i n o t h e r  J.  AL F u r t h e r  may  respects.  D i s c u s s i o n o f the I s o m e r i z a t i o n  Mechanism  I t has a l r e a d y been p o i n t e d out t h a t the base catalyzed isomerization of (X-cyano-cis-stilbenes o r d e r i n base and f i r s t o r d e r i n r e a c t a n t . i t has a l s o been shown t h a t the base  is first  In addition,  catalyzed  isomerizations  go t o c o m p l e t i o n , and t h a t no s u b s t a n t i a l  side reactions  occur.  A mechanism, s i m i l a r t o t h a t proposed by Rappoport, Degani and P a t a i ( 7 7 ) can t h e n be proposed f o r the base c a t a l y z e d i s o m e r i z a t i o n o f  tX-cyano-cis-stilbenes.  Scheme I I I OR PIL  ^Ph  NC  H  + XXXV c i s  XXXIV  Ph.  H  NC  Ph  + OR  XXXVI  XXXV t r a n s  16k  I n t h i s mechanism, t h e f i r s t s t e p i s the r e v e r s i b l e a t t a c k o f t h e n u c l e o p h i l e on t h e u n s a t u r a t e d forming  system  t h e c i s - c a r b a n i o n (XXXV c i s ) . S i n c e t h e h i n d r a n c e  t o t h e r o t a t i o n around t h e 0(-|3  carbon bond i n XXXV, o r  t o the r a p i d i n v e r s i o n o f the carbanions,  should n o t be  g r e a t , a r a p i d e q u i l i b r i u m s h o u l d be e s t a b l i s h e d between XXXV c i s and XXXV t r a n s .  The l a s t s t e p i n t h e r e a c t i o n  t h e n i n v o l v e s t h e e l i m i n a t i o n o f t h e n u c l e o p h i l e f r o m XXXV t r a n s t o form t h e C X - c y a n o - t r a n s - s t i l b e n e A steady  (XXXVI).  s t a t e t r e a t m e n t o f t h e above scheme t h e n  gives the e x p r e s s i o n  dfcj  k  i 2 3 [l M  dt  k  k  ~  C  k  _i 3 k  +  k  k  -l -2 -3 M k  -l -2 k  O] 6  k  +  k  k  where T, C and B r e f e r t o t h e t r a n s - i s o m e r , isomer and t h e base r e s p e c t i v e l y . o b s e r v e d w i t h the t r a n s - i s o m e r  (93)  2 3  the c i s -  S i n c e no r e a c t i o n was  under t h e c o n d i t i o n s u s e d  t o study t h e i s o m e r i z a t i o n o f the t X - c y a n o - e i s - s t i l b e n e s , t h i s must mean t h a t the e q u i l i b r i u m l i e s f a r towards t h e trans-isomer. k_^k_2 _3' k  ^  T h i s means t h a t k-]_k2k3 must be g r e a t e r  than  p r e v i o u s l y been s u g g e s t e d t h a t t h e  r a t e o f a t t a c k o f a n u c l e o p h i l e on a c i s - i s o m e r i s approximately  t h e same as t h a t on a t r a n s - i s o m e r  (77).  T h i s means t h a t k^ and k_^ a r e e s s e n t i a l l y e q u a l and t h a t  165  kpk^^k^k^.  The e x p e r i m e n t a l r a t e c o n s t a n t k  Q X  p in  e q u a t i o n (93) t h e n r e d u c e s t o  k  kexp _  1 = —  +• k  - : L  l  /k  +  2  •  k_ k_ /k k3' 1  2  S i n c e k^k^ i s c o n s i d e r a b l y , g r e a t e r t h a n k_]_k_2? k_]_k_ /k k^ 2  2  c  a  n  (94-)  2  then  t>e i g n o r e d w i t h r e s p e c t t o u n i t y and  e q u a t i o n (94) i s reduced  t o the expression  I f t h i s a n a l y s i s were c o r r e c t , t h e n a c c o r d i n g t o Rappoport, Degani and P a t a i ( 7 7 ) , (a.)  there a r e three possible  situations:  When t h e e l i m i n a t i o n s t e p i s f a s t e r  the r o t a t i o n , t h e n k _ i > k  k  exp  than  and t h e e q u a t i o n  2  k, k  9  k_  1  (  9  6  )  results. (b.)  When t h e r a t e s o f e l i m i n a t i o n and r o t a t i o n  are approximately  t h e same, t h e n k_]_^sk and 2  e q u a t i o n (95) a p p l i e s . (c.)  When t h e r a t e o f r o t a t i o n i s f a s t e r t h a n t h e  166  e l i m i n a t i o n , then k > k  r e s u l t i n g i n the  2  equation k  In  e x p  =  k  (97)  x  the p r e s e n t case, e q u a t i o n (96) can be  e l i m i n a t e d because t h e f i r s t p o s s i b i l i t y i m p l i e s t h e e x i s t e n c e o f a p r e - e q u i l i b r i u m . I n a mechanism w i t h a p r e - e q u i l i b r i u m , the a c t i v i t y c o e f f i c i e n t o f t h e t r a n s i t i o n s t a t e , f * , would e i t h e r resemble t h a t o f t h e c i s - c a r b a n i o n (XXXV c i s ) o r some i n t e r m e d i a t e form between t h a t o f XXXV c i s arid XXXV t r a n s .  I n such a case, s i n c e t h e  a c t i v i t y c o e f f i c i e n t s f o r XXXV c i s and XXXV t r a n s s h o u l d be n e a r l y i d e n t i c a l , t h e c o r r e l a t i o n o f t h e k i n e t i c s w i t h t h e H^- f u n c t i o n s h o u l d g i v e a s t r a i g h t l i n e o f u n i t slope.  S i n c e u n i t s l o p e s were n o t o b t a i n e d t h e  f i r s t p o s s i b i l i t y can be r e n d e r e d  unlikely.  The a v a i l a b l e d a t a cannot d i s t i n g u i s h between t h e o t h e r two p o s s i b l e s i t u a t i o n s .  I n both cases, the  e x p e r i m e n t a l r a t e c o n s t a n t would n o t be f a r d i f f e r e n t from k-^. The v a l u e s f o r t h e energy o f a c t i v a t i o n f o r t h e i s o m e r i z a t i o n (Table X X I I I ) a r e i n t h e range o f 1*4-.9 t o 17.3 k c a l . mole"" . 1  v a l u e s o f 11.7,  These compare v e r y c l o s e l y w i t h t h e  13'1 and l 6 . 2 k c a l . mole"" f o r t h e base 1  catalyzed h y d r o l y s i s of 4—methoxybenzylidenemalononitrile,  167  ethyl  CX-cyano-p - 4 - m e t h o x y p h e n y l a c r y l a t e  cX-cyano-  and  |3 - 4 - m e t h o x y p h e n y l a c r y l a m i d e r e s p e c t i v e l y ( 8 6 ) . cases the r a t e d e t e r m i n i n g s t e p was  I n these  c o n s i d e r e d t o be  a t t a c k o f the h y d r o x i d e i o n on the carbon-carbon bond.  I n the base- c a t a l y z e d h y d r o l y s i s o f  values of 2 0 . 0  kcal..mole"!  a n  ^  the  double  chalcone,  „ i o . 6 e.u. were r e p o r t e d  f o r the energy of a c t i v a t i o n and the e n t r o p y o f a c t i v a t i o n respectively (140).  Here a g a i n the a t t a c k by the  h y d r o x i d e i o n on the carbon-carbon  double  bond  was  c o n s i d e r e d t o occur i n the r a t e d e t e r m i n i n g s t e p .  From  t h i s comparison i t can be seen t h a t the a c t i v a t i o n parame t e r s f o r the base c a t a l y z e d i s o m e r i z a t i o n o f  CX-cyano-cis-  s t i l b e n e s c o r r e s p o n d q u i t e c l o s e l y t o those found i n cases i n v o l v i n g a slow r a t e d e t e r m i n i n g a d d i t i o n o f a n u c l e o p h i l e t o a carbon-carbon  double  bond.  This supports  the  c o n t e n t i o n t h a t the e x p e r i m e n t a l r a t e c o n s t a n t i s governed l a r g e l y by the r a t e c o n s t a n t f o r the f i r s t s t e p (k-^). The a c t i v a t i o n parameters i n Table X X I I I  can  a l s o be compared w i t h those f o r the c y a n o e t h y l a t i o n o f alcohols.  F e l t and Z i l k h a  of a c t i v a t i o n of 18.7 a c t i v a t i o n of - 7 . 2 methanol.  (141)  k c a l . mole  r e p o r t e d an energy 1  and an e n t r o p y  of  e.u. f o r the c y a n o e t h y l a t i o n o f  The r a t e d e t e r m i n i n g s t e p was  c o n s i d e r e d t o be  the a t t a c k o f the methoxide i o n on a c r y l o n i t r i l e .  The  h i g h e r energy o f a c t i v a t i o n f o r the c y a n o e t h y l a t i o n r e a c t i o n t h a n f o r the i s o m e r i z a t i o n may  be due t o a l e s s  168  a c t i v a t e d double bond i n a c r y l o n i t r i l e t h a n i n CX-cyanocis-stilbene.  S i m i l a r i l y , the l e s s n e g a t i v e  entropy o f  a c t i v a t i o n f o r t h e c y a n o e t h y l a t i o n r e a c t i o n may w e l l be due  to a l e s s hindered unsaturated  t h a n i n t h e case o f O C - y c  a n o  *-  c i s  system i n a c r y l o n i t r i l e  --stilbenes.  This  again  s u p p o r t s the v i e w t h a t k p£i=k^. eX  From t h e p r e v i o u s  d i s c u s s i o n , i t i s seen t h a t  the e f f e c t s o f s u b s t i t u e n t s on the r a t e o f i s o m e r i z a t i o n of CX-cyano-cis-stilbenes that the p  value  are twofold.  F i g u r e 17 shows  i s f a i r l y l a r g e and p o s i t i v e f o r t h e  isomerization, i n d i c a t i n g that a considerable negative  amount o f  charge i s d e v e l o p e d on t h e CX-carbon atom i n  the t r a n s i t i o n s t a t e .  From Table X X I i t can be seen t h a t  the s u b s t i t u e n t s a l s o have a n e f f e c t on the s l o p e s o f the l o g k^-RR- c o r r e l a t i o n . T h i s s l o p e , termed CX. i n equation  (92), was shown t o be a measure o f how c l o s e l y  the t r a n s i t i o n s t a t e resembled t h e i n t e r m e d i a t e I n the s t r u c t u r e o f t h e c a r b a n i o n  intermediate  carbanion. from t h e  a d d i t i o n o f methoxide i o n t o 0 ( - c y a n o - c i s - s t i l b e n e , one u n i t of negative  charge can be r e p r e s e n t e d - a s r e s i d i n g  on t h e OC-carbon atom even though i t i s r e a l i z e d t h a t the g r e a t e r p o r t i o n o f t h e charge must be d e l o c a l i z e d i n t o t h e p h e n y l r i n g and t h e cX-cyano group.  The t r a n s -  i t i o n s t a t e i n t h e methoxide i o n c a t a l y z e d i s o m e r i z a t i o n of <X-cyano-cis-stilbene  can t h e n be r e p r e s e n t e d  by .  169  structure  XXXVII  S"0CH P  h  3  ^s N  CN XXXVII  The p o r t i o n o f the n e g a t i v e charge r e s i d i n g on the C X c a r b o n i n XXXVII, i . e . i n the  -  C X - p o r t i o n o f the m o l e c u l e ,  would be about h a l f t h a t o f the t o t a l n e g a t i v e charge i n the t r a n s i t i o n s t a t e .  As the s u b s t i t u e n t s i n the CX-phenyl  r i n g become more e l e c t r o n w i t h d r a w i n g , the p r o p o r t i o n o f the n e g a t i v e charge r e s i d i n g i n t h e C X - p o r t i o n o f t h e m o l e c u l e i n t h e t r a n s i t i o n s t a t e becomes l e s s .  The  e v i d e n c e f o r t h i s i s the observed decrease i n t h e s l o p e o f the l o g k-H - c o r r e l a t i o n as the s u b s t i t u e n t s i n t h e CX-phenyl r i n g become more e l e c t r o n ' w i t h d r a w i n g .  With  s t r o n g l y e l e c t r o n w i t h d r a w i n g groups i n the Q ( - p h e n y l  ring,  the double bond c h a r a c t e r o f t h e 0(-|B c a r b o n bond may be l e s s e n e d due t o some c o n t r i b u t i o n o f resonance such as X X X V I I I t o the t o t a l s t r u c t u r e .  structures  I n such a.case,  a s m a l l e r amount o f bond f o r m a t i o n between the methoxide i o n and t h e |3-carbon atom may be n e c e s s a r y b e f o r e r o t a t i o n about t h e 0(-j3  carbon bond i s p o s s i b l e .  T h i s would  e x p l a i n t h e decrease i n the s l o p e CX as t h e s u b s t i t u e n t s become more e l e c t r o n w i t h d r a w i n g .  170  XXXVIII  I n . a d d i t i o n t o the mechanism proposed i n Scheme I I I , another p o s s i b i l i t y e x i s t s .  Cram ( 8 l )  Hunter and  found t h a t c i s - s t i l b e n e underwent base  catalyzed  i s o m e r i z a t i o n as w e l l as d e u t e r i u m exchange t h r o u g h a v i n y l carbanion.  T h i s suggests t h a t the  (X-cyano-cis-stilbenes  of  may  isomerization  take p l a c e by a p r o t o n  removal r e a c t i o n g i v i n g a t r a n s i t i o n s t a t e of s t r u c t u r e s i m i l a r to XVIII.  I f t h i s were the mechanism, t h e n  CX.-eyano-CX?-methoxy-cis-stilbene s h o u l d not under b a s i c c o n d i t i o n s .  Since  shown t h a t (X-cyano-  i t was  (X -methoxy-cis-stilbene d i d isomerize 1  isomerize  i n DMSO-methanol  c o n t a i n i n g 0 . 0 1 M sodium methoxide, t h i s must mean t h a t  the  i s o m e r i z a t i o n mechanism does not take p l a c e t h r o u g h a v i n y l c a r b a n i o n of s t r u c t u r e X V I I I . by the f i n d i n g by Z i n n e t a l (115)  This i s supported that e t h y l  (X-phenyl-  cinnamate d i d not undergo d e u t e r i u m exchange when t r e a t e d w i t h c a t a l y t i c amounts of sodium e t h o x i d e  in  deuterioethanol.  171  K.  The R e a c t i o n o f l , l - B i s - ( 4 — n i t r o p h e n y l ) e t h e n e i n H i g h l y B a s i c Systems When l , l - b i s - ( 4 - - n i t r o p h e n y l ) e t h e n e (XXXIX)  was r e a c t e d w i t h tetramethylammonium h y d r o x i d e  i n DMSO,  had a m o l e c u l a r w e i g h t o f 544, as  t h e . i s o l a t e d product  determined.by t h e R a s t method, and the a n a l y s i s c o r r e s p o n d e d t o t h a t c a l c u l a t e d f o r the compound w i t h s t r u c t u r e X V I . T h i s compound can be a c c o u n t e d f o r by the f o l l o w i n g reaction route:  (4--N0 Ph) C=CH 2  2  0 H ~ ^ (4~N0 Ph) C-CH 0H  +  2  2  2  2  JN  XXXIX  (4-N0 Ph) CH-CH 0~ 2  (4-N0 Ph) Cft~CH 02  2  2  (4-N0 Ph) C=CH  +  2  2  2  2  ^  2  (4--N0 Ph) ™ CH - CH 0CH -C-(Ph-4--N0 ) 2  2  2  2  2  2  acetic acid  V (4--N0 Ph ) -CH-CH 0CH-CH- (Ph-4-N0 ) 2  2  2  2  2  XVI The  i s o l a t i o n o f t h e d i e t h e r (XVI) i l l u s t r a t e s t h e  c o m p l i c a t i o n s w h i c h can a r i s e when a t t e m p t i n g hydroxide  i o n as a Lewis base.  has been added t o an u n s a t u r a t e d  to use  Once t h e h y d r o x i d e i o n system, the p r o t o n  172  can s h i f t from the oxygen t o the carbon atom.  This  l e a v e s a n a l k o x i d e i o n as base w h i c h can undergo f u r t h e r r e a c t i o n s a s a Lewis base. When XXXIX was r e a c t e d w i t h methoxide i o n i n DMSO, the p r o d u c t  i s o l a t e d had a NMR spectrum and a n a l y s i s  i n agreement w i t h the s t r u c t u r e o f l , l - b i s - ( M — n i t r o p h e n y l ) 2-methoxyethane ( X V I I ) .  I n the NMR spectrum, t h e  s i n g l e t a t 6.56C*~ i s i n the r e g i o n a s s o c i a t e d w i t h t h a t o f a methoxy group (1+2).  The i n t e g r a t e d peak h e i g h t s o f  the t r i p l e t , d o u b l e t and s i n g l e t were i n the r a t i o o f l:2s3.-. The  T h i s i s a l s o i n agreement w i t h s t r u c t u r e X V I I .  t r i p l e t can be a s s i g n e d t o the s i n g l e p r o t o n a t t h e  o ( - p o s i t i o n , the d o u b l e t t o the two p r o t o n s a t the p o s i t i o n and'the s i n g l e t t o the t h r e e p r o t o n s  Im-  i n the  methoxy group. F u r t h e r i n s i g h t i n t o the r e a c t i o n o f XXXIX w i t h a l k o x i d e i o n s i n DMSO was o b t a i n e d from the spectra.  electronic  When sodium e t h o x i d e was added t o a s o l u t i o n o f  the ethene (XXXIX) i n about 90 mole % DMSO i n e t h a n o l , a n a b s o r p t i o n peak c e n t e r e d a t 710 my. was was  evident.  This  l i k e l y due t o the a n i o n formed by the a d d i t i o n o f  e t h o x i d e i o n t o the ethene s i n c e the a n i o n o f H-,V - d i n i t r o diphenylmethane has a maximum a b s o r p t i o n a t 70+ m j X ( 5 l ) . I t would be e x p e c t e d  t h a t the two i o n s would have v e r y  similar absorption spectra.  The a d d i t i o n o f a c e t i c a c i d  caused the a b s o r p t i o n a t 710 mu.to d i s a p p e a r .  This  1 7 3  s u p p o r t s t h e c o n t e n t i o n t h a t t h i s peak was due t o t h e a n i o n . However, the a d d i t i o n o f a c e t i c a c i d d i d n o t r e g e n e r a t e t h e e t h e n e ; i n s t e a d , a m i x t u r e o f the ethene and the a l c o h o l a d d i t i o n p r o d u c t was formed.  The p r o p o r t i o n  o f each o f  t h e s e p r e s e n t depended on the e x t e n t o f i o n i z a t i o n p r i o r t o the a d d i t i o n o f a c e t i c a c i d .  As t h e s o l u t i o n s  became more b a s i c due t o a n i n c r e a s e d c o n c e n t r a t i o n o f DMSO, the a d d i t i o n o f e t h o x i d e i o n t o the ethene became more complete as e v i d e n c e d by t h e i n c r e a s e i n t h e a b s o r p t i o n a t 7 1 0 mp.with the p o s i t i o n o f the a b s o r p t i o n maximum o f the a c i d i f i e d s o l u t i o n b e i n g s h i f t e d from 3 0 6 mjj. t o 2 8 2 mjx. I t i s n o t e w o r t h y t h a t the e l e c t r o n i c  spectrum  o f X V I I has a maximum a b s o r p t i o n a t 2 8 3 mju. i n DMSO solution.  S i n c e t h e r e p l a c e m e n t o f a methoxy group by  a n ethoxy group s h o u l d have l i t t l e e f f e c t on t h e e l e c t r o n i c spectra,  the p r o d u c t from the r e a c t i o n o f XXXIX w i t h  sodium e t h o x i d e i n DMSO f o l l o w e d  by the a d d i t i o n o f  acetic acid i s likely'l,l-bis-(4—nitrophenyl)2-ethoxyethane ( X L ) .  (1+-N0  2  C5H ^)2 CH - CH 2 -° CH 2 CH^  XL  The r e a c t i o n o f XXXIX w i t h sodium e t h o x i d e i n DMSO-ethanol s o l u t i o n s  can be i l l u s t r a t e d by t h e scheme:  174  (4-N0 C H^) C=CH 2  6  2  2  +  OEt  (4-N0 C H^) Q-GH -GCH CH3 2  XXXIX  6  k  2  2  2  K acetic acid or ethanol  2  NJ  k  -2  (4-N0 C^r^) -CH-CK -0CH CTi3 2  2  2  2  XL An i d e a as t o t h e r e l a t i v e importance o f the two e q u i l i b r i a i n t h i s scheme can be o b t a i n e d f r o m a n e s t i m a t e o f t h e pK v a l u e s f o r XXXIX and XL.  XXXIX was, a c c o r d i n g t o  s p e c t r a l measurements, h a l f i o n i z e d i n 6 9 mole % DMSO i n e t h a n o l w h i l e l , l - b i s - ( 4 - n i t r o p h e n y l ) e t h a n e , a s a model f o r XL, was h a l f i o n i z e d i n 5 6 mole % DMSO i n e t h a n o l . T h i s suggests  t h a t the second e q u i l i b r i u m ( k / k _ 2 ) may 2  make some c o n t r i b u t i o n t o t h e o v e r a l l  equilibria,  e s p e c i a l l y a t lower DMSO c o n c e n t r a t i o n s when XXXIX would be o n l y p a r t i a l l y i o n i z e d .  L.  The R e a c t i o n o f 4 , 4 - D i n i t r o b e n z o p h e n o n e w i t h >  Hydroxide, i o n i n DMSO The s t u d y o f t h e r e a c t i o n o f 4 , 4 ' - d i n i t r o benzophenone w i t h h y d r o x i d e  i o n i n DMSO-water s o l u t i o n s  was p r e l i m i n a r y i n n a t u r e .  The s p e c t r a l e v i d e n c e  o u t l i n e d p r e v i o u s l y suggests of the products  t h a t 4 - n i t r o p h e n o l i s one  i n this reaction.  The p r o d u c t i o n o f  175  h-nitrophenol  i n such a r e a c t i o n c o u l d a r i s e by  f o l l o w i n g routes  the  176  SUGGESTIONS FOR FURTHER WORK  I n t h i s t h e s i s i t has been shown t h a t  ethoxide  and methoxide i o n s c a t a l y z e t h e i s o m e r i z a t i o n o f CX-cyanocis-stilbenes.  Other n u c l e o p h i l e s  such as t h i o a l k o x i d e s  and  f l u o r i d e i o n s may a l s o c a t a l y z e t h i s  The  r e a c t i v i t y of small anions,  isomerization.  such a s t h e f l u o r i d e i o n ,  i s greater i n polar a p r o t i c solvents than i n p r o t i c ones  The c a t a l y t i c s t r e n g t h o f such  ( 1 4 3 ) .  nucleophiles  as w e l l as h o w . t h e i r c a t a l y t i c b e h a v i o r changes on i n c r e a s i n g the proportion.of  a polar aprotic solvent,  such as'DMSO, i n a p r o t i c s o l v e n t may be a f r u i t f u l area of study. I t may a l s o be p o s s i b l e t o measure t h e Lewis b a s i c i t y o f some a d d i t i o n a l a n i o n s u s i n g  CX-cyanostilbenes  as i n d i c a t o r s Compounds such as C X - c y a n o s t i l b e n e s a r e known to hydrolyze  r e a d i l y i n aqueous base ( 7 3 » 8 5 , 8 6 ) .  r a t e s o f t h e base c a t a l y z e d h y d r o l y s i s o f and  The >  (X-cyano-cis-  t r a n s - s t i l b e n e s may f u r n i s h some i d e a o f t h e Lewis  b a s i c i t y o f the h y d r o x i d e i o n and how t h i s v a r i e s w i t h an i n c r e a s e  i n t h e DMSO c o n t e n t i n aqueous s o l u t i o n s .  A p r e l i m i n a r y s t u d y was r e p o r t e d  on the r e a c t i o n  o f 4 , 4 ' - d i n i t r o b e n z o p h e n o n e w i t h h y d r o x i d e i o n i n aqueous DMSO s o l u t i o n s .  A n a n a l y s i s o f t h e UV spectrum  indicated  177  t h a t H ~ n i t r o p h e n o l was one o f the p r o d u c t s .  This i s  p e c u l i a r i n t h a t c l e a v a g e o f ketones u s u a l l y r e s u l t s i n a mole o f a c i d and a mole o f h y d r o c a r b o n b e i n g formed (.Ikk- - 14-6).  A complete p r o d u c t a n a l y s i s and  k i n e t i c study of t h i s r e a c t i o n should help i n e l u c i d a t i n g the mechanism. I n t h i s t h e s i s r e s u l t s were p r e s e n t e d w h i c h suggest t h a t t h e H _ s c a l e i n DMSO-ethanol s o l u t i o n s f o r c a r b o n a c i d s , as determined by Bowden and S t e w a r t (5l)j  may need t o be r e d e t e r m i n e d u s i n g  indicators  f o r w h i c h the e l e c t r o n i c s p e c t r a a r e n o t s o l v e n t dependent. The s u b s t i t u t e d 9 - p h e n y l f l u o r e n e s ( X L I ) w i t h t h e s u b s t i t u e n t s i n t h e p h e n y l r i n g may be a p r o m i s i n g system.  XLI  XLII A R_ s c a l e has r e c e n t l y been r e p o r t e d f o r  c a r b o x y l i c s u b s t i t u t e d a n i l i n e s and d i p h e n y l a m i n e s (14-7) • S I m i l a r i l y , a H = s c a l e may.be o f i n t e r e s t u s i n g . R  i n d i c a t o r s such as c a r b o x y l i c s u b s t i t u t e d stilbenes (XLII).  cX.-cyano-  178  BIBLIOGRAPHY  1.  R. P. B e l l , "Acids and Bases", Methuen Co. L t d . , London, 1952, Chapter 1.  2.  R. P. B e l l , "The P r o t o n i n Chemistry", Cornell U n i v e r s i t y P r e s s , I t h a c a , New York, 1959, p. 7..  3.  G. N. Lewis, "Valence and the S t r u c t u r e of Atoms and Molecules", The Chemical C a t a l o g Company Inc., New York, 1923, p. 14-2.  4-.  R. J . G i l l e s p i e , I n " F r i e d e l - C r a f t s and R e l a t e d Reactions", G. A. Olah ed., V o l . 1, I n t e r s c i e n c e P u b l i s h e r s , New York, 1966, p. 174-.  5.  J . Hine, " P h y s i c a l Organic Chemistry", McGraw-Hill Book Co. Inc., New York, 1962, (a.) Chapter2, (b.) Chapter 4-.  6.  R. A. Robinson and R. H. Stokes, "Electrolyte Solutions", Butterworths S c i e n t i f i c P u b l i c a t i o n s , London, 1959, Chapter 2.  7.  R. G. Bates, " D e t e r m i n a t i o n o f pH Theory and .'. Practice", John W i l e y and Sons, Inc., New York, 1964-, (a.) Chapter 6, (b.) p. 32.  8.  G. Kortum, W. Vogel and K. Andrussow, "Dissociation Constants o f Organic A c i d s i n Aqueous S o l u t i o n s " , Butterworths, London, 1961.  9.  L. P.^ Hammett and A. J . Deyrup, 5k, 2721 (1932).  J . Am.  and  Chem. S o c ,  10.  L. P. Hammett, " P h y s i c a l Organic Chemistry",,.V McGraw-Hill Book Co., Inc., New York, 194-0, Chapter 9«  11.  M. A. Paul and F. A. Long,  12.  N. C. Deno, i n "Survey of Progress i n Chemistry", A.F. S c o t t ed., V o l . 2, Academic P r e s s , New York, 1964-. .  Chem. Rev.,  £ 2 , 1 (1957).  :  13.  E . M. A r n e t t and C. Y. Wu, 8k, 1680 (1962).  J . Am.  Chem. S o c ,  179  14.  Y. Chiang and E. B. Whipple,  J . Am. Chem. S o c ,  85, 2763 ( 1 9 6 3 ) . 15.  F. A. Long and J . S c h u l z e , 86, 327 ( 1 9 6 4 ) .  16.  J . T. Edward and I . C. Wang, 966 ( 1 9 6 2 ) .  17.  A. R. K a t r i t z k y , A. J . Waring and K. Y a t e s , Tetrahedron, 1 £ , 4-65(1963).  18.  R.-B. Moodie, P. D. Wale and T. J . W h a i t e , J . Chem. S o c , 4-273 ( 1 9 6 3 ) .  19..  E. M . A r n e t t and G. W. Mach, 86, 2671 ( 1 9 6 4 ) .  20.  R. L. Hinman and J . Lang, 86, 3796 ( 1 9 6 4 ) .  21.  M . J . J o r g e n s o n and D. R. H a r t t e r , J . Am. Chem. S o c , 85,  J . Am. Chem. S o c , Can. J . Chem., 40,  J . Am. Chem. S o c ,  J . Am. Cham. S o c ,  878 ( 1 9 6 3 ) .  22.  K. Y a t e s and H. W a i , J . Am. Chem. S o c , 8 6 , 5408 ( 1 9 6 4 ) .  23.  K. Y a t e s , J . B . Stevens and A. R. K a t r i t z k y , Can. J . Chem., 4 2 , 1957 (1964). K. Y a t e s and J . B. S t e v e n s , Can. J . Chem., 4 3 . 529 ( 1 9 6 5 ) .  24. 25.  K. Y a t e s and J . C. R i o r d a n , Can. J . Chem.,  43.,  2328 ( 1 9 6 5 ) . 26.  V. Gold and B. W. V. Hawes, J . Chem. S o c , 2102 ( 1 9 5 D .  27.  N. C. Deno, J . J . J a r u z e l s k i and A. S c h r i e s h e i m , J . Org. Chem., 12, 155 (1954). N. C. Deno, J . J . J a r u z e l s k i and A. S c h r i e s h e i m , J . Am. Chem. S o c , 21, 3044 (1955). N. C. Deno, H. E. Berkheimer, W. L. Evans and H. J . P e t e r s o n , J . Am. Chem. S o c , 8 1 , 2344 (1959).  28. 29.  30.  N. C. Deno, P. T. Grover and G. S a i n e s , S o c , 81, 5790 ( 1 9 5 9 ) .  J . Am. Chem.  180  3 1 .  J. N. P h i l l i p s ,  3 2 .  R. H. Boyd,  33.  K. Bowden,  34.  G. Schwarzenbach and R. S u l z b e r g e r , 22,  35.  J . Phys. Chem., 6 2 , Chem. Rev., 66,  3 4 8  1 1 9  7 3 7  ( 1 9 6 1 ) .  ( 1 9 6 3 ) .  ( 1 9 6 6 ) .  H e l v . Chim. A c t a ,  ( 1 9 4 4 ) .  J . T. Edward and I . C. Wang, 399  36.  A u s t . J . Chem., 14, 183  Can. J . Chem.,  40,  ( 1 9 6 2 ) .  R. S t e w a r t and J . P. O'Donnell,  Can. J . Chem.,  42, 1 6 8 1 (1964). 37.  H. S c h a a l and G. Lambert, 1 1 6 4  38.  F. Peure and R. S c h a a l , 2 6 3 6  39.  J . Chim. Phys., 5 9 ,  ( 1 9 6 2 ) .  B u l l . Soc. Chim. F r a n c e ,  ( 1 9 6 3 ) .  R. A. M. 0 ' F e r r a l l and J . H. R i d d , 5 0 3 0  J . Chem. S o c ,  ( 1 9 6 3 ) .  J . Chem. S o c , 676  4 0 .  C. H. R o c h e s t e r ,  4 1 .  C. H. R o c h e s t e r , J . Chem. S o c , ( B ) ,  42.  K. N. Bascombe and R. P. B e l l , Soc,  43.  24,  1 5 8  2 3 7 6  N. C. Deno,  45.  R. S c h a a l and P. F a v i e r ,  47.  F. Masure and R. S c h a a l ,  2 0 3 9  ( 1 9 5 2 ) .  B u l l . S o c Chim. F r a n c e ,  J . Chim. Phys.,  52,  7 8 4  ( 1 9 5 5 ) .  B u l l . S o c . Chim. F r a n c e ,  ( 1 9 5 6 ) .  C. H. L a n g f o r d and R. L. B u r w e l l , J r . ,  Soc, 49.  J . Am. Chem. S o c ,  ( 1 9 5 9 ) .  R. S c h a a l ,  48.  Discussions Faraday  J . Am. Chem. S o c , 2it?  46.  1 1 3 8  ( 1 9 6 6 ) .  ( 1 9 6 3 ) .  44.  2 0 1 1  1 2 1  ( 1 9 5 8 ) .  G. Y a g i l and M. Anbar, 12,  ( 1 9 6 5 ) .  J . Am. Chem.  8 2 , 1 5 0 3 (I960).  D. Dolman, Ph. D. T h e s i s , U n i v e r s i t y o f B r i t i s h Columbia, Vancouver, I 9 6 6 .  181  50.  R. S t e w a r t , J . P. O'Donnell, Tetrahedron,  18,  917  D. J . Cram and B. R i c k b o r n , (1962).  51.  K. Bowden and R. S t e w a r t , . T e t r a h e d r o n ,  52.  R. S t e w a r t and A. B u c k l e y ,  53.  R. S c h a a l , Comp. Rend., R. S c h a a l and G. Lambert,  5H-.  1151  unpublished 232,  1036  results.  (1954-).  J . Chim. Phys.,  59.  (1962).  Ann., 323.,  55.  J . Meisenheimer,  56.  M. R. Crampton and V. G o l d , 298  2 1 , 2 6 l (I965).  205  (1902).  P r o c . Chem. S o c ,  (1964-).  57.  M. R. Crampton and V. G o l d ,  58.  C . . H . Rochester,  59.  C. H. R o c h e s t e r ,  60.  F. A. Long and M. A. P a u l , Chem. Rev., 5Z> 935 ( 1 9 5 7 ) . M. Anbar, M. B o b t e l s k y , D. Samuel, B. S i l v e r and G. Y a g i l , J . Am. Chem. S o c , 8£, 2 3 8 O (I963).  61.  J.C hem. S o c , 4-293 (196+).  T r a n s . Faraday S o c , 59_, 2820 (1963). J . Chem. Soc., 24-04-  (1965).  62.  M. F. L. A l l i s o n , C. Bamford and J . H. R i d d , Chem. and I n d . , 21,' 718 (1958).  63.  R. A. M. 0 ' F e r r a l l and J . H. R i d d , 5035  64-. 65.  68.  J . Chem. S o c ,  (1963).  1790  J.  Am.  Chem.  Soc,  (1962).  R. S c h a a l and F. Peure, 2638  &+,  (1962).  M. Anbar and G. Y a g i l , 8]±,  67.  J . Am. Chem. S o c ,  D, Samuel and B. L . S i l v e r , 289  66.  (1963).  G, Y a g i l and M. A n b a r , 1797  J . Chem. S o c ,  B u l l . S o c Chim. F r a n c e ,  (1963).  R. S c h a a l and J . L. L a t o u r , F r a n c e , 2177 (1964-).  B u l l . S o c . Chim.  182  69.  F. T e r r i e r ,  70.  V. I . L a z a r e v , Y. 7. Moiseev and S. M. Golyand, Russ. J . o f Phys. Chem., 3 2 , 193 ( 1 9 6 5 ) .  71.  C. H. R o c h e s t e r , T r a n s . Faraday S o c , 1 2 , 2826 ( 1 9 6 3 ) .  Comp. Rend.,  2 6 l , 1001  7 2 . . S. P a t a i and Z. Rappoport,  (1965).  J . Chem. S o c , 377  ( I 9 6 2 ) .  73 •  S. P a t a i and Z. Rappoport, i n "The C h e m i s t r y o f . A l k e n e s " , S. P a t a i ed., I n t e r s c i e n c e P u b l i s h e r s , London, I 9 6 4 - , Chapter 8 .  7*+.  G. R. Clemo and S. B, Graham, 213  J . Chem. S o c ,  (1930).  75.  K. N o z a k i ,  J . Am. Chem. S o c , 6 3 , 2681  76.  M. D a v i s and F. P. Evans,  (194-1).  Trans. Faraday S o c ,  il, 1506 ( 1 9 5 5 ) . 77. 78. 79« 80.  Z. Rappoport, C. Degani and S. P a t a i , J . Chem. S o c , 4-513 ( 1 9 6 3 ) . S. P a t a i and Z. Rappoport, J . Chem. S o c , 396 ( 1 9 6 2 ) . S. I . M i l l e r and P. K. Yonan, J . Am. Chem. S o c , 1% 5931 ( 1 9 5 7 ) . D. E. Jones, R, 0 . M o r r i s , C. A. Vernon and R. F. M. W h i t e , J . Chem. S o c , 234-9 ( i 9 6 0 ) .  81.  D. H. Hunter and D. J . Cram, 86 , 54-78 ( 1 9 6 4 - ) .  82.  A. Z w i e r z a k and H. P i n e s ,  J . Am. Chem. S o c , .  J . Org. Chem.,  gZ, 4-084-  (I962).  83.  F. T e r r i e r , P. P a s t o u r 2605783 ( 1 9 6 5 ) .  84-.  V. G o l d and C. H. R o c h e s t e r , J . Chem. S o c , 1692, 1697, 17oh, 1710, 1717, 1722, 1727 (1964-).  85.  S. P a t a i and Z. Rappoport, J . Chem. S o c , 383 ( 1 9 6 2 ) .  86.  S. P a t a i and Z. Rappoport, J . Chem. S o c , 392 ( 1 9 6 2 ) .  and R. S c h a a l ,  Comp. Rend.,  183  87.  A. I . V o g e l , "A Textbook o f P r a c t i c a l Organic Chemistry", Longmans Green and Co. L t d . , London, 1 9 % , ( a ) p. 1 6 8 (b) p. 169 (c) p. 607 (d) p. 601 (e) p. 762.  88.  H. H. J a f f e and M. O r c h i n , "Theory and A p p l i c a t i o n s of U l t r a v i o l e t S p e c t r o s c o p y " , John W i l e y and Sons, I n c . , New Y o r k , 1962, Chapter 2 0 .  89.  H. H. Szmant and R. Y o n c o s k i e ,  J . Org. Chem.,  21, 78 (1956). . 90.  H. H. Szmant and J . F. D e f f n e r ,  J . Am. Chem.. Soc*,  91.  A. F a i r b o u r n e and H. R. Fawson,  J . Chem. S o c . ,  81, 958 (1959).  46 (1927).  r  92.  R. Merckx,  93.  Z. C s u r o s , G. Deak. and J . S z o l n o k i , A c t a Chimv Acad. S c i . Hung., 33, 3 4 1 (1962), Chem. A b s . ,  B u l l . S o c . Chim. B e i g e s . , £8,  4 6 0  ( 1 9 4 9 ) .  1 8 , 7863d.  ;  94.  A. Schonne, E. Braye and A. B r u y l a n t s , Chim. B e i g e s . , 62, 155 (1953).  95.  S. P a t a i and Y, I s r a e l i , 8A,  179  B u l l . Soc.  B u l l . Res. C o u n c i l  Israel,  ( 1 9 5 9 ) .  96.  S. G a b r i e l and R. O t t o ,  97.  W. M e l l i n g h o f f , Ber.., 22, 3207 (I889).  98.  F. B e l l and D. H. W a r i n g ,  99.  V. N. I p a t i e f f , H. P i n e s ,  B e r . , 20, 2224 (I887).  J . Chem. S o c , 1024- (1948).  J . E. Germain, J . Org. Chem.,  W. W. Thompson a n d 1 £ , 272 (1952).  100.  R. P s c h o r r and G. Hoppe,  101.  J . D. Loudon and G. Tennant,  102.  H. Meerwein, E. Buchner and K. v a n Emster, Chem., 152, 237 (1939).  Ber., 4 l ,  2543 (1910).  J . Chem. S o c ,  3466 (i960). J . Prakt.  184  103.  B. E. R o s e n k r a n t z , E. I . B e c k e r ,  104-.  R. L. Bent, J . C. D e s s l o c h , F . C. Duennebier, D. ¥. F a s s e t t , D. B. G l a s s , T. H. James, D. B. J u l i a n , W. R. Ruby, J . M. S n e l l , J . H. S t e r n e r , T. R. T h i r t l e , P. W. V i t t u m and A. W e i s s b e r g e r , J . Am. Chem. S o c , Z3  105.  L. C i t a r e l , G. E.'Heihsohn and J . Chem. Eng. D a t a , 8, 237 (19^3).  3100 ( 1 9 5 D .  5  M. P i r a u x and A . - B r u y l a n t s , B u l l . S o c . Chim. B e i g e s . , 68,  4-91  (1959).  106.  Ro E. B u c k l e s and K . Bremer,  107.  J . Fo C o d i n g t o n and E. M o s e t t i g ,  108.  J.  12,, 1027  109.  Org. Syn., H ,  70 (1953).  ' J . O r g o Chem.,  (1952).  I . Cadogan, E. G. D u e l l and P. W. Inward, Jo Chem. S o c , 4164 (1962). P . Schmid, U. S. A t . Energy Comm. TJCRL 8883, 114  (1959).  110.  Wo W i s l i e e n u s , G. B u t t e r f a s s and G. Koken, Ann.,  111.  Jo M a t t i and P. Reynaud,  436, 410  112.  69 ( I 9 2 5 ) . (1954).  A . H. Wragg, J.  B u l l . S o c Chim. F r a n c e ,  T. S. Stevens and D. M. O s t l e ,  Chem. S o c , 4057 (1958).  113.  J. J  114.  J . Fo B u n n e t t , i n "Technique o f O r g a n i c C h e m i s t r y " , A. W e i s s b e r g e r ed., V o l . V I I I P a r t I , I n t e r s c i e n c e P u b l i s h e r s , I n c . , New Y o r k , 196l, Chapter 6.  115.  M. F . Z i n n ,  116.  J . Am. Chem. S o c , 85, 71 (1963). Ro S t e w a r t , J . P. O ' D o n n e l l and K . Bowden, Can. J . Chem., 4l» 1225 (1965).  117.  C. A. K i n g s b u r y ,  18.  o  Lindberg,  F i n s k a K e m i s t s . Medd.,  T. M. H a r r i s ,  21? 78 (1962).  D. G. H i l l and C, R. Hauser,  J . Org. Chem., 2J£, 3262 (1964).  L. P a u l i n g , "The Nature o f t h e C h e m i c a l Bond", C o r n e l l U n i v e r s i t y P r e s s , New Y o r k , i960, p. 473«  185  119.  W. D r i n k a r d and D , K i v e l s o n , 62, 14-94- (1958).  120.  J . E. L e f f l e r and E, Grunwald, "Rates and E q u i l i b r i a Of O r g a n i c R e a c t i o n s ", John W i l e y and Sons, I n c , New Y o r k , 1963, ( a ) p. 269 (b) p. 172 ( c ) p. 173 (d) p. 178.  121.  M. K i l p a t r i c k and C, A. A r e n b e r g , 25.1 3812  J . Phys, Chem,,  J . Am. Chem. S o c ,  (1953).  122.  G. F. F r e e g u a r d , R, B. Moodie and D. J . G, Smith,' J , A p p l . Chem., 15, 179 (1965).  123.  H. H. J a f f e ,  124-.  A. F i s h e r , M, A. R i d d o l l s and J . Vaughan, J . Chem. S o c . ( B ) , 106 (I966).  125.  J . T. Edward,  126.  J . K. Adams, " B a s i c S t a t i s t i c a l C o n c e p t s " , H i l l Co. I n c . , New Y o r k , 1955, p. 163.  127.  A. J . Kresge and Y, C h i a n g , 81  Chem. Rev,, H , 191 (1953).  2, 313 (1964-),  T r a n s . R o y a l S o c Canada,  (1961).  P r o c Chem, S o c ,  128.  A. J . Kresge and Y. C h i a n g , 83, 2877 (1961).  129.  D. S. Noyce, W. A. P r y o r and P. A. K i n g , J , Am. Chem. S o c , 81, 5^23 (1959).  130.  D. S. Noyce,  P. A. K i n g ,  J . Am. Chem. S o c ,  McGraw  J , Am. Chem. S o c ,  F. B. K i r b y  8!+, I632  and W. L. Reed,  (1962).  131.  D. S. Noyce, and H. S. Avarbock, 8it, 164-4- (1962).  132.  D. S. Noyce, H. S. Avarbock and W. L. Reed, J . Am. Chem. S o c , 8^f, 164-7 (1962).  133.  D. S. Noyce, D. R. H a r t l e r and F. B. M i l e s , J . Am. Chem. S o c , 86, 3583 (1964-).  134-.  A. J . K r e s g e , R. A. M. O ' F e r r a l l , L. E. Hukka and V . P. V i t u l l o , Chem. Comm., 4-6, (1965).  J . Am. Chem. S o c ,  186  135.  C W. L. Bevan,  136.  L. N. F e r g u s o n , "The Modern S t r u c t u r a l Theory o f Organic Chemistry", P r e n t i c e - H a l l , I n c . , Englewood C l i f f s , N. J . , 1963, p. 511.  137.  D. J . Cram,  J . Chem. S o c ,  B. R i c k b o r n ,  655 (1953).  C. A. K i n g s b u r y and  P. H a b e r f i e l d , J . Am. Chem. S o c , 8^, 3678 ( 1 9 6 1 ) . 138.  D. D. R o b e r t s ,  139.  C. A. Bunton, "Nucleophilic Substitution at a S a t u r a t e d Carbon Atom", E l s e v i e r P u b l i s h i n g Co., London, 1963, p. 27. E. A. Walker and J . R. Young, J . Chem. S o c ,  IH-0.  20+5  J . Org. Chem., 3 0 , 3516 (1965).  (1957).  14-1.  B. A. F e i t and A. Z i l k h a , J . Org. Chem., 28, 4-06 ( 1 9 6 3 ) .  14-2.  R. M. S i l v e r s t e i n and G. C. B a s s l e r , " S p e c t r o m e t r i c I d e n t i f i c a t i o n o f O r g a n i c Compounds", John W i l e y and Sons, I n c . , New Y o r k , 1963, p. 125.  I4-3.  A. J . P a r k e r , Q u a r t . Rev., 16, 163 (1962).  14-4-.  P. G. Gassman and F. V. Z a l a r ,  14-5.  E. H. H u n t r e s s and M. K. S e i k e l ,  1.4-6.  G. A. Swan,  14-7.  K. Bowden,  l+o, 3031 (1964-). 61, 816 (1939).  Soc,  Tetrahedron L e t t e r s , J . Am. Chem. S o c ,  J . Chem. S o c , 14-08 (194-8). A. B u c k l e y 88  5  and R. S t e w a r t ,  9+7 (1966).  J . Am. Chem.  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0061994/manifest

Comment

Related Items