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UBC Theses and Dissertations

Strongly basic systems Albagli, Alain 1969

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STRONGLY BASIC SYSTEMS  by  ALAIN ALBAGLI  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of Chemistry  We accept t h i s t h e s i s as conforming t o the required standard  THE UNIVERSITY OF BRITISH COLUMBIA October, 1969  In p r e s e n t i n g an  this  thesis  advanced degree at  the  Library  shall  fulfilment of  University  of  make i t f r e e l y  I f u r t h e r agree that for  the  in p a r t i a l  permission  s c h o l a r l y p u r p o s e s may  by  his  of  this  written  representatives.  be  available  granted  gain  permission.  Department  Date  for  for extensive by  the  It i s understood  thesis for financial  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  British  Columbia  shall  requirements  Columbia,  Head o f my  be  I agree  r e f e r e n c e and copying of  that  not  the  that  study.  this  thesis  Department  copying or  for  or  publication  allowed without  my  ABSTRACT Supervisor :  Professor Ross Stewart  In the l a s t decade there has been considerable i n t e r e s t i n s t r o n g l y b a s i c s o l u t i o n s and Hammett H  a c i d i t y functions have  been defined f o r various solvent systems.  However some doubts s t i l l  remain about the i o n i z a t i o n modes o f c e r t a i n i n d i c a t o r s which were used t o determine these H  f u n c t i o n s , and the pK  values assigned t o  weak carbon acids. A c a r e f u l anchoring o f the H dimethylsulfoxide-water-0.011  s c a l e f o r the system  molar tetramethylammonium hydroxide  with 2,4,4'-trinitrodiphenylamine was undertaken.  The lower region  of t h i s scale c o r r e l a t e s w e l l w i t h the r e c e n t l y published H  function  f o r the more b a s i c regions. To study the dependence of H  functions on i n d i c a t o r  s t r u c t u r e , the i o n i z a t i o n o f nitrogen and oxygen acids were compared i n s t r o n g l y b a s i c systems.  The solvent systems used i n the study  were dimethylsulfoxide-methanol-0.01  molar sodium methoxide and  dimethylsulfoxide-ethanol-0.01 molar sodium ethoxide. r i s e o f the  The shallow  f u n c t i o n f o r phenols as compared t o that of the  f o r diphenylamine i s b e l i e v e d t o be caused by the smaller degree o f  charge d e r e a l i z a t i o n i n the phenolate anions than i n the amide ions. The d i s s o c i a t i o n constants of 15 s u b s t i t u t e d n i t r o d i p h e n y l amines were determined i n the two p r e v i o u s l y mentioned a l c o h o l i c dimethylsulfoxide systems, and i n the aqueous dimethylsulfoxide system. The " s i m i l a r colour i n d i c a t o r " postulate was elaborated on the observation that the r e l a t i v e a c i d i t y of Hammett-type i n d i c a t o r s remains constant through changes i n solvent environment only i f t h e i r s p e c t r a l c h a r a c t e r i s t i c s are s i m i l a r . Linear free energy r e l a t i o n s h i p s between the pK  values of  30 s u b s t i t u t e d diphenylamines and the s u b s t i t u e n t constant, a°, were drawn.  The p value i n excess of 4 f o r monosubstituted diphenylamines  compared with p values of the order of 2 f o r n i t r o s u b s t i t u t e d diphenylamines, r e s u l t s from the low degree of conjugation between,the c e n t r a l N atom and the r i n g substituent whenever a n i t r o group i s present i n the other r i n g . The base-catalyzed  rates of d e t r i t i a t i o n of various hydro-  carbons were determined i n dimethylsulfoxide mixtures.  The  logarithm  of these rates were c o r r e l a t e d with the thermodynamic b a s i c i t y of the •  N  medium as measured by the H l i n e s with slopes around 0.8.  f u n c t i o n and gave e x c e l l e n t s t r a i g h t The t h e o r e t i c a l b a s i s o f such  c o r r e l a t i o n s i s discussed, and i t was concluded that the logarithm of the rates should be c o r r e l a t e d with H  + log a —  D n u  . In the case of  Run  methanolic dimethylsulfoxide the a c t i v i t y of methanol has been determined, g i v i n g corrected c o r r e l a t i o n s with slopes around  0.9.  - iv -  The q u a l i t a t i v e l i m i t a t i o n due t o the use of H  N  instead of H  C  functions i s also discussed. The a c t i v a t i o n parameters f o r these d e t r i t i a t i o n s have been determined.  The enthalpies o f a c t i v a t i o n were found t o increase with  decreasing a c i d i t y o f the hydrocarbon.  These v a r i a t i o n s i n enthalpy  of a c t i v a t i o n , coupled with v a r i a t i o n i n the k i n e t i c isotope e f f e c t and the observed Bronsted r e l a t i o n s h i p have been i n t e r p r e t e d i n terms of a mechanism i n v o l v i n g a rate-determining p r e - e q u i l i b r i u m step with a t r a n s i t i o n s t a t e of i n c r e a s i n g asymmetry C A c r i t i c a l examination  o f the H  scale f o r carbon acids  i n dimethylsulfoxide-ethanol-0.01 molar sodium ethoxide was made.  The  f a i l u r e o f the s c a l e probably r e s u l t s from the f a c t t h a t , f o r a number of i n d i c a t o r s , proton a b s t r a c t i o n i s followed by a r e a c t i o n between the carbanion and the n e u t r a l molecule t o give a r a d i c a l and r a d i c a l anion.  The carbanions o f three nitrophenylmethanes were prepared i n  hexamethylphosphoramide and unequivocally i d e n t i f i e d by high r e s o l u t i o n nuclear magnetic resonance.  The s p e c t r a l c h a r a c t e r i s t i c s o f the  carbanions were recorded and compared with p r e v i o u s l y published values. The r a d i c a l anions of these nitrophenylmethanes were generated e l e c t r o c h e m i c a l l y and t h e i r e.s.r. spectra measured. in  14  The v a r i a t i o n  N hyperfine coupling constant (a^) of these r a d i c a l  anions  i n d i c a t e d a large solvent s h i f t i n the absorption maxima.  - V -  TABLE OF CONTENTS Page INTRODUCTION ...... I.  The H  II.  Carbon Acids  III.  Nitrogen Acids  IV.  Oxygen Acids  V.  A p p l i c a t i o n of the H  . .  ..  1  a c i d i t y function  4 9 15 •••  ^  Function t o K i n e t i c s and Mechanisms  of Base C a t a l y s i s  19  A.  Kinetic-Thermodynamic  B.  Isotope e f f e c t s  relationships  23 29  SCOPE OF THE PRESENT RESEARCH .  31  EXPERIMENTAL  •  .  33  I.  P u r i f i c a t i o n of solvents  33  II.  Base  III.  Preparation of s o l u t i o n s  34  IV.  Spectral measurements  35  V.  Treatment of data and c a l c u l a t i o n s  35  VI.  Probable e r r o r i n H  VII.  K i n e t i c measurements  "•. • •  and pK a  values ...  34  36 . 37  V I I I . Treatment of the k i n e t i c data  39,  IX.  Reactions of nitrophenylmethanes-  43  X.  Computer treatment of data  XI.  Preparation of compounds used i n t h i s work  ;  44* 44  - vi Page RESULTS AND DISCUSSION '.  ...  51  Part I : Indicator measurements  51  N I.  II.  Diphenylamine i n d i c a t o r s H  .  •..  A.  V a l i d i t y of the  scale i n a l c o h o l i c DMSO  B.  C o r r e l a t i o n of Structure with A c i d i t y  Phenol i n d i c a t o r s Part I I : Evaluation  II.  A c t i v a t i o n parameters  III.  K i n e t i c thermodynamic  8-2 89  of the k i n e t i c s  109 117  c o r r e l a t i o n f o r hydrocarbon  ionization  122  Change of isotope e f f e c t with the pK Part I I I :  65  Base catalyzed d e t r i t i a t i o n of hydrocarbons .... 100  I.  IV.  51  of hydrocarbons .... 124;  Interactions of Nitrophenylmethanes with base . 127  I.  N.m.r. i n v e s t i g a t i o n  129  II.  E.s.r. i n v e s t i g a t i o n  . 138  CONCLUSION .......  146  BIBLIOGRAPHY  147  APPENDIX A:  I o n i z a t i o n Ratio Data  . ..  154  APPENDIX B:  Rate C o r r e l a t i o n Data  162  APPENDIX C:  Computer Program.  168  - vii LIST OF TABLES Table I  Page Degree o f i o n i z a t i o n of weak a c i d s , HA, i n 0.01 M OH solutions  II  2  Degree o f i o n i z a t i o n o f a n i l i n e , pK = 27.3, i n aqueous DMSO, [0H ] =0.01  2  _  III  pK of carbon acids i n ethanolic DMSO and i n DMSO  11  a  IV  p K values of hydrocarbons and "best v a l u e s "  13  V  pK of various diphenylamines as determined i n the  &  aqueous DMSO system  54  N  VI  H values f o r the system DMSO-water-0.Oil M t e t r a methylammonium hydroxide  VII  55  pK of various diphenylamines as determined i n the methanolic DMSO system  58  N •  VIII  H  values f o r the system DMSO-methanol-0.01  M sodium  IX  methoxide pK of various amines as determined i n the ethanolic a DMSO system. ••••  59  r  62  N  X  H values f o r the system DMSO-ethanol-0.01 M sodium  XI  ethoxide P BH+ °^ K  w e a  63 k bases i n s u l f u r i c a c i d media gathered  from the l i t e r a t u r e XII  Summary o f the pK values of diphenylamines determined i n t h i s work  XIII  71  ,  77  Absorption maxima and molar a b s o r p t i v i t i e s o f the i n d i c a t o r s i n absolute ethanol  78  - viii -  Table XIV  Page Absorption maxima and molar a b s o r p t i v i t i e s o f i n d i c a t o r sanions i n DMSO-ethanol  XV  79  L i n e a r free energy c o r r e l a t i o n o f diphenylamines s a c i d i t i e s computed by a l e a s t squares method ...  "XVI  ..  values f o r the systems DMSO-methanol-0.01 M sodium AHiethoxide and DMSO-ethanol 0.01 sodium ethoxide  ;XVII  a  XX  —  C o r r e l a t i o n o f l o g k with  f o r the base catalyzed  d e t r i t i a t i o n o f hydrocarbons  ....  C o r r e l a t i o n o f log k with H_ and H  + l o g a^Q^ f o r the  140  Spectral data o f nitrophenylmethanes i n s t r o n g l y b a s i c solutions  XXIV  118  S p l i t t i n g constants a^ f o r BNPM and 3,4'-DNPM i n methanolic DMSO mixtures  XXIII  115  A c t i v a t i o n parameters f o r the base catalyzed d e t r i t i a t i o n of hydrocarbons  XXII  95  105  base c a t a l y z e d i s o t o p i c exchange i n methanolic DMSO ... XXI  94  Absorption maxima and molar a b s o r p t i v i t i e s o f phenolate anions .........  XIX  92  p K values o f phenols determined i n aqueous s o l u t i o n s . .^and i n methanolic and ethanolic DMSO  'XVIII  85  144  Experimental values o f log I f o r diphenylamine i n d i c a t o r s i n the system DMSO-water-tetramethylammonium hydroxide (0.0011 M)  154  - ix Table XXV  Page Experimental values o f l o g I f o r diphenylamine i n d i c a t o r s i n the system DMSO-methanol-sodium methoxide (0.01 M)  XXVI  156  Experimental values o f log I f o r amine i n d i c a t o r s i n the system DMSO-ethanol-sodium ethoxide (0.01 M)  XXVII  158  Experimental values o f l o g I f o r the s u b s t i t u t e d phenol i n d i c a t o r s i n the system DMSO-methanol-sodium methoxide (0.01 M)  XXVIII  160  Experimental values o f l o g I f o r the s u b s t i t u t e d phenol i n d i c a t o r s i n the system DMSO-ethanol-sodium ethoxide (0.01 M)  XXIX  161  Rates o f d e t r i t i a t i o n (£. m o l e s e c -1  1  ), k  - at 25° f o r  UK  various hydrocarbons i n b a s i c DMSO-ethanol s o l u t i o n s .. XXX  Rates o f d e t r i t i a t i o n (5,. mole *sec  , k^^- a t 25° f o r  various hydrocarbons i n b a s i c DMSO s o l u t i o n s XXXI  164  I o n i z a t i o n rate constants (£. m o l e ^ s e c ) , k(DMSO), at 1  25° f o r DMSO i n basic DMSO s o l u t i o n s XXXII  162  Rate-temperature data f o r the base catalyzed  165 detritiation  of hydrocarbons i n DMSO-ethanol-0.01 M sodium ethoxide.  167  - X -  LIST OF FIGURES Figure 1.  Page T y p i c a l f i r s t - o r d e r rate p l o t s f o r the d e t r i t i a t i o n o f 9-phenylfluorene i n absolute methanol at 25° .........  40  2.  T y p i c a l f i r s t - o r d e r rate p l o t f o r the t r i t i a t i o n of DMSO  42  3.  P l o t s o f l o g I (A/AH) versus H  f o r the system:  DMSO-water-0.001 M TMAOH 4.  53  Plots o f l o g I (A/AH) versus H_ f o r the system: DMSO-methanol-0.01 M sodium methoxide  57  N 5.  H  a c i d i t y function f o r the system:  DMSO-methanol-0.01 M  sodium methoxide .......... 6.  P l o t s o f log I (A/AH) versus H  60 f o r the system:  DMS0-ethanoI-0.01 M sodium ethoxide . 7.  61  a c i d i t y function f o r the system: DMSO-ethanol-0.01 M sodium ethoxide  8.  Plots o f l o g I (A/AH) versus mole percent DMSO f o r the system:  9.  66  DMSO-methanol-0.01 M sodium methoxide  67  P l o t s o f l o g I (A/AH) versus mole percent DMSO f o r the system:  11.  DMSO-water-0.011 M TMAOH..  Plots o f log I (A/AH) versus mole percent DMSO f o r the system:  10.  64  DMSO-ethanol-0.01 M sodium ethoxide  68  P l o t s o f log I (A/AH) versus mole percent DMSO f o r the amine i n d i c a t o r s used t o e s t a b l i s h the  function i n :  DMSO-methanol-0.025 M sodium methoxide from reference 33. 81  Hammett c o r r e l a t i o n o f the a c i d i t y o f s u b s t i t u t e d diphenylamines P l o t s o f l o g I (A/AH) versus H_ f o r the phenols used t o e s t a b l i s h the H^ scale i n DMSO-methanol-0.01 M sodium methoxide P l o t s o f l o g I (A/AH) versus H  f o r the phenols used t o  e s t a b l i s h the H^ scale i n DMSO-ethanol-0.01 M sodium ethoxide H^ a c i d i t y functions  f o r the systems:  DMSO-methanol-  0.01 M sodium methoxide and DMSO-ethanol-0.01 M sodium ethoxide 0 H  N and H  a c i d i t y functions  f o r the system:  methanol-0.01 M sodium methoxide O N H_ and H a c i d i t y functions f o r the system:  DMSODMSO-ethanol  0.01 M sodium ethoxide Plots o f l o g k versus H^ f o r the d e t r i t i a t i o n o f hydrocarbons i n DMSO-ethanol-0.01 M sodium ethoxide P l o t s o f l o g k ( d e t r i t i a t i o n o f hydrocarbons) versus log k (DMSO exchange) i n DMSO-ethanol-0.01 M sodium ethoxide N P l o t o f l o g k versus H  f o r the d e t r i t i a t i o n o f  fluorene-9t i n DMSO-water-0.011 M TMAOH.  - xii -  Figure 21.  Page P l o t o f log k versus  f o r the DMSO i s o t o p i c exchange  r e a c t i o n i n DMSO-water-0.01 M TMAOH 22.  106  N P l o t o f l o g k versus H f o r the DMSO i s o t o p i c exchange r e a c t i o n i n DMSO-ethanol-0.01 M sodium ethoxide ....... N  23.  P l o t o f log k versus H  107  N ( l i n e 1) and H_ + l o g |^ Qjj a  f  o  r  e  the DMSO i s o t o p i c exchange i n DMSO-methanol-0.01 M sodium methoxide  108 N  24.  N  P l o t o f l o g k versus H_ ( l i n e 1) and H_ + l o g ^ q  H  for  the d e t r i t i a t i o n o f 9-phenylfluorene-9t i n DMSO-methanol0.01 M sodium methoxide 25.  116  P l o t s o f log k versus 1/T°K f o r the d e t r i t i a t i o n o f hydrocarbons i n e t h a n o l i c DMSO ( h o r i z o n t a l )  26.  P l o t s o f log k versus 1/T°K f o r the d e t r i t i a t i o n o f hydrocarbons i n e t h a n o l i c DMSO ( v e r t i c a l )  27.  123  N.m.r. spectra o f tris-(p-nitrophenyl)methane and anion i n HMPT  29.  I  2  134  N.m.r. s p e c t r a o f 3,4'-dinitrodiphenylmethane and anion i n HMPT  31.  3  N.m.r. s p e c t r a o f bis-(p-nitrophenyl)methane and anion i n HMPT  30.  120  C o r r e l a t i o n o f k i n e t i c and thermodynamic a c i d i t i e s o f some hydrocarbons  28.  119  ...'....  136  P l o t o f the average s p l i t t i n g constant versus mole percent DMSO f o r the r a d i c a l anion o f 3,4'-dinitrodiphenylmethane i n methanolic DMSO  141  - Xlll  -  Figure 32.  Page P l o t o f the average s p l i t t i n g constant versus mole percent DMSO f o r the r a d i c a l anion of bis-(p-nitrophenyl) methane i n methanolic DMSO  142  - xiv -  ACKNOWLEDGEMENTS I would l i k e to thank Professor Ross Stewart f o r h guidance throughout t h i s research p r o j e c t . I would a l s o l i k e to thank Dr. J.R.Jones and D.E. Kennedy and J.A.MacPhee f o r t h e i r h e l p f u l suggestions and criticisms.  INTRODUCTION 1 In a r e c e n t l y published review on H  acidity functions,  strongly b a s i c systems have been a r b i t r a r i l y defined as those s o l u t i o n s which i o n i z e acids with an a b i l i t y equal to or greater than 0.1 M aqueous a l k a l i metal hydroxide s o l u t i o n s . There are several methods of producing s t r o n g l y basic systems. Of the two most common, the f i r s t c o n s i s t s of preparing a s o l u t i o n of a p r o t i c solvent and a s a l t of i t s conjugate base (e.g., sodium hydroxide water), the b a s i c i t y of the system i n c r e a s i n g with increase of the base concentration.  The second one, which produces s t a r t l i n g e f f e c t s , makes  use of a binary solvent system:  a p r o t i c and a p o l a r a p r o t i c solvent  with a small concentration o f the conjugate base o f the p r o t i c partner. In t h i s case the a b i l i t y o f the base to remove  a  proton from a weak a c i d  i s increased by i n c r e a s i n g the concentration o f the p o l a r a p r o t i c solvent 2 Indeed there have been cases reported i n the l i t e r a t u r e  i n which these  methods were coupled, i . e . i n c r e a s i n g the base concentration i n a system c o n s i s t i n g o f a f i x e d percent p o l a r solvent i n a p r o t i c one. The increase i n a b i l i t y o f hydroxide ions to remove a proton from a weak a c i d by a d d i t i o n o f a p o l a r a p r o t i c solvent l i k e dimethyls u l f o x i d e (DMSO) can be i l l u s t r a t e d by the data i n Table I which shows the e f f e c t o f DMSO on the degree o f i o n i z a t i o n of three aromatic amines i n s o l u t i o n each 0.01 M i n hydroxide i o n .  - 2TABLE I Degree o f I o n i z a t i o n of Weak A c i d s , HA, i n 0.01 M OH Solutions Water  HA  92 mole % DMSO  99.6 mole % DMSO  undetectable  complete  complete  (C H ) NH  undetectable  half  complete  C,H NH 6 5 2  undetectable  undetectable  one-tenth  °2 A  /r- 2  n  m  6  5  C  2  0  14 E f f e c t i v e l y there i s a 10  f o l d increase i n the b a s i c i t y o f the system  toward aromatic amines by r e p l a c i n g water by DMSO. Table I I shows how the degree o f i o n i z a t i o n o f a n i l i n e ( K = 27.3) v a r i e s with solvent P  a  enrichment i n DMSO. TABLE I I * Degree of I o n i z a t i o n o f A n i l i n e , p K = 27. ,3 i n aqueous &  DMSO, [OH ] =0.01 -  [C H NH-] 6  wt - % DMSO  mole - % DMSO  H_  5  [C H NH ] 6  0 20  S  0  12.0  io-  1 5  5.45  12.6  io-  1 5  io" -12  40  13.4  13.6  t — 60  25.7  15.1  10  80  48,0  17.3  io"  90  67.6  19.2  io"  8  95  81.5  20.8  io"  7  26.2  0.1  t  99.6 99.9 i n 66 wt % DMSO [C H NH"] = [C H NH ] 6  5  6  5  3  Table I and I I are taken from reference (3)  1 4  1 0  2  - 33 4 This increase i n b a s i c i t y has been r a t i o n a l i z e d ' by considering the e f f e c t o f a d d i t i o n of DMSO on the e q u i l i b r i u m shown i n equation ( l a )  HA  + OH ( H 0 ) 2  3  *•  A" + 4H 0  (la)  2  By a d d i t i o n o f DMSO the a c t i v i t y of water w i l l be lowered^. This lowering i n the a c t i v i t y o f the p r o t i c partner by increasing the concentration of the a p r o t i c solvent was also noted i n the s u l f o l a n e water system the  7  and i n the DMSO-methanol system.  8  But t h i s lowering i n  a c t i v i t y of water cannot account f o r a l l the increase i n b a s i c i t y  when DMSO i s added to aqueous s o l u t i o n s of hydroxide i o n . Another f a c t o r o f importance i s the state o f s o l v a t i o n o f the species OH DMSO.  and A  i n equation (la) as we go from aqueous s o l u t i o n s to  In water a small i o n l i k e hydroxide i o n i s surrounded by water  molecules and i s s t a b i l i z e d by strong hydrogen bonds while i n DMSO the hydroxide ion i s weakly solvated and thus i t s a c t i v i t y w i l l increase with increasing DMSO content. This argument i s based on the premise that an unsolvated i o n w i l l be more r e a c t i v e than a solvated one which must be snatched from i t s sheath o f solvent molecules before a r e a c t i o n can occur.  U n t i l r e c e n t l y , i t was widely accepted that large d e l o c a l i z e d  anions l i k e amide ions or carbanions were more solvated i n DMSO than 9 i n a p r o t i c solvent,  but t h i s premise was r e c e n t l y challenged. Fuchs  et a l . " " ^ measured enthalpies of s o l u t i o n o f l i t h i u m and potassium halides i n DMSO and found that the order o f s o l v a t i o n of h a l i d e ions i n DMSO The species H^O^ complex H„0. 94 r  +  i n equation (la) corresponds t o the secondary hydrate  i n acid solutions.**  - A -  i s the same as i n water.  They therefore postulated that d i f f e r e n c e s o f  s o l v a t i o n between i o n s , whether large or s m a l l , i n DMSO i s minimal. The main e f f e c t of a d d i t i n g DMSO to the system shown i n equation ( l a ) seems to be to desolvate OH . Besides these two large e f f e c t s , there are s e v e r a l minor ones. Lowering the concentration of water i n the system w i l l tend t o s h i f t the e q u i l i b r i u m to the r i g h t .  DMSO i t s e l f i s coordinated to two water  molecules,*"'' thus a d d i t i o n o f DMSO f u r t h e r lowers the water concentration by complex formation.  A f a i r estimate o f the increase i n H up to 12  about 50 wt percent DMSO (20 mole percent) can be made  by considering  only the e f f e c t o f DMSO on the concentration o f the i n d i v i d u a l species i n equation ( l a ) .  With f u r t h e r increase o f the DMSO content, the  v a r i a t i o n i n the a c t i v i t y of water w i l l be the predominant f a c t o r , and at very high DMSO content greater than 95 percent the d e s o l v a t i o n o f the hydroxide i o n w i l l have a dramatic e f f e c t on H_ values.  A l l these  f a c t o r s w i l l tend t o s h i f t the e q u i l i b r i u m ( l a ) to the r i g h t as DMSO replaces water as a solvent. On the other hand, the a c t i v i t y c o e f f i c i e n t o f the n e u t r a l a c i d HA w i l l tend to f a l l as water i s replaced by DMSO as i n d i c a t e d by . the g e n e r a l l y higher s o l u b i l i t y of aromatic amines and hydrocarbons i n DMSO than i n water.  This i s the only f a c t o r which w i l l tend t o s h i f t  the e q u i l i b r i u m to the l e f t . I.  The H  acidity function The H  a c i d i t y f u n c t i o n describes the proton-abstracting  a b i l i t y of a solution.  The f o l l o w i n g e q u i l i b r i u m e x i s t s between an a c i d  - 5 uncharged  and i t s conjugate base A" i n aqueous s o l u t i o n of a base;  AH  ^—>-  A  +  H  (lb)*  +  The thermodynamic e q u i l i b r i u m constant f o r equation (lb) can be expressed as:  " .  ~  a  HA  "  I>*1  ' AH f  H  (  )  or i n a l o g a r i t h m i c form as f l 0 g  {m}  =  l0  S HA K  "  l0  S  f^  a  H  +  C 3 )  The symbols [ ] , a, f , r e f e r to concentration, a c t i v i t y and a c t i v i t y coefficient  r e s p e c t i v e l y ; and are r e l a t e d by the equation a^ = f ^ [ i ] .  In very d i l u t e s o l u t i o n s when the a c t i v i t y c o e f f i c i e n t s approach u n i t y t h i s equation reduces to  Since the simple term - log [H ] or pH measures the proton, +  a b s t r a c t i n g power i n d i l u t e aqueous s o l u t i o n , t h e n the equivalent terra i n equation (3) can be used i n s t r o n g l y b a s i c media, and thus defines the f u n c t i o n  *  A l l these species are hydrated but are not so denoted, f o r the sake of s i m p l i c i t y .  - 6 -  H  V  =  - l o g -fAH  a +  (5)  Hammett's a c t i v i t y c o e f f i c i e n t postulate states that f o r H_ to define A~ the a c i d i t y of the medium,-5— AH £  of the i n d i c a t o r  should be independent o f the s t r u c t u r e  and only dependent on the solvent  composition.  S u b s t i t u t i n g (5) i n t o (3) and r e w r i t i n g we get:  H  -  P HA  =  K  •  +  C 6 )  The Hammett i n d i c a t o r - o v e r l a p or stepwise technique of determining t h i s a c i d i t y function H years.  has been used by a number of workers i n the past  I t involves the comparison of b a s i c i t y of i n d i c a t o r s i n d i f f e r e n t  media s t a r t i n g i n the water region. F i r s t l e t us consider an a c i d HA whose pK i n aqueous b u f f e r s o l u t i o n s .  P HA K  =  lo  can be determined  We can r e w r i t e equation (2) as  s  [F]  "  l 0  * V  TT  ( 7 )  AH  S i m i l a r l y f o r another a c i d HB, another equation can be w r i t t e n :  P HB K  Subtracting  =  lo  [BH1  s JS=f ~  l o g  _ f—V  V  HB  ( 8 )  (8) from (7) gives the f o l l o w i n g equation:  *  pK^, P^  HB  are the pK  &  values o f the acids HA and HB r e s p e c t i v e l y  - 7-  P HA " P HB  [HA] . tH" "  *?*  =  [HB] l 0 g  WT  .  f  + lGg  HA B"  . ...  f  (9)  Now i f , and only i f , the l a s t term i n equation (9) i s equal t o zero (Hammett's a c t i v i t y c o e f f i c i e n t postulate) equation (9) becomes:  P HA - P HB K  K  =  l 0  Hence, t o e s t a b l i s h an H  S W)  '  l G g  [Ff  .  ( 1 0 )  scale r e f e r r e d to a standard s t a t e o f i n f i n i t e  d i l u t i o n i n water, an a c i d i n d i c a t o r HA i s required whose pK can be determined i n aqueous b u f f e r s and whose i o n i z a t i o n range spans the upper end o f the pH s c a l e and the beginning o f the H_ s c a l e .  This  i n d i c a t o r i s then used t o determine the H_ value f o r several d i f f e r e n t s o l u t i o n s e.g. , DMSO-water aqueous t o non-aqueous.  where the solvent character changes from  I t i s then p o s s i b l e to determine i n the same  s o l u t i o n s the f r a c t i o n o f an i n d i c a t o r HB that i s i o n i z e d and by use of equation (10) determine i t s pK . I f the'Hammett p o s t u l a t e holds there should be a constant d i f f e r e n c e i n the pK 's obtained from equation a  (10), f o r two acids i n a s e r i e s o f s o l u t i o n s o f d i f f e r e n t b a s i c i t y . This procedure can be a p p l i e d repeatedly f o r successive i n d i c a t o r s , and pK 's assigned to these i n d i c a t o r s . pK r  a  values are then used t o c a l c u l a t e H  These i n d i v i d u a l  values f o r each s o l u t i o n i n  which the i n d i c a t o r ' s i o n i z a t i o n r a t i o can be measured with reasonable [A"l accuracy, "pj^j between 0.1 and 10.  This procedure r e s u l t s i n several  measured H values f o r each s o l u t i o n and these values are then averaged.  - 8 -  I t i s evident from equation  (6) that a p l o t of log  versus  H  should give a s t r a i g h t l i n e of u n i t slope and i n t e r c e p t equal to the pK  of the i n d i c a t o r . The advantage of using a water-anchored H  f u n c t i o n , where H • = pH i n d i l u t e aqueous s o l u t i o n s , i s that the protona b s t r a c t i n g power of any medium i s then always expressed on the same scale.  I f i t were p o s s i b l e to determine experimentally a very small  amount of i o n i z a t i o n , one should f i n d values s i m i l a r to those i n Table I I f o r the degree of i o n i z a t i o n of a n i l i n e (of the order of 10 i n pure water with [OH ] = 0.01). The v a l i d i t y of t h i s treatment r e l i e s h e a v i l y on Hammett's assumption that 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 of a base and i t s conjugate a c i d depends only on the solvent composition and i s independent of the nature of the a c i d i n d i c a t o r . This assumption has been proven q u i t e r e l i a b l e i n determining H functions i n the a c i d region, although i t has broken down i n c e r t a i n cases.  One of the l i m i t a t i o n s which has  a r i s e n i s that the i n d i c a t o r s must be of s i m i l a r s t r u c t u r e .  It i s  d i f f i c u l t to define the degree of s i m i l a r i t y required but i t i s known that even primary and t e r t i a r y amines produce d i f f e r e n t H  q  scales.  Bowden's review of a c i d i t y functions f o r s t r o n g l y b a s i c s o l u t i o n s * l i s t s the H  data f o r 29 d i f f e r e n t solvent systems. But i n  view of the dependence of H  functions on i n d i c a t o r s t r u c t u r e i t i s o  advisable to d i s t i n g u i s h between H  a c i d i t y functions determined with  d i v e r s e i n d i c a t o r types. The i o n i z a t i o n behaviour i n b a s i c s o l u t i o n s of each of the f o l l o w i n g type of i n d i c a t o r s w i l l be compared: carbon (H^), nitrogen (H ^) and oxygen (H^) a c i d s . 1  neutral  - 9 II.  Carbon Acids Although carbon acids and t h e i r conjugate bases, carbanions,  undoubtedly occupy a p o s i t i o n of prime importance i n organic chemistry, i t i s only r e c e n t l y that a monograph*^ has been w r i t t e n on the subject of carbanion chemistry, with a d e t a i l e d d i s c u s s i o n on thermodynamic and k i n e t i c a c i d i t i e s of hydrocarbons. Bowden and Stewart  17  published i n 1965 an H  based s o l e l y on the i o n i z a t i o n of carbon a c i d s .  C  a c i d i t y function  The main d i f f i c u l t y i n  C establishing a H  scale i s that most hydrocarbons are i n s o l u b l e i n water,  even at spectroscopic concentrations  10  M), and thus the anchoring  of the scale i n d i l u t e aqueous s o l u t i o n s i s impossible. circumvented t h i s obstacle by f i r s t measuring the pK i n aqueous s o l u t i o n (pK  These authors  of m a l o n o n i t r i l e  = 11.14) and then i n d i l u t e s o l u t i o n s of 3  ethanolic sodium ethoxide. They then proceeded to measure the pK  of  two other carbon a c i d s , 9-cyanofluorene and ..methyl fluorene-9-carboxyl a t e , i n solutions of various concentration of sodium ethoxide i n ethanol.  malononitrile  9-cyanofluorene  methyl fluorene-9-carboxylate  F i n a l l y they anchored the scale i n 0.01 M sodium ethoxide with tris-(pnitrophenyl)methane  /  V  3  - 10 .Subsequent work i n t h i s laboratory, much of which i s described i n t h i s t h e s i s , revealed that f o r some o f these carbon acids the ;carbanion undergoes an unusually large s p e c t r a l s h i f t (y 100 my) as the ^degree o f i o n i z a t i o n r i s e s .  Indeed, t h i s behaviour was noticed by the  - o r i g i n a l authors f o r tris(p-nitrophenyl)methane. •Kroeger and Stewart  18  C i n attempting t o set up an H_ scale f o r  -^comparison t o t h e i r H - scale found cases where d i s t i n c t l y n o n - p a r a l l e l K  " i o n i z a t i o n slopes  occurred. 19  •alndependently,  R i t c h i e and Uschold  suggested the existence  C ^of-flaws i n the H  scale.  By use o f the glass electrode they measured  the a c i d i t i e s o f a number of weak acids i n DMSO s o l u t i o n s r e l a t i v e t o a -standard s t a t e i n the same solvent.  They e s s e n t i a l l y t i t r a t e d potentio*  - m e t r i c a l l y these acids with dimsyl cesium s o l u t i o n s , a f t e r having -standardized the glass electrode with d i l u t e p-toluenesulfonic a c i d solutions.  The pK 's o f fluorene (20.5) and triphenylmethane (28.8)  thus measured were i n agreement with values measured by Steiner and 20 ** Gilbert, by a stepwise method with 4 - n i t r o a n i l i n e as an anchor. -measured the pK 's o f four o f Bowden and Stewart a  They  i n d i c a t o r s (Table I I I )  and concluded that the overlap o f i n d i c a t o r s used by Bowden and Stewart •was not v a l i d ; though i t i s not obvious how they a r r i v e d at t h i s conclusion. Dimsyl cesium i s the cesium s a l t o f the conjugate base of DMSO. 4 4 - N i t r o a n i l i n e was found by Dolman and Stewart t o be a non-Hammett i n d i c a t o r slope o f l o g I.vs H 0.92, pK =18.9.  - 11 TABLE I I I pK  fl  17 19 o f carbon acids i n ethanolic DMSO and i n DMSO solvent  Acid  solvent  ;malononitrile  11.14  water  11.0  »tris-(p-nitrophenyl)methane  14.32  DMSO-EtOH  12.0  '9-phenylfluorene  -18.59  f luorene  .'22.1  DMSO  16.4 DMSO-H 0  C  ,20.5  2  •Bowden and Stewart r e f . 17. ^  R i t c h i e and Uschold r e f . 19. Bowden and C o c k e r i l l r e f . 23.  R e l a t i v e a c i d i t i e s o f a number of compounds are reversed by the change of solvent from water to DMSO. The pK 's o f a c e t i c a c i d and hydrazoic a  a c i d f o r example, are 11.6 and 7.9 r e s p e c t i v e l y , while i n water they -both have a pK o f 4.8. a  On the other hand the pK of p-nitrophenol i s a  10.4 i n DMSO and 7.1 i n water.  -  21 S t r i e t w i e s e r et a l .  determined e q u i l i b r i u m a c i d i t i e s o f  various hydrocarbons toward l i t h i u m and cesium cyclohexylamide i n c y c l o hexylamine.  They measured the e q u i l i b r i u m constants between two  hydrocarbons i n cyclohexylamine when treated with an i n s u f f i c i e n t amount of l i t h i u m o r cesium cyclohexylamide to produce the e q u i l i b r i u m shown i n Equation(11)where HA and HB are two hydrocarbons. HA  +  B~Li  +  HB  + A Li  (ID  Since a l l the hydrocarbons studied were more a c i d i c than cyclohexylamine e q u i l i b r i u m (12) l a y f a r to the r i g h t and the spectrum  - 12 AH  + Li NHC H j  A Li  +  6  1  +  + C H NH  of each hydrocarbon salt could be measured.  6  n  (12)  2  The ultraviolet and visible  spectra of the mixture (11) can then be compared with the spectra of the lithium salts of the two hydrocarbons in equation (12) and knowing the i n i t i a l concentrations, the equilibrium constants determined. The main drawback of this procedure is that the conjugate bases involved are  actually cesium carbanide ion pairs (contact) or lithium carbanide  21 Streitwieser et al. chose 9-phenyl22 fluorene (pK 18.59) as their anchor, although they subsequently 3  solvent-separated ion pairs.  reduced their values uniformly by 2.3 units to conform to those of 19 Ritchie and Uschold. 20a Steiner and Gilbert  have used a similar method to determine  the acidity of a few hydrocarbons in both methanolic and aqueous DMSO. Their anchor was 4-nitroaniline pK 18.4 (c*f. footnote page 10). 3. 2 Ob later re-examined their pK values &  indicators less acidic than fluorene.  They  and added 1.6 pK units to a l l the Although the literature is in a  state of some confusion as to the absolute pK to be assigned to these &  22 hydrocarbons, i t seems that a certain consensus has lately been reached between the four different group of workers.  Table IV l i s t s the  different pK values published and also the "best values". A l l these &  values are based on a pK value of 16.4 for 9-phenylfluorene except for Steiner's values which are based on 4-nitroaniline pK =18.4. a 24 C Kuhn and Rewicki determined an H • scale for DMSO-glacial acetic acid - 0.01 M sodium acetate, with various olefinic hydrocarbons 1  - 13 TABLE IV pK values of hydrocarbons and "best values" &  Compound  Experimental pK  9-phenyIfluorene  16,.4 18 .5 18,.5 16,.2 18,.59 18..2  Indene  18..2,  4,5-methylphenanthrene >19.,5 >19,,5 2,3-benzofluorene  best value h  &  16,.4  18,.5 20,.24 19,.93 17..6 20..0 22,.60 22..63 20..3 21..19 20. 1  23,.17 20..9  >19,.5 >19,.5  f luorene  20,.5  20,.5  20..5 22,.83 22,.74 20,.4 22,.10 20,.5  9-phenylxanthene  24,.3  25 .9  28,.5 26,.2  26,.0  triphenylmethane _  27..2  28,.8  31,.48 29,.2  29,.0  diphenylmethane ,  28,.6  30,.2  33,.1 30,.8  30,.5  28,.0  Steiner and Gilbert, ref. 20a, used as anchor 4-N0 An., pK 18.4, from Z. 3 Stewart and O'Donnell ref. 13. o  Steiner and Gilbert, ref. 20b, increased a l l values above fluorene by 1.6, as they found an error in the relative acidities of 9-phenylxanthene and fluorene. Ritchie and Uschold, ref. 19, the validity of this scale is based on the agreement with: 20 13 1. Steiner and Stewart on the pK value of 2,4-dinitroaniline, 14.7. 20 2. Steiner on the pK value of fluorene. a  &  ^  Streitwieser et a l . , ref. 21, solvent separated ion pairs.  The pK  a  values were determined with lithiumcyclohexylamide in cyclohexylamine. Streitwieser et a l . , ref. 21, contact ion pairs.  The pK  values were  determined with cesium cyclohexylamide i n cyclohexylamine. f pK  values presented by Streitwieser et a l . , at the symposium in  San Francisco ref. 22. ^  Bowden and Cockerill, ref. 23. The pK values were determined in &  aqueous. DMSO. h The author's judgement.  - 14 as indicators.  The H values of the medium decrease  with increase  25 in acetic acid content of the solution.  They also measured the pl(  of a number of other olefinic hydrocarbons in the above mentioned system, and also i n the systems DMSO-tri-n-propylamine,  and hexamethyl25  phosphoramide-tri-n-propylamine.  The major drawback of their technique  is that the equilibrium between carbanions and hydrocarbon is not instantaneous.  Kuhn and Rewicki chose 9-cyanofluorene, whose pK 3 17  (11.4) was determined in ethanol  by direct overlap with malonomtrile.  24 Kuhn and Rewicki  determined a pK  of 19.6 for 9-phenylfluorene based  on a pK value of 11.4 for 9-cyanofluorene in DMSO-tri-n-propylamine, 3 which i s irreconcilable with the Ritchie and Uschold results. Indeed fluorene i t s e l f is half ionized in a 90 mole percent DMSO-water-0.01 M N TMAOH solution, which gives a pK value of 22.0 i f the H scale a — C 23 resembles the H  scale,  and since the relative acidities of tris-p-  nitrophenylmethane, 9-phenylfluorene, and fluorene are the same whether measured potentiometrically or spectrophotometrically (stepwise), i t is not at a l l evident that the pK erroneous.  assignment by Bowden and Stewart i s  Though this does not mean that their (Bowden and Stewart)  pK values are correct, since the various substituted CH-acids are &  not really similar to the various fluorenes.  The nitrophenylmethane  anions are much more delocalized than the fluorenes.  Moreover, i t  should be noted that Bowden and Stewart's extinction coefficients for  9-phenylfluorene, fluorene and tris-(p-nitrophenyl)methane  anions do not agree with other reported values.  It i s thus  of prime importance to determine the ionization behaviour of these  - 15 carbon-acids, and hopefully to find a series of hydrocarbons which ionize to give solely carbanions. .  III.  Nitrogen Acids An H  function has been determined for both primary and  secondary amines in aqueous dimethylsulfoxide containing 0.01 M TMAOH 4 (tetramethylammonium hydroxide) by Dolman and Stewart . This scale starts at 10 percent DMSO-water with 2,4-dinitrodiphenylamine as the reference indicator, the pK 13 method by O'Donnell  of which  was measured using the stepwise  and taken as 13.84.  It appears that a single  acidity function will describe the ionization behaviour for both types of amines.  The existence of only one H  that separate H  q  scale contrasts with the fact  scales are required for primary, and tertiary amines  in sulfuric acid water mixtures.  This is not surprising, i f the  cause of the latter effect i s , as suspected, hydrogen bonding between the protons on cationic nitrogen and water." H OIL +  R.-N-H. . .OH3 2  I  2  R- N-H OH. +| 2 H....0H 2  Hydrogen bonding of this type in amide ions should be of l i t t l e importance because of the negative charge on the nitrogen atom. Solvation will occur on the nitrogen atom because of i t s negative charge.  - 16 An  N  15 scale has also been established by Bowden, Buckley and Stewart  using anionic acids such as diphenylamine carboxylic or sulfonic acids, or aminobenzoic acids  which ionize as follows:  HA  -  —•-  H  +  + A" 2  (13)  (15)  This  scale appears to rise slightly less- rapidly than the previously  evaluated H  scale.  In 97 mole percent dimethylsulfoxide-water-0.01 M  TMAOH the H value is some two powers of ten higher than the corresponding H  2  value.  This may be caused by the higher solvation requirement  of the dianion with respect to the single ion reflecting a relatively large increase in the activity coefficient of the dianion.  IV.  Oxygen Acids The only oxygen acids that are sufficiently weak to be  incompletely ionized in strongly basic media are alcohols and stereochemically hindered phenols. for pK  The spectrophotometric method is unsuitable  determination of alcohols, as they do not undergo significant  spectral shifts on ionization. Coggeshall and Glessner  28  studied the ionization of several  phenols in ethanol-water solutions containing sodium hydroxide and found that those phenols with t-butyl groups in the ortho position required the highest base concentration to produce complete ionization. This is presumably due to steric inhibition to the solvation of the phenoxide anions. They pointed out that the difference of energy of transition between the ground and f i r s t excited state for the neutral molecule and the phenolate ion depends upon the type of phenols. *  phenols  A(l/A)  unhindered  2100 cm  1  partially hindered (2-t-butyl-)  2300 cm  1  hindered (2,6-di-t-butyl)  3200 cm"  1  They tentatively explained this phenomenon by considering the energy of polarization of the large ortho groups. 29 Cohen and Jones  measured the dissociation constants for a  series of 4-substituted phenols and the corresponding 2,6-di-t-butyl-4substituted phenols and found that the reaction constant p in water for the hindered phenols is 57% greater than for the unhindered phenols. Cohen and Jones suggested that the extremely weak acidity of hindered phenols may be attributed to the confinement of solvation on the phenolate oxygen, due to the concentration of negative charge on this atom. Cohen and Jones also correlated the ultraviolet spectral data of the 4substituted and 2,6-di-t-butyl-4-substituted phenols and their corresponding anions with substituent parameters. Since p (ultraviolet * A(l/A) is the difference in frequency of maximum absorption between the molecules and the phenolate ion in each series expressed in wavenumbers.  - 18 -  s p e c t r a l s h i f t ) f o r the 2 , 6 - d i - t - b u t y l s e r i e s i s only s l i g h t l y greater than p f o r the hindered phenols they concluded that the phenolic 0-H bond i s coplanar with the aromatic r i n g . Further proof f o r the i n h i b i t i o n to s o l v a t i o n by ortho 30 substituents was provided by Fischer et a l . who measured the d i s s o c i a t i o n constants of 4-substituted-2,6-dichloro and 2,6-dimethyl phenols i n aqueous s o l u t i o n s .  Since the chloro- and methyl-substituents are of o  s i m i l a r s i z e (van der Waals r a d i i are 2.0 and 1.8 A r e s p e c t i v e l y )  but  have opposite i n d u c t i v e e f f e c t s simple s t e r i c i n h i b i t i o n to s o l v a t i o n of the phenoxide anion should give s i m i l a r r e a c t i o n constants P f o r both s e r i e s polar effect.  i f the ortho s u b s t i t u e n t s e x h i b i t s no, or very l i t t l e , Fischer et al.found a p value of the same order of  magnitude f o r both series and higher than f o r unhindered phenols. order of decreasing values i s 2 , 6 - d i - t - b u t y l 3.50,  2,6-dimethyl  The 2.70,  2,6-dichloro 2.61, phenols 2.24, which i s consistent with the expected magnitude f o r purely s t e r i c e f f e c t s , thus confirming the suggestion that i n h i b i t i o n to s o l v a t i o n and not the p o l a r e f f e c t of the a l k y l group i s the cause f o r the acid-weakening  e f f e c t of ortho s u b s t i t u e n t s  i n hindered phenols. 31 Rochester  has r e c e n t l y studied the i o n i z a t i o n of s i x t - b u t y l  s u b s t i t u t e d phenols i n methanolic sodium methoxide s o l u t i o n s , and  found  the r e s u l t s to be consistent with an a c i d i t y f u n c t i o n which d i f f e r s from that obtained using a n i l i n e s and diphenylamines.  Indeed, he  suggests  that a small d i f f e r e n c e e x i s t s between the functions governing the i o n i z a t i o n of p a r t i a l l y hindered and hindered phenols. Rochester used *32 the method of O ' F e r r a l l and Ridd and obtained pK values based on a r  *  p l o t t i n g log (I-[0Me ]) vs [OMe t i o n of sodium methoxide.  ] and e x t r a p o l a t i o n to zero concentra-  - 19 methanol as the standard state.  The H° function differs by up to  0.5 unit in 3 M sodium methoxide from the the greater.  function, the latter being  It would thus be interesting to compare the H acidity  functions for amines and phenols.  The most appropriate solvent system  to use in this study would be methanolic and/or ethanolic DMSO since most phenols are completely ionized in 0.01 M aqueous base.  V.  Application of the H  Function to Kinetics and Mechanisms of Base  Catalysis As i n the case of the H establishing an H  Q  function, the main purpose of  function, besides equilibrium measurements of weak  acids, i s i t s possible correlation with rates of base-catalyzed reactions. These correlations are indeed a powerful tool i n the elucidation of reaction mechanisms.  Few such correlations have appeared i n the l i t -  erature and they i n general involve breaking of a C-H bond i n the rate determining step.  The rate of racemization of (+)-2-methyl-3-  33 phenylpropionitrile  i n dimethylsulfoxide containing sodium methoxide N has been correlated with the H function of the medium. A log k vs H plot i s approximately linear with a slope of 0.87 over a range of rates 34 greater than six powers of ten.  A correlation  i s also obtained between  the logarithm of the rates for the methanolysis of chlorinated hydrocarbons and the H  function of methanolic sodium methoxide solutions.  A reasonable straight line is obtained with a mean slope of 0.8. It 35 was suggested however, that this correlation  was fortuitous because of  ion association in concentrated solutions of sodium methoxide in methanol.  - 20 36 Jones and Stewart  have reported a correlation between the 3  logarithm of the ionization rate constant of (a- H) acetophenone and the H of the medium.  The systems studied were:  DMSO-water-0.01 M  TMAOH, DMSO-methanol-0.01 M sodium methoxide, DMSO-ethanol-0.01 M sodium ethoxide.  The slopes of these correlations though are only ^ 0.5  but this might be accounted for by the fact that the H function for the ionization of a ketone must be quite different from the ionization of an amine.  Keto-enol tautomerism should render an H function more  sensitive to DMSO addition than a hydrocarbon or an amine. Jones and 37 Stewart  correlated also the logarithm of the rate of ionization of  DMSO i n a DMSO-water-0.01 M TMAOH solutions with the H of the medium. N  They observed a linear relationship with a slops of 0.9. 38 Anbar et al. derived equations which correlate the rate constants of various base-catalyzed reactions with the H value of the medium.  If the f i r s t step of the reaction is a proton abstraction,  Anbar et al differentiate between the following cases: a) A rapid preequilibrium is established between the base and the substrate followed by a f i r s t order  rate determining step to  give the products R-H  + 0H~ R n  ^ slow  R" + H 0 , >- products  (16a)  2  In this case the logarithm of the rate constant  (16b)  correlates with the H .  The above mentioned alkaline decomposition of chloroform is an example of such a case.  b)  A r a p i d preequilibrium i s also established as i n case a)  but i t i s followed by a second order  r a t e determining r e a c t i o n with  another reactant Y  R-  + Y  s l 0 W  >  products  (17)  Here also there exists a l i n e a r r e l a t i o n s h i p between the logarithm of the rate constant and the H . The r e a c t i o n between chloramide and ammonia i n aqueous s o l u t i o n s to form hydrazine i s an example o f such a c o r r e l a t i o n and has a slope o f 0.9. b')  I f Y i s a solvent molecule and thus the r e a c t i o n i s  pseudo f i r s t order,the logarithm o f the r a t e constant should c o r r e l a t e with H  +log Cj. Q. c)  In the case where the proton a b s t r a c t i o n i s the slow step,  followed by a f a s t r e a c t i o n to give the products, Anbar et a l suggested that the rate constants w i l l also c o r r e l a t e with H_ + log C„ n  2 S. H  S  "  + OH" f a S t  S l 0 W  >  >  S" + H 0  (18a)  2  products  CI8b)  This s i m i l a r i t y i n r a t e c o r r e l a t i o n between case b') and c) i s not s u r p r i s i n g since the t r a n s i t i o n states i n both o f these cases should be s i m i l a r .  The decomposition of d l - s e r i n e phosphate t o form  pyruvate phosphate and ammonia i s an example o f such a r e a c t i o n type. OH" + " P0 OCH CH(NH )COO" — 2  3  2  2  CH^OCOO" + NH^ + PO " (19) 3  - 22 A plot of log k against H  + log  ^ for this decomposition has a 2 '2  slope of 0.98. More recently Cram and Kollmeyer  have correlated the  logarithm of the rates of potassium methoxide catalyzed isotopic exchange of carbon acids with the H_ of the medium. They proposed two mechanisms to account for the linear relationship observed. (a) The f i r s t one involves a slow ionization step RH + CH 0~  ^y%-  3  R  + CH OH  f a S t  3  >  product  (20)  This mechanism occurs when APK (pK, , , -pK , .) has a low hydrocarbon methanol Jt  r  positive value.  r  r  The transition state i n this case can be represented  by DOCH _  I  H  C  i  0-CH,  I (b)  3  The second mechanism involves a rapid preequilibrium  followed by a rate-limiting reaction with the solvent  RH + CILO 3  Ke «-  R  + CH 0H 3  ^ ' slow  product  (21)  This mechanism occurs when ApK is large and the transition state in this case resembles H0CH  3  — C'r '•DOCH.  - 23 For both o f these r e a c t i o n paths Cram et al.suggested that there i s a l i n e a r r e l a t i o n s h i p between l o g ^ ^ and H . The H 0  s  functions used  23233353637 i n these c o r r e l a t i o n s »  »  »  »  »  have been derived using diphenyl-  amine and a n i l i n e i n d i c a t o r s , and thus r e f l e c t the e f f e c t of changing medium on n i t r o g e n acids r a t h e r than on carbon a c i d s .  This i s r e f l e c t e d  i n the f a c t that the slope e of the c o r r e l a t i o n was always found t o be lower than u n i t y . 39 Kresge  suggests that k i n e t i c a c i d i t y dependence i s a property  of the substrate and should not be i n t e r p r e t e d as a mechanistic c r i terion.  He b e l i e v e s that such c o r r e l a t i o n s can be used to provide an  i n s i g h t i n t o t r a n s i t i o n s t a t e s t r u c t u r e i n r e a c t i o n s of known mechanism, r a t h e r than t o provide evidence u s e f u l i n choosing between two or more p o s s i b l e mechanisms. A.  Kinetic-Thermodynamic  relationships  'The r a t e o f proton t r a n s f e r i n the i o n i z a t i o n o f carbon acids has been looked upon as a measure of the k i n e t i c a c i d i t y o f these a c i d s .  The  k i n e t i c a c i d i t y i s defined as the forward rate of exchange., on a r e l a t i v e logarithmic s c a l e R-H + B - ±-* R k r  + BH ,  (22 )  b u t u n t i l r e c e n t l y no systematic study of kinetic-thermodynamic r e l a t i o n s h i p s had been made f o r simple hydrocarbons.  This i s because  they are much too weak as acids to i o n i z e i n common b a s i c aqueous s o l u t i o n s , 43 S p e c i a l experimental techniques  had t o be developed i n order to study  isotope exchange rates o f hydrocarbons i n l i q u i d ammonia and i t i s only  - 24 -  i n the l a s t decade that the use of non-aqueous solvents as r e a c t i o n media has gained a c e r t a i n p o p u l a r i t y . Following Eigen's treatment, i t i s advantageous t o consider that an intermediate (hydrogen-bonded) complex i s formed between the acid and the base as i n equation (23): R-H + B  -  l .  k  ,  R-H---B  k  - l  k  k  2  B-H + R  (23)  -2  Normally the concentration of the complex R-H  B  i s very small compared  with the concentration of e i t h e r reactants or products.  Using the  steady-state assumption the forward (k£) and reverse ( k ) rate constants r  can be expressed as f o l l o w s : k., k _ .— i k_ k  k. =  k  1  f  1  +  r  k ^ k ~* - l 2  =  1  k  2  +  k  The e q u i l i b r i u m a c i d i t y i s r e l a t e d t o the r a t i o of forward and reverse rate constants, u s u a l l y as the negative logarithm, or log k - l o g k £  r  =  pK^  -  pK  =  B H  A(pK)  (24)  The well-known Bronsted equation r e l a t e s the k i n e t i c and e q u i l i brium a c i d i t i e s . log k  In i t s simplest form i t i s w r i t t e n :  A  =  log G  A  -  a log K  &  (25)  where k. i s the r a t e constant f o r acid catalysed r e a c t i o n and K the A . a  - 25 equilibrium acidity of the acid A, or of the conjugate acid of the base B.  and a are constants.  Considering equation (24), one may rewrite  40 the simple Bronsted relation (25) in the following form d log k — — d A (pK) f  =  a  where a is the Bronsted slope.  (26)  It i s evident from equation (26) that a  is zero i f A (pK) has a large positive value and unity i f A (pK) i s large negative.  In the transition region between these extremes where  A (pK) - 0, a has an intermediate value between 0 and 1.* The integrated form of the Bronsted equation (equation 25) was . proposed in 1924 to correlate the catalysed decomposition of nitramide as 41 shown in equation (27).  Bronsted  emphasized the fact that his equation  is limited to a study of reactions catalysed by a small number of compounds H  2 2°2 N  >  H  2°  with comparable acid strength.  +  N  2°  ( ) 27  Indeed Eigen^ pointed out that the  decomposition of nitramide shows a continuous variation of the coefficient a i f studied over a wide range of reactivities. Even in the classical case of the base-catalysed halogenation of 42 ketones  , Eigen showed that in a wider pK range a is not constant and  that a l l the curves can be constructed on the basis of the generalized relationship (26). At high A (pK) value - whether negative or positive - the rate of proton transfer is diffusion controlled. *  In the vicinity of A (pK) = 0  55 Bordwell et al. recently measured Bronsted coefficients larger than unity and smaller than zero for proton abstraction of nitroalkanes.  - 26 there is a transition where log k is linearly related to A (pK) and takes a value between 0 and 1.  Normal acid-base systems are those which  show a sharp narrow transition region. OH-  (phenols), NH-  (aniline), NH-  Such acids are usually of the  (pyridinium ion) type, whose pK  values  l i e in the range -1 to 15. CH-acids (or pseudo-acids) and some normal acids with special structural characteristics (internal hydrogen bonding for example) have broad, transition regions. This transition from a = 0 to a = 1 will occur gradually so that a might appear to have a constant value. Carbon-acids show wide transition regions because usually deprotonation i s associated with resonance stabilization and the recombination rate may therefore be relatively low.  Many examples of curvature of log k  -A pK relationships have been found and i t is now a well accepted fact that Bronsted plots are usually non linear i f a wide enough range of reactivities is examined.  The log k-A pK relation approaches ideal be-  havior when: (i) both donor and acceptor belong to the classical hydrogen bond formers (0- and N-type). (ii) the electronic and spatial configurations of the acids and their conjugate bases are similar.  If the limiting values of k are identical (the  extrapolated straight lines at a = 0 and a = 1 intersect at A pK = 0) then the slope of log k-A  pK plot at A pK = 0 is often close to 0.5.  If how-  ever, the limiting values of k differ, then the center of symmetry--point of intersection of the straight line a =0  and a = 1 --is displaced along  the A pK axis by the difference of the logarithms of these limiting value. The closer the value of k at A pK = 0 is to the limiting value, the narrower is the transition region, where a appears to be constant. T h i s  - 27 symmetric behavior with respect t o A pK = 0 i s only v a l i d f o r reactions of symmetric charge type. HX + Y~ XH  +  + Y  * —  X" + HY  (28a)  X + YH  (28b)  +  However i f the r e a c t i o n shows an asymmetry of charge, the log k-A  pK  curve becomes asymmetric with respect to A pK = 0.' HX + Y  —*  X" + YH  (28c)  +  22 Recently S t r e i t w i e s e r et a l . measured the k i n e t i c a c i d i t i e s of a s e r i e s of hydrocarbons by hydrogen isotope exchange i n methanolic sodium methoxide.  The thermodynamic a c i d i t y of these same hydrocarbons have  already been measured i n cyclohexylamine by him, ( c f . p. 12-13). Bronsted p l o t of log k~ (second order rate constant) vs. pK  A  i n cyclo-  hexylamine showed d i s t i n c t curvature with a varying from about 0.4 near the fluorenes t o 0.8 f o r d i - and tri-arylmethanes. Cram and Kollmeyer also published a kinetic-thermodynamic a c i d i t y c o r r e l a t i o n of carbon acids.  Rate constants and a c t i v a t i o n para-  meters f o r potassium methoxide c a t a l y z e d exchange of a few hydrocarbons i n methanol-O-d-dimethyl-d^-sulfoxide  (~ 15 mole percent) were measured.  These k i n e t i c a c i d i t i e s varied by a rate f a c t o r of seven powers of t e n , and the thermodynamic a c i d i t i e s by a f a c t o r of ten powers of ten. Bronsted p l o t was also curved. f o r the strongest acids (pK (pK  a  =28  + 2).  The slope of the l o g k vs. pK  &  The  curve was ~ 0.  = 23 ± 3) and u n i t y f o r the three weakest acids  - 28 44 'Shatenshtein et al> have studied e x t e n s i v e l y i s o t o p i c exchange -reactions of hydrocarbons i n non-aqueous s o l v e n t s , at f i r s t mainly i n 43 -liquid ammonia , but l a t e r also i n cyclohexylamine, dimethylsulfoxide 44 45 46 44 and others ' ' . Shatenshtein proposed a two-step mechanism s i m i l a r t o the one shown i n equation (23). The f i r s t stage of t h i s r e a c t i o n i s the l i m i t i n g stage, and thus k ^  = k^, i . e . the observed  rate constants of the r e a c t i o n i s equal t o the rate constant f o r the .^ionization of the R-H bond.  I t i s only i n t h i s case that the k i n e t i c s o f  hydrogen exchange can c h a r a c t e r i s e the a c i d i t y o f t h i s C-H bond. 44 ''"^Shatenshtein  suggested that there i s no d i r e c t r e l a t i o n between the  .^observed r a t e constant o f the exchange r e a c t i o n and the i o n i z a t i o n rate ^constant, i n the case where the second step i n equation (23) i s rate k ^determining; since k ^ = 1 k., = Kk^ . -l 44 45 g  k  Shatenshtein  '  a l s o pointed out that the r e l a t i v e k i n e t i c  - a c i d i t i e s can vary with change i n the solvent medium.  Very large d i f f e r -  e n c e s i n r e l a t i v e k i n e t i c a c i d i t i e s were found i n comparing the k i n e t i c s of deuterium exchange i n DMSO and i n ammonia.  For example the rate  ^constants f o r the exchange of deuterium i n the methyl group and i n the r i n g of toluene i n DMSO d i f f e r by a f a c t o r of 10^ while they d i f f e r only 2 by a f a c t o r o f 10 i n ammonia.  He d i f f e r e n t i a t e s between C-H bonds i n  aromatic or heteroaromatic r i n g s and those i n methyl groups attached t o aromatic r i n g s , when p l o t t i n g r e l a t i v e strengths of carbon acids i n one. solvent against the r e l a t i v e strength of the same acids i n another solvent. 44 Shatenshtein  found that there i s no d i f f e r e n t i a t i n g e f f e c t when the  solvents belong t o the same category (aprotic or p r o t i c ) , f o r example DMSO ys. methyl-bismethoxymethyl-phosphine oxide, (CH^OQ^)2PO.CH.J, o r ammonia v s . cyclohexylamine. He found 45 though, that i f the solvents  - 29 do not belong to the same group, DMSO vs. t-butanol or DMSO vs. ammonia, the points for the alkyl groups in alkylbenzenes l i e on one line while those for benzene derivatives containing ring deuterium l i e on another line. Shatenshtein concludes that the differentiating action of solvents on the kinetic acidity of carbon acids depends on the structure and the solvation of the transition states formed during the isotopic exchange reactions.  He also points out that the problem of determining acidities  (thermodynamic and kinetic) of hydrocarbons is s t i l l quite complicated due to our limited knowledge of solvent effects. B.  Isotope effects Primary kinetic isotope effects for the base catalysed proton ab-  straction from aromatic hydrocarbons have been measured by many workers. 47 Streitwieser et a l . have measured the kinetic isotope effect k^/k^ for the exchange of the methyl hydrogens of toluene in the cyclohexylamine cyclohexylamide system.  r  k They found values greater than 10 for H/k^,, 48  while in the DMSO - potassium-t-butoxide system Hofmann et al \ measured k a  D/k^ slightly less than unity. Hofmann et al believed that their  results showed that the rate determining step was not i n i t i a l ionization of the C-H bond, but the formation of a tight complex between the incipient carbanion and the alcohol. 49 50 This view was challenged by J.R. Jones . Both theory and exper51 52 53 iment  ' *  indicate that the isotope effect for proton transfer be-  tween acid-base systems has a maximum value when the A pK value between &  the two acids is equal to zero.  In Streitwieser s case the pK of ?  t-butanol is ^ 20, while the pK of toluene is ^ 40.  &  Thus, we should  expect to have a high isotope effect in cyclohexylamine, and a negligible  - 30 one i n d i m e t h y l s u l f o x i d e . K i n e t i c isotope e f f e c t s f o r proton a b s t r a c t i o n r e a c t i o n s 2 22 have been measured f o r other hydrocarbons ' discussed l a t e r i n t h i s t h e s i s .  but these w i l l be  - 31 -  SCOPE OF THE PRESENT RESEARCH As emphasized i n the i n t r o d u c t i o n , the i n d i c a t o r s used t o determine H  functions can be d i f f e r e n t i a t e d i n t o oxygen, nitrogen  and carbon acids.  Part o f t h i s work was undertaken to determine the  degree of divergence o f a c i d i t y functions caused by v a r i a t i o n i n N indicator structure.  The i o n i z a t i o n behaviour o f diphenylamines (H )  and phenols (H^) were therefore determined i n d i m e t h y l s u l f o x i d e methanol containing 0.01 molar sodium methoxide and d i m e t h y l s u l f o x i d e ethanol containing 0.01 molar sodium ethoxide.  These weak acids  e x h i b i t a strong bathochromic s h i f t on i o n i z a t i o n , and t h i s provides a simple way o f determining the p o s i t i o n of t h e i r i o n i z a t i o n e q u i l i b r i a . N A redetermination of the H  function i n low percentage  dimethylsulfoxide i n water was also considered necessary as some doubts were r a i s e d on the i o n i z a t i o n mode o f the p r e v i o u s l y used anchor,. 2,4,6-trinitroaniline.. Preliminary r e s u l t s i n d i c a t e d that the p - n i t r o substituent had an overwhelming e f f e c t .  I t was thus important t o study the e f f e c t  of s u b s t i t u t i o n on the a c i d i t y of diphenylamines i n the presence o f the n i t r o group i n the other r i n g . H  The main purpose i n e s t a b l i s h i n g an  f u n c t i o n , apart from i t s use i n e q u i l i b r i u m measurements o f weak  - 32 -  a c i d s , i s i t s p o s s i b l e c o r r e l a t i o n with rates of base-catalyzed reactions. Base-catalyzed rates of d e t r i t i a t i o n of various hydrocarbons were determined i n dimethylsulfoxide mixtures.  These rates (on a  logarithmic scale) were then c o r r e l a t e d with the thermodynamic b a s i c i t y of the medium as measured by the H  function.  The shape  of these c o r r e l a t i o n s would then give us i n f o r m a t i o n on the a p p l i c a b i l i t y of these H  f u n c t i o n s , and on the s t r u c t u r e of the t r a n s i t i o n  state i n base-catalyzed proton a b s t r a c t i o n r e a c t i o n s .  Hopefully a  kinetic-thermodynamic r e l a t i o n s h i p might also be derived from these rate measurements. In view of the d i s p a r i t y between published pK pK  and r e l a t i v e  values of carbon a c i d s , and the disagreements on s p e c t r a l  c h a r a c t e r i s t i c s of t h e i r carbanions formed on i o n i z a t i o n , a c l o s e examination of the i o n i z a t i o n behaviour should be undertaken.  I t was  of prime importance to prepare and c h a r a c t e r i z e the carbanions of these nitrophenylmethanes and determine t h e i r s p e c t r a l c h a r a c t e r i s t i c s . One could then decide whether these carbon acids had i o n i z e d by proton a b s t r a c t i o n i n p r e v i o u s l y reported work.  A l s o , the cause of the  dependence of s p e c t r a l c h a r a c t e r i s t i c s on the solvent should be investigated.  EXPERIMENTAL Most of the handling techniques pertaining to the determina4b tion of the H functions are described in f u l l detail elsewhere.  An  outline of these procedures i s given below. I.  Purification of solvents DMSO was stirred in a closed vessel over powdered calcium *  hydride for at least two days and then d i s t i l l e d in a stream of nitrogen at reduced pressure. A Perkin triangle was used to cut fractions, and the f i r s t and last 20% of the d i s t i l l a t e were discarded.  The DMSO was  stored in glass stoppered flasks over molecular sieves 4A and under nitrogen.  The water content of the DMSO was measured prior to i t s use,,  by the Karl-Fischer method, and was shown to be less than 0.01%. Hexamethylphosphoramide (HMPT) was fractionally d i s t i l l e d twice from molecular sieves 13X. late were discarded each time.  The f i r s t and last 20% of the d i s t i l As HMPT dissolves most commercial vacuum  greases, a d i s t i l l a t i o n apparatus with "clear-fit" joints was used. The d i s t i l l e d HMPT was stored in stoppered bottles over molecular sieves 4A. Carbonate-free water was prepared by boiling d i s t i l l e d water and then bubbling nitrogen through as i t cooled. * The nitrogen gas used throughout was grade "L" (Liquid Air) as grade "G" contains small amounts of oxygen.  - 34 "Super dry" methanol and ethanol were prepared according t o 54 standard procedures i n Vogel  and were stored over molecular sieves 3A  and under n i t r o g e n . Dryness was checked p r i o r t o use by K a r l - F i s c h e r titration. toluene was Baker analyzed reagent grade and was d i s t i l l e d before use.  I I . Base Tetramethylammonium hydroxide was obtained from Eastman Organic Chemicals e i t h e r as a 10% aqueous s o l u t i o n or as the c r y s t a l l i n e pentahydrate and was used without further p u r i f i c a t i o n . Sodium methoxide and ethoxide were prepared from the required amount o f sodium and the corresponding a l c o h o l to produce a 1 M s o l u t i o n . .  This was done i n a rubber stoppered b o t t l e under a stream o f n i t r o g e n . 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 stock s o l u t i o n s were t i t r a t e d against standard a c i d .  The stock s o l u t i o n s were kept under  nitrogen and stored i n the freezer compartment o f a r e f r i g e r a t o r .  No  s o l u t i o n older than 1 month was ever used.  I I I . Preparation of s o l u t i o n s The DMSO-protic solvent (H 0, MeOH, EtOH) stock s o l u t i o n s 2  were made up according to weight at approximately 5 mole percent i n t e r v a l s from 0 to 100 percent DMSO. Dry NO-SOL-VIT b o t t l e s with w e l l f i t t i n g rubber stoppers - sleeve type - were weighed.  Into each of  these was syringed the required volume o f DMSO, and the b o t t l e s were  - 35 reweighed to give the weight of DMSO. To this was syringed the appropriate amount of protic solvent and the bottles weighed for the final time to give the weight of the solvent.  Nitrogen was then bubbled through  these solutions for 3 minutes and they were then stored in a desiccator over Drierite.  It was found that the amount of moisture which  was picked up by the solvents during preparation was very small and did not warrant the extra precaution of using a drybox.  IV. Spectral measurements Indicator measurements were made with a constant  concentra-  tion of base (0.011 M tetramethylammonium hydroxide or 0.01 M sodium alkoxide).  A l l measurements of spectra were made on a Bausch and Lomb  model 502 recording spectrophotometer, with the cells thermostated at 25° by means of a constant temperature cell holder. 13 developed previously by O'Donnell  The procedure  and used since then in these  laboratories to protect the system from oxygen was followed.  This  involves the use of silicone rubber disks to seal absorption cells and syringes  to introduce the indicators and the base.  was bubbled through the solution for about 2 minutes.  Dry nitrogen  None of the  indicator anions used seemed to react in any way for at least 15 minutes, as.their spectra showed no change during this lapse of time. V.  Treatment of data and calculations From the spectral measurements on solutions of indicators i n  the aprotic-protic-base system, the ratios of the concentrations of ionized to unionized indicator (I =.(A )/(HA)) are obtained.  From these  - 36 -  r a t i o s are then obtained the r e l a t i v e pK 1  and the H  values of the amine i n d i c a t o r s a  values f o r the s o l u t i o n s i n which the measurements were made. The r e l a t i v e pK  values were obtained by comparing the  i o n i z a t i o n r a t i o s o f overlapping i n d i c a t o r s i n the same s o l u t i o n .  The  quantity l o g I was p l o t t e d a g a i n s t the solvent composition f o r each i n d i c a t o r and a smooth curve drawn through the points f o r each p l o t . Values o f l o g I between -1 and +1 corresponding t o 10% and 90% i o n i z a t i o n , r e s p e c t i v e l y , were used i n the p l o t s .  Where successive curves  overlapped, d i f f e r e n c e s were taken at r e g u l a r i n t e r v a l s and the r e s u l t s averaged.  These averages gave the d i f f e r e n c e s between the pK  a  values  of the i n d i c a t o r s . The H - values were then c a l c u l a t e d from the pKa values of r  the i n d i c a t o r s and the values of l o g I obtained from the smoothed curves mentioned above. This was accomplished by using equation ( 6 ) .  H  - P a =  K  +  For a given s o l u t i o n , H  ( 6 )  i s g e n e r a l l y an.average of the values obtained  from two or more i n d i c a t o r s .  VI. Probable e r r o r i n H_ and pK  a  values  With a l l a c i d i t y functions i t i s d i f f i c u l t to estimate the u n c e r t a i n t y i n the H values and i n the pK used t o determine them.  values of the i n d i c a t o r s  The f u r t h e r the a c i d i t y f u n c t i o n i s from the  usual pH range, the greater the l i k e l i h o o d of e r r o r s because of the  - 37 stepwise procedure used to e s t a b l i s h i t .  The errors can be minimized by  using a large number of overlapping i n d i c a t o r s so that the H  value f o r  a given s o l u t i o n i s not dependent on the data from any one i n d i c a t o r , and by using i n d i c a t o r s of the same s t r u c t u r a l type to ensure that the Hammett a c t i v i t y c o e t f i c i e n t postulate i s obeyed as c l o s e l y as p o s s i b l e . 4 The previous estimate on the low s i d e .  of the u n c e r t a i n t y as 0.05 pK u n i t appears to be  A more reasonable estimate would be around t 0.2-0.3.  I t i s to be noted that the p r e c i s i o n of the UV measurement f a r exceeds the method's o v e r a l l accuracy.  A change i n absorbance of 0.02  a l t e r s log I by only ^ 0.04 i f -0.5 < log I < +0.5 and by -0.5 > log I >  0.08 i f  +0.5.  It was also noticed that s o l u t i o n s of i n d i c a t o r s can be kept for an extended period of time (12 months) without any damage. . V I I . K i n e t i c measurements A.  ,.  Hydrocarbon exchange  A weighed amount (10-30 mg) of t r i t i a t e d hydrocarbon was weighed i n a 125 ml erlenmeyer with a B24 stopper, and 100 ml of the appropriate mole percent DMSO-alcohol s o l u t i o n was introduced i n t o the flask.  A f t e r complete d i s s o l u t i o n of the hydrocarbon was assured, the  f l a s k was immersed i n a w e l l - s t i r r e d thermostated bath.  After  suffic-  i e n t time was allowed f o r temperature e q u i l i b r a t i o n , 1.0 ml of a 1 M s o l u t i o n of sodium ethoxide i n ethanol was added.  A l i q u o t s were  withdrawn at f i x e d time i n t e r v a l s and introduced i n t o a 125 ml separatory funnel containing 50 ml of cold water (to stop the reaction) and 15 ml of l i q u i d s c i n t i l l a t o r (3.5 gm of 2,5-diphenyloxazole per  - 38 l i t r e of toluene). layer run off. sulfate.  The funnel was shaken by hand and the aqueous  The toluene solution was dried over anhydrous magnesium  An aliquot (10 ml) of the dried toluene was transferred into  a counting v i a l .  The latter was stored for 20 min. then counted in a  Nuclear Chicago Mark I model 6860 liquid scintillation counter. The counting efficiency was roughly determined for each sample by the external standard technique u t i l i z i n g the b u i l t - i n barium-133 gamma source.  A l l vials which did not have the average efficiency were  discarded.  The usual count at time zero was around 500,000 counts  per minute.  In general the reaction was taken to ^ 70% completion.  However for each hydrocarbon, at least one run was allowed to proceed to greater than 90% completion. The base concentration was determined by simple titration against standard acid using phenolphthalein indicator. The tritiated hydrocarbons were prepared (cf. preparation of compounds  for details) by one of the following methods: 1.  quenching of an ethereal solution of the sodium salt of the hydrocarbon with HTO,  2.  catalytic exchange between the hydrocarbon and HTO*^.  B.  DMSO exchange  Solutions {y 30 mis) of appropriate mole percent DMSO-protic solvent were prepared as previously described and 0.1 ml of tritiated DMSO or protic solvent, as the basicity of the medium warrants, was added.  After thermal equilibration 0.3 ml of 1 M base solution was  added.  If the reaction was fast the base concentration was determined  - 39 by simple titration.  Aliquots (3 mis) were withdrawn and injected into  tubes containing 7 ml of methanol.  The CH^OT thus formed was separated  from the DMSO by fractional d i s t i l l a t i o n , dried and then added to 7 ml of the liquid scintillator, cooled and counted.  If the reaction was  slow 3 ml aliquots were withdrawn into vials and sealed under nitrogen and kept in the constant temperature bath.  At appropriate time  intervals, the vial was broken and 7 mis of MeOH was added and the same routine followed. Tritiated DMSO was prepared by allowing 20 gm of DMSO to equilibrate with 0.1 ml of HTO (100 mcuries/ml) in the presence of a pellet of sodium hydroxide for 6 hours.  The contents were neutralized  with hydrochloric acid and 10 ml of methanol was added.  The solution  was dried, the methanol was removed by d i s t i l l a t i o n and the DMSO was purified by vacuum d i s t i l l a t i o n .  Tritiated methanol and ethanol were  prepared by allowing 10 ml of alcohol to equilibrate with 1 ml of HTO (4 mcurie/ml) for a half hour.  The alcohol was then fractionally dis-  t i l l e d and dried.  VIII.Treatment of the kinetic data The pseudo f i r s t order rates for the detritiation of hydrocarbon are described by equation 29.  k  =  IWTt  l o g [c]  C29)  where the [C] terms refer to the radioactivity of the hydrocarbons at various time intervals.  No infinity correction was made as the hydrocarbon  Figure 1.  T y p i c a l f i r s t - o r d e r r a t e p l o t s f o r the d e t r i t i a t i o n of 9-phenylfluorene i n absolute methanol at  25°.  - 41 loses almost a l l of i t s a c t i v i t y to the solvent s i n k .  An i n f i n i t y point  showed an a c t i v i t y of % 1000 c/min which i s n e g l i g i b l e with respect to the average a c t i v i t y o f 200,000 c/min. from each run and k C against t .  Eight points were obtained  was determined from the slope o f the p l o t of log  Duplicate runs showed the r a t e constants to be i n  agreement w i t h i n t 5%. A representative p l o t o f a d u p l i c a t e d e t r i t i a t i o n measurement - 9-phenylfluorene  i n absolute methanol - i s shown i n  f i g u r e 1. In the case of the DMSO exchange the equations V  V trit  V  v  2  -303 [OR J  ,  [(MeOT) - (MeOT)J o  [ e O T ) - (MeOT) ]  t  2.303  • W r i t " [OlFTT  are:  (M  , l0  *  o  [(MeOT)~ - (MeOT) ] p  [ ( M e 0 T ) r o  .  ( M e 0 T ) t ]  ( 3 1 )  A t y p i c a l p l o t f o r the t r i t i a t i o n of DMSO - i n 55% DMSO-water - i s shown i n f i g u r e 2. In the case where the base concentration d i f f e r e d from the standard value 0.01 M a c o r r e c t i o n was made using the equation:  H_ = H_ (0.01) >  log  J£jLl  The c o r r e c t i o n was never more than 0.1 u n i t .  (32)  This c o r r e c t i o n i s  warranted by the f a c t that the H_ f u n c t i o n f o r various concentrations o f p r o t i c solvent and i t s conjugate base f o l l o w t h i s equation f o r d i l u t e basic solutions.  - 43 -  IX. Reactions of a.  nitrophenylmethanes  Nuclear magnetic resonance (n.m.r.):  A solution of the  nitrophenylmethane in HMPT was prepared  in a drybox under nitrogen atmosphere.  An n.m.r. spectrum of this  solution was then recorded on a 100 M.Hz. Varian H.A.-100 spectrometer. A small amount of solid sodium methoxide was added to the solution and another spectrum was recorded immediately.  The solution was then  filtered through glass wool into another n.m.r. tube and a subsequent spectrum was recorded. Aside from the fact that the filtered solution gave "cleaner" spectra than the unfiltered one, there was no difference between them. This same solution was then used for the determination of the spectral characteristics of the anionic species. Chemical shifts are reported in p.p.m. from an internal tetramethylsilane reference.  A Cary spectrophotometer Model 16 was  used for the measurements of the visible absorption spectra (up to a wavelength of 800 my), and a Cary recording spectrophotometer Model 14 was used in the near infrared region (beyond 800 mu). b.  Electron spin resonance (e.s.r.)  Tetra-n-propylammonium  perchlorate (TPAP) was used as  supporting electrolyte, and was prepared from tetra-propylammonium hydroxide and perchloric acid. (1:9) DMSO-water mixture.  The product was recrystallized from a  The electrolysis cell used in this work  was designed by D.E. Kennedy^ and spectra were recorded on a Varian 1  E. 3 spectrometer. The  nitrophenylmethane and TPAP were weighed i n .  dry NO-SOL-VIT bottles, which were then fitted with rubber stoppers  - 44 (sleeve type).  Aliquots of the appropriate mole percent DMSO-methanol  solution were injected into these bottles.  After complete dissolution  of the solid nitrogen was bubbled through the solution for 10 minutes. The solution was then transferred to the electrolysis c e l l and degassed by connecting the c e l l to the vacuum system. of the supporting electrolyte was methane ^ 0.01 M.  The concentration  0.1 M and that of the nitro-phenyl-  The potential applied to the cell for electrolysis  was measured with respect to the mercury pool electrode, and was ^2 volts with a current of ^ 50 u amp.  i  X.  Computer treatment of data A least square program with a plotting routine was used for  treatment of much of the data.  I would like to thank Messrs. A.M..  Smolensky and D.E. Kennedy for help in writing the program. A l l the figures in this thesis are reproductions of plotting output.  The program and a sample of input and output is listed in  Appendix C for reference. XI. Preparation of compounds used in this work A.  Amines  a.  2,4-dinitrodiphenylamine series:-  2,4,4'-Trinitrodiphenylamine:  was prepared by nitration of  2,4-dinitrodiphenylamine with nitric acid-acetic acid mixture accord57 ing to the method of M.P. Juillard.  The product was recrystallized  from toluene, acetic acid and finally from alcohol, L i t . m.p.  188°.  57  melted at 187-188°.  - 45 I  2,4,3"-Trinitrodiphenylamine: purified previously in this laboratory.  has been prepared M.p. 192-194°.  12  and  Recrystallized  from pyridine. 2,4-Dinitro-4'-trifluoromethyldiphenylamine:  has been  synthesized and purified by Dr. A. Buckley in this laboratory by condensation of the chloro-dinitrobenzene with p-trifluoromethylaniline. M.p. 125-126.5°. Analysis  Recrystallized from acetic acid and ethanol.  calcd.  C 47.71  H. 2.46  F 17.42  N 12.84  found  47.57  2.62  17.16  12.01  2,4-Dinitro-3 -trifluoromethyldiphenylamine: 1  has been  synthesized and purified by Dr. A. Buckley in this laboratory. 123-125°. Analysis  M.p.  Recrystallized from acetic acid and ethanol. calcd.  C 47.71  H 2.46  17.42  F N - 12.84  found  47.79  2.98  17.27  13.05  2,4-Dinitro-3 -chlorodiphenylamine: 1  purified by Dr. A. Buckley in this laboratory.  has been prepared and M.p. 180-182°. 58  Recrystallized from ethanol. L i t . m.p. 182-183°. 2,4-Dinitrodiphenyiamine:  obtained from Eastman Organic  Chemicals and recrystallized from ethanol. M.p. 155-156°. 155°.  59  2,4-Dinitro-3'-methyldiphenylamine:  obtained from Aldrich  Chemicals and recrystallized from ethanol. M.p. 161-162°. 160°.  L i t . m.p.  L i t . m.p.  60  2,4-Dinitro-4'-aminodiphenylamine:  obtained from Columbia  Organics passed down an alumina column with a benzene/chloroform (1:1) mixture, then through another alumina column with chloroform as eluent.  - 46 M.p.  183-184°.  Analysis  Lit. m.p.  189°.  61  calcd.  C 52.55  H 3.65  N 20.44  found  52.76  3.75  20.20 12  (cf. spectral data as they differ from published b.  values).  4-Nitrodiphenylamine series:-  4,4'-Dinitrodiphenylamine:  has been prepared and purified  12 previously  in this laboratory and was recrystallized from dioxane- .  water pair.  M.p.  213-216°. 4  3,4'-Dinitrodiphenylamine:  has been prepared  and purified  previously in this laboratory and was recrystallized from benzene- . petroleum ether pair.  M.p.  215-216°.  4-Nitro-3'-trifluoromethyldiphenylamine:  was prepared by  condensation of 2-chloro-5-nitrobenzene sulfonic acid with m-trifluoromethylaniline followed by desulfonation according to the method of 62 F. Ullmann and R. Dahmen.  (Another sample was previously prepared  by Dr. A. Buckley in this laboratory).  The product was  from acetic acid and ethanol. M.p. 137.5-139°. C H N Analysis calcd. 55.31 3.19 9.93 found  55.42  3.32  F 20.21  10.00  4-Nitro-3'-chlorodiphenylamine:  19.92  prepared by the above  mentioned method and purified by Dr. A. Buckley in this laboratory. Recrystallized  from ethanol. M.p.  4-Nitrodiphenylamine:  129-130°.  L i t . m.p.  129°.  obtained from Aldrich Chemicals and  was recrystallized from acetic acid.  M.p. 131-133°.  Lit. m.p.  133°.  - 47 4-Nitro-3'-methyldiphenylamine: Dr. A. Buckley in this laboratory.  synthesized and purified by  M.p. 127-128°.  Recrystallized  from ethanol. Analysis  calcd.  C 68.40  H .5.30  N 12.28  found  68.24  5.29  12.12  4-Nitro-4'-aminodiphenylamine:  prepared and purified by fV  Dr. A. Buckley in this laboratory. c.  Aniline  M.p. 206-207°.  was obtained from Eastman Chemicals  and recrystallized from ethanol, acetic acid. 192-195°.  M.p. 191-192°. L i t .  63  2,4-Dinitroaniline: recrystallized from ethanol.  was obtained from Eastman Chemicals and 63 M.p. 180-182°. L i t . m.p. 180°.  4-Chloro-2-nitroaniline: Co. and recrystallized from ethanol. 116°.  207-208°.  series:-  2,4,6-Trinitroaniline:  m.p.  L i t . m.p.  was obtained from Brothers Chemicals M.p. 115.5-116.5°.  L i t . m.p.  63  B.  Phenols  A l l the phenols used were commercially available and were recrystallized from absolute ethanol under a nitrogen atmosphere and sublimed before a final recrystallization under nitrogen.  C.  Hydrocarbons  2,4,2',4'-Tetranitrodiphenylmethane:  was prepared in this 64  laboratory according to the method of Parkes and Morley  and recrystal-  - 48 lized from acetic acid.  M.p.  173-174°.  Lit. m.p.  173°.  4,4' ,4"-Trinitrodiphenylmethane (-tris-(p-nitrophenyl)methane) : was prepared by direct nitration of triphenylmethane with concentrated sulfuric and n i t r i c acid mixture according to the method of Shoesmith, Sosson, Hetherington.^  After several recrystallizations from chloro-  form-ether, the product was recrystallized from toluene and melted at 214-215°.  L i t . m.p.  214.5°.  65  4,4'-Dinitrodiphenylmethane (-bis-p-nitrophenyl-methane): was obtained from Eastman Chemicals and recrystallized from benzene. compound melted at 183-183.5°.  Lit. m.p.  3,4'-Dinitrodiphenylmethane:  183°.  The  66  was prepared from p-nitrobenzyl 67  alcohol and nitrobenzene according to the method of Gattermann and Rudt The product was recrystallized from ethanol and melted at 104.5-105.5°. Lit. m.p.  103°.  67  9-Phenylfluorene:  was prepared by dehydration, of triphenyl68 carbinol in phosphoric acid according to the method of Kliegl. The product was recrystallized from ethanol and melted at 62 Lit. m.p.  145°.  The tritiated  compound was prepared by exchange 53  according to the method of J.R. Jones.  9-Phenylfluorene (1 gm) was  dissolved in 5 ml of a (1:1) Dioxan-DMSO mixture.  Tritiated water  (0.1 ml of activity 10 mc/ml) was added and a few crystals of tetramethylammonium hydroxide pentahydrate.  After three days the solution  was neutralized with acid, and the solvent evaporated.  The solid  was added to 100 mis of water, to dissolve the salt, and the solution filtered.  This dissolution - f i l t r a t i o n  step was repeated thrice before  recrystallization of the 9-phenylfluorene-t from ethanol.  - 49 2,3-Benzofluorene:  was obtained from K § K Laboratories and  was recrystallized from petroleum ether. M.p. 207-208°.  Lit. m.p.  63 208°.  The tritiated compound was prepared by Dr. J.R. Jones in this  laboratory. Fluorene:  was obtained from K § K Laboratories and recrystal-  lized from benzene/petroleum recrystallized.  ether (30-60°), then sublimed, then  The product melted at 116.5-117.5°.  Lit. m.p. 116-  63 117°.  The tritiated compound was prepared by direct exchange. 9-Ethylfluorene:  was prepared by direct alkylation of fluorene  in hexamethylphosphoramide in the presence of sodium hydride, according 70 to the method of T.Cuvigny and H. Normant. The product was vacuum 70 d i s t i l l e d twice.  B.p. , 102-104°. lf  L i t . b.p.  1c  160°  and then purified  by gas chromatography on a 20% silicone SF96 column temp. 240°.  The  tritiated compound was prepared by direct exchange. 9-Phenylxanthene:  9-phenylxanthenol was prepared from phenyl-  magnesium bromide and xanthenone in dry benzene.  The xanthenol was  then reduced by a formic acid/sodium formate mixture.  The product  was recrystallized from benzene-ethanol, then sublimed and recrystallized. 71 M.p. 144.5-145°.  Lit. m.p. 145°.  The tritiated compound was  prepared by Dr. J.R. Jones by direct exchange. Triphenylmethane-t:  triphenylchloromethane was prepared from  triphenylcarbinol and acetyl chloride in benzene then treated with sodium amalgam in ether to give triphenylmethanesodium. was  The sodium salt  then neutralized with HTO to give the tritiated hydrocarbon.  After  f i l t e r i n g off the NaOH thus precipitated, the solvent was evaporated. The product was then redissolved in ether and refiltered to take off  -. 50 any remaining NaOH. This evaporation-filtration step was repeated thrice, before recrystallization of the triphenylmethane-t from ethanol.  - 51 -  RESULTS AND DISCUSSION PART I : Indicator Measurements N Diphenylamine i n d i c a t o r s H  I.  From the d e r i v a t i o n o f the H  f u n c t i o n (pp. 4-6), i t i s evident  that the anchoring o f the scale i n the water region i s the most important step i n the establishment of t h i s s c a l e . 13 Stewart and O'Donnell chose 2 , 4 , 6 - t r i n i t r o a n i l i n e (pK = / a * N 12.20) as t h e i r anchor f o r the H scale i n DMSO-water-0.001 M TMAOH. 72 The pH o f an 0.01 M aqueous sodium hydroxide s o l u t i o n i s 11.939. The pH o f a 0.011 M aqueous TMAOH s o l u t i o n as measured on a Beckman pH meter model G (standardized at pH 12.45 and 10.00) i s 11.95. The N above mentioned H  13 function  does not extrapolate t o the expected  value o f 11.95 but t o 11.65. I t i s now known that 2 , 4 , 6 - t r i n i t r o a n i l i n e forms a Meisenheimer 73 complex i n methanolic DMSO containing sodium methoxide.  In t h i s  work no such complex was detected by n.m.r. i n aqueous DMSO, neverthe-  *less  the u.v. spectrum o f the i o n i z e d molecule shows some d i s t u r b i n g A c a r e f u l re-examination o f the i o n i z a t i o n o f 2 , 4 , 6 - t r i n i t r o a n i l i n e i n aqueous buffers and i n sodium hydroxide s o l u t i o n s gave a pK value of 12.30. A subsequent determination o f H values gave the following results. mole o o.5 1. 5. 10. %  D M S 0  log I H  -.25  -.16  -.08  12.05 12.14  12.22  .30  .50  12.60 12.80  . \  :/.  - 52 features.  Besides the peak at 414 my- assigned to the anion a smaller 74  band appears at 470 my. Schaal  also noticed a band at 470 my i n  concentrated ethylene diamine solutions, and treated i t as indicative of a second ionization for which he estimated a pK value of 17.55. a r  This band (470 my) disappears after 12 hours in a 24 percent DMSO-water0.3 M TMAOH solution, while the ion peak did not decrease in intensity and shifted to slightly higher wavelength 426 my. The 470 my band was not observed in sodium hydroxide solutions. These features led us to seek a more suitable anchor for the scale and our choice was 2,4,4'-trinitrodiphenylamine. Its pK was determined in aqueous glycine buffers and in sodium hydroxide solutions and was found to be 12.30 and 12.26 respectively.  The value  12.30 was then used to determine H values for aqueous DMSO solutions up to 10 mole percent of DMSO. This same value was also used with the relative pK values of a series of substituted 2,4-dinitrodiphenylamines and 4-nitrodiphenylamines to calculate their thermodynamic pK  &  values.  Table V contains a l i s t of these indicators and their pK a values determined in this work. These pK values were then used to a r  calculate the H values for DMSO-water solutions up to 50 mole percent DMSO (this was done by using equation 10). and the results are summarized in Table VI.  These H_ values are averaged These H values are in 4  excellent agreement with the values of Dolman 2,4-dinitrodiphenylamine, pK 13.84.  which are based on  Figure 3 is a plot log I (log  A /AH) versus H_ for the indicators in Table V and is a reproduction of a computer output for the least squares f i t for the lines.  - 54 TABLE V pK values of various diphenylamines as determined i n the aqueous a  DMSO system. 6  r  1,.002  .999  5. 396.,6  1..002  .999  4  341.,3  2 , 4 - D i n i t r o - 4 ' - t r i f l u o r o m e t h y l - 12. 87 diphenylamine  0,.999  .999  3  205.,8  2 , 4 - D i n i t r o - 3 ' - t r i f l u o r o m e t h y l - 13..06 diphenylamine  1,.004  .999  3  409..6  2,4-Dinitro-3'-chlorodiphenylamine  13.,17  1,.004  .999  3  463..8  2,4-Dinitrodiphenylamine  13.,85  1..001  .999  4  394..1  2,4-Dinitro-3'-methyldiphenylamine  13.,90  0..999  .999  3  168.,9  2,4-Dinitro-4'-aminodiphenylamine  14,,48  14.64*  1 .005  .999  3  452,.3  14.08*  —  -  —  PKa reported 2,4,4'-Trinitrodiphenylamine  12. 30  2,4,3'-Trinitrodiphenylamine  12. 59  4,4'-Dinitrodiphenylamine  *  12.25 12.65*  13.83*  N-  T  3,4'-Dinitrodiphenylamine  14,,62  14.66  +  1 .005  .999  3  274,.9  4-Nitro-3'-trifluoromethyldiphenylamine  14,,90  14.96  +  1 .001  .999  4  383,.6  4-Nitro-3'-chlorodiphenylamine  15,.00  1 .004  .999  3  504,.2  4-Nitrodiphenylamine  15,.67  0 .997  .999  4  413 .8  4-Nitro-3'-methyldiphenylamine  15 .60  1 .005  .999  3  422 .5  4-Nitro-4'-aminodiphenylamine  16 .40  0 .926  .997  3  138,.1  0  slope of p l o t of log I v s . H  r  coefficient of correlation  N  number of p o i n t s  T  student's t e s t  *  Stewart and J.P. O'Donnell, r e f . 13. Dolman and Stewart, r e f . 4.  t 15.67  55 TABLE VI H  values for the system DMSO-water-0.011 M  N  tetramethyl ammonium hydroxide mole % DMSO  „N -  U  N  . * - "ported  0.4  11.95  1.0  12.08  2.0  12.20  5.0  12.54  10.0  13.04  11.3  13.19.  13.34  16.0  13.73  13.96  20.3  14.29  14.49  24.1  14.72  14.88  29.7  15.34  15.42  33.6  15.75  15.88  36.0  16.02  16.12  43.0  16.74  16.77  49.1  17.35  17.38-  *  Dolman and Stewart, ref. 4.  - 56 The same set of indicators were also used to determine H functions for the systems DMSO-MeOH-0.01 M sodium methoxide and DMSO-EtOH-0.01 M NaOEt.  In alcoholic DMSO convergence of the scales  at H = pH = 11.98 need not occur since a l l the pK values refer to &  water as the standard state.  The anchor for the methanolic DMSO scale :  is the same as that for aqueous DMSO, i.e. 2,4,4'-trinitrodiphenylamine, and the anchor for ethanolic DMSO is 2,4-dinitrodiphenylamine. The pK values for the individual diphenylamines and the cl  H  values for different solutions were arrived at in exactly the  same way as for the aqueous DMSO system. Tables VII and IX l i s t the different pK values for these a indicators as arrived at in the two systems, methanolic and ethanolic DMSO. The acidity functions for these two systems are given in Table VIII and X. N It is to be noted that an H function for methanolic DMSO containing 0.025 molar sodium methoxide has already been determined by 33 Stewart, O'Donnell, Cram, and Rickborn.  If we assume that the  difference in H values of DMSO-MeOH solutions containing 0.01 M or 0.025 M sodium methoxide is constant with changing composition, N N then we can reduce the H_ (0.025) to an H (0..01) for comparison by using equation (32).  H_  = H_ (0.01) .+ log  (32)  Figure 4 is a reproduction of the least square f i t for plots of log I against H_ for the indicators in Table VII. analogous plot for the indicators in Table IX.  Figure 6 is the  Figures 5 and 7 are  plots of H- versus solvent composition for the methanolic and ethanolic DMSO systems.  - 58 TABLE VII pK  values of various diphenylamines as determined in the methanolic DMSO system. Pa K  reported  e  r  N  T  2,4,4'-Trinitrodiphenylamine  12.25  12.35*  1,.001  .999  5  261 .9  2,4,3'-Trinitrodiphenylamine  12.65  12.65*  0,.995  .999  4  372 .4  2,4-Dinitro-4'-trifluoromethyl- 12.85 diphenylamine  1,.000  .999  5  289 .6  2,4-Dinitro-3'-trifluoromethyl- 13. 03 diphenylamine  1,.000  .999  5  289 .6  2,4-Dinitro-3'-chlorodiphenylamine  13. 20  1,.000  .999  4  310 .5  2,4-Dinitrodiphenylamine  14.05  1 .000  .999  4  333 .3  2,4-Dinitro-3'-methyldiphenylamine  14.,10  0 .998  .999  5  557 .4  13.84*  2,4-Dinitro-4'-aminophenylamine 14.,95  14.64*  1 .001  .999  4  713 .0  4,4'-Dinitrodiphenylamine  14.,42  14.08*  0 .994  .999  5  125 .4  3,4'-Dinitrodiphenylamine  15..26  1 .001  .999  5  517 .4  4-Nitro-3'-trifluoromethyldiphenylamine  15.,69  1 .001  .999  5  544 .1  3-Nitro-3'-chlorodiphenylamine  15..85  1 .022  .997  4  171 .6  4-Nitrodiphenylamine  16,.59  1 .004  .999  4  493 .1  4-Nitro-3'-methyldiphenylamine  16,.50  1 .004  .999  4  557 .4  4-Nitro-4'-aminodiphenylamine  17 .35  1 .001  .999  4  299 .5  0  slope of plot of log I vs. H_  r  coefficient of correlation  N  number of points  T  student's test  *  15.90*  Stewart, O'Donnell, Cram and Rickborn, ref. 33.  59 TABLE VIII N H  values f o r the system DMSO-methanol-0.01 M sodium methoxide Mole % DMSO  „N -  U  N ' * H_ reported  0.3  11.95  11.83  1.0  12.0.2  11.92  2.0  12.10  12.01  5.0  12.28  12.23  10.6  12.68  12.57  15.0  13.08  19.2  13.38  25.0  13.80  29.7  14.17  ' 35.1  14.58  40.0  14.98  44.9  15.34  50.0  15.72  54.9  16.15  60.2  16.57  65.5  16.98  70.0  17.35  74.0  17.70  77.0  17.94  13.27  13.90  14.44  15.03  15.76  16.30  Stewart and O'Donnell, Cram and Rickborn, r e f . 33. 0.04 was substrated from each H_ value t o account f o r d i f f e r e n c e i n base concentration  - 62 -  TABLE IX values o f various amines as determined i n the ethanolic a DMSO system. Amine  P a K  6  r  N  T  2,4-Dinitrodiphenylamine  14. 05  1..002  .999  6  508..0  2,4-Dinitro-3 -methyldiphenylamine  14. 12  1 .003 •  .999  5  450.,5  2,4-Dinitro-4 -aminodiphenylamine  15. 05  0.992  .999  3  186,,2  1  1  4,4'-Dinitrodiphenylamine  • -  3,4'-Dinitrodiphenylamine  15..15  1 .002  .999  6  836,.1  4-Nitro-3'-trifluoromethyldiphenylamine  15. 63  1 .003  .999  5  622,.2  4-Nitro-3 -chlorodiphenylamine  15.,73  1 .005  .999  3  222,.8  4-Nitrodiphenylamine  16..63  1 .003  .999  5  599..6  4-Nitro-3'-methyldiphenylamine  16.,55  1 .009  .999  3  330,.1  4-Nitro-4 -aminodiphenylamine  17.,45  1 .003  .999  5  617,.5  2,4-Dinitroaniline  15.,27  .960  .999  5  52,.7  4-Chloro-2-nitroaniline  18.,05  1 .054  .999  5  39 .0  1  1  8  slope o f p l o t o f log I v s . H  r. c o e f f i c i e n t o f c o r r e l a t i o n N  number o f points  T  student's t e s t  - 63 TABLE. X values f o r the system DMSO-ethanol-0.01 M sodium ethoxide Mole % DMSO  H_  0.3  13.46  1.0  13.57  2.5  13.71  5.0  13.94  10.0  14.29  14.6  14.64  20.4  15.01  24.7  15.31  30.0  15.60  35.4  15.96  39.7  16.28  45.0  16.63  50.6  16.96  55.2  17.29  60.0  17.64  65.0  18.00  70.0  18.40  75.9  18.81  - 65 -  A.  N V a l i d i t y o f the H s c a l e i n a l c o h o l i c DMSO The v a l i d i t y o f the stepwise procedure i s based e n t i r e l y on  the r e l i a b i l i t y o f Hammett's p o s t u l a t e . The p o s t u l a t e states that the a c t i v i t y c o e f f i c i e n t term i n equation 9 can be equated t o zero.  •" „ P HA - P HB v  =  l Q  i [HA] g [A=t " L  i l  G  g  J  t  H B  [B=] L  +  ]  , l  0  f  HA B"  : .  f  g  C  9  )  HB A  J  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 o f the i n d i c a t o r and i n d i c a t o r anion f o r two overlapping acid i n d i c a t o r s being equal t o u n i t y i n any given solution.  • •'" f  HA f A  fB _ ' f HB  Applying t h i s c o n d i t i o n equation (9) reduces t o (10)  P HA - P HB " l K  K  0 g  #r  "  l 0 g  Tn  •  ( 1 0 )  One obvious experimental t e s t of the v a l i d i t y o f equation (10) i s that the term log -[^ry - l o g changed.  remains constant as the medium i s  This constancy can be best examined by the p a r a l l e l i s m i n  the. p l o t s o f l o g j i ^ j  (log I) versus solvent composition f o r the  different indicators studied. .  . In t h i s work, f i g u r e s 8, 9, and 10 are i l l u s t r a t i o n s o f t h i s  t e s t , and i t i s evident that the p l o t s o f l o g I vs mole percent DMSO  cv  Figure 9.  P l o t s o f l o g I (A/AH) versus mole percent DMSO f o r the system: DMSO-methanol• 0.01 M sodium methoxide.  CD o  t  0.0  10.0  _  j  20.0  I  I  30.0  MOLE  I  40.0  PERCENT  DMSO  50.0  60.0  70.0  80.0  CM  ,  0.0  • ,  10.0  :  ,  20.0  r  30.0  MOLE  1  40.0  PERCENT  DMSO  1  50.0  1  60.0  n  70.0  [—  80.0  - 69 remain parallel for a l l the indicators. The reproducibility of any one pK  determination using different solutions prepared over a period cL  of several months was better than  0.05 pK  unit, which exceeds the a  accuracy of the H_ values (cf. experimental). in the H  There is a good agreement  values calculated using different indicators. The slopes of  the lines of log I versus H  given in the pK  tables are calculated  by a least square method and are exceedingly close to unity. coefficients are also given and are close to unity.  Correlation  Student's test  T evaluates the significance of the correlation, as a high correlation coefficient may easily arise by chance i f the number of points plotted is small.  These results would thus indicate that an H  function can  be defined in these systems. It has been a prevalent opinion that the apparent relative strength (log 1 ^  - log I  B  = pK^  - pK^g)  of a series of Hammett 46  indicators must remain uniform through drastic changes in solvent. This requirement for the validity of an H function will  now  be examined and i t s applicability considered in strongly acidic media, since there is a larger amount of data published on pKg^ than on +  pK . &  The basis of Hammett's postulate is that i f the indicators f f A BH+ A and B are of similar structure one can expect -= . -~ = 1. AH+ B Thirty years of work on acidity functions resulted in more stringent limitations being placed on structural variations.  First  considered  was the molecular size, then the aromatic or aliphatic character then also the functional group - amino, amide, etc.  Amines themselves  existence of an H function sulfuric secondary acid systems been asserted, have been differentiated intoinprimary, and has tertiary. The  75  - 70 and primary a n i l i n e s were found to be r e l i a b l e Hammett bases.  78  Even  i n such an " i d e a l " system, with r e l i a b l e i n d i c a t o r s many discrepancies arise. The e a r l i e r c o l o r i m e t r i c work i s considerably less r e l i a b l e than more recent work i n which spectrophotometry  has been used.  76 Bascombe and B e l l  redetermined pK ,. n  y  values f o r a number of Hammett  BH+  i n d i c a t o r s and found f o r example t h a t , 4-methyl-2,6-dinitroaniline i s 75 0.48 pK u n i t away from the "best value" given by Paul and Long t h e i r review a r t i c l e .  in  Table XI l i s t s pKg^ values f o r primary +  a n i l i n e s , published between 1957 and 1964, a l l determined  spectrophoto-  *  m e t r i c a l l y , and a l l i n s u l f u r i c a c i d media. Although a l l the authors s t a r t with the same value f o r t h e i r anchor, 4 - c h l o r o - 2 - n i t r o a n i l i n e , or 2 - c h l o r o - 6 - n i t r o a n i l i n e , pK , DL  values  bn+ 77  f o r the other i n d i c a t o r s vary widely. Hogfeldt and B i g e l e i s e n measured t h e i r plC,, values i n H»0-H„S0. and i n D»0-D„S0.. The BH+ 2 2 4 2 2 4 r  average P^g^  +  d i f f e r e n c e (ApK) between the deuterio acid i n heavy water  s o l u t i o n , and the p r o t i o acid i n water s o l u t i o n i s 0.56 pK u n i t but some i n d i c a t o r s show a much smaller ApK value methylaniline ApK =0.40.  e.g. 2,6-dinitro-4-  From t a b l e XI one can see  that there i s a  small d i f f e r e n c e between pKg^ values i n ^SO^-^O and i n D20-D2SO^, +  while there i s a marked d i f f e r e n c e i n pKg^ between aqueous s u l f u r i c +  and ^ S O ^ - s u l f o l a n e . This i s probably due to the f a c t that there i s * Paul and Long best values are only given as a reference, since 78  Jorgensen and Harter  re-evaluated the pKg^ values o f 2-bromo-4,6+  d i n i t r o a n i l i n e and 2 , 4 , 6 - t r i n i t r o a n i l i n e and found them d i f f e r e n t from the best value by 0.23 and 0.38 pK u n i t r e s p e c t i v e l y .  - 71 TABLE XI pK + o f weak bases, i n s u l f u r i c a c i d media, from the l i t e r a t u r e DU BH  Anilines  pK + DIJ  water a 2-nitro-  D0  b  -0.29  c  2  Sulfolane  d  e  +0.30  -0.29  -2.42  -2 .43  2-chloro-6-nitro4-chloro-2-nitro-  -1.03  2,4-dichloro-6-nitro-  -3.32  2,6-dinitro-4-methyl-  -4.44  2,4-dinitro-  -4.53  2,6-dinitro-  -5.41  2-bromo-4,6-dinitro-  -6.71  2,4,6-trinitro-  -9.41 -9.03  -1.02  -0.46 -2.73  -3.37  -3.14  -4.36  -3.74  -4.04  -3.96  -4.03  -4.50  -5 .54  g  -6.64  f  -6 .68  -6.55  -6.06  -10 .10  -8.82  -8.21  g  a  "best value" from Paul and Long, r e f . 75.  b  Bascombe and B e l l , r e f . 76.  c  Jorgensen and Harter, r e f . 78.  d  Hogfeldt and B i g e l e i s e n , e f . 77 these values are pK values of the deuterio a c i d i n heavy water. The average d i f f e r e n c e ApK between r  P H S0 K  2  e  a n d 4  P D S0 K  2  1 5 4  °- * 56  Arnett and Douty, r e f . 79a.  f  A l d e r , Chalkley and Whiting, r e f . 80.  g  Value determined by Jorgensen and Harter, r e f . 78 based on the H values of Paul and Long.  Q  - 72 only a s l i g h t d i f f e r e n c e between water and heavy water while there i s an enormous d i f f e r e n c e between water and s u l f o l a n e as solvents. The v a r i a t i o n i n pKg^ value does not go on increasing with +  decreasing  b a s i c i t y o f the i n d i c a t o r s , and therefore i s a true d i f f e r e n c e and not due to a cumulative error i n p K  R H +  determination.  „ " BH+  Indicator  For example:  d i f f e r e n c e i n pK3^ values between authors +  2,6-dinitroaniline  ^5  1.04  2-bromo-4,6-dinitroaniline  ^6  0.62  ^8-10  1.90  2,4,6-trinitroaniline  Although most authors adopt a complaisant a t t i t u d e towards the p r i n c i p l e of pK values o f Hammett bases, the data i n Table XI do not warrant such a view.  A not p a r t i c u l a r l y d r a s t i c change i n solvent  system from aqueous t o s u l f o l a n i c can give r i s e to widely d i f f e r e n t pKg^ values. +  Unfortunately  few authors have published along with  t h e i r r e s u l t s spectroscopic data o f t h e i r i n d i c a t o r s . 19,69 Only two groups of workers " of a n i l i n e s by a non-photometric method.  have measured a c i d i t i e s 19 R i t c h i e and Uschold  measured p o t e n t i o m e t r i c a l l y the pK o f four a n i l i n e type i n d i c a t o r s i n DMSO and found that the r e l a t i v e a c i d i t i e s d i f f e r only s l i g h t l y from those measured spectrophotometrically i n aqueous DMSO by Dolman 4 69 and Stewart . B i r c h a l l and J o l l y measured the a c i d i t i e s of a s e r i e s o f s u b s t i t u t e d a n i l i n e s r e l a t i v e t o 2 , 5 - d i c h l o r o a n i l i n e , by o n.m.r. i n l i q u i d ammonia at 31. For the f i v e a n i l i n e s which have also 4 been determined by Dolman and Stewart none shows s i m i l a r r e l a t i v e  - 73 acidities, in contrast with the above mentioned observation by Ritchie and Uschold.  Therefore the relative acidities of anilines can vary 4,13  with change in solvent, contrary to accepted premises. . ' One must therefore study systematically Haramet type indicators to find a rationale for the fact that sometimes the acidity or the basicity of these indicators varies with solvent change and then sometimes does not. The pK of an acid whose ionization occurs in the nona  aqueous region i s related to the standard state in water through a series of indicators with which i t overlaps and with which i t bears structural similarity.  Ideally one would want to see a study of the  relative strength of acids (HX,  HX^...) with respect to a 81  fixed acid (HY) in different solvent systems.  Grunwald and Price  have noted that the relative strength of picric acid relative to acetic acid increases by almost two orders of magnitude in the solvent series HOH, CH^OH, 02^011, while that of trichloroacetic acid remains nearly constant.  Furthermore, the relative strength of picric acid  with respect to phenol increases by the same amount while picric acid strength with respect to 2,4-dinitrophenol is constant.  Therefore the  increase in relative strength is not due to the chemical nature of the reference acid or phenol since, schematically we have: change in relative „ pK values compound a  . increase picric acid picric acid  . constancy trichloroacetic picric acid __  reference  acetic acid  acetic acid  5  1  phenol  2,4-dinitrophenol  - 74 81 Grunwald and Price  postulated that this is due to disper-  sion effects which occur between the delocalized virtual electronic oscillators of the solute and the surrounding medium. Their argument i s that i f we compare a coloured indicator with a colourless reference compound (picric acid/acetic acid and picric acid/phenol) we can expect an increase in relative strength in the series HOH, CH^OH, C^U^OH; while i f we compare a colourless acid with a colourless reference (trichloroacetic acid/acetic acid) or a coloured acid with a coloured reference (picric acid/2,4-dinitrophenol) we can expect constancy in relative strength. 81  These authors,  HOPic  by studying the system  + BH OAc" +  ^  K 0 H  >  BH OPic" +  + HOAc  (33)  estimated the magnitude of these dispersion forces. The equilibrium constant K.,,. = f ^ ? ^ l>m.+^i -i increases by almost an order of BH+ [HOPic][BH OAc ] ' + + + magnitude in glacial acetic acid by varying BH from NH^ to (CH )gNH , C  +  while the corresponding equilibrium constant for trichloroacetic acid i s insensitive to the change in BH . +  Calculation using a model  in which BH is hydrogen bonded to the anionic oxygen atom in the ion +  pair gives a dispersion energy of -1.6 kcal/mole.  They also suggested  that the difference in relative base strength of aliphatic amines obtained by measurements in water or with colour indicators in solvents of low dielectric constant could be accounted for by the existence of strong dispersion effects.  - 75 The importance of d i s p e r s i o n e f f e c t s was also noted by 19 other workers.  R i t c h i e and Uschold  i n p o i n t i n g out the f a i l u r e of  C the H  scale suggested that the i o n i z a t i o n behaviour of hydrocarbon  acids which have h i g h l y coloured conjugate bases i s not the same as 82 that of acids whose conjugate bases are not d e l o c a l i z e d . J . J u i l l a r d studied the d i s s o c i a t i o n of a few c a r b o x y l i c acids i n methanol and and  water  found a d e f i n i t e , though imprecise, c o r r e l a t i o n between the  molecular p o l a r i z a b i l i t y of the acids and change i n pK with d i f f e r e n t solvent. A.J. Parker e t . a l . ^ '  8 3  i  n  t h e i r extensive studies on  s o l v a t i o n of ions i n p r o t i c and a p r o t i c solvents have also pointed out the necessity of taking i n t o account solvent s t r u c t u r e and mutual p o l a r i z a b i l i t y i n t e r a c t i o n s (dispersion forces) i f we want to explain the s i g n i f i c a n t changes i n the chemistry of anions on t r a n s f e r from water to methanol and d i p o l a r a p r o t i c solvents. I f we rearrange the t a b l e of pK of acids from reference 83 to take i n t o account a 1  colour, we f i n d that although each a c i d has a d i f f e r e n t pK  i n every a  solvent, the r e l a t i v e strength of two acids ApK of s i m i l a r colour remains constant through change i n solvent.  This i s not true,however,  f o r any two acids i n two d i f f e r e n t colour d i v i s i o n s . Acid  pK(H 0)  pK(MeOH)  2  ApK dichloroacetic chloroacetic benzoic acetic  1.29 2.86 4.20 4.76  2,4-dinitrophenol 4-nitrophenol  4.10 7.15  1.57  pK(DMF)  ApK  ApK  1.34 0.56  6.4 7.7 9.1 9.6  1.4 0.5  7.2 9.0 10.2 11.1  3.05  7.9 11.2  3.3  6.0 10.9  1.30  pKDMSO ApK  1.8 1.2 0.9  11.0 11.4  0.4  4.9  5.2 9.9  4.7  - 76 They also noted that for a l l the acids listed (17 of them) acidities in water and methanol show some correlation, as well as in DMF and DMSO, but there is no correlation between the acidities in a protic and an aprotic solvent. And so there is enough evidence of the nonuniformity of the relative strength for a series of related acids or bases, through changes in solvent, except i f their similarity extends to their spectral characteristics. By extending Grunwald and Price's argument to i t s logical conclusion, we can put forward the postulate that the relative strengths of indicators will remain unaltered through changes in solvent environment only i f their spectral characteristics in both ionized and unionized forms are similar. Indicators which will comply with this limitation will be referred to as "similar colour indicators." Table XII l i s t s the pK r  measured in this work for the a  substituted 2,4-dinitro, and 4-dinitrodiphenylamines  referred to here-  after as 2,4-dinitro series and 4-nitro series. Their spectral characteristics are listed in Tables XIII and XIV.  One can see that  the visible spectra of the 2,4-dinitro compounds are a l l quite similar with the exception of their 4'-nitro- and 4'-amino-derivatives.  The  substituted 4-nitro compounds also show a similarity in their absorbances, With again the exception of their 4'-nitro- and 4'-aminoderivatives . The main difference is between the ionized form of these two classes of indicators, the 4-nitro compounds absorb at a longer wavelength and their molar absorptivities their 2,4-dinitro analogs.  a r e  twice as much as those of  From Table XI one can also see that although  - 77 -  TABLE XII Summary of the pK  a  values of diphenylamines determined in this work  H„0  MeOH  EtOH  2,4,4'-Trinitrodiphenylamine  12.,30  12 .25  2,4,3'-Trinitrodiphenylamine  12,,59  12 .65  2,4-Dinitro-4'-trifluoromethyldiphenylamine  12,,87  12 .85  2,4-Dinitro-3'-trifluoromethyldiphenylamine  13.,06  13 .03  2,4-Dinitro-3'-chlorodiphenylamine  13..17  13 .20  2,4-Dinitrodiphenylamine  13..85  14 .05  14 .05  2,4-Dinitro-3'-methyldiphenylamine  13..90  14 .10  14 .12  2,4-Dinitro-4'-aminodiphenylamine  14,.48  14 .95  15 .05  4,4'-Dinitrodiphenylamine  14,,08(?)  14 .42 .  3,4'-Dinitrodiphenylamine  14,.62  15 .26  15 .15  4-Nitro-3'-trifluoromethyldiphenylamine  14,.90  15 .69  15 .63  4-Nitro-3'-chlorodiphenylamine  15,.00  15 .85  15 .73  4-Nitrodiphenylamine  15,.67  16 .59  16 .63  4-Nitro-3'-methyldiphenylamine  15,.60  " 16 .50  16 .55  4-Nitro-4'-aminodiphenylamine  16,.40  17 .35  17 .45  -•  - 78 TABLE X I I I Absorption maxima and molar a b s o r p t i v i t i e s o f the i n d i c a t o r s i n absolute ethanol  Observed Values X (mp) e max J  Reported Values X (my) e max^  Ref.  V J  2,4,4'-Trinitrodiphenylamine  390  18300  385  21900  2,4,3'-Trinitrodiphenylamine  354  20000  360  17850°  13  2,4-Dinitro-4'-trifluoromethyl . diphenylamine  354  17900  2,4-Dinitro-3'-trifluoromethyl diphenylamine  354  17500  2,4-Dinitro-3'-chlorodiphenylamine  356  17900  2,4-Dinitrodiphenylamine  361  16900  352  17700  4b  2,4-Dinitro-3'-methyldiphenylamine  365  19200  2,4-Dinitro-4 *-aminodiphenylamine  378  14400  375  18300°  13  4,4'-Dinitrodiphenylamine  418  33000  403  34100  a  4b  3,4'-Dinitrodiphenylamine  390  22200  375  23200  a  4b  4-Nitro-3'-trifluoromethyldiphenylamine  394  21800  381  19200  a  4b  4-Nitro-3'-chlorodiphenylamine  396  25500  385  22700  a  4b  4-Nitrodiphenylamine  402  22000  400  19550  4-Nitro-3'-methyldiphenylamine  410  24000  394  22300  4-Nitro-4'-aminodiphenylamine  420  19100  4-Chloro-2-nitroaniline  424  5300  417  3450®  2,4-Dinitroaniline  346 384  14400 6600  336  14900  a  i n 95.6% ethanol aqueous s u l f o l a n e  i n p y r i d i n e or aqueous p y r i d i n e  b  e  i n methanol  b  a  13  "4b a  4b  13 e  13  ° i n s u l f o l a n e or  - 79 TABLE XIV Absorption maxima and molar a b s o r p t i v i t i e s of i n d i c a t o r anions i n DMSO-ethanol Observed Values e Xmax (my) '  Ref.  b  13  c  13  2,4,4'-Trinitrodiphenylamine  530  29900  Reported Values X (my) e max • 27400 520  2,4,3'-Trinitrodiphenylamine  432  23600  450  18700  2,4-Dinitro-4'-trifluoromethyldiphenylamine  435 474  20400 19500  2,4-Dinitro-3'-trifluoromethyldiphenylamine  435 474  20000 18900  2,4-Dinitro-3'-chlorodiphenylamine  432 475  20400 18100  2,4-Dinitrodiphenylamine  432 485  19700 16500  434  19000  2,4-Dinitro-3'-methyldiphenylamine  434 480  23000 19700  2,4-Dinitro-4'-aminodiphenylamine  496  17400  495  18300°  13  4,4'-Dinitrodiphenylamine  590  51000  580  37000  13  3,4'-Dinitrodiphenylamine  324 504  15000 36100  4-Nitro-3'-trifluoromethyldiphenylamine  506  36500  4-Nitro-3 -chlorodiphenylamine  504  41800  4-Nitrodiphenylamine  505  34800  508  34600  13  4-Nitro-3 *-methyldiphenylamine  510  36200  4-Nitro-4'-aminodiphenylamine  518  29800  4-Chloro-2-nitroaniline  496 524  8300 8200  495 520  8440 8440  4  2,4-Dinitroaniline  388 392 502  17300 15400 12200  388 535  21100 15300  v  1  a i n DMSO-water  b i n pyridine  e i n sulfolane  a  b  a  b  4  13  - 80 the pK o f the 2,4-dinitro compounds remain a  the same i n the three *  systems, the 4 - n i t r o compounds are some 0.8 u n i t s higher i n DMSO-MeOH and DMSO-EtOH than i n DMSO-H 0. 2  The importance of the anchor i n the establishment  o f an H  f u n c t i o n has been p r e v i o u s l y emphasized (pp.51-£2). 2 , 4 , 4 ' - t r i n i t r o diphenylamine has been used as an anchor f o r the DMSO-water and DMSOmethanol systems, while 2,4-dinitrodiphenylamine DMSO-ethanol system.  was used f o r the  Therefore i f our assumption i s v a l i d we should  f i n d the r e l a t i v e strength o f a l l the s u b s t i t u t e d 2,4-dinitrodiphenylamines constant.  Also we should f i n d that the r e l a t i v e strength o f  the s u b s t i t u t e d 4-nitrodiphenylamines constant.  Only the r e l a t i v e  strength o f the 4-nitro s e r i e s with respect to the 2,4-dinitro s e r i e s should vary.  Also i f a l i n e a r free energy r e l a t i o n s h i p i s constructed  between the pK values versus Hammett substituent constants the p value f o r the 4-nitro s e r i e s should remain o f the same order of magnitude through change i n solvent system. seen from Figure 12 and Table XV. v a l i d i t y o f the H  Indeed t h i s i s the case as can be As c i r c u m s t a n c i a l evidence f o r the  scales defined, and the " s i m i l a r colour i n d i c a t o r "  assumption, the i o n i z a t i o n o f 2 , 4 - d i n i t r o a n i l i n e and 4-chloro-2-nitro*  N  An H f u n c t i o n i n DMSO-MeOH-0.025 M NaOMe has been determined by 33 Stewart, O'Donnell, Cram and Rickborn, and these authors found that the p K Values of a l l t h e i r i n d i c a t o r s agreed with the determined &  values i n aqueous DMSO.  But aside from the f a c t that t h e i r anchor  2 , 4 , 6 - t r i n i t r o a n i l i n e , has been shown subsequently to form Meisenheimer complex i n DMSO-MeOH-NaOMe, a p l o t o f log I versus mole percent DMSO shows several cases o f nonparallelism between the i n d i c a t o r s , Figure 11,  N  These f a c t s cast some doubt as to the v a l i d i t y o f the H 33 defined by Stewart et a l . , and t h e i r l i s t e d pK values.  function  I  I  0.0  :  !  12.5  I  25.0  H  37.5  MOLE  I  50.0  PERCENT  DMSO  !  62.5  I  75.0  :  I  87.5  1  100.0  - 82 -  aniline was studied in the system DMSO-EtOH-0.01 M NaOEt.  The pK  &  assigned are: pK  pK 3.  reported in  3.  DMS0-H 0, ref. 4. 2  3,4 -dinitrodiphenylamine  15.10  14.66  2,4-dinitroaniline  15.27  15.00  4-chloro-2-nitroaniline  18.05  17.08  1  The pK of 3,4'-dinitrodiphenylamine is also included as i t has a pK 3.  3.  similar to the one of 2,4-dinitroaniline in DMSO-EtOH, but i t s pK 3.  in DMSO-water is 0.5 unit lower than in ethanolic DMSO. One can see that the spectral characteristics of 2,4-dinitroaniline are somewhat similar to those of the 2,4-dinitrodiphenylamine series, while spectral characteristics of 4-chloro-2-nitroaniline are quite different. According to the similar colour assumption the pK 3.  of the former should be comparable in both media (0.27 pK  units  apart is within the experimental accuracy) while the latter should be quite different (1.00 pK units away). a. B.  Correlation of Structure with Acidity 13 Preliminary results  on the acidity of substituted diphenyl-  amines indicated the dominance of the nitro group, whose effect overwhelmed that of a l l other substituenfs.  Enough data have now  been gathered to make i t possible for us to compare the linear free 4 energy relationships of the A) substituted diphenylamines  (D. Dolman  results), B) 4-nitro substituted DPA, C) 2,4-dinitro substituted DPA,  - 83 D) 2 , 4 , 6 - t r i n i t r o s u b s t i t u t e d DPA (A. Buckley, unpublished r e s u l t s ) . Figure 12 shows a p l o t o f pK versus o°and i t i s obvious that there i s a a good c o r r e l a t i o n .  Table XV l i s t s the p v a l u e s , c o r r e l a t i o n c o e f f i c i e n t s and *  Students t e s t ' s T computed f o r the p l o t i n Figure 12. The substituent constant a°usually  correlates r e a c t i v i t i e s  f o r r e a c t i o n i n which there i s no conjugation between the substituents and the r e a c t i o n center.  They were derived by interposing a methylene  group between the benzene r i n g and the r e a c t i o n center, so that the resonance e f f e c t would be e s s e n t i a l l y constant f o r such a r e a c t i o n series, and  o  i s used f o r r e a c t i o n i n which there i s d i r e c t conjugation,  a f o r systems that possess the l i m i t e d amount of conjugation  present i n benzoic acids. For the "normal" substituents m-methyl, m-chloro, m - t r i f l u o r o , p - t r i f l u o r o and m-nitro the a°values are very s i m i l a r t o the a value so one cannot r e a l l y draw any conclusions from the c o r r e l a t i o n with o° except that there i s no d i r e c t resonance i n t e r a c t i o n between these groups and the amide i o n . * In l i n e "A" the 4'-nitro substituent has been omitted from the c a l c u l a t i o n since i t requires an exalted a value.  - 85 -  TABLE XV Linear free energy c o r r e l a t i o n o f diphenylamines a c i d i t i e s computed by a least squares method  Z Ar  System  2,4,6-trinitropheny1  aqueous b u f f e r s  -1 .88  0..06  8  .997  32 .1  DMSO-.H0  -1 .79 . 0. .03  8  .999  60 .0  2,4-dinitrophenyl  2  DMSO-MeOH  phenyl  r  T  0..08  8  .996  27 .4  DMSO-H 0  -1 .75  0..12  7  .987  13 .6  DMSO-MeOH  -2 • 17  0,.20  7  .979  10 .8  DMSO-EtOH  -2 .12  0'.12  7  .993  17 .3  DMSO-H 0  -4 .34  0..14  7  .997  31 .0  2  N  number o f i n d i c a t o r s used.  r  c o e f f i c i e n t of c o r r e l a t i o n .  T Student's t e s t .  N  . -2.17  2  4-nitrophenyl  p+ Ap  f  - 86 However the pK  &  values for the p-amino substituent do not  correlate with a but with o°.  This is because there is very l i t t l e  resonance between the amino substituent and the amide ion, and correlation with a° (no resonance) is expected.  For the p-nitro  resonance interaction of the following type is of prime importance.  The substituent constant value for the 4-nitro group  is 0.78 in the  ionization of benzoic acids (a); 0.82 in ionization of phenylacetic acids (o°);  1.27 in the ionization of phenols and anilinium ions (a ). 84  Recently  a value of 1.70 was ascribed for a-naphthol dissociation and 4 1.81 for a-naphthoxide methylation. D.Dolman assigned a a value of 1.65 for the 4-nitro substituent in the ionization of diphenylamine, 1  and D. Kroeger  8  -  assigned a a of 1.73 to account for the effect of the  p-nitro group in the a-ring on the Lewis acidity of a-cyanostilbenes. It is surprising that this same compound correlates well with the a° value in line b when i t is looked upon as unsubstituted 4-nitrodiphenylamine instead of a diphenylamine substituted with a p-nitro group. Since the acidities of diphenylamines  correlates with a°, we could  conclude that there is very l i t t l e conjugation between the substituent and the central atom. This brings us to the dichotomy in the magnitude of P. between diphenylamines  and nitro-diphenylamines.  The magnitude of the p-value is a measure of the susceptibility of diphenylamine ionization on the polar effect of the substituent Z.  - 87 Nitro-substituted diphenylamines have a p-value around 2, with a minimal increase from the 2,4,6-trinitro series to the 2,4-dinitro series and the 4-nitro series; while diphenylamine i t s e l f shows a higher response to substituent changes and has a -value of 4.34. p  These p-values should  be compared with p's of 1.00 for benzoic acids, 2.23 for phenols and 2.89 for anilinium ions in aqueous systems at 25°, and 5.3 for anilines 69 in liquid ammonia.  Thus the p-value for the ionization of diphenyl-  amine is similar to the one for anilines and is twice as large as the P-value for the ionization of phenols; the latter being similar to the P for the ionization of nitrodiphenylamines. This dichotomy probably results from the greater enjoyment of charge derealization by the diphenylamines and aniline anions than by the anions of nitro-substituted diphenylamines and phenols. Thus the dominating feature of the p-nitro substituent can be put in i t s proper perspective.  For nitro-diphenylamines a low  degree of conjugation between the amino centre and the substituent is noted, since the negative charge on the amide ion is already delocalized into the nitrated ring, which is obvious from the need for an exalted a"value for the p-nitro substituent in the diphenylamine correlation.  For B, C, D, the orientation of the ring with the  Z-substituent i s such that much of i t s contribution is sacrificed so  - 88 -  that the p - n i t r o group can heighten i t s conjugation.  While f o r A  maximum overlap occurs between the nitrogen o r b i t a l s and the r i n g with the s u b s t i t u e n t Z, thus the greater p value.  Remembering, that  a c i d i t i e s of s u b s t i t u t e d diphenylamine c o r r e l a t e with cr°, there should be only a minimal and constant amount of resonance energy a v a i l a b l e f o r the r i n g and i t s s u b s t i t u e n t s ,  50 that i n the case o f the n i t r o  diphenylamines the " p i e " has t o be d i v i d e d between both r i n g s while f o r the u n - n i t r a t e d diphenylamines a l l of i t goes to the r i n g with the s u b s t i t u e n t Z. Dolman and Stewart  4  ' have explained deviations from a d d i t i v i t y  of the e f f e c t o f n i t r o groups i n compounds with n i t r o groups i n both r i n g s to the i n a b i l i t y o f both r i n g s t o a t t a i n simultaneously maximum overlap with the nitrogen atom, which i s a s i m i l a r type o f argument.  - 89 II.  Phenol i n d i c a t o r s Many of the phenol i n d i c a t o r s used i n e s t a b l i s h i n g the  scales  i n DMSO-methanol-0.01 M sodium methoxide and DMSO-ethanol-0.01 M sodium 31 ethoxide are the same as those used by Rochester  to construct h i s  s c a l e i n methanolic sodium methoxide. The methanolic dimethylsulfoxide scale was anchored with _2-isopropyl phenol (pK =10.5) and then checked with phenol i t s e l f (pK =9.98) a a which i s h a l f ionized i n a 0.01 M sodium methoxide s o l u t i o n . The ethanolic dimethylsulfoxide scale was anchored with 2,6-diisopropyl phenol (pK =11.0). Figures 13 and 14 show computer output p l o t s of the measured values of l o g I versus  H  f o r the phenol i n d i c a t o r s i n methanolic  and ethanolic DMSO s o l u t i o n s . The p l o t s are p a r a l l e l  a n  d the slopes  are very close to u n i t y , as can be seen i n Table XVII. The pK values assigned to these phenols are also l i s t e d i n Table XVII. The thermodynamic a c i d i t i e s of the anchors were determined i n aqueous b u f f e r s and therefore the p K values obtained are r e l a t i v e &  31 to water as the standard s t a t e . The p K values determined by Rochester 32 were deduced by the method o f Ridd and O ' F e r r a l l and are r e l a t i v e 29 &  to methanol as the standard s t a t e . Cohen and Jones  values were  determined spectrophotometrically i n aqueous s o l u t i o n s and agree with the values determined i n t h i s work except f o r 2 , 4 - d i - t - b u t y l - and 2-t-butyl-phenol. The H° a c i d i t y functions f o r methanolic and ethanolic DMSO are given i n Table XVI,and are p l o t t e d i n Figure 15. A summary o f  Figure 14.  10.0  10.5  Plots of log I (A/AH) versus H for the phenols used to establish the if* DMSO-ethanol-0.01 M sodium ethoxide.  11.0  11.5  12.0  H MINUS  12.5  13.0  13.5  scale i n  14.0  - 92 TABLE XVI values f o r the systems DMSO-methanol 0.01 M sodium methoxide and DMSO-ethanol 0.01 sodium ethoxide  DMSO 0.0  H_(DMSO-MeOH) 9.92  1.0  H_(DMSO-EtOH) 10.62 10.77  5.0  10.17  11.02  10.0  10.35  11.21  15.0  10.53  11.41  20.0  10.73  11.56  25.0  10.94  11.74  30.0  11.17  11.91  35.0  11.36  12.10  40.0  11.55  12.26  45.0  11.75  12.46  50.0  11.98  12.62  55.0  12.20  12.75  60.0  12.42  12.98  65.0  12.63  13.11  70.0  12.84  13.31  .94 TABLE XVII pK  values o f phenols determined i n aqueous s o l u t i o n s and i n methanolic and ethanolic DMSO Phenols  unsubstituted  pK m water  pK„ i n (9) DMSO-MeOH  pK„ i n (9) DMSO-EtOH  9.98  PKa reported 9.97tl4.10t  2-isopropyl  10.51  10.49(1.016)  2,6-di-isopropyl  11.00  10.98(1.000)  11.00(  2-jt-butyl  11.70  11.67(1.004)  11.67(1.008)  11.33*16.25t  12.10(  12.12(1.002)  11.56*16.53t  2,4-di-t-butyl 2,6-di-t-butyl  .999)  .999)  ?  11.70*17.08t  2,6-di-t_-butyl-4-methyl  12.28(  2,4,6-tri-t-butyl  12.28(1.081)  *  Cohen and Jones, r e f . 29  t  Rochester, r e f . 31  0  Slope of p l o t of log I vs. H.  .982)  12.23*17.50t 12.19*17.40t  - ?5 TABLE XVIII Absorption maxima and molar a b s o r p t i v i t i e s o f phenolate anions  Phenols  unsubstituted  in DMSO s o l u t i o n s X e x 10-4 max  in 85% DMSO-EtOH X E X IO" max  ^ i n MeOH-MaOMe X e x IO max m  312  290  290  .28  4  2-isopropyl  290  .42  2,6-di-isopropyl  300  .46  - 4  290  2-t-butyl  318  .39  300  291  .36  2,4-di-t>butyl  320  .37  306  296  .34  2,6-di-t-butyl  318  -.50  306  298  .52  2,6-di-t-butyl-4-methyl  325  .53  317  307  .49  2,4,6-tri-t-butyl  325  .50  312  302  .44  *  Rochester, r e f . 31.  - 96 the absorption maxima and molar a b s o r p t i v i t i e s f o r the phenol molecules and t h e i r conjugate base i s given i n Table X V I I I . 2,6-di-t^butylphenol was not used i n determining the  s c a l e since the p l o t of log I versus  *  solvent composition  was not p a r a l l e l to s i m i l a r p l o t s f o r 2 - t - b u t y l -  and 2,4-di-t-butyl-phenols. In p o i n t o f f a c t i t i s more ionized i n a 20 mole percent DMSO-ethanol s o l u t i o n than 2,4-di-t-butylphenol and l e s s i o n i z e d i n a 55 mole percent s o l u t i o n . The other two hindered phenols 2,4-di-t-butyl-6-methylphenol and 2,4,6-tri-t-butylphenol had slopes of 0.98 and 1.08 r e s p e c t i v e l y f o r p l o t s o f l o g I versus These two i n d i c a t o r s determined only two percent DMSO-ethanol. Since the other  H.  values i n 65 and 70 mole values determined by these  i n d i c a t o r s d i d not d i f f e r from those determined by p a r t i a l l y hindered phenols, they (65 and 70 percent values) were also included. Figures 16 and 17 show c l e a r l y that the  s c a l e s , based  on the i o n i z a t i o n of phenols, d i f f e r s markedly from those based on the i o n i z a t i o n of nitrogen and carbon a c i d s , a given s o l u t i o n being always more b a s i c towards the l a t t e r than the former.This r e s u l t i s not unexpected s i n c e the negative charge o f the anion i s mainly centered on the phenolate oxygen. We can therefore expect the phenolate anion t o r e a c t to solvents changes much l i k e a small i o n which i s s t a b i l i z e d by hydrogen bonds i . e . i t w i l l be desolyated as the concentration o f DMSO i n the medium i s increased, causing an i n c r e a s e i n i t s a c t i v i t y . T h i s w i l l s h i f t the e q u i l i b r i u m shown i n *  2,6-di-t-butylphenol i n DMSO-ethanol mole %DMSO 10 20 30 40 ' 11.21 11.57 11.91 12.26  45 55 12.47 12.75  log  +0.39  ri  I  -0.63  -0.22  +0.07  +0.28  +0.53  - 99 equation  (34) to the r i g h t ,  t n u s  p a r t i a l l y counterbalancing  the increase  i n a c t i v i t y o f the alkoxide i o n .  AH  +  R0~  t  A"  +  ROH  (34)  Conversely the amide i o n and carbanions enjoy a large degree of charge d e r e a l i z a t i o n and t h e i r s o l v a t i o n requirements are much l e s s s t r i n g e n t , thus s h i f t i n g the above e q u i l i b r i u m to the r i g h t . Presumably alcohols with no formal charge d e r e a l i z a t i o n p o s s i b l e i n t h e i r anions would generate a shallower H  scale i n which any increased  b a s i c i t y would be due merely to a concentration e f f e c t on the equlibrium shown i n equation (34). C One can a l s o note from f i g u r e 17 that the H s c a l e , with N a l l i t s d e f e c t s , p a r a l l e l s the H scale i n ethanolic DMSO. This f a c t N gives some v a l i d i t y to the use of the H  s c a l e i n the estimation of  the a c i d i t i e s o f weak carbon a c i d s , and f o r the c o r r e l a t i o n with rates of r e a c t i o n s where the r a t e determining from a carbon atom.  step i s an i o n i z a t i o n process  - 100 -  PART I I : Base catalyzed d e t r i t i a t i o n of hydrocarbons  Rate constants f o r the base catalyzed d e t r i t i a t i o n of 9-phenylfluorene,  2,3-benzofluorene, fluorene, 9-ethylfluorene,  9-phenylxanthene, and triphenylmethane  have been measured i n various  ethanolic DMSO mixtures. These rates are l i s t e d i n Tables XXIX, XXX. The logarithm of these r a t e s , l o g k, were c o r r e l a t e d with the N H  value  of the medium and the l i n e a r r e l a t i o n s h i p s obtained are  shown i n f i g u r e 18.  9-phenylfluorene  2,3-benzofluorene  9-ethylfluorene  9-phenylxanthene  Fluorene  Triphenylmethane  - 103 -  Table XIX l i s t s the slopes of each of these l i n e s and the corresponding  c o e f f i c i e n t s of c o r r e l a t i o n and student's t e s t T.  The  slopes are s i m i l a r i n magnitude f o r a l l the hydrocarbons and have an average value of 0.87.  In the f i r s t approximation,  the less-than-  u n i t slope can be a t t r i b u t e d to the f a c t that the H  scale used was  derived with amine i n d i c a t o r s and not with hydrocarbons; t h e r e f o r e , the H_ scale r e f l e c t s the response of nitrogen acids rather than carbon acids to the change i n medium. Indeed, i t i s s u r p r i s i n g that such a good c o r r e l a t i o n i s N obtained, suggesting that the H_  C and H N  One way to compensate f o r the use of H_  scales are q u i t e s i m i l a r . C instead of H  scale would  be to p l o t log k f o r the various hydrocarbons against log k f o r a reference carbon a c i d to be chosen a r b i t r a r i l y .  I t was  thought that  DMSO would be the most appropriate reference a c i d , since the solvent mixtures contain DMSO. And indeed, i f we p l o t log k, , , vs ' • hydrocarbon r  log k^gQ  the slopes of the c o r r e l a t i o n s are much c l o s e r to u n i t y  (average of 0.95).  Figure 19 shows a p l o t of such a c o r r e l a t i o n .  The rates of d e t r i t i a t i o n of fluorene i n DMSO-water-0.01 M TMAOH have been measured, and Figure 20 shows a p l o t f o r the N c o r r e l a t i o n between log k and the H '  value of the medium.  - The rates of the base-catalyzed  t r i t i a t i o n of DMSO and  d e t r i t i a t i o n of DMSO-t i n the three media (aqueous, methanolic and N e t h a n o l i c DMSO) were c o r r e l a t e d with t h e i r r e s p e c t i v e H  values.  Figures 21, 22, and 23 show p l o t s of such a c o r r e l a t i o n .  Figure  (2)  - 105 -  TABLE XIX N C o r r e l a t i o n of l o g k with H_ f o r the base catalyzed d e t r i t i a t i o n of hydrocarbons Compound  0(slope)  r  N  T  9-phenylfluorene DMSO-EtOH  .873  .998  5  30.7  2,3-benzofluorene  "  .809  .999  4  80.5  fluorene  "  .782  .997  8  38.4  9-ethylfluorene  "  .804  .999  9  62.3  9-phenylxanthene  "  .848  .999  5  82.1  triphenylmethane  "  .937  .999  3  53.4  DMSO  "  .901  .995  9  26.6  .790  .998  4  21.1  9-phenylfluorene DMSO-EtOH  .983  .999  5  35.3  2,3-benzofluorene  "  .904  .999  4  39.1  fluorene  "  .914  .999  8  47.0  9-ethylfluorene  "  .908  .998  9  46.4  9-phenylxanthene  "  .928  .999  5  56.6  1.029  .999  5  23.6  a) l o g k vs. H.  fluorene  DMSO-water  log k vs. l o g k (DMSO)  triphenylmethane  11  r  i s the c o e f f i c i e n t o f c o r r e l a t i o n  N  i s the number of points  T  i s the student's t e s t  - 109 -  shows a t y p i c a l run f o r the  t r i t i a t i o n o f DMSO  One can n o t i c e  that the points are much more s c a t t e r e d than f o r hydrocarbon detritiation. ±10%,  Although the r e p r o d u c i b i l i t y o f the run i s w i t h i n  the r e p r o d u c i b i l i t y o f any one point i s quite u n r e l i a b l e . This  i s mainly due t o the method o f a l i q u o t preparation. As explained i n the experimental s e c t i o n , 3.5 mis o f methanol was d i s t i l l e d from a DMSO and methanol mixture o f t o t a l volume 8 mis. These 3.5 mis were then d r i e d .  A 3 mis a l i q u o t was withdrawn and 85  added t o 7 mis o f the s c i n t i l l a t o r s o l u t i o n .  I t has been found  that  methanol acts as a d i l u t e r - a solvent which i n the presence o f decreasing toluene concentration produces a gradual drop i n pulse height - while water i s a strong quencher.  The counting e f f i c i e n c y  i n the DMSO exchange runs were h a l f as much as the counting e f f i c i e n c y i n the hydrocarbon runs, and a small v a r i a t i o n i n the dryness o f the methanol o r i n i t s p u r i t y w i l l a f f e c t the r e p r o d u c i b i l i t y o f any s i n g l e determination.  Nevertheless the rates o f t r i t i a t i o n o f DMSO  i n aqueous DMSO determined i n t h i s work compare favorably with the 37 values published by Stewart and Jones . The l i n e drawn i n f i g u r e 37 (21) i s the l e a s t square l i n e from Stewart and Jones r e s u l t s  and  the points are those determined i n t h i s work. I , Evaluation o f the k i n e t i c s We are measuring i n these k i n e t i c s the r a t e o f l o s s o f a c t i v i t y o f a t r i t i a t e d hydrocarbon.  The r a d i o a c t i v e isotope  - 110 -  concentration i s very small at the beginning of the run ( i n trace quantity) and almost a l l of the a c t i v i t y i s l o s t to the solvent sink. In a t y p i c a l run where the a c t i v i t y at time zero i s ~ 500,000 counts/ min the a c t i v i t y at time i n f i n i t y i s less than 1000 counts/min. I n t e r n a l r e t u r n was shown to be of small importance even 86 f o r the l e a s t a c i d i c of these hydrocarbons. .  By i n t e r n a l r e t u r n i s  meant the r e a c t i o n i n which the hydrocarbon i s i o n i z e d and the leaving group i s then recaptured by the newly formed carbanion.  For a l l these  reasons i t seems reasonable to associate the rate of d e t r i t i a t i o n of 44 87 these hydrocarbons with t h e i r rate of i o n i z a t i o n  V  .  The slow step of the i s o t o p i c exchange i s undoubtedly the d i s s o c i a t i o n of the carbon a c i d i . e . the removal of the t r i t o n by the base.  The simplest mechanism one can w r i t e i s a simple one step  a b s t r a c t i o n with a hydrogen bonded t r a n s i t i o n s t a t e as ArT + RO" —* Ar" + ROH  66^ [Ar...T... OR] » Ar + ROT 6 - 6 y [kv...H...OR] —* ArH + RO"  (35) (36)  The reverse r e a c t i o n of equation (35) i s w r i t t e n i n equation (36) to describe the i s o t o p i c exchange.  This mechanism though, does not  account f o r the p o s s i b i l i t y o f i s o t o p i c exchange with r e t e n t i o n of c o n f i g u r a t i o n , i f the carbon attached t o the exchangeable  hydrogen  i s asymmetric t h i s base catalyzed i s o t o p i c exchange with high r e t e n t i o n 86 of c o n f i g u r a t i o n has been noticed by Cram et a l . on o p t i c a l l y a c t i v e  - Ill 4-biphenylmethoxyphenylmethane OCH P- 6 5 6 C  H  C  |-  H 4  C  3  H ( D )  6 5 H  and 2-phenylbutane-2-d C H 2  5  C,H,.-*C-D(H)  j  DO  CH  -•  3  and 1-phenylmethoxyethane-l-d OCH  I  C H -*C-D(H) 6  5  I  CH  3  Another mechanism f o r proton t r a n s f e r can be v i s u a l i z e d . an e q u i l i b r i u m step, g i v i n g r i s e t o a hydrogen-bonded  I t involves  carbanion,  followed by an i s o t o p i c exchange step, and f i n a l l y a collapse o f the complex t o give the non-radioactive hydrocarbon.  Considering only the  forward r e a c t i o n ,  k  ArT + OR"  l  k  >  Ar~...TOR  2  *  Ar"...HOR  • -i ' k  I  II  III  *  ArH + OR"  (37)  - 112 we w i l l t r y t o deduce the nuclear c o n f i g u r a t i o n of the t r a n s i t i o n s t a t e and i n p a r t i c u l a r where the proton ( t r i t o n ) l i e s . Applying a steady-state treatment d[Ar ...TOR] dt  =  [ArT][OR"] - k  k  l -  k  [Ar-...TOR] = k  d[Ar ...HOR] dt  =  -l  +  [Ar~...TOR] - k [Ar"...TOR] = 0  [ArT] [OR ] k  (39)  2  k [Ar"...TOR] =  —  2  k k  and therefore k , ° 2  (38)  2 l  L l  +  [ArT] [OR ]  (40)  -  k  2  •  k  =  (41) k_  b S  1 +  k  2  Cram et a l have proposed a dual mechanism ( c f i n t r o d u c t i o n ) d i f f e r e n t i a t e d according to the r e l a t i v e magnitude of k_^ and k i.e.  2 >  If k  2  »  k ^  i f I I goes t o I I I f a s t e r than i t returns t o I then equation (41)  reduces t o (42) k  obs  =  k  l  < > 42  The proton t r a n s f e r takes place immediately a f t e r the hydrogen bonded complex i s formed and before they can separate due t o the thermal motion, i.e.  i t s equivalent t o having no p r e e q u i l i b r i u m as i n equations (35)  and (36). If k ^ »  k  2  i . e . some kind of p r e e q u i l i b r i u m i s r a p i d l y  e s t a b l i s h e d followed by a rate determining step. (41) reduces to:,  In t h i s case equation  - .113 -  k  k  obs  =  l  — k  k  2  =  K k  W  2  -l  Obviously the t r a n s i t i o n states corresponding t o these two mechanisms are quite d i f f e r e n t from one another, and i t would seem q u i t e unexpected to obtain a good Bronsted c o r r e l a t i o n f o r a l l these hydrocarbons, i f the t r a n s i t i o n states are not s i m i l a r . Also the slope 0 o f these c o r r e l a t i o n s (log k vs H_) are o f the same order o f magnitude and therefore i t would seem somewhat u n l i k e l y that a change i n mechanism occurs.  Cram also proposed a s i n g l e mechanism f o r the i s o t o p i c  exchange o f hydrocarbons where the rate determining step i s I — > I I and with a t r a n s i t i o n state o f i n c r e a s i n g asymmetry.  In t h i s case the  rate equation can be expressed  .  =  dr  [ArT] [HO"]  k a  f which gives  One  k  Q b s  f A r  l f  °"  (44)  +  f -  = k [RO"].'-MJ«L a  can derive the H  f R  (45)  f u n c t i o n f o r an e q u i l i b r i u m (46) by  considering the AH + RO" — ^  A" + ROH  (46)  e q u i l i b r i u m constant _ ROH A~ a  a  HA ~ a  H A  a  AH RO  1-4/J  - 11.4 -  [A"] LAH]  and therefore  f  h  f  AH  AH  f RO  f RO  ROH  [RO"]  (48)  [RO"]  (49)  ROH  Combining equation (49) and (45) we get  k , = k .(h) obs a v  a , ROH nr  ArT  f  A-  u  (50)  AH  t a k i n g the logarithms log k  obs  log k  a  + H_ + log a  + log  R Q H  ArT AH  (51)  The a c t i v i t y c o e f f i c i e n t term has t r a d i t i o n a l l y been assumed t o be constant - i f not equated to zero - because of the s i m i l a r i t y between the i n d i c a t o r acids (AH) used to generate the H  scale and the k i n e t i c  substrate (ArT) and also the s i m i l a r i t y between the t r a n s i t i o n s t a t e (^  and the i n d i c a t o r anion (A ).  Therefore equation (51) reduces t o :  log k , .= constant + H + l o g a-,-,, obs ROH 6  6  (52)  ,38 Equation (52) resembles the one derived by Anbar et a l f o r base catalyzed reactions where the slow step i s a proton a b s t r a c t i o n from the reactants ( c f . i n t r o d u c t i o n p.21 ), which i s s i m i l a r to the mechanism proposed f o r the d e t r i t i a t i o n of hydrocarbons and shown i n equation (37).  - 115 -  There are no published data f o r the a c t i v i t y o f ethanol i n DMSO-ethanol mixtures, but a c t i v i t y c o e f f i c i e n t s have been determined f o r water i n DMSO-water  6  and sulfolane-water  7  mixtures and a l s o f o r  8 methanol i n DMSO-methanol 9-phenylfluorene  mixtures.  The rates of d e t r i t i a t i o n o f  (9-t) were therefore determined i n methanolic DMSO  containing 0.01 M sodium methoxide. The l i n e 1 i n Figure 24 represents the c o r r e l a t i o n between log k and H while l i n e 2 represents the c o r r e l a t i o n between l o g k and H  + l o g a^ Q^. e  The l i n e s 1 and 2 i n  Figure 23 are the corresponding c o r r e l a t i o n s f o r the i s o t o p i c exchange of DMSO i n methanolic DMSO. TABLE XX C o r r e l a t i o n o f l o g k with H  and H  + log a^Q^ f °  r  the  base catalyzed i s o t o p i c exchange i n methanolic DMSO. .  Compound  System  6  r  N  T  a) l o g k vs. H 9-phenylfluorene DMSO  DMSO-MeOH "  .770  .996  8  27.2  .730  .993  12  27.1  .859  .997  8  30.5  .878  .994  12  28.1  b) l o g k vs. H_ + l o g a ^ y . ' 9-phenylfluorene DMSO  DMSO-MeOH "  - 117 -  The net r e s u l t o f p l o t t i n g l o g k f o r 9-phenylfluorene and DMSO versus H_ + l o g a^gQj^ i s thus t o steepen the curve as can be seen from Table XX.  The value o f l o g ^ q^ q  i s p r a c t i c a l l y equal t o zero up t o  10 mole percent DMSO and decreases slowly t o -0.21 f o r 30 mole percent DMSO then more r a p i d l y as the DMSO content increases t o 100 percent. Therefore since the slopes o f l o g k, , r  6  ,  hydrocarbon  vs l o g k^ ,_ p l o t s are Wf  6  DMSO  r  very close t o u n i t y (Table XIX) and that l o g k vs H_ + l o g a^gOH have C slopes which are 0.1 l e s s than the former c o r r e l a t i o n s , the H f o r DMSO systems should r i s e  scale  only s l i g h t l y more r a p i d l y w i t h the  DMSO content than the corresponding  scale.  A j u s t i f i c a t i o n f o r the observed l i n e a r c o r r e l a t i o n between the logarithm o f the rate constants and H has thus been obtained. I I . A c t i v a t i o n parameters A c t i v a t i o n parameters f o r these d e t r i t i a t i o n reactions have been measured h o r i z o n t a l l y and v e r t i c a l l y i n Figure 18.  By horizon-  t a l l y i s meant that an a r b i t r a r y rate constant at 25° was chosen f o r a l l the hydrocarbons (obviously the medium was quite d i f f e r e n t ) and the enthalpy o f a c t i v a t i o n was measured.  V e r t i c a l l y means that the a c t i v a -  t i o n parameters were measured i n one and the same medium (65% DMSOEtOH) and the temperature range v a r i e d although the temperature l i m i t s are  only 60° apart (from -5° to +55°).  Table XXXII  appendix B l i s t s  the rate-temperature data f o r these d e t r i t i a t i o n reactions and Table XXI l i s t s the a c t i v a t i o n parameters deduced from these k i n e t i c s .  - 118 -  TABLE XXI A c t i v a t i o n parameters f o r the base-cataiyzed d e t r i t i a t i o n of hydrocarbons.  %DMSO  kcal.mole  AS e, u.  Triphenylmethane  62.5  23.3 ± 0.6  -2.3 ± 2.0  9-phenylxanthene  62.5  21.1 ± 0.9  0.5 ± 3.0  9-ethylfluorene  62.5  16.7 ± 0.7  5.9 ± 2.6  Fluorene  62.5  14.4 ±0.3  10.2 ± 1.2  9-phenylxanthene  70  22.1 ± 1.0  5.6 ± 3.2  9-ethylfluorene  35  18.6 ± 0.8  -7.1+2.6  Fluorene  10  17.2 ± 0.3  -12.4 ± 1.1  T  a) v e r t i c a l  b) h o r i z o n t a l  4,4',4"-Trinitrotriphenylmethane has an a c t i v a t i o n energy o f 11.3 ± 0.2 k c a l . mole ' f o r i t s i o n i z a t i o n by sodium ethoxide i n an ethanoltoluene mixture  One can see that as the hydrocarbon becomes l e s s a c i d i c the enthalpy o f a c t i v a t i o n r i s e s .  This general trend i n the enthalpy o f  a c t i v a t i o n has a l s o been observed by two other groups of workers 2 22 Cram et a l • and S t r e i t w i e s e r et al'. - and would tend t o i n d i c a t e . that the amount of bond-breaking  i n the t r a n s i t i o n s t a t e increases  with i n c r e a s i n g b a s i c i t y of the hydrocarbon.  The enthalpy o f  - 121 -  a c t i v a t i o n should increase as ApK increases, since the extent o f the bond breaking i n the t r a n s i t i o n s t a t e w i l l increase as the R0~ moiety binds the proton more c l o s e l y .  Thus the greater the a c t i v a t i o n energy  the more the t r a n s i t i o n s t a t e resembles the product I I . The s i g n i f i c a n c e o f the rather small v a r i a t i o n i n a c t i v a t i o n entropy i s uncertain owing t o the l i m i t e d number o f hydrocarbons and the high experimental e r r o r .  One can n o t i c e a trend toward more p o s i t i v e  values as the hydrocarbon becomes less a c i d i c and conclude that the charge must be more d e l o c a l i z e d i n the t r a n s i t i o n state derived from •J* the weaker a c i d s . Although Cram has found a change i n AS o f 22 e.u. f o r the d e t r i t i a t i o n o f hydrocarbons i n 75% DMSO-MeOH-KOMe at 75°, t  S t r e i t w i e s e r found a very small change i n AS  (6 e.u.) f o r the same  r e a c t i o n i n methanol at 45°. A l s o the rate - increase on going t o higher DMSO concentration (higher H  values) i s accounted f o r mainly t  by the decrease i n enthalpy o f a c t i v a t i o n ; AH f o r fluorene i n 10% DMSO i s 17.2 and i n 62.5% DMSO i s 14.4. This dependence has also been observed by Cram et a l . i n the catalyzed racemization o f (+)-2-methyl-3-phenylpropionitrile i n DMSO88 methanol s o l u t i o n s . Parker and coworkers  a l s o noted that p r o t i c -  ^dipolar a p r o t i c ) s o l v e n t e f f e c t s on rate are u s u a l l y r e f l e c t e d i n the enthalpy r a t h e r than i n the entropy o f a c t i v a t i o n , and are quite s t r o n g l y temperature dependent.  This i s t o be expected since these  e f f e c t s are mainly a t t r i b u t e d t o hydrogen bonding i n t e r a c t i o n s solvation.  - 122 -  I I I . K i n e t i c Thermodynamic c o r r e l a t i o n f o r hydrocarbon i o n i z a t i o n (log k vs  ApK)  In the case of hydrocarbons the e l e c t r o n i c and s p a t i a l c o n f i g u r a t i o n of the acids and t h e i r conjugate bases are not i d e n t i c a l , and therefore the Bronsted p l o t w i l l show a broad t r a n s i t i o n from a = 0 to a = 1, which occurs over a wide ApK range. By e x t r a p o l a t i o n of the l i n e s i n Figure 18 t o an H  of  f o r a 0.01 M e t h a n o l i c sodium ethoxide s o l u t i o n ) we  can  N 13.45  (H  compute a k i n e t i c a c i d i t y f o r these hydrocarbons, and taking a value of 16.0 f o r the pK  of ethanol, ApK values can be c a l c u l a t e d .  The  3.  c o r r e l a t i o n of k i n e t i c and thermodynamic a c i d i t i e s i s shown i n Figure 27.  The average slope a of the l i n e i s 0.5 but a curve w i l l f i t b e t t e r  the r e s u l t s with an i n i t i a l slope of 0.3 and a f i n a l slope of  0.6.  The thermodynamic a c i d i t y of fluorene and 9-ethylfluorene 22 are s i m i l a r  while t h e i r k i n e t i c a c i d i t y d i f f e r s by ~2 pK  &  units.  S t r e i t w i e s e r c o r r e l a t e d the rates of d e t r i t i a t i o n of 9 - a l k y l subs t i t u t e d fluorenes with the pK  of the corresponding  a c e t i c acids and :  3.  found that the r e l a t i v e rates are i n the prder F > 9-MeF > 9-EtF. But e q u i l i b r i u m measurements showed that the order of decreasing a c i d i t y i s 9-Me  > F =  9-Et > 9-isopropyl > 9 - t - b u t y l , which i n d i c a t e s  a kinetic.effect i n this series. of.the log k -ApK  In Figure 29 at ApK = 0, the slope  curve i s not 0.5 but 0.3.  though since the acceptor ROH  This i s to be expected  and the donor RgCH are of d i f f e r e n t  acid-type, 0- and C- type r e s p e c t i v e l y ^ .  a  Figure 27.  o"  C o r r e l a t i o n of k i n e t i c and thermodynamic a c i d i t i e s of some hydrocarbons,  I  1  ApK 9-phenylfluorene  cO. I  0.4  2,3-benzofluorene 4.0  CD O as. I  Fluorene  4.5  9-ethylfluorene  4.6  9-phenylxanthene  10.0  Triphenylmethane 13.0  o o  •—». I  o  I  -2.0  0.0  2.0  4.0  DELTA  6.0  P K  a.o  10.0  12.0  14.0  - 124 -  IV. Change o f Isotope e f f e c t with the pK^ .of hydrocarbons No measurements o f isotope e f f e c t s were made by us, i n the 2 e t h a n o l i c DMSO system, but both Cram et a l . and S t r e i t w i e s e r and 21 coworkers  found a general trend i n the v a r i a t i o n o f the magnitude  of the isotope e f f e c t with the p K values.  Cram et a l . i n 75% DMSO-  a  MeOH (by volume) - 0.0026 M potassium methoxide found an isotope e f f e c t ky/kp o f 6.75 at 25° f o r 2-(N,N-dimethylcarboxamido)-9-methyl fluorene (pK ~20) and 2.5 at 126° f o r 4-biphenylmethoxy phenylmethane (pK ~30) a. 21 S t r e i t w i e s e r and coworkers  found a primary isotope e f f e c t k^/k^, i n  sodium methoxide o f 2.5 (25°) f o r 9 phenylfluorene kp/k^, f o r triphenylmethane  i s 1.3 (99°).  (pK 16.5)  while  3-  The progressive decrease i n  the isotope e f f e c t i s q u i t e marked, and one should note that f o r triphenylmethane,pK  29.2, (ApK ~ 13) the isotope e f f e c t i s about  h a l f that f o r 9-phenylfluorene  f o r when pK  16.5 ( pK ^ 0).  This lowering i n k i n e t i c isotope e f f e c t with i n c r e a s i n g ApK w i l l tend t o i n d i c a t e an increase i n asymmetry i n the t r a n s i t i o n s t a t e 51 53 This i s i n l i n e with recent suggestions,  '  that the isotope e f f e c t  w i l l be greater when the t r a n s i t i o n state i s symmetrical  and the  symmetrical s t r e t c h i n g mode v w i l l not involve any motion o f the proton.  This would probably happen when both anion A and B are  (A....H....B (v, no motion o f H) o f s i m i l a r strength i . e . ApK - 0. When on the other hand one anion i s stronger than the other, the proton w i l l be c l o s e r t o the weaker base and the s t r e t c h i n g w i l l become unsymmetrical and w i l l lead t o a smaller A...H...B (imaginary  - 125 -  frequency i v ^ ) isotope e f f e c t .  This i s exactly what we n o t i c e when  ApK > 0 and the proton i s c l o s e r to the RO moiety than to the carbanion. -  This mechanism thus does not r e q u i r e the isotope e f f e c t t o vanish f o r high ApK values and i s one more reason t o p r e f e r t h i s mechanism t o Cram's dual mechanism.  Of course i f at ApK ~ 0 there i s  a maximum i n the isotope e f f e c t c o r r e l a t i o n with ApK one should be able to f i n d an isotope e f f e c t o f less than 7 f o r r e a c t i o n s where the carbon acid i s a weaker base than ROH.. Thus a l l the k i n e t i c data are accommodated by mechanism (37). There i s no r e a l way t o d i s c r i m i n a t e - at the present time between mechanisms (35) and (37) . ArT + RO" — * Ar" ....TOR ^ * ;  k  Ar"  =  HOR - j — * .  ArH + RO" (37)  f  ArT (H) + RO  ; k  Ar + ROT (H)  (35)  r  In both cases the rate equation i s the same, and the c o n f i g u r a t i o n o f the t r a n s i t i o n state o f highest energy appears to be [Ar  T.. . .OR]"  with T i n a symmetrical p o s i t i o n i f ApK~ 0 and with c l o s e r t o RO i f ApK > 0 and with  k  H  A  n  <  k  H  A  n  ~7 and  7 and c l o s e r to Ar i f ApK < 0  and with k^/k^ < 7. But o f course the mechanism shown i n equation (35) cannot account f o r i s o t o p i c exchange r e a c t i o n with r e t e n t i o n o f . . 86 configuration :  - 126 -  I d e a l l y one would l i k e to have an H_ s c a l e f o r carbon acids and use these same i n d i c a t o r s f o r i s o t o p i c exchange measurements, thus eliminating  the uncertainty i n the value of the a c t i v i t y  coefficient  terms i n equation (51) f  ArT f  t  f -  2A  f All  Also i f one had values f o r the a c t i v i t y of ethanol i n DMSO mixtures that would e l i m i n a t e the other unknown parameter i n equation (51), namely l o g a  R Q H  .  - 127 -  PART I I I :  I n t e r a c t i o n s o f Nitrophenylmethanes  with base.  An attempt to measure the degree o f i o n i z a t i o n o f 3-4'dinitrodiphenylmethane i n e t h a n o l i c sodium ethoxide showed that the u.v. absorption maximum of the "anion" had s h i f t e d t o 430 mu from the 575 mu value observed i n DMSO containing sodium ethoxide. E.s.r. spectroscopy i n d i c a t e d the presence o f a large concentration of r a d i c a l s (~10 medium.  -4  M i n -10  - 2  M i n d i c a t o r s o l u t i o n ) i n these b a s i c  A s i m i l a r behaviour was observed f o r two other carbon acids  i n d i c a t o r s , namely t r i s - and b i s Bowden and Stewart  17  (p-nitrophenyl)methane.  and R i t c h i e and Uschold  19  a l s o noted  that the spectrum o f the conjugate base o f tris-(p-nitrophenyl)methane showed a pronounced solvent e f f e c t (A.  of'582 mu i n ethanol, and  - 128 "Since the formation  of h i g h l y coloured s o l u t i o n s i n the presence  of base has often been considered reference  i n d i c a t i v e of proton abstaction (e.g.  see  17) t h i s large s h i f t i n absorption maxima suggests that another  process i s t a k i n g place. A v a r i e t y of i n t e r a c t i o n s can occur between aromatic nitro-compounds and the unshared e l e c t r o n p a i r of the base, with i n most cases, a conco90 amitant formation  of h i g h l y coloured s o l u t i o n s . Buncel, N o r r i s and R u s s e l l  i n t h e i r review l i s t e d the d i f f e r e n t species r e s u l t i n g from such reactions ^and the a n a l y t i c a l techniques used to define them. For example, a p a r t i a l ^transfer of e l e c t r o n i c charge from the base to the aromatic nucleus can ^give r i s e to n-complexes (charge-transfer complexes). A r a d i c a l - a n i o n  can  -be produced i f an e l e c t r o n i s completely t r a n s f e r r e d from the base to the n i t r o compound. The formation  e l e c t r o n p a i r of the base can also p a r t i c i p a t e i n the  of a covalent bond with an aromatic carbon atom to give a  .o-complex or " Meisenheimer " type complex. Because the n i t r o group has a strong a c i d strengthening  e f f e c t , the base could abstract a proton to  form a carbanion. The p o s s i b l e existence of ion p a i r s as w e l l as free ions i n the cases of proton a b s t r a c t i o n and radical-anion.formation  further  complicates the p i c t u r e . Ion p a i r s themselves can be d i f f e r e n t i a t e d i n t o solvent separated and contact i o n p a i r s . 91 R u s s e l l and Janzen  have studied extensively the reactions of  o- and p- n i t r o t o l u e n e s i n strongly b a s i c systems. They postulated a spontaneous d i s p r o p o r t i o n a t i o n  that  r e a c t i o n takes place to form the 91  r a d i c a l - a n i o n derived from the parent n i t r o t o l u e n e . These authors suggested a mechanism f o r t h i s d i s p r o p o r t i o n a t i o n r e a c t i o n i n t-butanol containing potassium t-butoxide, i n which the rate l i m i t i n g step i s the  - 129 i o n i z a t i o n of the b e n z y l i c proton.  p-N0 C H CH 2  p-N0 C H CH " 2  6  4  2  6  4  3  +  B"  + p-N0 C H CH 2  6  4  •  3  p-N0 C H CH " 2  6  4  +  2  • p-NO^H CH " 2  BH  (53)  + p-'CH C H N0 * (54) fi  2  Two molecules o f the r a d i c a l p-NC^C^H^H,^'- then couple t o give p - p ' - d i n i t r o b i b e n z y l (p-NO^^H^H^H^^H^C^-p) which can be i s o l a t e d from the r e a c t i o n mixture . In 80 percent DMSO-t-butanol-potassium t-butoxide, the d i s p r o 91 p o r t i o n a t i o n r e a c t i o n i s very r a p i d . R u s s e l l and Janzen  postulated a  d i f f e r e n t mechanism i n t h i s case: The rate determining step i s now the one shown i n equation 54 and the i o n i z a t i o n step shown i n equation 53 becomes a f a s t p r e - e q u i l i b r i u m . This i s probably due t o the higher b a s i c i t y o f the DMSO s o l u t i o n s . R u s s e l l and Janzen suggested that t h i s d i s p r o p o r t i o n a t i o n r e a c t i o n i s quite general and would occur whenever hydrogen atoms are a t o an e a s i l y r e d u c i b l e group which a l s o promotes the a c i d i t y o f these hydrogens. I. N.m.r. i n v e s t i g a t i o n The d i s p a r i t y i n the pK values o f the carbon acids reported i n Tables  I I I and IV , the high degree of solvent dependence o f the  anions' s p e c t r a l c h a r a c t e r i s t i c s and the presence o f appreciable amounts of r a d i c a l - a n i o n s i n b a s i c s o l u t i o n s o f nitrophenylmethanes  l e d t o the  u t i l i z a t i o n o f high r e s o l u t i o n n.m.r. as an independent method f o r the  - 130 -  c h a r a c t e r i z a t i o n o f the i o n i c species formed i n basic s o l u t i o n s . N.m.r. has been used p r e v i o u s l y t o define a l k l i n e media a  73  the mode of i o n i z a t i o n  o f amines i n  92 . Crampton and Gold have shown that 2 , 4 - d i n i t r o a n i l i n e  and 2,4-dinitrodiphenylamine i n DMSO as a solvent and i n the presence of methanolic sodium methoxide i o n i z e t o give an amide i o n v i a proton abstraction. 69 In 1966 B i r c h a l l and J o l l y  e s t a b l i s h e d a scale o f a c i d i t i e s  f o r a n i l i n e s i n l i q u i d ammonia* i n presence o f sodium amide by an n.m.r. 69 93 method. The same authors  '  have attempted t o study some hydrocarbons  using the same technique but have not yet published the r e s u l t s o f t h e i r investigation. A b a s i c system i n which, h o p e f u l l y , only proton a b s t r a c t i o n occurs was sought f o r the nitrophenylmethanes. Since hexamethylphosphoramide (HMPT) containning sodium methoxide i s e a s i e r t o handle than l i q u i d ammonia, i t was used f o r t h i s purpose.Preliminary r e s u l t s show HMPT-0.01 M TMAOH s o l u t i o n i s some 1 0 times more b a s i c * 4  0.01 M TMAOH s o l u t i o n . Tris-(p-nitrophenyl)methane  that an  than a DMSO-  TNPM  The n.m.r. spectrum o f TNPM i n HMPT (0.042 M s o l u t i o n ) c o n s i s t s of a sharp resonance at 6= -6.60 ( r e l a t i v e area 1) which i s assigned t o 94 Badoz-Lambling et a l . have developed a hydrogen electrode s u i t a b l e f o r a c i d i t y measurements i n l i q u i d ammonia at -60°. Lagowski et a l have also used l i q u i d ammonia as a s t r o n g l y basic system and determined spect r o p h o t o m e t r i c a l l y the a c i d i t y of o- and p- n i t r o a c e t a n i l i d e and d i - p t o l y l - and d i - p - a n i s y l - methane. In a 91.2 mole % HMPT-water s o l u t i o n containning 0.01 M TMAOH, A n i l i n e (pK =27.3) i s one-tenth i o n i z e d and 3 - t r i f l u o r o m e t h y l a n i l i n e (pK =25.4) is completely i o n i z e d . These r e s u l t s would thus i n d i c a t e an H y^alue of ~26.4. The H value f o r the corresponding DMSO s o l u t i o n is21.2  - 131 -  the  methine hydrogen  and an AA'XX' m u l t i p l e t centered around 6 = -8.02  ( r e l a t i v e area 12) due to the aromatic hydrogens  ( f i g u r e 28a ) . The addi-  t i o n of less than one equivalent of anhydrous sodium methoxide to t h i s s o l u t i o n gives an intense green c o l o u r a t i o n . The i n t e n s i t y o f the spectrum of the nitrophenylmethane decreases with the simultaneous appearance o f another m u l t i p l e t at higher f i e l d ( f i g u r e  28b ). Both m u l t i p l e t s are quite  sharp i n d i c a t i n g a r e l a t i v e l y slow rate of exchange between the two species. When more than one equivalent of base was added the o r i g i n a l spectrum completely vanished leaving only the new m u l t i p l e t centered around 6 = -7.56 ( f i g u r e 28c ) . This spectrum i s i n agreement with that expected f o r the e x c l u s i v e formation of an anion by proton removal from the methine carbon.  The v i s i b l e spectrum of the i o n was determined d i r e c t l y i n a 0.0024 M s o l u t i o n and e x h i b i t e d an absorbance at a X of 770 my max (e = 43,400).  - 132 Figure 28.  •  N.m.r. spectra of tris-(p-nitrophenyl)methane and anion in HMPT. •• '•  1  9  i  •  I 8  • .....  I  •  I  .  1  I  7  .  I 6  - 6 ( p p m ) ——  »  - 133 -  Bis-(p-nitrophenyl)methane  BNPM  The n.m.r. spectrum of BNPM i n HMPT (0.058 M s o l u t i o n ) c o n s i s t s of a s i n g l e resonance at 6 = -4.45 ( r e l a t i v e area 1 ) due t o the methylene hydrogens and a AA'XX m u l t i p l e t centered at 6 = -8.04 ( r e l a t i v e 1  area 4) assigned t o the aromatic hydrogens ( f i g u r e 29 a ) . Addition o f anhydrous sodium methoxide t o t h i s s o l u t i o n gives a dark green c o l o u r a t i o n and causes a decrease i n the i n t e n s i t y o f the spectrum o f BNPM along with the appearance of a new spectrum at higher f i e l d ( f i g u r e 29 b ) . Both resonances are quite sharp and complete conversion t o the spectrum at higher f i e l d i s p o s s i b l e with the a d d i t i o n of more base. The-.new spectrum consists o f a sharp resonance at 6 = -5.44 ( r e l a t i v e area 1) and a AA'XX m u l t i p l e t centered around <5 = -7.27 ( r e l a t i v e area 8) 1  (figure 29 c ) . This new spectrum i s i n d i c a t i v e of the formation of the BNPM carbanion.  —  The v i s i b l e spectrum of the carbanion was determined d i r e c t l y i n a 0.024 M s o l u t i o n and e x h i b i t e d an absorbance at a A o f 787mmy max (e = 58,300).  - 134 Figure 29.  N.ni.r. spectra of bis-(p-nitrophenyl)methane and anion in HMPT.  9  8  7  6 -&(ppm)  »-  5  - 135 -  3,4'-dinitrodiphenylmethane  3,4'-DNPM  The n.m.r. spectrum o f a 0.065 M s o l u t i o n of 3-4*-DNPM i n HMPT i s shown i n f i g u r e 30 a and c o n s i s t s o f a sharp resonance at 6= -4.43 ( r e l a t i v e area 1) due t o the two methylene protons as w e l l as a s e r i e s of l i n e s at low f i e l d C l " t i v e area 4) assigned t o the aromatic protons. r e  a  The resonances due to the protons from the 4'-nitro r i n g are d i s t i n c t from the resonances from the 3-nitro r i n g because o f t h e i r symmetrical arrangement . They c o n s i s t s of a m u l t i p l e t at 5 = -8.05 with J - XX' J  =  2  ' ' 2  J  AX'  =  J  A'X  =  0  ' ' 5  J  AX  =  J  A'X<  ".  8 =  2  AND  VAX  =  A A  , = 2.2  46.1.cps.  where v 6 represents the chemical s h i f t between n u c l e i A and X. o AX A V  R  C a r e f u l a d d i t i o n o f an equivalent o f sodium methoxide t o t h i s s o l u t i o n r e s u l t s i n the disappearance of the substrate spectrum with the appearance o f a new spectrum at higher f i e l d s .  But u n l i k e the two pre-  vious nitrophenylmethanes studied, a d d i t i o n o f less than one equivalent of base causes a broadening  ( s p e c i a l l y at high substrate concentration  ii 0,5 H) i n both spectrum at high and low f i e l d s . The second spectrum can be r a t i o n a l i z e d i n terms of the format i o n o f the carbanion o f 3,4'-DNPM. ,N0„  \\  /  H  \ H  C-^H  NO, The resonances at 6 = -7.95 and -7.38 are assigned t o the 2 and  - 136 Figure 30.  N.m.r. spectra o f 3,4 *-dinitrodiphenylmethane i n HMPT.  and anion  - 137 4,5,6 hydrogens r e s p e c t i v e l y . The hydrogens o f the symmetrical r i n g give r i s e t o four doublets o f major s p l i t t i n g s ~8 c.p.s. and smaller s p l i t t i n g s - 2 c.p.s. centered at 6 = -6.02, -6.70, -7.26 and -7.44 ppm.. I f t h i s i s indeed the case, then the doublet at 6 = -7.44 must be p a r t i a l l y hidden by the resonances o f the second r i n g . I t i s p o s s i b l e t o achieve p a r t i a l decoupling o f the m u l t i p l e t at 6 = -6.7 by i r r a d i a t i o n of the resonance at 6 = -7.44. S i m i l a r l y , the doublet at 5 = -6.02 i s decoupled by i r r a d i a t i o n o f the doublet centered at 6 = -7.26 and v i c e versa. These decoupling experiments thus confirm the v a l i d i t y of the peak assignment. The v i s i b l e spectrum o f the carbanion was determined d i r e c t l y i n a 0.0073 M s o l u t i o n and e x h i b i t e d an absorbance at a A o f 593 mp max (e = 28,000). No detectable amount o f i o n i z a t i o n by proton a b s t r a c t i o n was found by n.m.r. f o r 3,4'-DNPM, when DMSO i s used as a solvent instead 96 of HMPT. B i s - and t r i s - (p-nitrophenyl)methane i o n i z e i n DMSO  only  *  t o the extent of ^35 and - 75 percent r e s p e c t i v e l y . A d d i t i o n o f 10 — 20 percent methanol t o a s o l u t i o n containing a mixture o f the anion and n e u t r a l BNPM i n HMPT causes s u b s t a n t i a l broadening  of the substrate spectrum, but does not a f f e c t the anion  spectrum. This probably r e s u l t s from rapid exchange between the substrate and the radical-anions produced i n the system. At high methanol concent r a t i o n s both spectra broaden and eventually disappear. *  The apparent molar a b s o r p t i v i t y of tris-(p-nitrophenyl)methane i n DMSO containning sodium methoxide i s =70 percent o f the value obtainned i n HMPT c o n t a i n i n g sodium methoxide.  - 138 Both these observations would i n d i c a t e that i f the solvent system i s not b a s i c enough to i o n i z e the nitrophenylmethane by proton  abst-  r a c t i o n , side reactions become very important. This i s obvious from the fact that the r e l a t i v e amount of carbanion formation increases with i n c reasing a c i d i t y of nitrophenylmethanes i n II.  the DMSO-sodium methoxide system.  E.s.r. i n v e s t i g a t i o n 91 R u s s e l l and Janzen  noted that 2,4-dinitrotoluene r a d i c a l - ,  anions are produced only when the solvent mixture i s d e f i c i e n t i n base, while o- and p- n i t r o t o l u e n e s radical-anions are produced at a l l base concentrations. This observation can also be explained since 2 , 4 - d i n i t r o toluene i s probably completely i o n i z e d i n the DMSO-t-butanol mixture while o- and p- n i t r o t o l u e n e s are not. To examine the nature of the absorbing species at lower wavelength, the radical-anions of the nitrophenylmethanes were generated e l e c 14 trochemically i n DMSO-methanol mixtures. I t was found that the N hyper97 f i n e s p l i t t i n g constant  (a^) was s t r o n g l y solvent dependent. Nitrobenzenes  99 and n i t r i c oxides  r a d i c a l - a n i o n s a l s o e x h i b i t strong solvent dependent 98 99  N s p l i t t i n g s . Adams et a l a^  dependence on solvent  and Pannell  reported several cases of  composition.  A q u a n t i t a t i v e treatment has been given by Gendall et  al^P^  who assumed that the changes i n s p l i t t i n g s a r i s e from r e d i s t r i b u t i o n of the n-electron s p i n density near the functional group. Gendall et  al  1 0 0  also assumed that the i n t e r a c t i o n between the solvent and the r a d i c a l i s s g n i f i c a n t only at the s i t e of the f u n c t i o n a l group. Furthermore, i n a binary solvent mixture, i f the exchange between the two s o l v e n t - r a d i c a l  - 139 complexes i s r a p i d enough, a model can be derived which can account f o r *  the hyperbolic dependence o f the hyperfine s p l i t t i n g s composition  with the solvent  ratio.  Kennedy"^ has shown that a simple extension of t h i s model w i l l give a l i n e a r dependence of the s p l i t t i n g on the mole f r a c t i o n o f the solvent. Table XXII l i s t s the N s p l i t t i n g s a^ with the mole percent DMSO i n methanolic DMSO mixtures and these values are p l o t t e d i n f i g u r e s 31 and 32. I t i s obvious that a good s t r a i g h t l i n e can be drawn through these p o i n t s , thus confirming the correctness o f the model proposed by Gendall'''^ and a l t e r e d by K e n n e d y i . e . the solvent complexes are long l i v e d with respect t o t h e i r exchange time and the major e f f e c t on the s p i n density comes from the i n t e r a c t i o n of the solvent with the functional group. The e.s.r. spectra of tris-(p-nitrophenyl)methane r a d i c a l - a n i o n s were r a t h e r broad and although a d e f i n i t i v e change i n a^ values was noted i n going from pure methanol t o pure DMSO, the inaccuracy i n the measurements d i d not warrant t h e i r p l o t t i n g . 102 Chambers and Adams  reported that the absorption maximum o f  the r a d i c a l - a n i o n of nitrobenzene  s h i f t s t o lower wavelength with i n c r e a -  sing water concentration i n dimethylformamide (DMF). A blue s h i f t o f 42 my. was observed..for an a d d i t i o n o f 20 weight percent water t o DMF. 102 Chambers and Adams  c o r r e l a t e d t h i s solvent s h i f t of the absorption  maximum with the change i n a^. Although i n t h i s work, no d i r e c t determination o f the u.v. spectrum of e l e c t r o c h e m i c a l l y generated r a d i c a l - a n i o n s was attempted, a change i n the colour o f these r a d i c a l s was observed v i s u a l l y . twice the d i f f e r e n c e o f the average s p l i t t i n g from the a r i t h m e t i c mean  - 140 -  TABLE S p l i t t i n g constants  XXII  a^ f o r BNPM and 3,4'-DNPM i n methanolic  DMSO mixtures.  3,4'-DNPM  BNPM  TNPM  mole % DMSO  0  13.3  colourless  1  13.3  colourless  13.15  colourless  13.6±1.6 c o l o u r l e s s  24  12.7  faint yellow  12.5  faint yellow  12.5+0.6  53  11.8  blue  11.6  light blue  73  11.24 greenblue  11.0  blue  97  10.15  green  10.1  blue  100  10.0  green  9.611.6 green  - 141 -  Figure 31.  Plot of the average splitting constants versus mole percent DMSO for the radical-anion of 3,4•-dinitrodiphenylmethane in methanolic DMSO.  2,0 MOLE  40 60 PERCENT  80 DMSO  100  - 142 -  - 143 Table XXII l i s t s the colour of the d i f f e r e n t DMSO-methanol s o l u t i o n s a f t e r the r a d i c a l - a n i o n s were generated. One can estimate at -200 my the s h i f t i n absorption maxima between methanol and DMSO. I f we assume that there e x i s t s a q u a n t i t a t i v e  correlation  between the absorption maxima of the r a d i c a l - a n i o n s and t h e i r s p l i t t i n g * constants , then we can account f o r the large solvent s h i f t s observed i n basic e t h a n o l i c DMSO s o l u t i o n s . The carbanions of the nitrophenylmethanes have been i d e n t i f i e d by  ** n.m.r. and t h e i r u.v. spectra d i r e c t l y recorded  i n the same s o l u t i o n s .  Therefore the u.v. s p e c t r a l c h a r a c t e r i s t i c s of these carbanions are unequivocally defined and any absorption which occur at lower wavelength probably a r i s e s from other i o n i c species. Table XXIII l i s t s the s p e c t r a l data determined i n t h i s work, 17 18 as wel as those determined by Bowden and Stewart and Kroeger The accumulated evidence thus suggests that i n the methanolic 18 sodium methoxide system, the u.v. absorption observed nitrophenylmethane  a r i s e from the  r a d i c a l - a n i o n s . In e t h a n o l i c DMSO the s i t u a t i o n i s  more complex, since both carbanions and r a d i c a l s are present i n the same s o l u t i o n . At high DMSO concentrations TNPM i s probably almost completely i n the carbanionic form (X = 800 my) while the absorption at a X • max • . max J  r  of 580 my i n ethanol i n d i c a t e s a preponderance of r a d i c a l s . As a r u l e of thumb, the absorptions around 750-800 my f o r TNPM and BNPM and around 600 my  f o r 3-4'-DNPM can be a t t r i b u t e d t o the carbanions, while those  _ i.e.  a c o r r e l a t i o n s i m i l a r t o the one observed by Chambers and Adams.  **  u.v. c e l l s of path-length 0.1 and 0.01 mm have been used,but i t was necessary t o d i l u t e the s o l u t i o n s by a f a c t o r o f -15 t o be able t o determine the molar a b s o r p t i v i t y on a Cary Model 16 spectrophotometer.  - 144 TABLE XXIII S p e c t r a l data of nitrophenylmethanes i n s t r o n g l y b a s i c s o l u t i o n s , Compound/solvent  DMSO/EtOH  HMPT/NaOMe  c  X TNPM  max  my  e  775  BNPM  43,400  787  3,4'-DNPM  58,300  593  my  max  28,000  MeOH/NaOMe  e  e  X max my  707  19,300  809  30,300  810  63,000  704  40,600  707  41,900  550  31,700  570  28,800  530  25,600  534  28,000  d  e  8  430  f  g  values determined i n t h i s work i n HMPT containing sodium methoxide b  17 values determined by Bowden and Stewart i n ethanolic DMSO containing 0.01 M sodium ethoxide  c d  values determined by Kroeger  18  i n methanolic sodium methoxide 0.01  — M[0R]  value determined i n t h i s work i n DMSO containing sodium methoxide DMS0 ~  P. g • e 19 value determined by R i t c h i e and Uschold i n DMSO f E  7 0 %  °  £t  h  HMPT ° *  e £  £  f o o t n o t e  a  e 1 3 7  value determined i n t h i s work i n methanolic sodium methoxide, the molar a b s o r p t i v i t i e s could not be measured as the medium i s not b a s i c enough t o completely i o n i z e t h i s compound. g  value redetermined i n t h i s work i n 90% DMSO-ethanol-0.01 M sodium ethoxide.  - 145 at lower wavelength a r i s e e i t h e r from the exclusive presence of r a d i c a l s or a mixture of r a d i c a l s and carbanions. Preliminary  i n v e s t i g a t i o n of the i n t e r a c t i o n s between n i t r o -  phenylmethanes and basic DMSO solutions showed that a v a r i e t y of synergic reactions  occur. These should be i n v e s t i g a t e d more c a r e f u l l y as t h i s 91  type of r e a c t i o n appear t o be quite general  . The nitrophenylmethanes  cover a wide range of a c i d i t i e s and are thus i d e a l l y s u i t e d f o r such an investigation.  - 146 -  CONCLUSION  I t i s obvious from the r e s u l t s i n t h i s t h e s i s that only carbon acids which i o n i z e by proton a b s t r a c t i o n should be used t o determine a c i d i t y functions. In t h i s area o f study evidence should be obtained using more than one a n a l y t i c a l technique since the t r a d i t i o n a l method, 90 u.v. spectrophotometry, i s inadequate  f o r the i d e n t i f i c a t i o n o f  i o n i z a t i o n processes. The whole f i e l d of a c i d i t y determination, both thermodynamic and k i n e t i c , i s s t i l l i n i t s infancy as a r e s u l t of our l i m i t e d knowledge of solvent e f f e c t s . Probably a step i n the r i g h t d i r e c t i o n would be to conceive a reference electrode whose response i s independent o f the 103 medium. Recently Brenet  considered the t h e o r e t i c a l  reference electrode i n non-aqueous systems.  aspects o f such a  - 147 Bibliography 1.  K. Bowden, Chem. Rev., 66_, 119 (1966).  2.  W.D. Kollmeyer and D.J. Cram, J . Am. Chem. S o c , 90_, 1784, 1791 (1968).  3.  R. Stewart, Quart. Reports on S u l f u r Chem., 3_, 99 (1968).  4.  a) D. Dolman and R. Stewart, Can. J . Chem., 45_, 911 (1967). b) D. Dolman, Ph.D. Thesis, U n i v e r s i t y of B r i t i s h  Columbia,  Vancouver, 1966.  -  5.  M. Eigen, Angew.Chem. Intern. Ed., 3_, 1 (1964).  6.  J . Kenttamma and J . J . Lindberg, Suomen K e m i s t i l e h t i , B33, 98 (1960)  7.  R.L. 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DMSO a / p  <  to CN  o  1  to  **  CN  12.30  CN  12.59  0.4  -.35  1.0  -.20  -.53  2.0  -.12  • -.38  5.0  +.21  10.0  +.74  11.3  a. a to u -1  1CN o  CN  z/ V 1  CN  12.87  <  a, Q p- to' u— •  to1  CN  /—%  O  CN  z \-—' 1  CN  13.06  < r-l  to1  CN  /—\  o  2  v  —i  CN J  CN  13.17  <  a,  Q CN — CN O  r  v  s  —I'  CN  13.85  M) <  <  a. Q  0)  oc  a, Q  a  -1  (0.011  S -i . toi CN  t—\ CN O v  —I  j  CN  13.90  CN  -i  ^1i-  CN  /—"\  o  CN  1  ^-  «\  CN  14.48  11.95  -.10.  12.08 .. -.32  -.48  12.20  -.61  12.54 13.04  +.35  +.10.  +.05  -.64  +.84  +.66  +.55  -.10  -.15  -.75  13.73  20.3  +.40  +.35  -.16  14.29  24.1  +.88  +.82  +.24  14.72  16.0  +.57  13.19  - 155  TABLE XXIV - Continued  < a, Q cxi SH  o  o  CM  "z  +j  aj  n—/  I  O  •H  T> C I—I ™°in /pK  t  cQ<v. to  ^ &<; , a  <c a, a  O  u  S  to I  o  CM  2  I  o  CM  IZ i  < a. Q  o  -i to I  CM  o  CN  CM  ' 2  -i I o  CM  • Z i . • "tf 15.67 15.60 16.40 2  .  14.90  20.3  -.29  -.58  24.1  +.07  -.22  -.30  -.90  -.82  14.72  29.7  +.69  +.45  +.34  -.32  -.24  15.34  +.83  +.74  +.11  +.19  0  33.6 .36.2 43.2  1  15.00  i  . Z i  •* to 14.62  %  i  -i to  cu<a  Assigned H_  14.29  +.34  -.61  15.75  . -.35  16.01  +.39  16.74  - 156 -  TABLE XXV. Experimental values of log I f o r diphenylamine i n d i c a t o r s i n the system DMSO-methanol-sodium methoxide (0.01 M) < < Cl, a  to  ,—>  o  CM  Z,  u o +->  —  I  o  a. Q to I N O  «\  CM  1—1 % / p K  a  1 2 , 2 5  i  CM  z,  —1  to  •H TJ  DMSO  <  CM  1 2 , 6 5  <  a. Q to a. U CM  u  -1  CM  o  O  z,  z  1  .  •  1  CM  CM  1 3 , 0 3  ,—\  /—\  CM O  z  v/ CM  1 3 , 2 0  s  <  a, Q  1  ^t-  o, Q<D  toi  CM  —\  CM  <  a, a i-H  to1  r—\ CM  1 2 , 8 5  <  Q tu,to  CM  O  z  CM  —  J  1  CM  1 4 , 0 5  1  1 4 , 1 0  CM  o  CM  z,  1  *t  a, QCM P C z -I •31  CM  /—\  o  CM  z,  1  CM  CN  1 4 , 9 5  A s s i  g  n e d  H  -  0.3  -.30  11.95  1.0  -.23  12.02  2.0  -.16  -.54  5.0  +.10  -.30  -.64  -.84  10.6  +.50  +.12  -.22  -.40  -.60  12.68  +.51  +.22  -.02  -.18  13.08  19.2  +.56  +.39  +.24  -.73  -.78  13.42  25.0  +.100  +.80  +.62  -.28  -.36  13.81  +.12  +.04  14.20  15.0  29.7  12.10 12.31  33.0 35.1 40.0  -.52 +.58  +.46 +.87  14.43 14.59  -.08  15.00  46.0  +.51  15.46  49.0  +.75  15.70  157  -  -  TABLE XXV - Continued  < aCN t—\ CN  <  a, $H  O +J  crj O  •H TJ q  Mole% DMSO '  QCN  r—\ CN  CN O O  CN  o O zZ  zZ  v _ > w*—' 1 1 I I  -  -to"tf*  -  -  * >*'  .4.42  15.26  <  a, a to  <c a,  CJ U  CJ CJ  -1 -I to tO  1 ICM  o o zZ  CM  i  15.69  <  a, a <u  a  i—i -- iI  i  15.85  -1  &. B.  1 ICN O CN  • o zZ  S  < <  to tO  tO  QCN i  o o Z Z  CN  I  .  •  o Z  CN  i  <  O CN  x  z  " I  CN  o  2  i  16.  25.0  --61  13.81  29.7  -.22  14.20  35.1  +.14  -.68  40.0  +.54  -.29  -.70  44.9  +.91  +.07  -.36  -.49  15.34  +.41  +.06  -.10  15.72  50.0  14.59 15.00  52.0 54.9  -.57 +.93  +.45  +.29  -.48  59.0  -.05  60.2 63.0  16.14  +.93  +.71  -.07  16.59  +.32  '  65.5  +.39  69.5  +.76  -.57 16.98  +.81  -.05  17.37  74.0  +.35  17.70  77.0  +.59  17.94  - 158 TABLE XXVI Experimental values o f log I f o r amine i n d i c a t o r s i n the system DMSO-ethanol-sodium ethoxide (0.01 M)  < o <D  «: a, Q CM  ^1  s  — J  to  < a. o  X  CM  Z  -1 •>*  CN /—\ CM O  i CM r—\ CM o  1  o  l—N CN  cd O •H X)  V*  •z.  1  1  i  CN  CM  +J  O  R  i—i  CM  !Ix°io/pK DMSO a  Z  /—s CM o  z  1 CM  14.05  14.12  0.3  -.60  -.65  13.46  1.0  -.50  -.52  13.57  2.5  -.34  5.0  -.09  -.20  13.94  10.0  +.26  +.14  14.29  14.6  +.60  +.46  % r  15.05  - <:  15.27  Assigned H -  13.71  -.37  -.59  20.4  -.03  -.27  15.01  24.7  +.23  +.04  15.31  30.0  +.33  35.4  +.66  /  -  14.64  15.60 15.96  - 159 -  TABLE XXVI - Continued  <  a. o  u O  +->  rt CJ •H  •  o  CN  to  ™™ /pK %  Q  • **  -  15.15  .  to  1  i  ^  o2  CN O  <  <  Q i—I CJ -J  to  to  v-^  n  UMbU  a  2  t) G  <CU  a,  <  CN  a,  Q CD  < a CN a,  o2  -i  to  1  o2  CN  2  ' "sf 15.63  a. Q  X2  CN  -1 *t 1  o2  CN  ]  >*  15.73 5.73  16.63  16.55  17.45  <;G  o2  CN  i  CN  1  i—l CJ |  18.0  Assigned H  10.0  -.86  14.29  14.6  -.47  14.64  20.4  -.13  -.63  24.7  +.13  -.32  15.01 -.40  29.0  -.15  30.0  +.44  -.01  35.4  +.77  +.35  38.0 39.7  15.31  15.60 -.65 .  +.66  +.45  16.18 -.35  45.0  +.01  50.6  +.33  52.2 55.2  15.96  16.28 +.08  16.63 -.49  16.96  +.52 -.16  -.81  17.29  60.0  +.19  -.41  17.64  65.0  +.55  +.01  18.00  70.0  +.95  +.38  18.40  +.80  18.81  75.9  +.66  +.80  17.07  "  - 160 TABLE  XXVII  Experimental values o f log I f o r the s u b s t i t u t e d phenol i n d i c a t o r s i n the system DMSO-methanol-sodium methoxide (0.01 M)  rH  >>  4->  r-l •  c CD  o  4-> •H •P  u  o U)  VI  •H 1  £1 3  co  DMSO ^  CN  / p K  a  1 0 , 4 9  rH  cu o u  P< o V)  •H I •H  1 \D n CN  1 0 , 9 8  X +J  rH  *l  1 •H -d i  +->  rQ 1 .  1  CN?  CN  1 1 , 6 7  Assigned H_  1 2 , 1 0  0.0  -.60  5.0  . -.33  -.80  10.17  10.6  -.13  -.64  10.35  15.0  +.04  -.46  10.53  19.2  +.24  -.26  -.94  10.73  25.0  -.04  -.74  10.94  29.7  +.15  -.47  11.16  35.1  +.35  40.0  +.56  44.9  9.92  10.35 -.09  11.55  +.08  11.75  46.0 50.0  -.24  --  +;30  12.97  53.0  +.03  • ' .  59.0  +.26  12.36  63.0  +.44  12.54  69.7  +.69  12.79  r  12.13  - 161 TABLE XXVIII Experimental values of l o g I f o r the s u b s t i t u t e d phenol i n d i c a t o r s i n  mole% . 11.00 DMSO a / p K  rH X +J 3  £> i  CN 11.67  2,4-di-t-butyl  Substituent  2,6-di-isopropyl  -methyl  DMSO-ethanol-sodium ethoxide (0.01 M)  12.12  i  i—i  rH X +-> 3  X  rd  3 .£>  1 •H  •H  u  4->  M i 1  \o  CN 12.28  4->  12.28 CN  Assigned 10 .62  0.0  -.40  -1.03  1.1  -.18  - .92  10 .78  5.0  + .02  - .66  11 .02  10.0  + .20  - .46  11 .21  14.8  + .40  - .26  11 .40  20.4  + .57  - .10  24.7  + .72  + .07  30.0  + .25  35.4 39.7  11 .73 -.21  + .60  + .95  11 .91  -.36  - .02  45.0 50.6  11 .56  -.58  -.20  12 .10  + .14  -.04  -.04  12 .25  + .35  + .17  + .21  12 .47  + .40  12 .63  + .48  55.2  + .63  + .46  + .56  12 .77  60.0  + .84  + .70  + .71  12 .98  65.0  + .80  13 .11  70.0  + .99  13 .31  - 1.62 -  Appendix B:  Rate c o r r e l a t i o n data  TABLE XXIX  Rate of d e t r i t i a t i o n (1. mole "''sec '), ^Q^- at 25° f o r various i n b a s i c DMSO-Ethanol  hydrocarbons  solutions  Compound  mole" DMSO  [OEt] M  9-Phenylfluorene  0.0 5.0 10.0 14.6 20.4  .01 .0098 .01 .0105 .01  13.46 13.93 14.29 14.66 15.01  7,.684 2,.327 4,.600 8,.726 1..844  2,3-Benzofluorene  0.0 5.0 33.5 39.2  .01 .0087 .0103 .0086  13.46 13.88 15.78 16.21  1..535 3 .516 1,.250 2,.523  X  Fluorene  10.0 12.5 20.2 24.4 30.3 35.0 39.2 44.6  .0102 .0112 .01 .0095 .01 .0103 .0086 .01  14.30 14.50 15.01 15.26 15.60 15.95 16.21 16.63  2 .723 4 .186 8 .746 1 .520 2 .766 4 .808 7 .443 2 .083  X  12.5 29.9 35.0 39.2 44.5 49.1 54.6 59.6 64.9  .0107 .0091 .0095 .009 .0091 .01 .0085 .009 .0092  14.48 15.56 15.94 16.18 16.55 16.88 17.19 17.55 17.92  3 .241 2 .575 4 .218 7 .563 1 .631 2 .934 5 .540 8 .884 1 .811  X X  9-Ethylfluorene  OR X X X X X  -3 10 -2 10 -2 10 -2 10 -1 10'  -3 10' -3 X 10' -1 X 10' -1 X 10  X X X X X X X  X X X X X X X  -3 10 -3 10 -3 10 -2 10 -2 10 -2 10-2 10 -1 10 -4 10 -3 10 -3 10 -3 10 -2 10 -2 10 -2 10 -2 10 -1 10  - 163 -  TABLE XXIX - Continued N Compound  mole% DMSO  [OEt] M  H  k -  9-Phenylxanthene  49 .1 64 .9 70 .3 75 .0 .94 .0  .0094 .01 .014 .015 .01  16.,85 17,,96 18,.42 18,,83 20,.63  3,.514 2,.956 6,.528 1,.645 5,.530  83 .5 87 .0 20 .6  .01 .01 .01  19,.59 19,.93 20,.63  6,.448 1 .287 5,.990  Triphenylmethane  X X X X X X X X  10 10 10 10 10 10 10 10  164 TABLE XXX Rates o f d e t r i t i a t i o n (l.mole  1  sec ' ) , k  - at 25° f o r various UK  hydrocarbons i n basic DMSO solutions mole % DMSO  [OMe] M  9-phenylfluorene  0.0  .0093  11.91  1.525 x 10  i n DMSO-methanol solutions  5.3  .0095  12.30  4.849 x 10"  9.7  .0104  12.68  1.035 x 10"  15.7  .0108  13.18  2.25 x 10"'  19.4  .0105  13.42  3.673 x 10"  28.8  .0108  14.15  1.1 x 10"  35.7  .0105  14.63  2.513 x 10-1  40.1  .0099  14.98  4.664 x 10'  mole % DMSO  [TMAOH] M  H_  a)  b)  1  fluorene  27.1  .011  15.02  1.832 x 10  i n DMSO-water solutions  33.0  .011  15.65  4.473 x 10"  36.4  .011  16.05  1.200 x 10  49.2  .011  17.37  1.225 x 10  - 165 TABLE XXXI I o n i z a t i o n rate constants (l.mole  1  sec "*"), k (DMSO), at 25° f o r DMSO  i n Basic DMSO s o l u t i o n s . mole % DMSO  . [OR]"" M  detritiation H»  tritriation  k  k.  a) In water-DMSO s o l u t i o n s with TMAOH as base 0.0  .01  11.98  3.046 x 1 0 "  8  0.0  .05  12.71  7.235 x 1 0 "  8  0.0  .10  13.01  2.175 x 10"  33.5  .01  43.3  .01  55.3  .01  7  t  9.63 x 10"  15.9 16.84*  1.06 x 1 0  t 17.88  5  - 3  5.23 x 1 0 "  3  9.92 x 1 0 "  5  1.00 x 1 0 "  3  7.43 x 1 0 "  4  3.43 x 1 0 "  3  b) I n Ethanol-DMSO s o l u t i o n s with NaOEt as base 0.0  • .01  13.46  5.077 x 1 0 "  34.6  .01  15.96  50.6  .011  17.00  50.6  .022  65.5  .01  18.00  80.0  .098  19.21  4.57 x 1 0 "  2  80.4  .01  19.24  4.79 x 10"  2  90.1  .01  20.05  3.61 x 1 0  95.4  .098  20.62  2.88  +  t 17.30 +  7  _ 1  .../continued  - 166 TABLE XXXI continued mole% DMSO  [OR]" M  detritiation k  tritiation k  In Methanol-DMSO s o l u t i o n s with NaOMe as base  c) 0.0  .01  11.95  9.14 x 10"  30.0  .01  14.19  3.89 x 10"  36.0  .0095  14.74  36.0  .01  14.76  50.1  .01  50.1  8  6  1.54 x 10"  5  15.75  1.05 x 10"  4  .013  15.85  1.07 x 10"  4  60.1  .01  16.57  8.91 x 10"  4  63.0  .0097  16.86  4.09 x 10"  4  60.1  .024  16.95  4.26 x 10"  4  74.0  .01  17.70  1.74 x 10"  3  93.4  .01  19.50  3.15 x 10"  2  94.6  .01  19.70  3.99 x 10"  2  The H  9.55 x 10"  6  value of these s o l u t i o n s were determined spectrophotometrically,  with amine i n d i c a t o r s .  - 1.67 . TABLE XXXII Rate-temperature data f o r the base catalyzed d e t r i t i a t i o n of hydrocarbons i n DMSO-EtOH-0.01 M NaOEt Hydrocarbon  Temp°  1/T°(K)  a  55  0..003047  6.630  triphenylmethane  45  0,.003143  35  9-phenylxanthene  9-ethylfluorene  fluorene .  OR-  k  (  mole  sec )  loc ; k/T  X  io-  4  -5,.6946  2.207  X  ID"  4  -6,.1589  0,.003245  6.140  X  io"  4  -6,.7009  45  0..003143  2.399  X  io"  2  -4,.1227  35  0..003245  9,.02  X  IO"  3  -4..5337  25  0.,003350  2.955  X  io"  3  -5,.0040  15  0..003470  6.692  X  IO"  4  -5,. 6332  25  0..003354  1 .811  X  io"  1  -3,.2165  15  0..003470  6.092  X  io"  2  -3,.6747  5  0..003595  2.218  X  io"  2  -4,.0984  15  0..003470  4.207.  X  io"  1  -2 .8358  5  0..00359  1 .577  X  io"  1  -3 . 2464  -5  0,.00373  5 .970  X  io"  2  15  0,.003470.  1 .845  X  IO"  3  -5,.1937  25  0..003350  6 .526  X  io"  3  -4 .6603  35  0,.003245  2.019  X  io"  2  -4,.1836  45  0..003143  7.995  X  io"  2  -3 .5998  15  0..003470  1 .444  X  io"  3  -5 .2990  25  0..003350  4 .218  X  io"  3  -4 .8499  35  0..003245  1 .097  X  io"  2  -4 .4486  45  0,.003143  3 .49  X  io"  2  -3 .9597  15  0..003470  1 .02  X  io"  3  -5 .4510  25  0,.003350  2.776  X  io"  3  -5,.0315  35  0,.003245  7.433  X  io"  3  -4,.6176  45  0,.003143  1 .9  X  io"  2  -4 .2239  •  -3 .6524  b 9-phenylxanthene 70% DMSO  9-ethylfluorene 35% DMSO  fluorene 10% DMSO  - 168 C C C C C" c  A L A I N /O.K./ A.M., S. T Ill S PROORAM DOES A LEAST SqtJA^tS l I T F OR TH E i s A s i C M i r i c y ^ i C L TEST F i K A S 1 " \ I ",HT L IN': :  f  00 12 0013 0014 .0015 00 I 6 0017 0018 0019 0020 00 21 C022 . 00 2 3 0024 C025 C026 0027 C028 00 29 00 30 003 L CO 32 0033 0034 CC35 C036 00 37 • 003 8 CO 39 0040 00 41 C042 0043 004 4 0045 CO 46 00 47 004 n C049  4  11  6  .  1  2  10  IS  A S l G N l P l C A N C l : TI:ST FOR A STRAIGHT  L IN!:  CALL PLOTS DIMENSION LABELX(T 5 ) , L A B E L Y ( L5) DIMENSION XX (?) , YY ( 2 ) 0 I MEMS I_ON _X (_3_0_) »;Y (_30J 0 I ME N S I C N~ H TLJiG 12 0 ) DIMENSION TITLE ( 2 0 )  31 3  con  EXPRESSION Y = A + liX  ;  READ(5,3,END-99) T I T L E G FORMAT ( 2 OA-'. ) WRITE(6, A) T I T L E G FOR,", AT ( I H I » 30X » 20A 4) Rt AD (5 , 1 ) M READ!5,11) XU,XL,YU,YL FORMAT(4E 10,5) XMIN=XL YMIN=YL DX='{ XU-XL ) / 8 . 0Y={YU-YL ) / 6 . READ (5, 6 ) L X , L A B E L X • READ{5,6)LY,LATELY FORMAT( I 3, 15A4) CALL AXIS ( 0 . 0 , 0 . 0 , L A \'S E L X , -1. .,0.0,x X,B •11N,DX) ,9 0.0, Y •IN,I:Y) CALL A XI S ( 0. C , 0 , 0 , L A 2 ELY, L Y , 6. CALL PLOT! 0. C O . 0, 3) CALL P L O T ( 0 . 0 , 6 , 3 , 2 ) C A L L PLOT ( > ' • .5,6.3,1) CALL P L O T ( 8 . 5 , 0 . 0 , I ) CALL PLOT ( 8 . 0 , 0 , 0 , L) 0020 K = l , M REAO(5,3)11TLH WRITE(6,4 ) T I T L E READ (5, I ) M . . . .' . FORMAT( [ 2 ) RE A O ( 5 , 2 , E N 0 ^ 9 9 ) ( X ( I ) ,Y( I ) ,I=1,N) WRITE ( 5 , 2 ) ( X ( I) , Y ( 1 ) , I - 1 , N ) FORMAT(2E12.6) CALL LEAST ( X , Y,N ,;\A,BO) X X.MAX--AM AX (X ,N) X X MIN- AM[N(X,M) Y( N+l ) = AA+QB*XX.MIN Y(;'H-2 ) « A A + W1*.X.XM"AX X(N-M) =XXMIN X (M<-2 ) = XX<••'AX DO 10 l = l , f l X ( I ) = (X( I )-XMIN)/OX Y ( I ) = ( Y ( I )-YM l i D / O Y 0 ,4, .0,-1 ) C A L L S Y M i' 01. ( X( I ) , Y( I ) ,0 ,07 CON IINOE XX ( L ) - ( X ( N <- 1 )-XM IN )/0X •XX( 2 ) =( X ( \+2 )-XM[N)/D-X  - 169 -  C050 C051 0052 00 53__ CC54 * 0053 0056 C057 C058 CO 59 0060 CC61 0062 C063  0001 C002 0003 CQ. 04. CCO 5 0006 0007 0008 CC09 COOl CC02 C003 OOO't CC05 C006 0007 0008 0009  YY{1 ) = I Y ( N + " l ) - Y M H ) / l ) Y YY( J? ) = ( Y( + ? J-Y.M M J / D Y CALL LINE (XX,YY,?»+l) P = X( I )J . I S  ' 20  ( v  0 = Y ( T j - ~ . 15 A.M-K CALL NUMBt:R(P»O,O.l't»AM,O.0,-l) Cl'W INUG CALL SYMBOL ( 0 . 5 ,9.4 0. l't ,'TI rLGG,0 .0, 80) C A_LL_ JPL OT ( 1 1. 0. Q.C , - 3J GO r n 31 CALL PLOTND * STOP END r  99  1C  10  FUNCT ION  AMAX(X N)  DIMENSION  X{30)  f  B=X(l) DO 10 I-=2,N IF C X( I.) . GTB) CONTINUE AMAX-0 RETURN END  B = X( I )  AMlN(XtN) FUNCTION XC 30) DIMENSION B = X( I ) DO 10 I=2,N IE ( X ( I ) .'L T . B ) 8 = X ( I ) CONTINUE AMIN=B RETURN END  - 170 SUBROUTINE  I. C A S T { X Y , N , A A , B R ) F  DI MENS 1CN X ( 3 0 ) ,Y(30) ,A(30) B ( 3 0 ) , C ( 3 0 ) D ( 3 0 ) , E ( 3 0 ) , E ( 3 0 )  C C  t  L E A S T SQUARE INJTALIZE  r  c c  s x = o SY-0.0 Sxx=o„  .  F I T OF  '  .  "  STRAIGHT  .  "  "  .  V  LINE  :  Y = A +• BX  ~ " * " " • ' •  SYY=0.  c c c  CALCULATION  OF  SLOPE AND  INTERCEPT  DO 1 0 0 I - 1 ? N ITx^xTxTTT ' : ; sxx=sxx +x(I)*x(I) '• • SY=SY + Y ( I ) S X Y = S X Y \- X { I ) *Y { I ) " ' " " " ' " S Y Y = S Y Y + Y{ T ) *Y'( I ) - CONTINUE .' • ' ." " •• :  1 0 0  —  xT\ = (T  ~  :  :  "  7  '  '  '  ~~  BB=( XN*SXY-SX*SY)/(XN*SXX-SX*'SX) . A A-{SY-BU*SX)/XN SDSQR=O.O ' " " • DO 1 0 1 1 = 1 p N f _ U ) =_YJ I )-PO * X ( I ) - A A SDS"0= S'OS'O'k + F ( 1 ) * F T T J "' CONTINUE : WRTTE ( 6 , 2 ) SDSQR , ' WRITE ( 6 , 3 ) A A , BB S I GMAS=(SD S Q R / ( X N - 2 . 0 ) ) / ( X N * S X X - S X * S x ) SIG!'' AA = S0RT ( S I GMAS*S XX ) STT^Al'T^liTrTTSll^^rS-W) ~~~ ' WRITE (6,6)SIGMAA,SIG.MAB :  10 1  :  C C C  C A L C U L A T I O N OF  COEFFICIFNT"OF"CORRELATION R  X 3 = SX/XN Yli-SY/XN SC=o.o DO 1 0 2 I=1,N A ( I ) ~X { I )-XB 0 ( I ) = Y ( I-J-YB C( I ) = A( I ) * B ( I ) . 102  •CONTINUE SE=SC/(XN-1.0 . SAXX=0.0 DO 1 0 3 I = 1 , N  r_u 7_ LL 1  103  A  }  (  )  JJ  S A X x = S A~>TxTDTn CONTINUE SA xxp=SAXX/(XN-1 .0)  :  "  - 171 SBXX=0.0 DC lO'i 1 = 1 ,N E ( I ) = 3 ( I ) * B( I ) SRxx=SBxx + F( i ) • CONTINUE $Dxxp=SBxx/(XN-i.o} R=SF/SQRT ( SAXXP*SBXXP_) WRITE ( 6 , 4 ) R "  104  C C CALCULATION OF  *  C C  .  STUDENTS TEST T  U = R*R T = AB S ( R * S O R T ( X K - 2 . 0 ) / S Q R T ( 1 . 0 - U ) ) WRITE ( 6 , 5 ) T "V" CALCULATION OF  .  AVERAGE D E V I A T I O N DELTA  SD=0.0 DO 1 0 5 I=1,N _ _ _. SD=SO + A B S ( F ( D ) " 105 CUNT INUE ... DEL TA=SO/XN . ' WR ITF ( 6 , 1 9 ) DELTA • 2 FORMAT . (37H SUM OF THE SQUARES OF THE DEV I ATION=,E2 0.9/) 3 F 0 R M ATI I 2 H INTERCEPT = , 9X , E 1 5 .7 , 5X , 8H SLOPE = ,<3X,E15.7) 4 FORMAT(29H C O E F F I C I E N T OF CORRELATION =,E20.9/) 5 FCRMAT (17H STUDENT TEST T =,F20.9/) 6 F O R M A T ( ? 1 H ERROR IN INTERCEPT = , E 1 5 . 7 , 5 X 1 7 H FRROR IN SLOPE =, 1 El'5.7) 19 FORMAT (7H DEL TA=,E20.9) NR I T F ( * , 1 1 0 ) 110 FORMAT ( 6 2 H 0 * * * * THIS SECTION ONLY RELEVANT FOR ACTIVATION STUD IE IS ****//) SACT= ( A A - 1 0 . 3 1 8 7 ) --1=4.574 HACT=-ftS*0.004574 ; WRITE(f-.,7)HACT, SACT 7 FORMAT( 31 HOT HE ENTHALPY OF A C T I V A T I O N IS , G l 0 . 3 , 3 2 H K I LOGALORIES P IER MOLE PER 0GGPEF/3OH THE ENTROPY CF A C T I V A T I O N IS , G l 0 . 3 , 1 3 H E N T R 20PY U N I T S ) DM ACT = S I G M A B » 0 . 0 0 4 5 7 4 OSACT = SIG >AA*4.574 WRI TE{6,76)DHACT,OSACT 76 F O R M A T ( 1 X , 3 5 H ERROR IN ENTHALPY OF A C T I V A T I O N I S i E 1 0 . 5 , 2 1 UK ILCCALQ 1 R I E S PER M0LE/34H ERROR IN ENTROPY OF A C T I V U I O N I S , F 10 .5,13HFNTR0 2PY U N I T S ) RETURN * END t  V  Leaf 172 omitted i n page numbering.  - 173 -  SS1GN0N ALAN r-.i)?', P=20, PR10 = V ; %'iiOH LSvj.*oPLof 9 = - P L O I' R A T E O F I O N I Z A T I O N O F D M S O - T VS H . ' M I N U S I N - METHANOL IC DMSO __2_ __. _• _. 20.0 1.2.0 " -1 .00 -7.00"" " 7H MINUS 22L0G__i<L_ J.K. = RAT E JJF DMSO* ' ' METHANOL " ~ " ~ ~ " 12 _ 11.95 „77 .0391 _ _ __• "l4. 19 " -5 .4'i0~ ~" " '• ~ "' ~ ~ 14.74 -4.813 * 14.76 __-5,020 .__ _'• __ ~ " r i " . " T r - T,y w 15.85 -3.971 16.57 _ __-'3.0 30__ 16.'8 6 -3738d "" ~ T " 16.93 -3.371 _17.7 0 -2 .7 59 t  T 9 7 5 0 " - T r 5 0 2 ~ " "~~ .~ ' " " 19.70 -1.400 R_AJ E uF iOfU Li\ V, iuis uF_bMSO-T _VS _H._.M INUSu L06_A 12 "' """ " ' ' 11.95 -7.0391 • . __1 3j98 • b .4 10 ; ; _ 14.48 -4.8 13 14.50 -5.020 _15._2 9 _-?_.9Y9_ _ l-_ _ 15.39" '"" -379 71 ~~ —---•— - • -• - 15.96 -3.050 _ 16. 16 -3 . 388 16734 ~ * ' ~3~7'3 71 ' \ ~ ' 16.02 -2.759 _18._3 3 -1.302 ~ 16". 48 " -1.40CT " ~ ~ SENDF1LE z  $RuN *PLO_TQ BLANK"  4SIGNOFF.  :  J^^PLOT  - 174 -  RATF.  OF  IONIZATION  OF  DMSO-T  VS  H.MINUS  I N ~ME T H A N O I I C~"DTiSO  METHANOL 11 . 9 5 0 0 0 0  -7.039100  14.190000  -5.410000  14. 740000  -4.8  ]4 .759999  -5.020000  jZ?>.  _15 7J>000_0_ ?  13000 9J8999_  15 . 8 4 9 9 9 9  -3.9 71000  16.5 69992  -3.049999  16.8 5998 5  -3.3 0 0000  16.949997  -3.370999  17.699997  -2. 759000  19.5 0 0 0 0 0  -1.502000  19 . 6 9 9 9 9 7  -1  SUM  OF  THF.  INTERCEPT ERROR  IN  SQUARES  OF  TEST  THIS  T  00  0.27L073608E  OF OF  02  ONLY  ACTIVATION ACTIVATION  ENTHALPY E N T ROPY  OF  OF  IS IS  SLOPE ERROR  00  =  0.7 2 9 32 8 0 E  IN  0.2692217G-01  SLOPE  00  00  02  FOR  ACTIVATION  STUDIES  -0«334E-02KILOCALORIES -119.  ACT I VAT ION  A C T I V A T 1 O'N  0.385278523E  0.993264198E  =  RELEVANT  ENTHALPY I_N  0.44007 I4E  SECTION  ENTROPY IN  =  CORRELATION  00  THE  ERROR  DEVIATION^  0.13826996 IE  THE  ERR0 R  THE  - 0 . 1 5 6 3 9 0 IE-  INTERCEPT  DELTA= ****  OF  =  COEFFICIENT STUDENT  .400000  IS  IS  ENTROPY  PER  ****  MOLE  PER  UNITS  0 . 0 0 0 1 2K I L P C A L O R I E S 2 . 0 1 2 8 9 E N T RO P Y  UMTS  PER  MOLF  DEGREE  - 175 -  RATE 11.950000 -7.039100 13.980000 -5.410000 1.4.480000 -4.813000 14.500000 -5.020000 15.290000 - 3 . 9789 99 15.389999 -3.971000 15.959999 -3.049999 16.159908 -3.388000 16.339996 -3.370999 16.819992 -2.759000 _ 18. 32 9 9 87 U 50 2 000 18.4 799 9 h -1 .4 00 000 SUM OF THE SQUARES CF THE  OF  IONIZATION  OF  DMSO-T VS  > DFVI AT I ON-  0.358504772E  00  INTERCEPT = - 0 . 1 7 5 4 1 2 9 E 02 SLOPE = "ERROR IN INTERCEPT = 0 . 4 9 I 4 8 4 3 E 00 ERROR IN SLOPE C O E F F I C I E N T OF CORRELATION = 0 . 9 9 3 7 3 4 1 8 1 E 00 STUDENT TEST T .•= DELT A =  0. 2 8 1 1 5 5 7 0 1 E  0.U0043244E THIS  SECTION  H7MINUSQ LOG A  =  0.8780563E 00 0 . 3 1 2 2 9 9 LE-01  02  00  ONLY RELEVANT  FOR  ACTIVATION  STUDIES  ***»  THE ENTHALPY OF A C T I V A T I O N IS - 0 . 4 0 2 E - C 2 K I L O C A L C R I E S PER MOLE PER DEGREE THE ENTROPY OF A C T I V A T I O N IS -127. ENTROPY UNITS ERROR IN EN THALPY OF _ AC J_l V AT I ON IS 0.00014K I L PC AL OR I E S PER HOLE ERROR IN f.NTROPY OF ACT IV AT I ON I S 2 . 24 805 ENTROPY UNITS" PLOTTING K I L L TAKE APPROX. 2 MIN 56 SEC SUCCESSFULL PLOT. STOP EXECUTION  0 TERMINATED  SRUN *PLOTQ PAR=-PLOT EXECUTION BFGINS WHAT TYPE OF PAPER DO YCU WANT? REPLY PLOT F I L E IS OK "AND~ IS IN SYSTEM EXECUTICN TERMINATED  $SIGNOFF  "BLANK" OR  "LINED"  

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