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Mechanism of permanganate oxidation of alkanes, arenes and related compounds Spitzer, Udo Anthony 1972

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THE MECHANISM OF PERMANGANATE OXIDATION OF ALKANES, ARENES AND RELATED COMPOUNDS  BY  UDO ANTHONY SPITZER B.Ed., University of Saskatchewan, 1968 B.A., University of Saskatchewan, 1968 M . S c , University of Saskatchewan, 1970  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of CHEMISTRY  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA November, 1972  In  presenting  an  advanced  the I  for  shall  agree  s c h o l a r l y  by  his  of  t h i s  w r i t t e n  t h e s i s  in  at  U n i v e r s i t y  the  make  that  it  t h e s i s  purposes  f o r  p a r t i a 1• fu1filment  f r e e l y  permission may  r e p r e s e n t a t i v e s .  be  It  for  U n i v e r s i t y  Vancouver  8,  Dec.  of  B r i t i s h  Canada  18,  1972  by  gain  Columbia  for  the  understood  Chemistry  of  B r i t i s h  extensive  granted  is  f i n a n c i a l  of  a v a i l a b l e  p e r m i s s i o n .  Department  The  degree  L i b r a r y  f u r t h e r  t h i s  shall  the  reference  Head  be  requirements  Columbia,  copying  that  not  of  of  agree  and  of my  I  t h i s  or  allowed  without  that  study. t h e s i s  Department  copying  for  or  p u b l i c a t i o n my  - ii ABSTRACT Supervisor:  Professor Ross Stewart  The permanganate oxidation of alkanes and arenes has been studied in trifluoroacetic acid (TFA)-water.  This solvent system has the  unique advantage of being virtually inert to oxidative degradation and yet providing adequate solubilities for the reactants. The mechanistic investigation involved kinetic studies to determine the orders with respect to oxidant, substrate,and acid. Complementary techniques such as product studies, substituent  effects,  activation parameters, and isotope effects completed the mechanistic investigation.  The oxidation of several alcohols, aldehydes, and  ketones was also investigated to aid in the interpretation of the results. Because of the poor f i t of the kinetic data with the previously determined H function for TFA-water the H_ function was determined o R using the Hammett approach of overlapping indicators.  The identity of  the oxidants in the acidic medium was established by cryoscopic and spectrophotometric means.  It was found that the most vigorous  oxidant was permanganyl ion (MnO-+), with some contributing oxidation by both permanganic acid (HMnO^) and permanganate ion (MnO^ ) in the case of easily oxidized compounds such as alcohols, aldehydes, or enols. The mechanism of the acidic permanganate oxidation of alkanes (ethane to n-tridecane) was found to proceed via rate-determining homolytic carbon-hydrogen bond scission as depicted below.  -  RR1CH2 + Mn0 3 +  iii  *  [RR^CH + HMn03 ]  [RR^CH + HMnC>3+] [RR^H-O-MnC^H]  (I) I or (II) VTT I or (II) + Mn  ?  , slow , fast  (ID , fast  R^RCHOH + MnV >  RR-CHOH or RR C=0  V R R ^ O + 2Mn MnVI1 — >•  carboxylic  , fast acids  The -mechanism of arene oxidation was shown to proceed via ratedetermining electrophilic attack by permanganyl ion on the aromatic ring to yield ring degradation products.  Phenols are believed to  be intermediates in this process as depicted below.  fast  The mechanisms of the oxidation of alcohols, ketones,  aldehydes,  and formic acid were determined and shown to be consistent with mechanisms previously established under other conditions.  - iv The behaviour of two electrophiles, nitrosonium ion (N0+) and nitronium ion (N0- + ), generated respectively from sodium n i t r i t e and sodium nitrate, was examined in the TFA-water medium.  It was found  that the nitronium ions thus generated could be successfully used to carry out electrophilic aromatic nitrations in excellent yields but that the nitrosonium ions were inert. It was also determined that the tetra(n-hexyl)ammonium permanganate salt could be prepared in good yield and used as an oxidant for a variety of substrates in benzene solution.  1  ACKNOWLEDGEMENTS  The author wishes to express his sincere appreciation to Dr. Ross Stewart for his guidance during the course of this research and for his constructive criticism and suggestions during the preparation of this thesis. Grateful acknowledgement is also made to the Department of Chemistry of the University of British Columbia for providing f a c i l i t i e s to conduct the research and providing supplementary financial assistance.  Sincere appreciation is expressed to the National Research  Council for providing a scholarship for the entire duration of this investigation  from September 1970 to November, 1972.  Finally I wish to thank my wife, L e i l a , for encouragement and patience.  - vi -  TABLE OF CONTENTS Page 1.  2.  INTRODUCTION  1  1.1  Motives for the Investigation  1.2  Properties of the Trifluoroacetic acid-Water Medium  1.3  Acidity Functions  1.4  Behaviour of Permanganate i n Acidic Medium  7  1.5  Permanganate Oxidation of Organic Substrates  8  1.5.1  Oxidation of Hydrocarbons  8  1.5.2  Oxidation of Arenes  10  1.5.3  Oxidation of Alcohols  12  1.5.4  Oxidation of Ketones and Aldehydes  14  1.5.5  Oxidation of Formic Acid  15  L  2 .  4  1.6  Permanganate Oxidations i n Organic Solvents  16  1.7  Electrophilic Aromatic Nitration  17  1.8  Application of the Zucker-Hammett Hypothesis  18  SCOPE OF THE INVESTIGATION  3. EXPERIMENTAL  21  22  3.1  Reagents and Indicators  22  3.2  Kinetic Procedure i n Acid-Water Medium  31  3.3  Kinetic Analysis  34  3.4  Inorganic Product Study  3.5  Organic Product Studies  38 39  - vii Page 3.5.1  Permanganate Oxidations in TFA-Water  3.5.2  Nitration and Nitrosation Products in TFA-Water  39  43  3.6  Determination of Stoichiometrics  45  3.7  Freezing Point Depression Procedure  45  3.8  Determination of the H_ Function for TFA-Water  50  R  3.9  Vapour-Liquid Phase Equilibrium Study  56  3.10 Determination of pK for Permanganic Acid i n TFAH-0 and TFA-D-0  4.  61  3.11 Permanganate in Benzene  69  RESULTS AND DISCUSSION  75  4.1  Solvent System  75  4.1.1  B_ Function for the TFA-Water Solvent System  75  4.1.2  Identification of the Manganese VII Species  4.1.3  Generated in TFA-Water Mixtures  87  Nitration and Nitrosation in TFA  97  4.2  Products and Stoichiometrics  98  4.3  Oxidation of Alkanes  103  4.4  Oxidation of Arenes  126  4.5  Oxidation of Alcohols  141  4.6  Oxidation of Aldehydes  152  4.7  Oxidation of Ketones  155  4.8  Oxidation of Formic Acid  163  4.9  Oxidation by Permanganate in Benzene  165  - viii Page 5.  CONCLUSION  170  6.  SUGGESTIONS FOR FURTHER WORK  174  APPENDIX A  175  APPENDIX B  186  APPENDIX C  189  APPENDIX D  216  - ix LIST OF TABLES Table 1  Specifications of Compounds  2 3  Function Indicators for TFA-Water Organic Products from the KMnO^ Oxidations i n TFAWater Medium  4  Nitration and Nitrosation Products  5  Experimental Data for Stoichiometric Determinations for KMnO. Oxidations i n TFA-Water 4  6  Determination and Verification of  for Trifluoro-  acetic acid 7  Cryoscopic Data for Substrates i n Trifluoroacetic acid  8  Molarity of Weight % Solutions of TFA-Water  9  Vapour-Liquid Equilibrium Data for the TFA-Water System  10  Protonation Data for MnO ~ in Mediums of TFA-H 0 or 4 2 TFA-D 0 ' o  2  11  Spectral Properties of Tetra(n-hexyl)ammonium Permanganate i n Benzene  12  Properties of Tetra(n-hexyl)ammonium Permanganate ...  13  Permanganate i n Benzene, Oxidation Products  14  P R+  15  H Function  16  Temperature Dependence of pK^+  17  Thermodynamic Parameters for the Indicators used to  K  V  a  l  u  e  f ° Aryl Carbinols  s  r  for TFA-H_0  Determine H R  18  Activity of Water in Various Media  - xTable 19  Page pK for the Ionization of Permanganate Ion to Permanganyl Ion  96  20  Manganese Reduction Products from KMnO^ Oxidations ..  102  21  Order of Reactants Involved i n the Permanganate Oxidation of Alkanes in TFA-Water  105  22  Kinetic Isotope Effects i n the Permanganate Oxidation • of Cyclohexane  23  .  108  Comparative Reactivities of Methylene Groups i n Cycloalkanes Relative to those in the Corresponding n-Alkane  110  24  Comparative Reactivities of Cycloalkanes  110  25  Activity Coefficients i n Sulfuric Acid-Water Mixtures  116  26  Activation Parameters for Permanganate Oxidations in TFA-Water  27  118  * Calculated -a Values of Individual Carbon Atoms i n some n-Alkanes  121  28  Relative Ratios of Methylenes Present in n-Alkanes ..  123  29  Experimental Ratios for n-Alkane Oxidation Rates ....  124  30  Theoretical and Experimental Data for the Chromic Acid Oxidation of n-Alkanes  125  31  Order of Reactants Involved i n the Permanganate Oxidation of Arenes  32  Kinetic Isotope Effects for the Permanganate Oxidation of Arenes  33  132  Comparative Rate Ratios for the Permanganate Oxidation of Toluene, Ethylbenzene, and Cumene  34  127  130  Order of Reactants in the Permanganate Oxidation of Alcohols in TFA-Water  143  - xi Table  Page  35  Isotope Effects in the Permanganate Oxidation of Alcohols 1 4 7  36  Kinetic Isotope Effects in the Oxidation of Benzyl Alcohol  37  151  Order of Reactants in the Permanganate Oxidation of Ketones in TFA-Water  159  - xii LIST OF FIGURES Figure  Page  1  Freezing point apparatus  2  Indicator ratio plots for the  function  53  3  Vapour-liquid equilibrium study apparatus  58  4  Phase diagram of TFA-water mixtures  60  5  Log Q vs. IL^ for the ionization of MnO^~ in TFA-water  65  6  Log Q vs. H  66  7  Log Q vs. H  q  O  49  for the ionization of MnO^  in TFA-water  for the ionization of MnO^  i n trifluoro-  acetic acid-d^-deuterium oxide 8  9 10  67  Log Q vs. H for the ionization of MnO. o 4  in trifluoro-  acetic acid-deuterium oxide  68  Spectra of MnO^ with different cations and solvent..  70  Acidity functions in TFA-water  79  + 11  a  vs. pK^ for substituted triphenylcarbinols  12  Chromic acid oxidation of 2-propanol in TFA-water. Log k 2 vs. H and Particulation of potassium permanganate and sodium acetate in TFA Particulation of sodium nitrate and sodium n i t r i t e in TFA Spectra of side products (from the nitration of q  13 14 15  benzene) in acidic and basic media 16  88 91 92 99  Spectra of 1:1 mixture of ortho and para-nitrophenol in acidic and basic media  17  83  Log  •  100  vs. loglalkane] for the oxidation of a variety  of alkanes  106  - xiii Figure  Page  18  Log k- vs. H_ for the oxidation of a variety of alkanes  19  Substituent effects in the permanganate oxidation of ethane  20  107  Ill  Salt effects on the permanganate oxidation of cycloheptane  112  21  Oxidation rate vs. number of carbon atoms in n-alkanes  122  22  Log k- vs. log[arene] for the oxidation of toluene and benzene  128  23  Log k. vs. IL. for the oxidation of toluene and benzene  129  24  Salt effects on the permanganate oxidation of benzene  131  25  Substituent effects on the permanganate oxidation of benzene  26  134  Substituent effects on the permanganate oxidation of toluene  27  135  Revised p + vs. log k- / I ^ H P ^ o t ^  o r  t o  l  u e t i e s  -  Toluenes  considered as substituted benzenes 28  Log k- vs.  for toluene, benzyl alcohol, and  benzaldehyde 29  142  Log k- vs. log[alcohol] for the oxidation of a variety of alcohols  31  140  Decrease of oxidation rate with age of solution. Methanol in TFA-water  30  136  144  Variation of oxidation rate with acidity for the oxidation of alcohols in TFA-water  145  32  Salt effects on the permanganate oxidation of methanol  148  33  Log k- vs. log[aldehyde] for the oxidation of formaldehyde and benzaldehyde  153  - xiv Figure 34  Page Log  vs.  for the oxidation of formaldehyde  and benzaldehyde 35  154  Typical pseudo first-order plot for the oxidation of cyclohexanone  36  157  Typical zero-order plot for the oxidation of acetophenone  37  153  Log k^ vs. loglketone] for the oxidation of a variety of ketones  38  160  Log k^ vs. log[formic acid] for the oxidation of formic acid  164  39  Log k 2 vs.  for the oxidation of formic acid  40  Substituent effects on the permanganate oxidation of trans-stilbenes  in a medium of benzene  166  168  -  XV  -  ABBREVIATIONS AND SYMBOLS USED IN TEXT  i  a  a c t i v i t y of i t h component  c  constant of i n t e g r a t i o n  AG  change i n free energy  AH  change i n enthalpy  AS  change i n entropy  DPC  diphenylcarbinol  f.  a c t i v i t y c o e f f i c i e n t of i t h component  1  i  F  mole f r a c t i o n of i t h component  g  grams  h  Planck's constant  hr  hour  H  a c i d i t y function defined by protonation  o H  R  of primary a n i l i n e s  a c i d i t y function defined by i o n i z a t i o n of carbinols  k  Boltzmann constant  k n k,k'  rate constant, n = 0,1,2,3 p r o p o r t i o n a l i t y constants  kg  kilogram  °K  degrees K e l v i n  In  natural  log  base 10 logarithm  m  m o l a l i t y , moles per 1000 g of solvent  M  molarity, moles per 1000 ml of s o l u t i o n  logarithm  microliter ml  milliliter  min  minutes  - xvi n  number of particles  generated  n^  number of particles predicted by theory  N  normality, number of equivalent weights per l i t e r of solution  NMR  nuclear magnetic resonance  p^  pressure of ith component  s  seconds  TFA  trifluoroacetic acid  TPC  triphenylcarbinol  TPMC1  Triphenylmethyl chloride  vpc  vapour-liquid phase chromatography  r  reaction velocity  t  denotes transition state or activated complex  [ ]  denotes concentration in moles per l i t r e  1. 1.1  INTRODUCTION  Purposes of the Investigation In the past decade considerable attention has been focused on  environmental abuse by industrial pollutants.  The pollutant considered  as one of the most serious is o i l not only because of the large quantities usually involved but also because of the immediate and long term toxicity to the environment.  As a result of the economic  loss and public pressure considerable effort is being expended to understand how the ecosystem attempts to cope with sudden additions of large quantities of hydrocarbons. Researchers have found that certain micro-organisms can degrade 1-3 hydrocarbons by u t i l i z i n g them as a food source.  The i n i t i a l  approach of reseachers in this area was to u t i l i z e yeasts to profitably up-grade crude o i l s by the removal of waxy alkanes to yield some 2 marketable proteins for animal feed. Recently such micro-organisms have been recognized as potential o i l - s p i l l combatants which act by 3 degrading the o i l instead of dispersing i t .  Pilot batches have  shown promise, with the added advantage of not being toxic to shellfish, which is a serious drawback of dispersants. Presently, considerable interest is being focused on establishing the mechanism of this degradation process in order to maximize the  - 2 efficiency of these organisms.  The precise route of the degradation  is at present only speculative but some aspects of the process are now understood.  It is known that some micro-organisms u t i l i z e only  a specific series of hydrocarbons''" and that the attack occurs at the terminal carbon, sometimes involving incorporation of oxygen from the atmosphere, as ^ 0 studies have shown.^'^ Although the main purpose of this investigation was to establish the mechanism of the acidic permanganate oxidation of arenes and alkanes, we were aware of the possibility that this study might provide some fundamental information about the ways in which carbon-hydrogen bonds are cleaved in saturated hydrocarbons. elucidate  This information might help  the mechanism of microbiological oxidation of hydrocarbons.  Permanganate has been recognized as a versatile oxidant that is active in both acidic and basic media and is capable of oxidizing a wide variety of substrates.  5-7  c The mechanisms by which these  oxidations are performed are quite well understood with the exception of the oxidation of alkanes and arenes.  Very l i t t l e research has  been directed towards this problem, probably because of low solubilities of these substrates in media capable of dissolving permanganate. This study attempts to establish the mechanism of the oxidation of alkanes and arenes by acidic permanganate in a homogeneous medium.  1. 2 Properties of the Trifluoroacetic Acid-Water Medium Alkanes are known to have some solubility in water but the alkane content even in saturated solutions is very low, in the order of - 4 - 5 10 to 10  molar.  8  These concentrations are insufficient for kinetic  - 3 -  investigation by conventional means.  A co-solvent was required which  could dissolve both permanganate and the alkanes and yet be resistant to oxidation.  Trifluoroacetic acid (TFA) was found to be satisfactory  for this purpose.  TFA had the further advantage of allowing  variation of the acidity of the medium, since i t is a moderately strong acid with pK = -0.26. r a  9  Trifluoroacetic acid has been successfully used for a variety of reactions ranging from oxidations"^ to electrophilic aromatic substitutions."''"'"  Some of the properties of this solvent system are  briefly outlined below. Trifluoroacetic acid-water mixtures are not very strong protonating 12 media as shown by the work of Randies and Tedder. A maximum value 13 of H = -3.03 is reached in neat TFA (46% wt. sulfuric acid has o 14 sH = -3.03 ). The dielectric constant of neat TFA is _ - c = 8.3 + o 25 — O.I,"''"' which indicates that TFA is not a very strongly ionizing solvent. Conductivity studies confirm this but also show that salts containing ammonium cations are more dissociated than expected in this solvent, an effect which is thought to be due to hydrogen bonding."'""' Brown and Wirkkala"'""'" found TFA to be an exceptionally good medium for aromatic electrophilic substitutions such as nitrations and brominations. The bromination kinetics were investigated and found to be simple second order without any of the complications which were encountered when acetic acid was used. Several groups have observed that TFA can have strong solvent interactions with compounds'^'^ and intermediates.  i t has  been reported that neat TFA can solubilize salts by hydrogen bonding  - 4 to the a n i o n . ^  Aromatic systems such as nitrobenzene and anisole  13 showed considerable  C shifts by the carbon para to the substituent,  indicating strong solvent-solute interactions."^  Mechanistic  investigations on desilylations and detritiations of aromatic compounds in various mixtures of TFA-water indicated considerable  18 solvation of the cationic transition state.  Rapid deuterium incorpora-  tion was observed in the alkyl group of tert-alkyl  trifluoroacetate  esters when the ester was dissolved in TFA enriched with deuterium. This is believed to be due to the unusual stability of the alkyl carbonium ion generated from the alkyl group of the ester. 1.3 Acidity Functions In this investigation the  19  acidity function is determined for  the TFA-water medium and acidity functions are used to explain the rate accelerations observed with increased acidity.  In order to make  the discussion more meaningful a description of the acidity-function concept w i l l be given. 20 The H  q  function originally derived by Hammett and Deyrup  measures  the tendency of the solution to donate a proton to a neutral base.  This  function is defined by a series of substituted anilines by the following derivation. + ArNH^  K  BH + v  ArNH2  (BH+)  BH+  K  +  + H ,  Ar5= phenyl group  (B)  =  a  BaH+/aBH+  '  3  =  a c t i v i t l e s  - 5 KBR+  =  [B] f_a H + /[BH + ]f_ H 4 :  The definition is then made that h Q =  ,  f = activity coeficient  f^a^ /f^^_. +  This then separat  those terms hard to determine from those easily accessible by experimental measurements. pKBR+  pK  or  H  =  BH+  =  =  q  -log  H  o "  pKgj-f  =  l 0 g  +  -log[B]/lBB+] - log h Q  tB1 /1 BH"*"]  log  [B]/IBH ] +  Another function often used is  which measures the tendency of  21  the medium to ionize carbinols.  The function is derived in the  following manner. H-0  +  (Ar)-C  (Ar)-COH  (R+)  V  =  + H  (ROH)  ROHaH+/aH_OaR+ - r R O H ] f R O H a H + / [ R + ] f R + a H 0  a  h  R  =  f  ROHaH+/fR+aH20  a n d  \ =  pK_+ = -log[ROH]/[R+] - l o g h R  = pK-+ + log [ROH] /[R + ]  h  R  - 6 Usually these functions are determined by using a technique referred to as "the method of overlapping indicators".  The method  consists of taking an indicator which has measurable ionization in a medium which has a measurable pH. Then the assumption is made that IL^ = pH in this very dilute region. then be calculated.  The pK for this indicator can  This pK value is used to then determine  stronger mixtures by measuring the new ionization ratio  for  ([B]/[BH + ]).  Eventually this indicator w i l l no longer be useful, which is arbitrarly defined to be when 0.1 < [B]/[BH+] < 10.  To then extend  a weaker  indicator has to be used which has measurable ionization in some solution of known H^, i . e . i t overlaps with the previous indicator. The pK can then be calculated since H is known and the new indicator x ratio can be measured. H  This overlapping process is continued until  is established for the entire medium range, or until no more .  suitable indicators are available to extend H . x It is important that only those indicators are used where the overlap is good and, most important, that the indicators have parallel responses to the medium changes, i . e . log f_. / f „ u = log c ( f „ /f D t l )» B^ 2 2 2 c = a constant. This condition must be f u l f i l l e d otherwise H has x no meaning because the overlap method uses  from the previous  indicator to determine pK of the next indicator.  This essentially  forces H (indicator 1) to be equal to H (indicator 2), -log  f B aH+/fBH  = "log f B aH+/fBH *  T h i S  c o n d i t i o n  c a n  b  i.e. e  tested  by checking to see that log [3]/[BH+] vs. H x plots give lines that are parallel for overlapping indicators. the deviant indicator should not be used.  If deviations are severe  - 7 1.4  Behavior of Permanganate in Acidic Medium The distinctive absorbance by permanganate ion has been shown to  22 23 be insensitive to solvent changes and cation variation, ' but i f the medium is made very acidic a distinct spectral change is observed from purple to light green  24  ^  m  a  x  28 29 ° ^ 8 r e e n species is 458 nm ' ).  The cause of this spectral change has not yet been resolved.  Symons  25 et a l .  have suggested from conductivity measurements that the spectral  change is due to the following process, KMnO/ + 4  3H.S0. 2 4  *• —  0oMn0S0_H + 3 3  H_0+ + 3  K+  +  2HS0." 4  26 but Royer  interpreted similar conductivity measurements and cryoscopic  data to be consistent with the reaction, KMnO. + 4  3H„S0. 2 4  -«—  K+  + MnO_+ 3  +  Ho0+ 3  +  3HS0." 4  27 Stewart  has suggested that these interpretations may be reconciled  by considering the following equilibrium. 0_Mn0S0oH 3 3  »• —  MnO.+ 3  + HSO." 4  This spectral change has been observed in partially aqueous media where 28 29 the process is taken to be a protonation. ' H+  +  MnO." 4  -—  HMnO. 4  - 8 -  Syraons et a l .  28  has established this pK& value to be -2.25 in perchloric 29 acid using H q but Stewart and Mocek found a value of -4.6 in sulfuric acid also using H . The difference in pK values has been o a attributed to the changes in the medium but there is considerable inconsistency in the interpretation of the spectral changes.  In  + 26 strongly acidic media the green color is attributed to MnO-  or  25 to 0-MnOSO-H  but in the more aqueous region permanganic acid is  thought to cause the green color. In this study i t w i l l be demonstrated that only three manganese species are present in TFA-water mixtures, namely permanganate ion (MnO^ ), permanganyl ion (MnO-+) and permanganic acid (HMnO^), and that their proportions depend upon the amount of TFA in the medium. 1.5 1.5.1  Permanganate Oxidation of Organic Substrates Oxidation of Hydrocarbons Very l i t t l e is known about the permanganate oxidation of alkanes  probably because of difficulties encountered as a result of their low solubility in aqueous media.  Some researchers have avoided this 30 31  problem by introducing inert solubilizing groups such as carboxyl.  '  It was found that oxidations of such substrates as 4-methylhexanoic acid could be carried out in neutral or basic media.  However the 30 31  carboxyl group was shown to participate in the oxidations.  '  These  oxidations were believed to proceed via hydrogen atom abstraction to give a radical pair trapped in a solvent cage.  The radicals quickly  recombine to give an ester which can decompose in several ways, as outlined b e l o w . ' " ^  -9 -  R„CH + MnO. 3 4  —>  [R-C-MnO.H ] 3 4  R3C-0|Mn03H" + H20 —>  R C40-Mn03H~  —> R 3 C + + MnV  or  (*0-MnO„H 3 R-C-CH2CH2  —*-  R J C=0  R„C-0-MnO„H 3 3  R3COH + MnV  or  3  —»•  R-C~CH 2 CH 2 R  0  C=0  0 18 The major pathway is thought to be through attack by water since 0 studies show that labelled oxygen from permanganate is found present 18 in the hydroxy group.  The amount of  0 incorporation was a minimum  31 of 25%. Although there are no further reports on the permanganate oxidation of alkanes the chromic acid oxidation of alkanes has been 33—36 well established.  Some of the mechanistic features are:  35 The rate law was found to be r = k[alkane][Cr0 3 ]h Q . A kinetic isotope effect of k /k = 2.5 was found for the ri D 36 oxidation of 3-methylheptane. (c) Hydrogen atom abstraction appears to occur in the rate o o 3^ determining step since the ratios of 1 :2 :3 were 1:110:7000, (a) (b)  similar values to those found for free-radical bromination. (d)  The methylenes in n-alkanes appear to be equivalent since  the rates increase only by a s t a t i s t i c a l factor for the series of C  4 H 10'  C  7H16»  C  9 H 20' C 11 H 24' C16H34'  a n d  C  22H46*  35  - 10 -  (e)  In cycloalkanes the transition state is thought to involve a  tri-covalent carbon rather than a penta-covalent carbon since the logarithm of the oxidation rates parallel the logarithm of the 33 solvolysis rates of corresponding tosylates. Although Rocek and Mares found that the methylenes in n-alkanes 35 were identical in their reactivity to chromic acid, other researchers have reported that in processes such as nitration the terminal methylenes 37 38 react faster than the internal methylenes.  '  Alkanes appear to be oxidized via a radical mechanism, not only in the case of chromic acid oxidation but also in the photochemical 39 reaction with oxygen. 1.5.2.  Oxidation of Arenes  From a variety of reports on the use of permanganate to oxidize arenes  40-43  only Cullis and Ladbury  44  and Lee and Singer  45  to study the mechanism of this oxidation in acidic media.  attempted Cullis and  44 Ladbury  were the f i r s t to attempt a thorough study of the oxidation  of toluenes in a medium of 54.2% w/v acetic acid-water.  Unfortunately  second order kinetics were not maintained and i n i t i a l rates had to be used.  The complicated kinetics were thought to be due to the participation  of intermediate oxidation states of manganese.  They reported that  some ring degradation occurred but that the major products, benzoic acid and benzaldehyde, resulted from side chain oxidation.  Electron-  donating substituents were observed to accelerate the rate and also to increase the degree of ring decomposition.  Salt effects were only  observed i f salts were added that interacted with higher oxidation states of manganese.  - 11 45 Recently Lee and Singer arene oxidation.  attempted to clarify the mechanism of  They used p_-toluenesulfonic acid to avoid the  solubility problems and perchloric acid to avoid the kinetic problems thought to be caused by the acetic acid.  Although the kinetics were  no longer complicated the sulfonate group caused important mechanistic changes.  They found that the order with respect to permanganate  changed from first-order to zero-order at higher acidities.  The  mechanism proposed is the following. p_-toluenesulfonate anion [arene]  k  l  k  -l  + VII [arene H ] + Mn  2  •*•  p_-toluenesulfonate + [arene H ]  *•  products  Using the steady state approximation on [arene H*"] the following rate law results.  r  =  k-k-[arene] [Mn V I *] k_- +.k 2 [Mn V I 1 ]  It was stated that the observed order shift could be explained as follows.  If, k_-^>  k-fMn  VTT  ],  If, k_- <$C k - [ M n V I 1 ] ,  r  VTT = Kk-[arene][Mn]  r = k.farene]  - 12 -  At higher acidities the protonation of the p_-toluenesulfonate ion became the rate-determining step. In general the oxidation of arenes seems to have a rate law of the form, r = kfarene][MnO^ ] in the acidic region but the exact mechanism is not completely clear. The alkaline permanganate oxidation of benzylic tertiary carbon40 42 43 hydrogen bonds to alcohols is quite well established.  '  '  The  process is known to have a rate law of r = k[arene][MnO^ ] in the dilute alkaline region ([OH ] < 0.01) but has the form of r = kfarene]42 [MnO^ J[OH ] in more concentrated a l k a l i . There is s t i l l some dispute as to how the hydrogen is abstracted in the rate-determining step. 42 Heckner et a l . have interpreted their data and their observed isotope effect of = 7.8 to indicate hydride abstraction but 43 Brauman and Pandell,  who observed an isotope effect of \L^/k^ =11.5  and some retention of configuration, interpret their data in terms of hydrogen atom abstraction. 1.5.3.  Oxidation of Alcohols  Since this investigation is primarily concerned with the permanganate oxidation of arenes and alkanes a l l subsequent compounds considered w i l l only have the pertinent features of their oxidation mechanisms outlined. Alcohols have been subjected to extensive mechanistic investigation in acid, neutral, and basic media.  Some of the features of the  oxidation mechanism are outlined below, (a)  Basic media (i)  In basic media the catalysis observed is due to the generation  - 13 -  46 of an alkoxlde ion from the alcohol. form r = (ii)  47 '  The rate law has  the  k[alcohol][Mn0 ~][0H~]. 4  The observed s a l t e f f e c t s are consistent with a  bimolecular  t r a n s i t i o n state r e s u l t i n g from the alkoxide ion and permanganate ion. ( i i i ) Carbon-hydrogen bond cleavage i s involved i n the r a t e determining step since substantial deuterium isotope e f f e c t s are observed.  These can become exceptionally large i n f l u o r i n a t e d  alcohols, e.g. k^/k^  = 16 for the oxidation of l-phenyl-2,2,2-  t r i f luoroethanol.^ (b)  A c i d i c media (i)  In a c i d i c medium the rate accelerations observed with  increased a c i d i t y are believed to be due  to the generation  of  48-50 permanganic a c i d . (ii)  The rate-determining  scission.  step involves carbon-hydrogen bond  Isotope e f f e c t s of k^/k^  the oxidation of cyclohexanols. hexanols e f f e c t s of ^/^-p ( i i i ) There was intermediate  =  - 2.4-3.2 are observed for In the case of 2-carboxycyclo-  7-8 were reported."''*  no evidence found  f o r the p a r t i c i p a t i o n of  oxidation states of manganese i n the  rate-determining  step f o r the oxidation of benzyl alcohol to benzaldehyde i n 52 p e r c h l o r i c acid-water mixtures. (iv) In most cases the rate law follows H « ^ 50,52 xri(p_-tolyl)carbinol was  48 exceptional i n that i t followed H .  dependence upon H  K  was  triphenyl c a r b i n o l .  53  Similar  found for the chromic acid oxidation of  - 14 48 (v)  Stewart and Banoo  found that the permanganate oxidation  of d i - and t r i - p h e n y l carbinols involved the i o n i z a t i o n of the carbinol to the carbonium ion which then formed a permanganate ester.  This ester then decomposed to products possibly v i a a  c y c l i c process s i m i l a r to that accepted for chromic acid 54 55 oxidations of alcohols. ' 1.5.4.  Oxidation of Ketones and Aldehydes  Ketones are subject to f a c i l e oxidation only i n t h e i r enol form. As such they are r a p i d l y oxidized i n a l k a l i n e and a c i d i c m e d i a . U n d e r most conditions permanganate oxidizes double bonds by c i s addition to yield cis diols,  57 58 ' but when the medium i s g l a c i a l a c e t i c acid the 59  major products are a-diketones (yields up to 80%).  Enolic double  bonds are not always degraded by c i s addition since Wiberg and G e e r ^ have presented evidence to show that the enolate ion generated from acetone reacts by electron transfer i n the following manner. 0~ 0 CH -C=CH. + 3 2  MnO ~ 4  0  s  l  o  w  >  CH--C-CH • 3 2  +  MnO. " 4 2  The oxidation pathway f o r acetone can be shown as a attack, with 60 subsequent carbon-carbon bond cleavage, 0 II CH -C-CH 3  3  0 II CH -C-CH 0H  —  3  CH -C0 3  2  2  or  0 II Ct^-C-CHO  —*  °2  C - C 0  2  —+  0 II Cl^-C-CO^  - 15 or i n a more general form for a l l enolizable ketones as; 0  0  H  II OH" I R-C-CHR' R-C=CRor H  Mn  VI1  » RCO-H + R-C=0  +  OH  R C=0  > etc. or H  Aldehydes are readily oxidized i n any medium, yielding chiefly the respective acid although some carbon-carbon bond cleavage may also occur, presumably v i a the enol."^  In basic media the reaction i s  believed to go v i a the aldehyde hydrate anion.  61 62 '  Wiberg and Geer  have shown that only such an intermediate can explain the incorporation of  18 62 0 from the medium i n the oxidation, of furfurals.  In basic and  acidic media the oxidative schemes have been found to be the following;  basic route:  R-CHC-H + OH Z  R-C-H —  Jf  '  OH  R_C=C-H  acidic route:  f  R-CH-C-H  I  • R-CHCO-H _  2.  »• carbon-carbon bond cleavage products  M  V  I  1  —  »  R-CHCO-H  Jf R2C=C-H  1.5.5  *  carbon-carbon bond cleavage products.  Oxidation of Formic Acid  The permanganate oxidation of formic acid to carbon dioxide has been thoroughly studied and the mechanism in both acidic and basic  - 16 solutions is well established.  63 6 A '  In aqueous solution more basic  than pH 5 the reaction clearly involves the formate ion and the  65—67  permanganate ion.  Carbon-hydrogen bond cleavage is taking place  in the transition state since isotope effects near 7 were observed.^  ^  Q = 2.7 (pH not  A substantial solvent isotope effect of k_  66  specified) was reported by Taylor and Halpern,  in contrast to the  value of kp -/k^ _ = 0.92 (again pH not specified) observed by Bell and Onwood.  64  2  2  There is some oxygen transfer from the permanganate to the  formic acid during the oxidation, since  18  0 from permanganate was  found in the product, carbon dioxide. As the medium becomes more acidic the rate decreases due to the  63  decrease in the concentration of formate ion  but when the acidity is  increased beyond 20% sulfuric acid the rate increases, which is believed  68 to be due to formation of permanganic acid.  Further rate increases  are observed at acidities beyond acid and these are VII - 50% sulfuric VI HCO+ Mn * CO-' + Mn , slow believed to be due to formation of permanganyl ion (MnO-+). TheT oxidation as successiveVIone-electron transfers VIIis visualized VI V CO+ Mn or Mn CO. + Mn or Mn , fast according to the following scheme.  1.6  Permanganate Oxidations in Organic Solvents Recently two methods have been described which extend the use of  permanganate as an oxidant into organic solvents.  Sam  and Simmons 69  - 17 -  were able to prepare crown polyether complexes of permanganate which are soluble i i organic solvents.  These complexes can be used in situ  or can be isolated and then used in some other solvent to achieve a 70  wide variety of oxidations. phase-transfer  Starks  was able to use the method of  catalysis to readily oxidize 1-octene to heptanoic acid  (author states hexanoic acid, possibly a printing error).  This  process involves the use of quaternary alkyl ammonium salts to extract the permanganate anion into the benzene layer.  In this investigation  Starks' method^ w i l l be extended by examining the oxidation of alcohols, aldehydes, and stilbenes by permanganate in benzene. 1.7  Electrophilic Aromatic Nitration One of the oxidants that might be generated in acidic media is  permanganyl ion (Mn0.j+). This species could attack the aromatic rings of arenes in a manner similar to that of the electrophile, nitronium ion (N0 2 + ).  Because of this possibility some of the features of  electrophilic aromatic nitrations w i l l be presented. Electrophilic aromatic nitrations are known to follow the function,  72 73 21 ' ' more precisely  + log a^ Q ,  73  carbon-hydrogen  bond cleavage does not occur in the rate-determining step since only very small (secondary) isotope effects are observed.^4 ^ nitration rates show some solvent dependence.^  The  The rate-determining  process is generally agreed to be electrophilic attack,^ ^ which 78  is followed by fast proton-loss to the solvent. Small amounts of phenolic products have been isolated from the  - 18 79  nitration products of toluene.  The mechanism of the process  yielding phenols is at present unknown.  It could be possible that the  complex resulting from 0 attack by nitronium ion can be hydrolyzed to yield phenols.  The following scheme accounts for the known facts and  proposes a route to the observed phenols. H20  HN03 + H  N attack,  + NO,  +  N02 ,  fast  +  slow (ArHN02+)  [ArHN02+]  ArN02  +  H,  fast  0 attack,  0-N=0  0-N=0  R-<^^)O-N=0+ H O 2  OH +  NO.  OH OH  + H  + HNO,  + H + , v. fast  NO-  1.8  Applications of the Zucker-Hammett Hypothesis An empirical test was proposed by Hammett and Zucker by which one  could determine whether an acid-catalyzed reaction proceeds via an A - l  -  or A-2 mechanism.  80s.  19 -  They proposed that i f log k- vs -H gives  linear plots with close to unit slope that an A - l mechanism is indicated but i f log k- vs log [H+] gives linear plots with close to unit slope that an A-2 mechanism is operative.  Although some  known A - l and A-2 reactions were found to be consistent with this 80b c r i t e r i a exceptions were reported  thus limiting the u t i l i t y of the  hypothesis. One feature of their hypothesis remains potentially very useful. This is the conclusion that when log k- vs -H gives linear plots with unit slope the ratio of the activity terms in the rate expression changes in the same way as does the ratio of the activity terms of the indicators used to establish the acidity scale, (k- is the experimentally determined rate constant, corrected only for substrate concentration). manner:  This postulate can be generalized in the following  For a general case of a bimolecular reaction k  A +  B  2  •  products,  k. is rate-determining  the measured rate law is r = k-[B][A] where k  l  =  k  2fAfB/ft'  If log k1 vs -H gives a linear plot this means that h = f f R / f f and i f h x is defined as h x = aH+f_ /f_ X  X  R +  then f A f f i / f +  = a^f.  /f_ X  R +  .  X  This reasoning in i t s e l f does not clarify any mechanistic features but i f some of the activity coefficients are known practical use can be  - 20 made of this relationship.  This relationship can be used to evaluate  a proposed mechanism by seeing i f the activity terms predicted do in fact show parallel solvent changes to those of the indicators used in setting up the acidity scale. In this investigation three different oxidants could be generated, which leads to at least three different mechanisms.  The choice made  between the three mechanisms listed below pas based on how log correlated with either H or L , The three mechanisms are: o R (a) Permanganate ion as oxidant. •/  MnO^  +  substrate  -—*•  r = kV[Mn04-][S] f  X  »•  products  f /f 4  (b)  Permanganic acid as oxidant.  MnO ~ + 4  H+  HMnO^ +  S  HMnO, 4 K+  t X  k+  *  products  r = KK+k+[Mn04-][S] V f M n O , - f S / f t 4 (c)  Permanganyl ion as oxidant  MnO " 4 M n 0  3  + +  2H+  s  Mn0_+ 3 7 ^  x  r - KK+kf[MnOA-][S] a j + f ^  /  + Ho0 2 >  4  products  f/aH  2  f+  - 21 -  2.  SCOPE OF THE INVESTIGATION  The purpose of this investigation is to determine the mechanism of the oxidation of alkanes and arenes by permanganate.  The medium  used to achieve the necessary solubilities was trifluoroacetic acidwater.  A pseudo first-order approach was used to determine the order  of the oxidant.  Concentration variations of substrate and acidity  established their respective orders.  Complementary techniques such as  product studies, substituent effects, activation parameters and isotope effects completed the mechanistic investigation.  The oxidation  mechanism of several alcohols, aldehydes, and ketones was also investigated to aid in interpreting the results obtained with alkanes and arenes. As a result of the poor f i t of the kinetic data with the previously determined H function the H function was determined for the medium o R of TFA-water.  The identity of the oxidants in this acidic medium was  established by spectrophotometry and cryoscopic means. Since the arene oxidation showed similarities to electrophilic aromatic substitution reactions the behavior of several electrophiles such as nitronium and nitrosonium ions was examined in the TFA-water medium.  -22 -  3. 3.1  EXPERIMENTAL  Reagents and Indicators Most of the compounds used for this investigation were available  commercially.  The reagents, their source, method of purification  and purity are presented in Table 1.  The indicators used to establish  the H acidity function along with pertinent physical data are R presented in Table 2. The trifluoroacetic acid (TFA) used throughout this investigation required special care in purification to minimize the decomposition of the oxidant, which was found to be due to minute impurities present in the acid.  This procedure, and the synthetic routes followed for  the preparation of the remaining compounds, are outlined below.  Trifluoroacetic acid:  The commercial product supplied by Eastman  could not be sufficiently purified by d i s t i l l a t i o n through a 12" Vigreaux column.  It was found that i f the acid was d i s t i l l e d from  small amounts of potassium permanganate, approximately 0.5 g per kg of acid, that the fraction collected between 7 1 . 0 - 7 1 . 5 ° had no significant permanganate decomposition for aqueous solutions less than 5 M and gave only small blank corrections, ranging from 1-10% of the observed rate, for solutions 5-12 M. This method of using small amounts of potassium  Table 1.  Specifications of Compounds.  Compound n-Pentane iso-Pentane n-Hexane n-Heptane n-Octane n-Nonane n-Decane n-Undecane n-Dodecane n-Tridecane Cyclopentane Cyclohexane Cycloheptane Cyclooctane Methanol Ethanol 2-Pentanol 3-Pentanol Formaldehyde 2-Pentanone 3-Pentanone Cyclohexanol Cyclohexanone Acetone Formic acid Propionic acid 2,4-Pentanedione Propionitrile Nitroethane 1,1,1-Trichloroethane  Source E E M E A F A A E A A E A A B F A A F E E E E E E F E E M F  Purification method v.p.c. column 1 used as received spectral grade dist. 9 7 . 5 - 9 8 . 0 ° used as received dist. 149.5-150.0° used as received v.p.c. column 1 dist. 215-216° used as received spectral grade U.A.R. spectral grade U.A.R. U.A.R. U.A.R. spectral grade U.A.R. distilled v.p.c. column 1 it  II  it  37.4% standard soln. v . p . c . column 1 II  II  II  dist. 158.0-158.5° dist. 151.0-151.5° spectral grade U.A.R. dist. 101.0-101.5° U.A.R. dist. 137.0-138.0° v.p.c. column 1 II  tt  II  II  II  II  Purity >99.8% >99.8% >99.8% >99.8% 99.5% 99.5% 99.6% 99.7% >99.8% >99.5% >99.8% >99.8% >99.7% >99.7% >99.9% >99.8% >99.8% >99.8%  -  >99.8% >99.8% 99.5% 99.8% >99.8% >99.8% >99.8% 99.5% >99.8% >99.8% >99.8%  Literature  Table 1 (Continued) Compound  Source  E Toluene Ethylbenzene E Cumene E t- Bu ty lb en z ene E Benzyl alcohol E Benzaldehyde E Acetophenone E TrifluoroacetoK & K phenone Benzene F Chlorobenzene E Fluorobenzene E Nitrobenzene E Anisole E 2-Phenyl-2-propanol A 2-Phenylethanol A 1-Phenylethanol A p-Bromotoluene E m-Bromotoluene F m-Chlorotoluene K & K KMnO 4 B Ethane M Propane M Butane M neo-Pentane FLUKA MSD Cyclohexane-d^2 Methanol-d^ MSD Deuterium oxide MSD Toluene-a-d3 MSD Toluene-ds MSD H 2 S0 4 B  Purification method dist. 109.0-109.5° v.p.c. column 1 II II  II II  ti  II  dist. 203.0-204.0° dist. 173.5-174.0° v.p.c. column 1 II  tt  ti  spectral grade U.A.R. dist. 129.0-130.0° dist. 8 2 . 5 - 8 3 . 0 ° dist. 207.0-208.0° dist. 150.0-150.5° U.A.R. U.A.R. U.A.R. recrystallized dist. 180.0-180.5° dist. 158.0-158.5° Baker analyzed U.A.R. U.A.R. U.A.R. U.A.R. U.A.R. U.A.R. U.A.R. U.A.R. U.A.R. U.A.R.  Purity >99.8% >99.8% >99.8% >99.8% >99.8% >99.8% >99.8% 99.5% >99.8% >99.8% >99.8% >99.8% >99.8% 99.5% 99.0% 99.5% >99.8% >99.8% >99.8% 99.5% 99.99% 99.5% 99.5% 99.92% 99% D 99% D 99.8% D 98% D 98% D 97.4%  Literature  — — — — 132°81a 85.2°81b 210.85°81c 155° 81d  — — —  184°81e 1 6 2 o81f  — — — — — — — — — — —  Table 1 (Continued) Compound  Source  Benzoic acid E p-Nitrotoluene E m-Nitrotoluene E p-Methylbenzoic acid E m-Methy-benzoic acid E Tetra-n-hexylammonium iodide E m-Nitrobenzyl alcohol E m-Methoxylbenzyl alcohol A p-Chlorobenzaldehyde E m-Me thylb enzaldehyde K &K p-Nitrobenzaldehyde K & K Benzophenone E cis-Stilbene K & K trans-Stilbene F Tolan A p-Nitro-transstilbene A p,p'-Dinitro-transstilbene A p,m'-Dinitro-transstilbene A Sodium nitrate B Sodium n i t r i t e F  Purification Method sublimed recrystallized dist. 230.0-231.0° recrystallized  Purity  Literature  mp 122.0-123.0 mp 50.0-51.0°  C  mp 178-180° mp 11.0-112.0°  U.A.R.  - 81g o81h 227 ° 181° lll-113° 12  0  52  811  81i  175-180° at 3 mm  81J  dist. 210.0-212.0° 10 mm  252  dist. 254.0-256.0° recrystallized dist. 201.0-202.0° recrystallized II  U.A.R. U.A.R. recrystallized  U.A.R. U.A.R.  mp 47.0-48.0°  o 8 1 k  47°91 201°  81m  mp 104.0-105.0° mp 48.0-49.0° fp 4-5° mp 121.0-123.0° mp 60.0-62.0°  106° 49° 81o 5-6° P 124° P o81q  mp 155.0-158.0°  155°  81r  mp 296-299°  288°  81a  mp 220-221° analar grade 96.6%  2]_y o 81s  8 1 n  81  81  6 2  5  to  Table 1 (Continued) A l l compounds except the l a s t 31 were checked by v.p.c  using column 1.  Column 1 - 20% Carbowax 20 M on f i r e b r i c k - 20' x 3/8" Column 2 - 20% Dionylphthalate on Chromosorb - 20' x 3/8" u. A.R. E F K & K A MSD B M  -  used as received Eastman Chemical Co. Fisher S c i e n t i f i c Co. K & K Laboratories Ltd. Aldrich Merck, Sharp and Dohme J.T. Baker Co. Matheson of Canada Ltd. > i ho  I  ON  Table 2. No.  IL, Function Indicators for TFA-H-0 Compound  Experimental mp r  Literature  max  log e °  81.0-82.0°  480  5.04  74.0-76.0°  487 427  4.93 4.67  111.0-113.0°  495 410  4 4,4',4"-TrimethylTPC 5 4-Methoxy TPC  91.0-92.5°  446  4.88 4.56 4.97  72.0-74.0°  469 394  4.82 4.38  6  4,4'-Dimethyl TPC  78.0-78.5°  451  4.81  7  4,4'-Diethoxy DPC  56.0-57.0°  506  5.22  163.0-164.0°  425 403  4.60 4.60  91.0-93.0°  460  502  93.5-94.0°90  465 2 1  96.5-98.0°  436 388  4.51 4.47  95.5-97.0°91  454 2 1  1 2 3  4,4',4"-Trimethoxy TPC 4,4'-Dimethoxy-4"methyl TPC 4,4'-Dime thoxy TPMCL  8 Triphenylcarbinol 9 10  4,4',4"-Trichloro TPC 4-Nitro TPC  A  mp  log £  max  81.0-82.0 ,21  Source  485 21 478 82  5.02 21 4.94 82  synthesized synthesized  500 94.0'  ,83 82,84  60.0 82.0°85  75.0°86 75.5-76.5 .87 80.0' •88  452  21  476 21  456 505  164-165°81t  21  87 87  431 2 1 ,425 8 2 404 2 1 ,410 8 2  5.47 5.03  21  Aidrich  21  lab stock  N  21  lab stock  -4.44 87  lab stock  89  lab stock  4.75  5.10  4.60 2 1 ,4.64 8 2 4.60 2 1 ,4.63 8 2 21 5.01"  |  lab stock lab stock lab stock  i  Table 2. 3  (Continued)  References 21, 87, 89 used a medium of H-SO^-H-0. Reference 82 used a medium of CF-CO-H-CCF-CCO-O. Values f o r the respective carbonium ion generated A l l compounds were checked by NMR for substituent i d e n t i t y  TPC  =  TPMCL DPC  =  triphenylcarbinol =  triphenylmethyl diphenylcarbinol  chloride N3 oo  - 29 -  permanganate avoided a problem also noted by Lee and Johnson.  It  was observed that a green species contaminated a l l of the d i s t i l l a t e when large quantities of potassium permanganate were used.  Water:  The water used for the determination of the pK of permanganic  acid and the H_ function was redistilled from basic permanganate through a 14" Vigreaux column.  For the kinetic analysis d i s t i l l e d  water was found to be satisfactory, causing no further permanganate decomposition.  Benzyl alcohol-q-d-;  This compound was prepared by the lithium  aluminum deuteride reduction of benzoic acid according to the following procedure.  A 100 ml solution of dry ether containing 0.01 moles of  benzoic acid was carefully added over a period of one hour to 0.008 moles of lithium aluminum deuteride suspended in 100 ml dry ether.  The  resulting mixture was allowed to reflux for a period of 14 hours.  The  solution was then quenched by the careful addition of 5 ml 95% ethanol followed by 10 mi water.  The complex was destroyed by the addition  of 50 ml 10% sulfuric acid.  The ether layer was recovered, washed  once with 50 ml 1 N sodium hydroxide, twice with 50 ml water and then dried over anhydrous magnesium sulfate. and flash evaporated.  The ether layer was recovered  The residue was purified by v . p . c . using a 20%  carbowax 20 M on firebrick column 20' x 3/8".  The yield was 20% of the  desired alcohol with an isotopic purity of 95% as determined by NMR. The i n i t i a l deuterium content of the lithium aluminum deuteride was 96.8%.  - 30 4,4',4"-Trimethoxytriphenylcarbinol: and V i l l i g e r  92  The method outlined by Baeyer  was used with minor modifications from Vogel.  93  To  a Grignard solution prepared from 0.10 moles of magnesium turnings and 0.10 moles of 4-bromoanisole i n 300 ml dry ether was added 0.10 moles of 4,4'-dimethoxybenzophenone dissolved in 100 ml dry ether at a rate to keep the ether refluxing.  The mixture was refluxed a  further two hours and then poured over a slurry of 750 g ice and 25 ml concentrated sulfuric acid.  Twenty-five grams of ammonium chloride  was then added to further decompose the magnesium complex.  The  ether layer was recovered, washed successively with 100 ml water, 100 ml 2% sodium bicarbonate, and 100 ml water.  The ether was removed by  flash evaporation yielding a viscous red o i l .  This o i l was steam  d i s t i l l e d and then dissolved in hot n-heptane.  Recovery of the  desired product was extremely d i f f i c u l t and the following somewhat primitive method was found successful.  The hot solution of n-heptane  was slowly cooled, whereupon a red substance oiled out.  Upon standing  for a day crystals were observed growing from the red o i l .  Several  seed crystals were choosen to impregnate a string, the solution was reheated to dissolve a l l substances, and then the seeded string was suspended in the solution which was allowed to cool slowly. Considerable crystal growth occurred on the string and beaker walls. These pale orange crystals were further readily recrystallized from n-heptane yielding 30% of the white product mp 8 1 . 0 - 8 2 . 0 ° , mp 8 1 . 0 - 8 2 . 0 ° . 2 1  literature  - 31 4,4'-Dimethoxy-4" - methyltriphenylcarbinol:  This compound was prepared  in a similar manner to that described for 4,4',4"-trimethoxytriphenylcarbinol with the exception that 4-bromotoluene was used to prepare the Grignard reagent. encountered.  Similar purification problems were also  The final white crystalline product, obtained in 10%  yield, had mp = 7 4 . 0 - 7 6 . 0 ° . Elemental analysis:  theoretical, C - 79.02%, H - 6.63%. experimental, C - 78.96%, H - 6.51%.  3.2  Kinetic Procedure in Acid-Water Medium In a l l of the kinetic experiments except numbers 180-184, 219-223,  240-249, 252-266 and 275-284, a pseudo first-order approach was used, the i n i t i a l substrate concentration being in a 20-fold excess or more. A l l of the rate constants were obtained by observing the disappearance of the 526 nm permanganate absorbance.  These spectrophotometric  measurements were made using a Bausch and Lomb 505 spectrophotometer except for some very slow reactions in which a Cary 16 was used. machines were equipped with thermostated c e l l compartments. kinetic experiments except where noted were performed at  Both  All  25.0+0.2°.  A typical kinetic run was initiated by placing nine parts (2.70 ml) of substrate stock solution into a cuvette, adding one part (0.30 ml) of potassium permanganate stock solution, stoppering, mixing thoroughly and then placing the cuvette into the c e l l compartment and observing the 526 nm absorbance with respect to time.  The permanganate stock  solution had previously been thermostated at 25.0° and was composed of a precisely weighed amount of potassium permanganate in 100 ml of  water to give a concentration close to 4.0 x 10 -4 concentration was then 4.0 x 10 of 0.9.  M. The kinetic  M which gave an i n i t i a l absorbance  The substrate stock solution was also thermostated prior to  use at such a temperature that the mixture reached a temperature of 25° upon mixing.  Usually the heat of mixing was no more than 2 ° .  After  the kinetic run the 3.00 ml sample was titrated with 2.00 N sodium hydroxide to obtain the acid molarity. Because a wide variety of compounds were examined several methods had to be used for the preparation of substrate stock solutions.  The  TFA-water solutions of the desired acid strength were prepared by making up to volume a measured quantity of water with TFA.  Stock  solutions of substates which were neither excessively volatile nor underwent reaction with the solvent (such as alcohols which esterified) were simply prepared by adding a known weight or volume of substrate to a known volume (usually 10.0 ml) of TFA-water solution and mixing thoroughly.  Stock solutions of alcohols were sometimes prepared in  this manner but had to be used within one minute because of esterification.  Some of the kinetic experiments involving larger quantities of  alcohol were initiated by adding several p £ of alcohol to a 9:1 mixture of acid-water and permanganate-water  solutions.  Stock solutions of the gaseous compounds investigated, namely neopentane, n-butane, propane and ethane, were prepared in the following ways.  Neopentane at 0° was syringed into a 25 ml volumetric  containing a known quantity of TFA-water solution.  The solution was  shaken vigorously, opened to the atmosphere and then reweighed.  The  increase in weight was taken as the amount of neopentane per known  - 33 volume of TFA-water solution.  Stock solutions of the other three  gases were prepared by subjecting 10.0 ml of TFA-water solution in a 25 ml volumetric flask containing a small magnetic stirring bar to 2 lbs pressure of the desired gas by means of a rubber tube connecting the gage and the flask.  The tubing, but not the flask had been  flushed with the desired gas to exclude a i r .  The solution was then  stirred at a moderate rate by means of the magnetic stirrer for a time not exceeding two minutes. amount of dissolved gas desired.  The stirring time depended upon the The connecting hose was removed and  the volumetric flask was restoppered and reweighed. was taken as the amount of gas uptake.  The weight gain  These solutions were usable  up to one hour after preparation after which time gas losses became serious.  The rate constants obtained from these experiments were of  fair reproducibility, ranging from the poorest, + 10% per duplicate and + 20% for k_ (k„= k , ,/[substrate]) over a 2.5-fold concentra— I I observed tion range for ethane, to the best, n-butane, which gave + 10% for duplicates and + 11% for Y.^ over a twenty-fold concentration range. It was concluded that these results were not biased by air displacement to an extent beyond their reproducibility. Some experiments were performed using a medium of sulfuric acidwater.  These experiments were carried out in the same manner as  described for those in which a medium of TFA-water was used. Unfortunately the results were unsatisfactory, as w i l l be demonstrated In Section 4.3.  - 34 -  3.3  Kinetic Analysis The time-absorbance data were analyzed by the method of least  squares by arranging the data in a linear form of y = mx + b.  The  least squares^ analysis was performed by a set of programs previously developed by the author.  94  The basic kinetic equations used vrere derived from the general rate equation (1) in the following manner.  [0 ] = [Mn0 ].  k_ = Boltzmann's constant  [S] = [substrate]  h = Planck's constant  h  = applicable acidity function  c = constant of integration  T  = temperature °K  n,m, and 1 are powers  x  (1)  4  -d[o„]/dt = k [o ] [s]V n  3  x  x  In the pseudo-order approach h, S and T are kept constant which reduces equation 1 to equation 2.  (2)  -d[o]/dt = k-[on]  wher e  k- = k - t s A  x  x  1  Only two values of n were encountered in this study, namely n = 1, a pseudo first-order case, and n = 0, a zero-order case. solved below.  These are  - 35 -  when n = 0:  (3)  -d[0 ]/dt 1 x  = k o  -d[0 x ]  kQdt  =  Integration of equation 3 yields equation 4.  (4)  [0 ]  =  x  k t  +  c  o  When [0 x ] is plotted against time the slope is the desired rate constant, k . ' o when n = 1: -d[o x ]/dt  (5)  =  -dIOx1/IOx]  =  k  l  d t  Integration of equation 5 yields equation 6.  (6)  -ln[0 ] x  =  knt 1  +  c  When -ln[0 x ] is plotted against time the slope gives the desired rate constant k^. In practise the actual analysis is performed by using absorbance values in equations 4 and 6 since by Beer's law (e = molar extinction coefficient).  = Absorbance  In the case where n = 0 the  - 36 -  slope is then equal to still  1  but in the case where n = 1 the slope is  since ln[0 1 = In Abs. - In z and In e is a constant which x  then only affects the intercept. Once k, or k had been determined for a set of different conditions 1 o the influence of the other parameters could be evaluated as follows. For a set of k, values (a parallel situation exists for k ) where 1 o only [S] varies,  k- = k - I s A  = k2[Sjm,  1  k =k h 2  1  3  and i t follows that log k- = m log[S] + log k^. When log k. is plotted against log [S] the slope is the order of the substrate.  By varying  the acidity one can in an analogous manner, establish which acidity function best f i t s the experimental data.  k  = k.h  2  log  k  2  =  1  l  =  1  o  g  h  ^/[sf  +  l o g  ^3  or in the more familiar form  -log k_ = 1 H 2 x  +  c  where the slope of the -log k vs H x plot gives the order of the 2  reaction with respect to h . r x The activation parameters were obtained in the usual manner by  - 37 converting the Wynne-Jones Eyring equation  k2  2  into a linear form.  -AG+/RT = (k T/h).e  AG+ =  k  95  AH1" - TAS1*  = (kT/h)-e  AS t /R  -AH+/RT  ln(k 2 /T) = -(AH+/RT) +AS+/R + ln(k/h)  f  When ln(k 2 /T) was plotted against 1/T the slope gave -AH /R and t t t the intercept was equal to AS /R - ln(k_/_h), from which AS and AH were easily obtained. The previously mentioned 45 t r i a l s which were not analyzed by a pseudo first-order approach were analyzed by equation 8 which is derived below.  This equation is valid for a l l similar kinetics  where the substrate is not in sufficient excess.  A l l that is  required is the stoichiometry of the reaction.  12[Mn04~] + 5[n-alkane]  —+ 5R'C02H + 5RC02H + 12Mn2+  the stoichiometry for this example is 12/5 = 2.4. The subscripts t and o denote time = t and time = 0, respectively  -dtO ]/dt x  =  k IO J .IS] 2  x  t  t  -  ^ t  *  tS]o -  •d[°x]t dt  TJ  - 2tVt k  -d[o ] x  (7)  38 -  «°x]o "  ( [ s ]  l°* t> ]  o-n Vo t  i4 °  +  [  t  [0xJ o  ] x  t  )  = k-dt  2^4 IVt>  Equation 7 can be readily integrated since i t is of type ^ — 1 . a+bx In  96  Q to give equation 8.  ,  [s ]  ln(  \  (8)  ,  [0]  ToV - TJ WT  . +  _ 7  In actual practice absorbance was used instead of [0 1 . v x t conversion was readily made by Beer's law, ^  3.4  x  l  t  =  dx (a+bx)  )  =  k  2  t  +  c  This  A/e.  Inorganic Product Study The inorganic products were determined by iodometric titration. -3  A 4 x 10  M solution of permanganate was made up in a TFA-water  medium in which the substrate had a fast oxidation rate.  Then to 10.0 ml  of this solution was added enough neat substrate to ensure at least a ten-fold excess.  The solution was thoroughly mixed by means of a  magnetic stirrer until no further reaction was observed but in no case were any reactions allowed to go past two hours.  After this time no  permanganate ion could be detected but in most cases manganese dioxide  - 39 precipitate could be observed.  The total solution was titrated for  remaining manganese oxidizing power (essentially the amount of -2 manganese dioxide present) by adding 10 ml of 4 x 10  M potassium  iodide in aqueous 2% sodium bicarbonate and then titrating with a standardized solution of sodium thiosulfate to a starch end-point. The Thyodene indicator was added near the end of the titration.  Blank  corrections for particular TFA-water solutions were made, i f necessary. 3.5  Organic Product Studies  3.5.1  Permanganate Oxidations in TFA-Water Organic products were determined for selected compounds which are  listed in Table 3 along with reaction medium and product detection methods.  Typically the procedure was to prepare 20-25 ml of the  desired TFA-water solution in which was dissolved 0.5 g of potassium permanganate.  When a l l of the potassium permanganate had dissolved  4.00 ml of the substrate was added quickly with constant stirring by means of a magnetic stirrer.  The reaction was allowed to proceed  for one hour or until a l l the permanganate was consumed.  The amount  of substrate added was enough to ensure at least a five-fold excess except for three substrates.  n-Pentane, cyclohexane and toluene were  not completely soluble so a two phase system existed in these cases. The reaction after completion or one hour duration was quenched by the addition of 40 ml water, saturated with sodium chloride and then extracted three times with 50 ml ether.  The ether extracts were  combined, dried over anhydrous magnesium sulfate and flash-evaporated to reduce the volume to 30 ml or less depending upon the v o l a t i l i t y  Table 3.  Products of KMnO. Oxidations i n TFA-Water Medium  Substrate  wt.  n-Pentane  2.5  2- Pentanol  3.2  a  -H^ 7.5  7.5  % Recovered 40%  89%  0  Products 2-Pentanone 3-Pentanone Propionic acid  wt.  %  --  66% 34%  —  —  2-Pentanone Propionic acid  —  -  —  -  d  —  -  Method 1 1 2 3 2 3 2  -  2  Propionic acid  -  —  -  2  83%  Cyclohexanol Cyclohexanone Adipic acid  *y0.01 M).01 0.2  5% 5% 90%  4 4 5  7.5  95%  Cyclohexanone Adipic acid Tar  ^0.03 0.35 0.03  4% 91% 5%  4 5  4.0  7.5  89%  Adipic acid Tar  0.5 0.05  90% 10%  5  Toluene  3.5  4.5  95%  Benzoic acid  .25  -  6  Toluene  3.5  7.5  82%  Benzoic acid  .05  —  6  3- Pentanol  3.3  7.5  90%  3-Pentanone Propionic acid  2- Pentanone  3.3  7.5  94%  Propionic acid  3- Pentanone  3.3  7.5  90%  Cyclohexane  3.1  7.5  Cyclohexanol  3.9  Cyclohexanone  Table 3 (Continued) Substrate  ^ a wt.  Benzyl alcohol  4.2  4.5  91%  Benzaldehyde  4.2  4.5  Acetophenone  4.1  1-Phenylethanol 2-Phenylethanol  -H  % Recovered  wt.  %  Benzoic acid  .3  93%  Benzoic acid  .4  7.5  92%  Benzoic acid  .2  -  4.1  5.0  95%  Acetophenone  .4  4.1  5.0  93%  Phenylacetaldehyde Phenylacetic acid  b  i n i t i a l amount of substrate added in grams; (products and reactants) recovered;  Products  b  (trace) .1  acidity of reaction medium;  c  d  Method 6 6 6  100%  7  99%  8 9  based on total materials  I  based only on products recovered.  1.  Collected from chromosorb 102 1/4" x 10' column, repurified on the 20% carbowax 20 M on firebrick 60/80 column 3/8" x 20' as a mixture. Identified as the ketones by retention times and NMR. Ratio determined from NMR integral.  2.  Collected from underneath the CF3CO2H peak from the chromosorb 102 column. Identified by NMR.  3.  Identified by retention times on chromosorb 101 and 102 columns against known compounds.  4. 5.  Identified by retention times on chromosorb 101 and Carbowax 20 M columns against known samples. Cyclohexanol existed as the trifluoroacetate ester. literature mp = 149-150c 81u Isolated, then purified by recrystallization, mp = 145-148  6.  Isolated, the purified by sublimation, mp = 121-122°, literature mp = 122  7.  Identified by retention times against known compound on the Carbowax 20 M and the 10% Silicon GE SF-96 firebrick 60/80, 1/4" x 10' columns.  8.  Collected from the Silicon GE SF-96 column  9.  Isolated, then purified, mp = 70-73  81q  Identified by NMR. 81v literature mp = 7 6 ° . Verified by NMR.  - 42 -  of the compounds.  It was observed that reaction would continue  after dilution with 40 ml water for the phenylethanols, which was probably due to the hydrolysis of esters formed with TFA (see Section 4.5).  For n-pentane a sample of the original ether extracts was  retained before flash-evaporation to determine the amount remaining after oxidation.  The concentrated ether extracts were then analyzed  by v.p.c. for volatile components on a Varian Aerograph 90-P coupled with a Varian A-25 recorder using the series of columns mentioned in Tables 3 and 4.  Non-volatile compounds, namely phenylacetic acid,  benzoic acid, and adipic acid were recovered by evaporating the extracts to dryness and then purifying the crude products.  Benzoic acid was  readily sublimed and adipic acid could be recrystallized from ether or water.  Phenylacetic acid, which was recovered from the oxidation  of 2-phenylethanol, was identified by NMR since after several recrystallizations from petroleum ether the melting point was s t i l l low. Several problems were encountered in the product analysis,  the  severest of which was that large quantities of TFA were extracted along with products.  This masked the acidic products from the C-5 series,  preventing yield calculations from being made. could be collected.  Only propionic acid  Although one would expect some acetic acid none  of the columns, even the Chromosorb 101 column which is  specifically  designed for low molecular-weight acids, were capable of separating i t from the larger amounts of TFA. It was also found that 2-pentanone and 3-pentanone could not be separated from each other.  This problem  was finally avoided by collecting the trace amounts present of this  - 43 ketone mixture and verifying their identities by NMR.  The 2-pentanone  to 3-pentanone ratio could be calculated from the peak integrals of the NMR spectrum of the mixture.  3.5.2  Nitration and Nitrosation Products in TFA-Water It was found from the freezing-point depression experiments that  the TFA medium could be used to generate nitronium ions from sodium nitrate and nitrosonium ions from sodium n i t r i t e .  It was considered  worthwhile to see how effectively nitration and nitrosation could be carried out in this medium. The general procedure was to dissolve 0.01 moles of the salt in neat TFA and then to add 0.01 moles of substrate while constantly stirring the mixture with a magnetic s t i r r e r .  The reaction was  allowed to continue for four hours after which time i t was quenched by the addition of 20 ml water.  The resulting solution was made basic  by the addition of either 6 N sodium hydroxide or sodium hydroxide pellets, then saturated with sodium chloride and extracted with three successive 50 ml portions of ether.  The ether extracts were combined,  dried over anhydrous magnesium sulfate, and reduced to 50 ml by flash-evaporation.  The resulting concentrates were analyzed by v . p . c .  The results are listed in Table 4. It was noted that the basic aqueous layers were highly colored. This color could be removed by acidification and restored by the addition of base.  Subsequent investigation of the u.v. characteristics of the  basic and acidic solutions indicated phenolic compounds.  The recorded  spectra strongly resembled those of ortho and para nitrophenol. Section 4.1.3 for further discussion and also reference 79.  See  - 44 -  Table\4.  Nitration and Nitrosation Products.  Reactants  % Recovered  % Converted  -  Phenol and NaN03  Products  black t a r 3  % of Product  Detection Method  -  -  97  Benzene and NaNC"3  100  100  nitrobenzene phenols  Toluene and NaN02  98  1-2  nitrotoluenes VL-2  1  Benzene and NaN02  97  2-3  nitrobenzene  1  \95  p-nitrotoluene 31.7 p_-nitrotoluene 67.0 Tfi-nitrotoluene 1.3 phenols <.05  1 1 1 2  Toluene and NaN03  100.0 <.05  ^2-3  1 2  rapid reaction could possibly be hazardous.  1.  V.p.c. using 10% Silicon GS SF-96 on firebrick 60/80 l/4"xl0' column at 1 6 2 ° , 40 cc helium per minute flow rate. Matched against known samples. Retention times were; o-nitrotoluene 8.5 min, p-nitrotoluene 11.1 min, m-nitrotoluene 10.5 min, toluene 1.5 min, benzene ^ 0.5 min.  2.  U.V. indicated the presence of phenols. See Section 4.1.3 and also reference 79 where similar phenols were isolated from the nitration of toluene.  - 45 3.6  Determination of Stoichiometri.es The stoichiometry could only be determined for those compounds  where the competitive decomposition of permanganate was small.  As a  result the stoichiometry for weak reductants such as ketones and some alkanes could not be determined. The general procedure was to make up substrate solutions in TFAwater of such strength that when 20-30 \iZ  was added to 3.00 ml of a  -4 solution 4 x 10  M in potassium permanganate made from the same  TFA-water solution as the substrate the oxidant was always in excess. The absorbance of the permanganate ion was determined before addition of substrate and then again when no further decrease in absorbance was noted.  This was done for both the reacting cuvette and the  control cuvette.  Then 2.00 ml from each was added to 10.0 ml of an  aqueous solution which was 4 x 10 in sodium bicarbonate.  M in potassium iodide and 2%  The liberated iodine was titrated with a  -4 2 x 10 point. 3.7  M standardized sodium thiosulfate solution to a starch end These experimental values are tabulated in Table 5.  Freezing-Point Depression Procedure It was observed that when potassium permanganate was dissolved  in neat TFA that a green species was generated similar to that 24 previously reported for sulfuric acid solutions of this compound. It was considered important to determine the identity of this species since i t could very well be involved in the oxidations. 26 attempts to identify the species in sulfuric acid 25 27 conclusive. '  Previous  had not been  It was felt that since TFA is a mono-protic acid the  - 46 Table 5.  Experimental Data for Stoichiometric Determinations for KMnO. Oxidations in TFA-H-O.  Compound  a R_  — b Moles substrate Moles Mn04 Difference Y/X applied = X x 1 0 x 1 0 in x 10 = Y Blank T r i a l 7  Isopentane n-Pentane n-Hexane n-Heptane n-Heptane n-Octane n-Nonane n-Decane n-Undecane n-Dodecane n-Tridecane Cyclopentane Cyclohexane Cycloheptane Cyclooctane Methanol Methanol Ethanol 2-Pentanol 3-Pentanol Cyclohexanol Cyclohexanol Formaldehyde Cyclohexanone Benzene Benzene Phenol Toluene Toluene Toluene Ethylbenzene Ethylbenzene Cumene Cumene t-Butylbenzene _t-Butylbenzene Benzyl alcohol Benzyl alcohol Benzyl alcohol Benzaldehyde  -8. 42 II  II II II II II II  ti II II  -7. 82 II II II II  -6. 70 -7. 90 II  ti  -7. 82 II  II II  -6. 70 . -7. 50 II  ti  -6. 70 -3. 65 -7. 50 -6. 70 it  -7. 50 -7. 50 -6. 70 -2. 30 -3. 65 -6. 70 -2. 30  7  7  5.15 2.60 2.30 1.36 2.72 2.46 1.67 1.54 1.40 0.88 0.82 4.82 4.17 3.72 2.23 5.56 5.56 5.13 2.76 5.55 1.92 5.77 5.27 3.05  9. 49 9. 37 9. 67 9. 43 9. 37 9. 49 9. 49 9. 25 9. 31 9. 31 9. 37 9. 67 9. 40 9. 12 9. 25 10. 10 11. 07 9. 37 9. 12 9. 37 10. 46 9. 37 10. 28 9. 82  3.95 8.36 8.09 8.15 6.45 6.08 6.42 6.05 5.99 6.57 6.51 6.69 6.72 6.69 6.99 5.90 9.91 6.99 8.09 6.69 9.61 7.24 5.23 8.18  5.54 1.01 1.58 1.28 2.92 3.41 3.07 3.20 3.32 2.74 2.86 2.98 2.68 2.43 2.26 4.20 1.16 2.38 1.03 2.68 0.85 1.95 5.05 1.64  1.08 0.39 0.68 0.94 1.08 1.39 1.85 2.08 2.33 3.13 3.45 0.62 0.64 0.65 1.01 0.76 0.21 0.46 0.37 0.48 0.44 0.34 0.96 0.54  3.37 1.13 0.611 0.941 2.82 8.47 0.817 1.63' 1.44 0.719 0.646 1.29 14.5 8.67 2.89 14.7  11. 07 7. 53 6. 86 6. 86 11. 01 10. 89 7. 47 11. 56 11. 19 7. 95 7. 59 11. 37 9. 79 10. 97 11. 19 9. 73  3.89 4.52 5.47 4.98 2.92 2.07 5.89 6.08 6.45 6.13 6.07 7.06 2.25 2.92 4.32 2.37  7.18 3.00 1.40 1.88 8.09 8.82 1.58 5.48 4.74 1.82 1.52 4.31 7.54 8.05 6.87 7.36  2.13 2.67 2.28 2.00 2.86 1.04 2.35 3.33 3.33 2.53 2.35 3.33 0.52 0.96 2.38 0.50  - 47 -  Table 5. (Continued) Compound  Benzaldehyde Benzaldehyde Benzaldehyde 1-Phenylethanol 1-Phenylethanol 2-Phenyle thanol 2-Phenylethanol Acetophenone C-H C-OH C-H -> C=0 C-H ->- CO-H C-OH -*- C=0 C-OH -> C02H C=0 + C02H R 2 CH 2 •> 2RC02H  Moles substrate Moles MnO ~ 4 applied = X x 107 x 107 in Blank T r i a l -2.30 -3.65 -6.70 -3.65 -7.50 -7.50 -3.65 -8.42  7.36 8.83 2.94 4.97 0.834 0.837 7.54 5.13  10.73 11.86 11.13 11.31 7.77 7.71 11.50 9.12  4.22 4.44 5.96 9.85 6.98 5.22 3.95 4.44  Difference'3 Y/X x 107 = Y  6.51 7.42 5.17 1.46 0.79 2.49 7.55 4.68  acidity of the TFA-H-0 medium in which the reaction took place. the moles of MnO^ used up according to the data.  0.88 0.84 1.75 0.29 0.95 2.97 1.0 0.91 0.40 0.80 1.20 0.40 0.80 0.40 2.40  - 48 -  data analysis would be simpler than in the case of sulfuric acid. We attempted to substantiate our conclusions by investigating analogous reactions in which known species are generated, such as nitronium and nitrosonium ions. A typical freezing-point depression experiment was carried out i n the following manner.  Using the apparatus illustrated in Figure 1 a  20.0 ml sample of pure TFA was supercooled to 10° below its freezing point by means of a dry ice-acetone bath.  Crystallization was induced  by touching the wall with a small piece of dry ice. completed frozen to degas i t and then remelted.  The solution was  Next i t was cooled to  one degree below the freezing point and crystallization was again induced with a piece of dry ice.  The resulting warming curve was  recorded until the temperature reached the equilibrium.plateau indicative of the liquid-solid equilibrium temperatures.  When the solution was  supercooled by no more than 2° this plateau extended over a time interval of 2 to 4 minutes, allowing precise determination of the freezing point.  Once the freezing point had been verified for the  pure compound the sample of interest was added and completely dissolved. Then using the same supercooling technique the new freezing point was determined and verified at least twice.  Sometimes when larger amounts  of compounds were added the solutions tended to supercool too much, giving no warming plateau.  Whenever this occurred the acetone-bath  temperature was slowly lowered until crystallization could be maintained. In this manner freezing points could be determined to + 0 . 0 1 ° . pure TFA the reproducibility was + 0 . 0 0 5 ° .  For  Fresh TFA was used for  each sample investigated and a l l determinations were performed under a  - 50 -  nitrogen atmosphere.  The results obtained are presented in Table 6  and 7.  3.8  Determination of the HK Function for TFA-Water — — — — — — — — — — — — When the i n i t i a l kinetic oxidation data were analyzed i t was  found that the order with respect to h Q was extremely high, in excess of five. The  It became apparent that this was not the proper function.  function was then considered as a possible alternative. The  function for TFA-water solutions was determined in the  following manner.  Stock solutions of the indicators were made up in  neat TFA of such concentration that when 0.50 ml was made up to 5.00 ml the fully ionized absorbance value would be near 0.8.  Stock solutions  in neat TFA were stable for up to several weeks with no indicator decomposition.  The absorbance of the cations in the series of solutions  used -<?as measured on a Cary 16 spectrophotometer at 2 5 ° . The uncertainty of the absorbance measurement was + 0.1%.  The acidity of  each solution used was then determined by titrating with 2.00 N sodium hydroxide. The Hammett approach of overlapping indicators was used.  The  series had good overlap, as Figure 2 illustrates, with quite parallel 97 slopes necessary for the approach.  Two indicators were used to tie  the function into the standard pH function. 1 and 2 (see Table 2) were used.  For this purpose indicators  Both were appreciably ionized in  solutions which had measurable pH values.  A Radiometer model No. 26  pH meter was used, equipped with a set of glass and calomel electrodes. This machine was standardized with Fisher pH = 2.00 standard solution.  - 51 Table 6.  Determination and Verification of  for Trifluoroacetic  Acid. Substrate  "oles of substrate  Molality = m  0.02250  0.7329  AT  Kf=AT/m  3.94 4.00 3.96 3.99 4.08 4.00  5.38 5.46 5.40 5.44 5.57 5.46  Determination Benzene  Kf=5.45+0.02 m =AT/K£ x f  n=m /m x  n  b o  Verification Toluene  0.01882  0.6130  3.46  0.6349  1.04  1.0  Sodium acetate  0.001533 0.001102 0.000625 0.000244 0.000244 0.000138  0.04993 0.03589 0.02035 0.00794 0.00794 0.00450  0.835 0.580 0.330 0.140 0.148 0.085 0.080 0.075  0.1532 0.1064 0.06052 0.02796 0.02569 0.01559 0.01468 0.01376  3.07 2.96 2.98 3.42 3.23 3.46 3.26 3.06  3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0  II  II II II  is the molal freezing point depression constant, n  is the number of particles predicted  theoretically.  - 52 Table 7. Substrate  Water ti  II II  KMnO.  4  it II  ti it it ti it ii ti II  Triphenylcarbinol it  it  Cryoscopic Data for Substrates in Trifluoroacetic Acid • Moles added  ti  ii it it II  ti it  Sodium nitrite  mx=AT/Kf  n=m / i X  0.5423 0.1808 0.5423 0.3619  3.41 1.28 3.65 2.37  0.6257 0.2349 0.6697 0.6349  1.15 1.30 1.23 1.20  0.001179 0.0009430 0.0008464 0.0006348 0.0004945 0.0002781 0.0003122 0.0006356 0.0001948 0.0001429 0.0001215  0.03840 0.03072 0.02757 0.02068 0.01611 0.009059 0.009912 0.02070 0.006345 0.004650 0.003958  0.63 0.60 0.56 0.39 0.33 0.22 0.16 0.37 0.17 0.13 0.11  0.1156 0.1101 0.1028 0.0716 0.0606 0.0404 0.0294 0.0679 0.0312 0.0239 0.0202  3.01 3.58 3.73 3.46 3.76 4.46 4.25 3.28 4.92 5.14 5.10  0.0007547 0.0004380 0.0001984  0.02458 0.01427 0.006463  0.46 0.26 0.135 0.140  0.08441 0.04771 0.02477 0.02569  3.43 3.34 3.69 3.83  0.001271 0.000475 0.000377 0.000233  0.04141 0.01548 0.01226 0.07604  0.000168  0.005461  0.000113  0.003675  0.575 0.28 0.205 0.142 0.165 0.105 0.110 0.090 0.095  0.1053 0.05138 0.0376 0.0261 0.0303 0.0193 0.0202 0.0165 0.0174  2.55 3.32 3.14 3.42 3.98 3.53 3.69 4.49 4.74  0.001401  0.04563  0.0009384  0.03057  0.0007304  0.02379  0.0003567  0.01167  0.0001471  0.004792  1.02 1.03 0.73 0.75 0.575 0.60 0.270 0.275 0.110 0.120  0.1872 0.1890 0.1339 0.1376 0.1055 0.1101 0.04954 0.05046 0.02018 0.02202  4.10 4.14 4.38 4.50 4.43 4.62 4.26 4.34 4.21 4.59  it  it  tt  tt  ti  "  AT  0.01665 0.00555 0.01665 0.01110  it  Sodium nitrate  Molality = m  it  it  it  it  ti  tt  it  it  it  it  ti  it  1.65  - 54 -  Since the H function established by Randies and Tedder J o  12  was  in terms of weight percent we found i t necessary to determine the molarity for these solutions so that the two functions could be compared.  These data are presented in Table 8.  The equation used to establish  is derived in the following  manner.  + • • * * + R + Ho0 z lRQH]  i . let  u h  - log  H+  =  R  a  H20  IL = u  .  r  or  pK^+ *  +  H  log  ROH "H 2 0 • i R+  IL  u  =  1 1  , ,  +  *  =  0  _ then  ROH  „  v  H,, *  -[RM ]-  -log \ +  1 1  R  V  — R+ T  f  f  afff  H20  l R + ] a  log  + ROH + H  >  log  . -log h R  [ROH] [R ] +  a .  1  +  log  [ROH] [R+]  Experimentally [R0H]/[R+] was determined as follows;  [R ] = Absorbance of cation observed [ROH]= Absorbance of fully ionized cation - absorbance observed. Since none of the indicators used had detectable decompositions spectrophotometric measurements were readily made.  Occasional!  - 55 -  Table 8.  Molarity of Weight % Solutions of TFA-Water.  Molarity  Weight % of TFA i n TFA-H-0  0.77  8.33  1.76  18.11  2.53  24.23  3.46  34.12  3.90  37.83  4.28  40.77  4.82  44.91  5.51  50.35  6.20  55.36  6.78  59.62  7.98  67.76  8.76  71.71  9.32  75.59  9.85  78.78  10.58  83.32  11.05  86.32  11.45  89.07  12.20  93.67  12.95  96.49  13.13  100  - 56 -  difficulty was encountered in determining the fully ionized absorbance, presumably because of solvent effects on the spectra of the carbonium ions.  There were no A shifts, only a small increase of absorbance max  with increased acidity.  Whenever this was the case the absorbance  values close to the region where the sigmoid curve leveled off were used to determine the fully ionized absorbance value.  Only one  indicator, 4,4',4"-trimethoxytriphenylcarbinol, had absorbance increases of more than 0.01 over a range of three H units beyond the approximate fullv ionized absorbance value. 3.9  Vapour-Liquid Phase Equilibrium Study In the previous section the H relationship was derived.  One of  R  the factors that determine its magnitude is a „ _.  The normal method  to determine a „ _ is to measure vapour pressure under isothermal 98 conditions varying substrate and then applying the equation a^ = kp^» where a^ = activity of solvent in solution p^ = vapour pressure of solvent over solution and k = proportionality constant. solvent a = 1 .'. familiar form a_^ =  1 = kpQ or k = 1/p P^/Po«  But for pure  so the equation takes the  We did not have the necessary equipment to  measure the vapour pressure at 2 5 ° directly but the amount of water present when vapour-liquid boiling equilibrium is achieved should be proportional to activity.  Boiling-point equilibrium studies were  quite simple to perform on the TFA-water system in the following manner. One hundred ml of one of the components was brought to reflux and the equilibrium temperature recorded; then 10 ml portions of the other component were added until the added component was in excess.  After each  - 57 -  10 ml addition the solution was brought to boiling-reflux equilibrium, the equilibrium temperature was recorded and a sample of the condensate was trapped by means of the apparatus illustrated i n Figure 3.  After cooling, a 2.00 ml portion of the condensate and  residue was titrated to determine the amount of TFA present in each sample.  In this manner by starting with each component in turn a  complete vapour-liquid phase diagram could be constructed. could be then approximated in. the following manner; a  The a^ _  - = mole fraction  of water in the vapour which results from the following deri\_tion. As previously mentioned a^ = kp^.  If one makes the assumption that the  partial pressure of the ith component is proportional to the mole fraction of i present in the vapour then p^ = k'F^ (F = mole fraction). Then a^ = kk'F^.  But for a system composed of pure component i the  activity of i ( a 0 ) ^ = 1> and the mole fraction of component i in the vapour must be unity. So, '  a  but,  p = k*F = k* r o o  then,  kk' = 1  therefore,  o  = 1 = kpr o  a^ =  It must be remembered that these values of a^ _ are only approximate since isothermal conditions did not exist. presented in Table 9. data.  The values obtained are  Figure 4 presents the vapour-liquid equilibrium  - 58 -  Figure 3.  Vapour-liquid equilibrium study apparatus.  - 59 Table 9. Boiling point 71.0 79.2 88.1 96.0 99.9 103.7 104.7 104.9 104.5 103.5 102.3 101.8 101.3 101.0 100.8 100.65 100.35 100.15 100.0 99.4 99.6 99.3 98.0  Vapour-Liquid Equilibrium Data for the TFA-Water System. N of  N of  liquid  vapour  13.0 12.40 12.0 11.65 11.30 10.60 10.30 10.00 9.70 9.00 8.40 7.80 7.35 7.00 6.55 6.20 5.65 5.00 4.20 3.30 2.30 1.30 0  13.0, 12.70 12.80 12.80 12.45 11.60 10.70 9.60 8.60 7.00 5.80 5.15 4.00 3.95 3.55 3.50 3.15 2.80 2.40 2.00 1.50 0.80 0  F„ * i n "2 liquid 0 0.254 0.346 0.410 0.466 0.556 0.585 0.614 0.641 0.693 0.731 0.765 0.785 0.800 0.821 0.837 0.858 0.881 0.905 0.928 0.953 0.975 1.0  F u * in 2 vapour 0 0.169 0.130 0.130 0.250 0.416 0.547 0.652 0.720 0.800 0.852 0.875 0.893 0.910 0.921 0.922 0.932 0.941 0.951 0.960 0.971 0.986 1.0  Log F vapour  -  -.772 -.886 -.886 -.620 -.381 -.262 -.186 -.143 -.097 -.070 -.058 -.049 -.041 -.036 -.035 -.031 -.026 -.022 -.018 -.013 -.006 0.0  F designates mole fraction of water present in solution or vapour.  - 60 110.0  - -i  0.0  Figure 4.  1  2.6  1  1  5.2 7.8 Molarity Phase diagram of TFA-water mixtures.  .  10.4  1  13.0  -  61 -  3.10 Determination of pK of Permanganic Acid In H^O and D^O It has been previously ..mentioned that permanganate exists as a green species in neat TFA. It was further noted that addition of water regenerated the permanganate ion, MnO^ .  It became apparent that an  equilibrium existed between these two species which was determined in the following manner.  Stock solutions of permanganate were prepared  in either 1^0 or D20 of such strength that when 50 ]il was added to 5.00 ml of the desired acid-water or acid-deuterium oxide solution that the maximum absorption for complete transformation into permanganate ion was approximately 0.8. 458 nm,  E  m  a  x  The equilibrium between the green species ( A  =  - 600) and permanganate anion was monitored by noting the  change in absorbance of the 546 nm absorption peak of permanganate ion by means cf a Cary 16 spectrophotometer, thermostated at 2 5 . 0 ° .  At this  wavelength no absorption was detected for the green species or any decomposition products.  For each experiment a timer was started at the time  of mixing to allow extrapolation of the absorbance to zero time for those solutions where decomposition occurred.  The pK value was calculated  by least squares analysis of the log ([green species]/[Mn0^]) vs H q or FL, data and was taken as that value of H or H where log ([green species]/ R o x ° ° [MnO^ ]) =0.  The data obtained are presented in Table 10.and analyzed  graphically in Figures 5 to 8. The assumption was made that [green species]^ = [MnO^ ]  - [MnO^ ]^,  where [MnO^ ]^ = absorbance of permanganate in some solution x where some green species was formed and [MnO^ ]  = absorbance of permanganate in a  solution where no green species was generated. log([green species]/[MnO^ ]) = 0.  Then the pK = H when x  - 62 -  Protonation Data for MnO.4  Table 10.  ~\  -H  o  in Mediums of TFA-H-0 or D-0.  Abs. F - Abs. = y  Q = y/x  log Q  0.0325 0.0449 0.0573 0.0777 0.1098 0.1869 0.2602 0.3585 0.4689 0.5459 0.6213 0.6631 0.7053 0.7281 0.7543 0.7701 0.8066 0.7982  0.7696 0.7572 0.7448 0.7244 0.6923 0.1652 0.5419 0.4436 0.3332 0.2562 0.1808 0.1390 0.0968 0.0740 0.0478 0.0320 Abs. F = 0.8021  23.680 16.864 12.998 9.323 6.305 3.292 2.083 1.237 0.711 0.469 0.291 0.210 0.137 0.102 0.063 0.042  1.374 1.227 1.114 0.970 0.800 0.517 0.319 0.093 -0.148 -0.329 -0.536 -0.679 -0.863 -0.993 -1.198 -1.381  0.1092 0.1609 0.2286 0.3120 0.4100 0.5710 0.6370 0.6840 0.7410 0.8310 0.8900 0.9110  0.8018 0.7501 0.6824 0.5990 0.5010 0.3400 0.2740 0.2270 0.1700 0.0800 0.0210 Abs. F = 0.9110  7.343 4.662 2.985 1.920 1.222 0.595 0.431 0.332 0.229 0.096 0.024  0.866 0.669 0.475 0.283 0.081 -0.225 -0.366 -0.479 -0.639 -1.017 -1.627  0.0406 0.0600 0.1139 0.2324 0.3544 0.4634 0.5628  0.7818 0.7624 0.7063 0.5900 0.4680 0.3590 0.2596  19.26 12.71 6.096 2.539 1.321 0.7747 0.461  1.285 1.104 0.785 0.405 0.121 -0.111 -0.336  x=Absorbance  H-0 - set #1 10.92 10.80 10.58 10.49 10.24 10.02 9.90 9.60 9.36 9.19 8.80 8.55 8.23 7.82 7.62 6.96 6.22 5.88  3.06 3.01 2.90 2.85 2.76 2.57 2.50 2.26 2.06 1.95 1.80 1.65 1.46 1.31 1.22 1.00  H-0 - set #2 10.26 10.14 9.94 9.71 9.42 9.30 8.96 8.58 8.32 7.56 7.02 6.18  2.78 2.66 2.52 2.35 2.09 2.02 1.82 1.67 1.50 1.21 1.02  D-O-CF 3 C0 2 H 10.92 10.51 10.09 9.72 9.50 9.34 9.12  3.06 2.88 2.63 2.36 2.18 2.03 1.92  - 63 -  Table 10 (Continued) -H o  •H_  R  x=Absorbance  Abs. F - Abs. = y  Q = y/x  log  Q  ^O (continued) 8.76 8.07 7.44 6.90 6.12 5.78  0.6263 0.7195 0.7678 0.7949 0.8236 0.8212  0.1961 0.1029 0.0546 0.0275 Abs. F = 0.8224  0.3131 0.1430 0.071 0.035  -0.504 -0.845 -1.148 -1.461  2.50 2.06 1.80 1.46  0.2682 0.4850 0.6409 0.7133 0.8218  0.5536 0.3368 0.1809 0.1085 Abs. F = 0.8218  2.069 0.6944 0.2818 0.1521  0.315 -0.158 -0.549 -0.818  2.50 2.06 1.80 1.46  0.2685 0.4659 0.6254 0.6979 0.8048  0.5363 0.3389 0.1794 0.1069 Abs. F = 0.8048  1.997 0.7274 0.2869 0.1532  0.301 -0.138 -0.542 -0.815  2.50 2.06 1.80 1,46  0.2557 0.4612 0.6151 0.7025 0.7982  0.5425 0.3370 0.1831 0.0957 Abs. F = 0.7982  2.122 0.7307 0.2977 0.1362  0.327 -0.136 -0.526 -0.866  0.2488 0.4530 0.6144 0.7023 0.8009  0.5521 0.3479 0.1863 0.0986  2.219 0.768 0.304 0.140  0.346 -0.115 -0.518 -0.853  1.74 1.44 1.18 0.99  l20 1 4 . 6 °  9.90 9.36 8.80 8.23 5.88 [20 20.0° 9.90 9.36 8.80 8.23 5.88 l20  25.0°  9.90 9.36 8.80 8.23 5.88 I20 9.90 9.36 8.80 8.23 5.88  30.5° 2.50 2.06 1.80 1.46  - 64 -  Tableau  (Continued)  -IL,  —H  x=Absorbance  Abs. F - Abs. = y  Q = y/x  log Q  0.5683 0.3768 0.1856 _0.1280  2.553 0.897 0.307 0.193  0.407 -0.047 -0.513 -0.714  0.4749 0.3518 0.3295 0.2394 0.1678 0.1521 0.1076 0.0895  9.479 2.031 1.685 0.838 0.470 0.408 0.258 0.206  0.977 0.308 0.227 -0.077 -0.328 -0.389 -0.589 -0.687  H20 35.3° 9.90 9.36 8.80 8.23 5.88  2.50 2.06 1.80 1.46  D20-CF „C0„D 3 2 10.06 2.61 9.45 2.11 9.34 2.04 8.96 .1.84 8.39 1.55 8.06 1.38 7.80 1.30 7.44 1.15 7.06 1.03 636 5.66 4.92  0.2226 0.4168 ^. 0.6053 ^ 0.6629 0.7909  0.0501 0.1732 0.1955 0.2856 0.3572 0.3729 0.4174 0.4355 0.5292 0.5048 0.5338 0.5559  Abs. V. => 0.5250  - 65 1.40  0 r = 0.983 slope = 0.74 pK = -9.29  V  1.05  o ©  0.70-  / ©  0.35  0.0 -\  / ©  /  -0.35-  ©  © ©  -0.701  © © -1.051  •1.40. O 6.9 Figure 5.  / 7.7  8.5  9.3 -H R Log 0 vs. H R for the ionization of MnO^ (Data set #1, Table 10).  10.0 in TFA-water,  10.9  - 66 1.40  set r 1.05  i  =  slope = DK =  0.70  H  0.35  H  set  #1  #2  0.995  r  1.32  slope =  -2.13  =  pK =  0.994  1.27 -2.10  0.0  -0.35 -i  -0.70  i  -1.05  -1.40  1.0  1.4  2.2  1.8  2.6  -H  Figure 6.  Log Q vs.  for the ionization of MnO^  in TFA-water.  ( © data set #1, © data set #2, Table 1 0 ) .  3.0  - 67 0.95 .,  Figure 7.  Log Q vs. H  o  q  for the ionization of MnO^  acid-cL-deuterium oxide.  in trifluoroacetic  - 68 1.34  0.64 I  0.29  4  -0.06 -  -0.41  -0.76 i  -l.lli  1.00  1.40  1.80  2.20 -H  o Figure 8.  Log Q vs. H q for the ionization of MnO acid-deuterium oxide.  2.60  3.00  in trifluoroacetic  - 69 -  3.11 Permanganate In Benzene It has been reported that permanganate anion can be extracted into benzene by using salts containing large alkylammonium c a t i o n s . ^ We found that tetra{n-hexyl)ammonium cation could be used to achieve this transfer.  This can be done by taking 50 ml of a benzene solution  containing the tetra(n-hexyl)ammonium iodide salt (for spectral concentrations of MnO^ , 0.10 g per 250 ml of benzene) and mixing i t vigorously with an aqueous solution of potassium permanganate.  In  short order the benzene layer has a deep colour of permanganate ion with the usual absorption, but better definition of the peaks as Figure 9 illustrates.  Table 11 l i s t s the spectral properties of this new salt  along with comparative values. It was possible to isolate the benzene-soluble salt by evaporating the benzene.  The crude product could not be successfully recrystallized,  even though a wide variety of solvents was used. purified in the following manner.  However, i t could be  The benzene solution of the salt was  carefully decanted leaving behind residues, then the benzene layer was flash-evaporated to recover the desired permanganate salt.  The  salt was redissolved in fresh benzene, the solution was again decanted to remove i t from the residue, and then again flash evaporated.  This  process was repeated at least four times after which the purity of the salt was 94% as determined by elemental analysis.  Table 12 l i s t s some  of the physical properties found. Some kinetic experiments were performed using this benzene-soluble salt.  A stock solution of permanganate in benzene was prepared by the  before mentioned extraction technique.  One part was then combined  with nine parts of a benzene solution containing the substrate.  The  -70 -  590~ Figure 9.  560  530 A nm  500  Spectra of MnO^ with different cations and solvent. , tetra(n-hexyl)ammonium cation, medium benzene , potassium cation, medium water  - 71 Table 11.  Spectral Properties of Tetra(n-hexyl)ammonium Permanganate in Benzene. Species  X nm  e  la  571 548 527.5 507.5 490 473  1,322. 2,286. 2,340. 1,771. 1,150. 831.  lb  571 548 527.5 507.5 490 473  1,306. 2,289. 2,337. 1,737. 1,121. 722.  2  565 546 525 508  1,810. 3,130. 3,170. 2,330.  3  546 526  2,380. 2,400.  1 - Tetra (n-hexyl)ammonium permanganate at two different a - 8.134 x 10 - 5 M; b - 5.0672 x 1 0 - 4 M.  concentrations  2 - KMnO^ complexed with dicyclohexyl-18-crown-6-ether as reported by Sam and Simmons.69 99  3 - Aqueous permanganate.  - 72 -  Table 12.  Properties of Tetra(n-hexyl)ammonium Permanganate,  rap = 86-88°. Elemental a n a l y s i s : 3  calculated - C, 60.86%; H, 11.07%; N, 2.96%. experimental - C, 57.42%; H, 10.63%; N, 2.73%.  S t a b i l i t y : several weeks i f dry and stored i n the dark. Solubility:  Solvent  Solubility  Stability  Half  life  N  —  SS  d  n-Hexane  N  —  —  n-Heptane  N  —  —  D i e t h y l ether  S  d  ^5 min  vs s  d  ^1 hr  d  ^2-3 hr  d  'v-l min  Water Cyclohexane  Acetone Carbon tetrachloride Dioxane Benzene  s vs..  d  —  o>5 min  M.2 hr  Elemental analysis on the sample a f t e r four successive benzene recoveries. This i s not intended as proof of composition but i s to indicate the p u r i t y of the sample. N SS VS S d  -  not soluble s l i g h t l y soluble, pale purple color very soluble soluble, purple i n color I. >-- >ot opaque decomposes.  disappearance of the 527 nm absorbance peak of permanganate was monitored by using a Cary 16 for slow runs and a Bausch and Lomb 505 for t r i a l s where the h a l f - l i f e was less than 10 minutes. A l l experiments were performed at 25.0° using thermostated c e l l compartments. In a l l cases blank decomposition corrections had to be made. The k i n e t i c analyses were performed using the before mentioned pseudo f i r s t - o r d e r technique. Product analysis was performed using a two phase system of 25 ml water containing 0.50 g potassium permanganate and 25 ml benzene containing 1.25 g of t e t r a (n-hexyl)ammonium iodide.  To this mixture  was then added approximately one gram of substrate with vigorous mixing by means of a magnetic s t i r r e r .  A f t e r the reaction had been  allowed to proceed f o r several hours the manganese dioxide had to be destroyed by the addition of aqueous b i s u l f i t e , otherwise emulsion formation prevented ether extraction.  The mixture was made basic to  pH >" 10 and extracted with three successive portions of ether to recover non-acidic products.  The extracts were combined, dried over anhydrous  magnesium s u l f a t e , and evaporated to reduce the volume.  The remaining  aqueous solution was a c i d i f i e d to pH < 3 by the addition of s u l f u r i c acid, saturated with sodium chloride and then extracted with three 50 ml portions of ether to recover a c i d i c products.  The basic extracts were  analyzed by v.p.c. and a c i d i c products were recovered by evaporating to dryness, a f t e r checking by v.p.c. f o r v o l a t i l e a c i d i c products.  In  a l l four cases the only product detected was benzoic a c i d , and i n low y i e l d as shown i n Table 13.  - 74 -  Table 13.  Permanganate i n Benzene Oxidation Products.  Substrate  Initial wt.  Unchanged wt.  Products  Recovered wt.  % Yield  Benzyl alcohol  1.0  0.65  Benzoic acid  0.15  (35%)78%  Phenylacetylene  1.0  0.60  Benzoic acid  0.10  (30%)69%  To lan  0.30  0.12  Benzoic acid  0.15  (87%)87%  trans-Stilbene  1.0  0.80  Benzoic acid  0.12  (60%)87%  Based on t o t a l materials recovered, r e s u l t s i n brackets based on material loss and products.  - 75 -  4. 4.1  RESULTS AND DISCUSSION  Solvent System  4.1.1  H Function for the TFA-Water Solvent System R It has been previously observed that the rates of many acidic  permanganate oxidations increase with increased acid content.  It has  been determined for some of these oxidations that plots of log k vs. H q give unit slopes, i . e . a correlation exists between the oxidation 45 48 rate and H q .  '  However, the permanganate oxidation of alkanes,  arenes, alcohols, ketones, and formic acid in the medium TFA-water does rot follow H q .  (A plot of log k- vs. H q gave slopes near five.)  Since i t is established that H- responds much faster to increased , , .i. r . r , _ . J 21,100,101 acid content than any other acidity function for a variety of acids,  '  i t was decided to determine H for the TFA-water solvent system to see K  i f a possible correlation exists between H and log k  (the oxidation  rate). The pK—(- values determined in this investigation for the indicators used to derive H are presented in Table 14 along with comparative K  values obtained in other solvent systems.  It is immediately obvious  that the pK—i- of indicator 1 differs by a small but significant amount from that reported for aqueous sulfuric and perchloric acids  in a  '  - 76 -  Table 14. P^-f Values f o r A r y l Carbinols,  Indicator  3  CF C0 H3 2 H0 o  o  2  HC10.4 H 0,  1 0 0  2  H„S0.-  H S0.2 4 H0 o  QI  CH C0 H 3  87  2  2  Ref. 100, Ref. 102 1. 4,4',4"-Trimethoxy TPC  +0.92  +0.82  2. 4,4'-Dimethoxy4"-methyl TPC  -0.28  -  3. 4,4*-Dimethoxy TPC  -0.97  4. 4,4',4"-Trimethyl TPC  -  +0.82  +0.82  -  -1.14  -  -1.24  -2.81  -  -  -3.56  5. 4-Methoxy TPC  -3.18  -3.59  -3.23  -3.40  -3.20  6. 4,4'-Dimethyl TPC  -3.78  -  -4.39  7. 4,4'-Dimethoxy DPC  -5.77  -  -  -5.71  -5.66  8. Triphenylcarbinol (TPC)  -6.25  -6.89  -6.65  -6.63  -6.44  9. 4,4*,4"-Trichloro TPC  -7.94  -8.01  -  -7.74  -7.43  -9.58  -9.76  -  -9.15  -9.44  CF,C0„H3 2 H 0l2  HC1H 0  H-SO.2 4 H 0l4  £-Nitroaniline  1.11  1.03  o-Nitroaniline  -0.13  -0.29  -0.25  4-Chloro-2nitroaniline  -0.94  -1.03  -0.97  b  -0.89 3  C  10. 4-Nitro TPC  2  a  i n  1 0 3  2  2  TPC - t r i p h e n y l c a r b i n o l ; DPC - diphenylcarbinol.  b  4,4'-Dimethoxytriphenylmethyl chloride used.  c  Comparative values are f o r 4,4'-dimethoxy DPC.  - 77 -  region of very low acid concentration where one expects to f i n d good agreement.  (Examination  of Table 14 indicates that pK of i n d i c a t o r s  show some v a r i a t i o n when the solvent system i s changed.)  For this  reason and because of the poor overlap of i n d i c a t o r s 1 and 3, i n d i c a t o r 2 was synthesized and used i n the determination of H_.  With two  indicators having measurable i o n i z a t i o n s i n the accessible pH region (indicators 1 and 2) i t was f e l t that the new function would s a t i s f a c t o r i l y t i e i n t o the pH scale.  Although i n d i c a t o r 3 i s an a l k y l c h l o r i d e , not  a c a r b i n o l , such changes are known to have no e f f e c t on the H_. f unction. ^ »  8  7  Values of H_ f o r the TFA-water medium are l i s t e d i n Table 15 and graphically depicted i n Figure 10.  This H  function was calculated from  the data l i s t e d i n Appendix A by the method of overlapping i n d i c a t o r s using the equations described i n Sections 1.3 and 3.8, i . e . H  =  K  pK 4. - log[R ]/[ROH].  Figure 10 also shows the H  +  D  O  K  for TFA-water.  The H  q  and J ' functions O  function o r i g i n a l l y derived by Randies and  12 Tedder i s extrapolated to 100% TFA (dotted l i n e ) using the value of 13 18 H = -3.03 reported by Hyman and Garber. Eaborn et a l . reported Q  s l i g h t l y d i f f e r e n t values of H  q  i n this region.  ted by • ) passed through a maximum value.  Their r e s u l t s  (designa-  The J ' function, depicted  i n Figure 10, w i l l be discussed s h o r t l y . When i t was attempted to extend R- past 100% TFA by the addition of t r i f l u o r o a c e t i c anhydride i t was observed that very l i t t l e change occurred i n the i o n i z a t i o n of 4 - n i t r o t r i p h e n y l c a r b i n o l u n t i l the medium was greater than 95% anhydride (the change i n absorbance was from 0.690 to 0.680).  When the medium was changed from 95% to 100%  - 78 -  Table 15.  Molarity 0.068 0.069 0.070 0.072 0.130 0.130 0.140 0.144 0.256 0.260 0.261 0.270 0.515 0.525 0.540 0.544 0.770 0.796 0.800 1.08 1.29 1.33 1.61 1.81 1.85 2.11 2.32 2.34 2.84 2.86 2.86 3.10 3.16 3.32  H„ Function for TFA-H.O.  ~\ -1.29 -1.31 -1.37 -1.29 -0.96,-1.04 -1.01,-1.04 -0.96 -0.97 -0.59 -0.66 -0.63,-0.60 -0.62 -0.05,-0.31 -0.18 -0.16 -0.18 0.23,0.02 0.12 0.26 0.35 0.51 0.58 0.78 0.96 0.98 1.12 1.34 1.34 1.80 1.75,1.75 1.82 1.71 2.05 2.22  Molarity 3.34 3.36 3.60 3.85 3.87 3.88 4.44 4.45 4.46 4.73 4.87 4.92 4.96 5.15 5.23 5.42 5.44 5.48 5.70 6.00 6.07 6.47 6.48 7.07 7.10 7.28 7.47 7.57 7.79 7.80 8.03 8.07 8.30 8.33  - y 2.26 2.34 2.65 2.87 2.75 2.92,2.89 3.27 3.21 3.42 3.50 3.65 3.63 3.70 3.85 3.91 4.08,4.06 4.03 4.06 4.30 4.36,4.50 4.61 4.82 4.84 5.12 5.07 5.31 5.47 5.43 5.63 5.64 5.80 5.85 5.91 6.06  Molarity  ~\  8.53 8.67 8.81 8.87 9.07 9.17 9.33 9.47 9.53 9.57 9.83 9.87 10.10 10.27 10.40 10.53 10.57 10.60 10.80 10.83 10.93 11.00 11.07 11.10 11.23 11.37 11.67 11.93 12.20 12.43 12.63  6.10 6.29 6.46 6.31 6.51 6.72 6.67,6.63 6.96 6.93 7.20,6.86 7.14 7.24 7.60 7.73 7.89 8.13 8.51 8.30 8.47 8.60 8.67 '8.77 8.91 8.99 9.13 8.96 9.30 9.78 10.09 10.38 10.63  10.8  Molarity of TFA-Water Figure 10.  A c i d i t y functions i n TFA-water.  - 80 anhydride the absorbance suddenly dropped from 0.680 to 0.02.  This  sudden change was found to be due to reaction of the anhydride with the carbinol to give the trifluoroacetate ester. identified by N.M.R. and I.R. spectroscopy. observed when 4,4'-dimethyldiphenylcarbinol The  This ester was  Similar behaviour was was used.  function does not appear to be very sensitive to  temperature changes.  The data contained in Tables 16 and 17 indicate  that there is no general trend for the function but that the changes caused by temperature are indicator dependent.  It seems that indicators  which have substituents that interact strongly by resonance are more dissociated at higher temperatures.  Similar results were reported  102 by Arnett and Bushick. When the pK + values from this study were correlated with Brown's R  o* values*^ deviations were found for those indicators with +  resonance-interaction When the a  +  substituents, as i s illustrated in Figure 11.  values derived by Deno and Evans*^"* for t r i - and diphenyl  carbinols were used the deviant points f e l l on the extrapolated line. These two observations on the behaviour of indicators which have resonance-interaction substituents can be explained by steric considerations. In order for these substituents to exert their f u l l influence in stabilizing the carbonium must become co-planar.  ton the rings with the substituents  This tt>.  R in a sterically crowded configuration.  Such steric barriers are known to exist.  The crystal structure of  the salt depicted below has been determined and the phenyl rings were found to make angles of 26.7 to 38.0° with the planes defined by the 106 central carbon atoms and their bonded neighbours.  Table 16.  Indicator 1  Temperature Dependence of  No.  14.8°  19.6°  0.91  2 3  15.2°  -0.33 -1.05  4  -2.89  pK-+.  20.6°  25.0°  29.8°  0.92  0.92  0.93  -0.30  -0.28  -0.99  -0.97  -2.82  -2.81  30.7°  30.8°  35.70°  36.0°  36.8°  0.95 -0.22  -0.23  -0.94  -0.86 -2.75  -2.71  5  -3.26  -3.22  -3.18  -3.15  -3.12  6  -3.83  -3.79  -3.78  -3.76  -3.74  7  -".75  -5.76  -5.77  -5.76  -5.78  8 9 10  -6.19 -7.91  -6.22 -7.92  -9.58  -6.25 -7.94  -9.58  -9.58  -6.30  -6.33  -8.00  -8.04 -9.58  -9.62  oo  - 82 -  Table 17.  Thermodynamic Parameters for the Ionization Equilibria of the Indicators Used to Determine H_.  1 2 3 4 5 6 7 8 9 10  e.u.  kcal/mole  AS°  This study  Ref.102  This study  Ref.102  -0.64 -2.24 -3.42 -3.44 -2.59 -1.56 +0.44 +2.24 +2.53 +0.61  -2.49  -6.40 -6.27 -7.07 -1.28 5.91 12.1 27.8 37.8 44.9 45.9  -12.10  Indicator no. AH°  -  -5.68  -3.41  -6.48  -2.49 +0.87  r  0.850 0.960 0.980 0.980 0.999 0.999 0.800 0.973 0.955 0.560  -7.10 18.0  -14.95  25.6 46.1  r , the correlation coefficient is for this study.  a  AH and AS were  calculated from the equation,  , 1 0 8  V  + R +  1  =  AH  T T303R  "  \ + -~—* ROH + H +  H-0  AS  2303R  [R0H][H+]/[R+][H-0]  '  _ =  _ _ g  a  S  c  o  n  s  t  a  n  t  10.8  mono,  8.8  — / p-N0  o  i  fi) 6.8  t r i , p-Cl  unsubstituted  4.8 J i  t r i P-CH. 2.8  d i , p-CH-O 0.8  and p-CH,  -1.2 -0.8  Figure 1 1 . a +  v s . pK_ f o r s u b s t i t u t e d t r i p h e n y l c a r b i n o l s . Q  Deho's 0" v a l u e s , © +  Brown's a  +  values.  - 84 -  2 SbClg  Furthermore, triphenylmethyl cations have been shown to exist in a 83 107 propeller-like configuration in solutions.  '  This steric  barrier accounts for the necessity of using smaller o values to +  correlate with the pK^+ values and for the observation that such carbinols are more ionized at higher temperatures. The most important feature of Figure 10 i s the large difference between H and IL^, larger in fact than that observed for any other q  acidic medium previously studied.  Most inorganic acids have  relatively small values of dH^/dH (< 2) compared to that observed for Q  TFA-water (> 5). Mathews  Only one previous investigation, by Stewart and  showed a similar trend.  The formic acid-water system  was found to have dIL,/dH > 3. o  Possibly two factors can account for the differences between H and H . It can be shown that PL. = H + log R  q  (derived from H = -log a ^ / f ^ q  Q  + log  and H = -log a R  H  +  f  f  R  +/  m  / ^  f B  R  f B H  R  +  +  Q  f R 0 H  > • One  of the contributing factors can thus be the activity of water. The data presented in Table 18 shows that the change in water activity in TFA-water solutions i s actually smaller than those observed for inorganic  - 85 -  Table 18.  A c t i v i t y of Water i n Various Media.  Acid molarity  0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5  CF C0 H 3  2  0.005 0.007 0.012 0.015 0.017 0.019 0.020 0.023 0.026 0.031 0.036 0.039 0.042 0.053 0.061 0.074 0.095 0.125 0.191 0.320 0.500 0.800 0.886 0.770  a  HC1  1  0  0.008 0.017 0.027 0.039 0.053 0.070 0.087 0.107 0.130 0.155 0.181 0.211 0.244 0.279 0.318 0.358 0.399 0.444 0.490 0.539 0.591  9  I^SC^  109  0.008 0.018 0.030 0.043 0.063 0.085 0.111 0.142 0.176 0.219 0.267 0.320 0.377 0.439 0.510 0.587 0.670 0.761 0.859 0.968 1.082  These values were approximated by the method discussed i n Section 3.9.  - 86 acids.  Thus i t is not surprising that J ' , which is defined as J ' = r b o o H + log a u does not approximate H (refer to Figure 10). The large o 2 value of dH /dH for TFA-water must then be chiefly due to changes in R o activity coefficients as the medium increases in acid content. Some activity coefficients have been determined in sulfuric acid108 water mixtures by Boyd log f_f R +/fBH+^ROH*  T  ^e  and the.. allow one to estimate the value of v a  ^ u e ° f this term changes from -0.39 in 9.62%  sulfuric acid to -3.71 in 50.5% sulfuric acid whereas log a_. - changes only from -0.03 to -0.3 over the same sulfuric acid range.  Clearly,  in sulfuric acid-water systems the differences between H and H_ are J o R largely accounted for by the changes in the activity coefficients of the indicators. In TFA-water the changes in the activity terms must also account for the difference between H q and fl_ since the change in log a_ _ that occurs is too small to account for differences that range from -0.08 to -8.0.  Although no activity coefficient data for solutes other than  water are available for TFA systems some of the solvent properties of TFA-water mixtures are consistent with the logarithms of the activity coefficient quotient as the TFA content increases.  gn+f ROH^ becoming increasingly negative <, It is known that TFA supports ionization  yet is not nucleophilic^'^'''"^'"''^''" and further, i t has been reported that TFA can stabilize carbonium ion intermediates."''8'''"^ It has been demonstrated for sulfuric acid-water mixtures that reactions which involve a positvely charged transition state as a result of formal hydroxide ion loss from a neutral molecule well with II-, giving close to unit slopes  correlate 21 72 112 113 for log k vs. H_ plots. ' ' '  - 87 -  One might expect similar correlations for such reactions in TFA-water. Only one data set is available in the literature to test this possibility.  Lee and Johnson examined the chromic acid oxidation of  2-propanol in TFA-water mixtures. correlate with H q and IL^.  Figure 12 shows how their data  The plot of log k^ against  has almost  unit slope up to the region where the reaction rates show irregularities because of changes in the identity of the oxidant.^  The oxidation is  proposed to proceed by the following scheme,  CrO ~ 4 HCr04  +  +  H+  R2CHOH  HCrO." 4 —R2CH-0-Cr03  + H^O  or R2CH-0-Cr03H R2CH-0-Cr03  k  2  >  R2C=0 +  IV Cr ,  + OH slow  A cyclic transition state as depicted below can be visualized where positive charge develops on the a-carbon atom.  4.1.2  Identification of the Manganese(VII) Species Generated in TFA-Water Mixtures  Before any mechanism can be established i t is first necessary to identify the reactants.  In this investigation only two substrate types  - 88 -  - 89 -  appear to undergo pre-oxidative changes which affect  their reactivity.  Ketones are subject to enolization and alcohols can be esterified. It is very unlikely that any of the other substrates  (alkanes,  arenes, and acids) are subject to reactions with the TFA-water medium since the aridity, as determined by R^, is low even for neat TFA where 13 the maximum value of H  q  is -3.03.  This is insufficient to protonate  even alcohols or ketones since ethanol is only half protonated at H 5 O -5.9,  1  1  4  Q  =  "7 £ 115 . acetophenone _ . „ -6.5. , „ 116 3-pentanone at. -7.6, and at  O  The oxidant, permanganate ion, is known to undergo a color change from purple to light green when the medium becomes concentrated in 27 acid. The nature of this color change is not yet clearly understood. It has been attributed to the formation of permanganic acid in both aqueous perchloric acid  28  and aqueous sulfuric acid,  29  but at higher  acidities the colored species has been assigned to permanganyl c.ation, -t* 26 25 MnO- by Royer, and to 0-MnOSO-H by Symons and Mishra.  There is  at present no agreement about the identity of this green manganese(VII) species.  One then has the choice of three species which could account  for the reversible color change.  H+  2H+  +  +  2HA +  MnO." 4 MnO " 4 MnO. 4  *  HMnO. 4 »  >«  Mn0_+ 3  + Ho0 2  0-MnA + 3  H.O + A 2  It was observed that the green species generated in neat TFA was  - 90 -  spectrally identical to that generated i n sulfuric acid  25  and perchloric  28 acid.  Since its identity has not been established and since i t could  be the active oxidant i t was decided to apply cryoscopic measurements to attempt to resolve this problem.  The cryoscopic data previously  listed in Tables 6 and 7 are illustrated in Figures 13 and 14. Since TFA is a mono-protic acid the selection of possible reaction schemes is simplified, and they are outlined below. (a) Potassium Permanganate. 1. CFoC0oH 3 2  +  KMnO. 4  »•  CF-CO.H 3 2  +  K+  +  MnO ~ 4  n=2  2. CF„C0oH 3 2  +  KMnO. 4  -  CF_C0 ~ 3 2  +  K+  +  HMnO. , 4  n=3  3. 2CF3C02H +  KMnO^  >•  2CF3C02~  4. 2CF3C02H + 2KMn04  •  2CF3C02~ + H20 + 2K+ + M n ^ ,  n=6/2=3  0„Mn0C0CFo + K + + H„0 + CF0CO  n=4  5. 2CFoC0oH +  KMnO,  3 2 (b) Sodium Nitrate  4  3  6. CF3C02H  +  NaN03  »  CY^CO^  7. CF3C02H  +  NaN03  •  CF3C02~  8. 2CF3C02H +  NaN03  >  2CF3C02~  +  K^O + K + + Mn0 3 + ,  3  2  + Na + +  N a +  +  + +  3  N0 3 ~, M  Na + +  °3» H20 +  n=5  2  n=2 n = 3  N 0 2 + , n=5  (c) Sodium Nitrite 9. CF„C0„H 3 ~ ~ 2 ~  + •  NaN0o —  > •  CF^CO^H + —3 ^ 2  + Na + NO^ , a . ..~2  n=2  10. CF3C02H  +  NaN02  *•  CF 3 C0 2 ~  Na +  n=3  +  +  HN02,  6  11  J  i  0  5  Figure 13.  1  i  10  15  :  1  20 Molality x 10  1  1  25  30  P a r t i c u l a t i o n of potassium permanganate and sodium acetate i n TFA.  1  35  I  40  6  1  1  i  12 Figure 14.  18  :  i  24 „ M o l a l i t y x 10  1  30  P a r t i c u l a t i o n of sodium n i t r a t e and sodium n i t r i t e i n TFA.  1  36  1  42  48  - 93 -  11. 2CF C0 H + 3  NaN0  2  2  2CF C0 ~ 3  +  2  Na  +  +  H0  +  2  N0 ,  n=5  +  (d) Sodium Acetate  12. NaOCOCH + CF^C^H 3  CH C0 H + 3  Na  2  +  CF C0 ~, 3  2  n=3  (e) Triphenylcarbinol  13. (})COH  +  CF C0 H  ct COH  +  CF C0 H ,  n=l  14. t() COH  +  CF C0 H  <|)COH +  CF C0 " ,  n=2  15. <j>COH +  CF C0 H  4) C  3  3  3  2  3  3  2  3  2  3  3  3  2  3  +  3  2  2  H0  +  2  CF C0 , 3  2  n=3  (f) Water  16. H 0  +  CF C0 H  H0  17. H 0  +  CF C0 H  H0  2  2  3  2  3  2  +  n=l  CF C0 ,  n=2  3  +  3  2  CF C0 H , 2  3  2  (g) Benzene or Toluene  18. Arene  +  CF CC" H 3  2  Arene  +  CF^O^H ,  n=l  (n r e f e r s to the number of p a r t i c l e s formed when the above reactions proceed completely to the r i g h t .  Experimentally n for water has a  value close to 1.2 i n d i c a t i n g p a r t i a l protonation, see Table 7). The various r e a c t i o n p o s s i b i l i t i e s f o r permangante have d i f f e r e n t values of n. Mn0  + 3  The experimental determination of n=5 suggests that  i s generated i n TFA (reaction 3).  However, i t remains to be  shown that known processes analogous to reaction 3 do indeed give experimental values of n close to f i v e .  The generation of nitronium ion  and nitrosonium i o n v i a schemes 8 and 11 are two such analogous reactions.  - 94 -  From the observation that benzene and toluene are readily nitrated by solutions of sodium nitrate in neat TFA (see Table 4) and from the results reported by Brown and Wirkkala"'"''' on aromatic nitration i n TFA i t seems certain that nitronium ions are, in fact, generated in TFA. The data contained in Table 7 and Figure 14 show that n varies from 2.5 to 4.7, indicating that nitronium ion becomes the major component of the equilibrium mixture at low concentrations of sodium nitrate. It is unlikely that any measurable amounts of n i t r i c acid would be generated since i t is a much stronger acid than TFA. 100% n i t r i c acid i s -6.3  1 1 7  (The H q value of  compared to -3.03 for TFA.) The decrease  of n as the concentration of sodium nitrate increases is possible due to simple dissociation via scheme 6. When sodium n i t r i t e was dissolved in TFA nitrosonium ions were detected by an absorption at X = 260 nm, e = 2,200. J max max  The reported  spectrum of nitrosonium ion in rperchloric acid has X = 260 nm, r max 118 £ = 4,200. The extinction coefficient recorded in neat TFA max suggested that the process for the generation of nitrosonium ion was 60% complete.  This predicts that n should be 3.9 i f the other process  is simple ionization or that n should be 4.3 i f the other process is generation of nitrous acid.  The experimental values ranged from 4.1  to 4.6 (see Table 7 and Figure 14).  These results suggest that the  cryoscopic method can be used to test which ionization process is occurring since the agreement between the spectroscopic and cryoscopic results is excellent. The experimental values of n for potassium permanganate varied from 3.0 to 5.1 depending upon the concentrations used.  Royer  26  also  - 95 reported similar v a r i a t i o n s of n.  The values of n near f i v e at concentra-  -3 tions less than 6 x 10 with scheme 3.  -3 molal (9 x 10  molar) are consistent only  The reaction shown by scheme 5, ester formation, i s not  consistent with the experimental data nor with evidence from systems.  analogous  At higher concentrations of permanganate the value of n can  be consistent with either scheme 2 or 4, but at present i t i s not possible to d i s t i n g u i s h between them. The changes recorded i n n with concentration changes are not due to v a r i a t i o n s i n K^.  The value of  f o r TFA, which was  determined  by using benzene as a solute with an assumed value of n = 1, was v e r i f i e d over the entire concentration range used by using toluene and sodium acetate as solutes.  The data i n Table 6 show only small  deviations from t h e o r e t i c a l values. It can be concluded that i n TFA the green species generated  from  permanganate i s permanganyl ion (MnO^) when concentrations of -3 permanganate are less than 9 x 10  molar.  No other reaction scheme  can accommodate the cryoscopic data. It was  found that permanganyl ion could be r e v e r s i b l y generated  from permanganate by varying the acid content of TFA-water mixtures. The pK values for t h i s process i n a v a r i e t y of solvents and at a v a r i e t y of temperatures  are l i s t e d In Table 19.  the i o n i z a t i o n correlated best with H . q  As was shown i n Section 3.10 The pK of -2.12  i s very  s i m i l a r to that reported f o r p e r c h l o r i c acid-water solutions, where 28 pK = -2.25.  I t should also be noted that i f a deuterated system i s  used that the i o n i z a t i o n i s half completed  at lower acid concentrations.  I t can be concluded that three manganese(VII) species are generated  - 96 Table 19.  pK for the Ionization of Permanganate Ion to Permanganyl Ion.  Solvent System^ -pK  H R units c Slope  r  H units o c -pK Slope  r  CF3C02H--H20, set #1  9.35  0.77  0.985  2.13  1.31  0.995  CF3C02H--H20, set #2  9.26  0.69  0.978  2.10  1.27  0.994  CF3C02H--D20  9.24  0.75  0.974  2.09  1.35  0.997  CF3C02D--D20  8.97  0.59  0.982  1.90  1.10  0.995  CF3C02H--H20, 1 4 . 6 °  9.52  0.68  0.991  2.23  1.12  0.995  >  20.0°  9.52  0.67  0.994  2.23  1.10  0.994  »  25.0°  9.49  0.71  0.997  2.21  1.17  0.997  >  30.5°  9.47  0.72  0.997  2.20  1.17  0.997  35.3°  9.39  0.69  0.985  2.14  1.13  0.986  II  II  II  II  ti  II  II  ti  »  pK is defined for the reaction, MnO^ + 2H+  MnC>3+ + H20  and was experimentally determined by the following equation, pK = H  q  (or H_) - log[Mn0 4 "]/[Mn0 3 + ].  The compounds used to make up the solutions. The original data is listed in Table 10. Note:  The H  q  or  values were assigned by determining the acid  content by titration. It was assumed that D = H and D = H_ since J o o R R i t is known that H and D are identical for 0.6 to 12.0 molar  °  ll9  sulfuric acid solutions  and that IL is identical to D i n 120 a l l sulfuric acid solutions. The same molar acid solutions, however, are more ionizing when deuterium is substituted for , , 119,120 hydrogen. Slope of log Q vs. H q or H x . See Table 10 and Figures 5 to 8.  - 97 i n TFA-water solutions and that their proportions depend upon the amount of TFA.  They are; permanganate ion (MnO^ ), confirmed by i t s  c h a r a c t e r i s t i c spectrum, permanganyl ion (MnO^ ), confirmed by the +  cryoscopic data, and permanganic acid (HMnO^), possibly present i n small amounts as a r e s u l t of the following e q u i l i b r i a .  or  4.1.3  MnO* 3  +  H„0 2  MnO " 4  +  H  +  —*• •*  *  H  +  + HMnO. 4  HMnO. 4  N i t r a t i o n and N i t r o s a t i o n i n TFA It was found that neat TFA could be used to generate nitrosonium  and nitronium ions respectively from sodium n i t r i t e and sodium n i t r a t e . The nitronium ions thus generated were used to achieve aromatic n i t r a t i o n s i n excellent y i e l d s as the data i n Table 4 i l l u s t r a t e .  The d i s t r i b u t i o n  of products from the n i t r a t i o n of toluene was found to be 31.7%  para,  67.0% ortho and 1.3% meta, quite s i m i l a r to the r e s u l t s of Brown and Wirkkala"''"'' who found 35.8% para, 61.6% ortho and 2.6% meta. Nitrosatlons were not successful.  Evidently the nitrosonium  ion i s too weak an e l e c t r o p h i l e to attack benzene or toluene.  I t was  observed that when the organic substrate was added to TFA solutions of sodium n i t r i t e a very dark solution resulted which could be decomposed by the addition of water to regenerate the substrates.  I t has been  previously reported that such complex formation r e a d i l y occurs between nitrosonium ions and aromatic rings without further reaction occurring. It was suspected that some phenolic products were formed during  121  - 98 the nitration of toluene and benzene (see Table 4).  Figures 15 and 16  show the spectral similarities of the suspected phenols with that of known phenols.  Unfortunately the yield of the phenolic products was  too minute to allow positive identification.  There is one report in  the literature of phenols being isolated in trace amounts as byproducts 79 from the nitration of toluene  and i t is known that nitrophenols can  be obtained in up to 85% yield from the oxynitration of benzene, a process which makes use of mercuric nitrate dissolved in concentrated -A n i t r i•c acid. 1  2  2  It is proposed that the phenols formed in small amounts in this investigation result from attack by the oxygen end of the nitronium ion via the following scheme.  ArH  +  NO-+  ArH-ONO+  ArONO  +  ArOH +  4.2  >  >•  ArH-0N0+  ArONO  + H+  H20  >  ArOH +  HN02  N02+  >  nitrophenol + H +  Products and Stoichiometries The organic products from the permanganate oxidation of a  variety of substrates in TFA-water are in most cases carboxylic acids.  0.8  440  420  400  380  ' 360  340  320  300  X nm Figure 15.  Spectra of side products (from the n i t r a t i o n of benzene) i n a c i d i c and basic media.  280  - 101 If an aromatic ring is present extensive degradation can occur yielding, usually, no identifiable products (see Table 3).  The inorganic  reduction products appear to be manganese dioxide, which could be observed as a fine precipitate, and manganese(II).  The respective  amounts of these two products are listed in Table 20. From these results the following reaction sequences can be outlined and these w i l l be further elaborated in subsequent discussions.  The  sequences are outlined for a five-equivalent change (Mn^**—*• Mn**). Another parallel series could be listed for a three-equivalent change , M VII IVN (Mn •* Mn ). note: n = m + £ + 2 (a)  Alkanes VII 5C H. + 12Mn n 2n+2  5C  (b)  mH2m+lC02H  —»  +  5 C  5 C  1H2^+1C°2H  +  i  m  ^  +  +  >• 5C H„ 0 n 2n  > 5C H. ,-,C0„H m 2m+l 2  +  8 M n 2 +  Ketones 5C H. 0 n 2n  (d)  1H2£+1C02H  >  Alcohols VII 5C H„ ..OH + 8Mn n 2n+l  (c)  5C H„ ^.OH —-> 5C H. 0 n 2n+l n 2n  +  VII 4Mn  —>  5C H. ...CO-H + 5C,H o 0 ,-C0.H + 4Mn m 2m+l 2 1 21+1 2  Aldehydes 5C H, 0 + 4Mn V I 1 n 2n  >  5C .H„ .CO.H + n - l 2n-l 2  4Mn 2+  2+  - 102 -  Table 20.  Manganese Reduction Products from KMnO, Oxidations.  Reductant  % Mn  % Mn0„  Reductant  2 36 2 2 5 53 62 58 24 27 21 21 20  Cyclopentane Cyclohexane Cycloheptane Cyclooctane Cyclohexanol Cyclohexanone Acetophenone 2-Pentanone 3-Pentanone Formaldehyde Acetone  % Mn  % MnO  H„ = -6.00 Toluene Benzene Ethylbenzene Cumene t-Butylbenzene Methanol 2-Pentanol 3-Pentanol Benzyl alcohol Benzaldehyde 1-Phenylethanol 2-Phenylethanol 2-Phenyl-2-propanol  98 64 98 98 95 47 38 42 76 73 79 79 80  = -8.00 n-Pentane n-Hexane n-Heptane n-Octane n-Nonane n-Decane n-Undecane n-Dodecane n-Tridecane Benzene Isopentane  50 50 50 49 49 49 44 42 38 96 74  50 50 50 51 51 51 56 58 62 4 26  DNR - did not react sufficiently.  Benzyl alcohol Benzaldehyde 1-Phenylethanol 2-Phenylethanol 2-Phenyl-2propanol  57 57 56 62 57 56 56 30 30 49  43 43 44 38 43 44 44 70 70 51  67 71 63 87 80  33 29 37 13 20  DNR  DNR  - 103 -  (e)  Arenes Arene  +  2.5Mn  decomposition products  +  2.5Mn  2+  These outlines are a l l consistent with the experimentally determined stoichiometries listed in Table 5.  4.3  Oxidation of Alkanes I n i t i a l l y a sulfuric acid-water medium was considered as a  possible solvent system to investigate the homogeneous oxidation of alkanes by permanganate. this solvent system.  Appendix B l i s t s the data obtained using  Although extreme care was taken to ensure  homogeneous solutions reproducibility was poor and, worst of a l l , the order with respect to alkane varied from 0.7 to 2.0 with no apparent pattern.  The kinetics were consistently f i r s t order with respect to  permanganate but the discrepancies with respect to substrate order could not be resolved.  Perhaps micelle formation is responsible for  the random rate increases with increased substrate content, since micelles are known to give rise to anomalously fast rates in some 123 cases. The TFA-water system, on the other hand, was found to be extremely satisfactory,  being capable of solubilizing a l l substrates examined  and y6t causing very l i t t l e decomposition of the oxidant.  A l l of the  alkane oxidation data are listed in Appendix C, trials 129-489, 1209-1216, and 1306-1307. The excellent correlation of the absorbance-time data for up to two half-lives of permanganate with the pseudo first-order rate  - 104 equation (see Section 3.3 for the equation) confirms a first order dependence upon permanganate (refer to correlation coefficients of the alkane t r i a l s ) .  The data presented in Table 21 and illustrated in  Figures 17 and 18 indicate that the rate law contains terms which show first-order dependence both upon alkane concentration and h^. The complete rate law can be written as,  -d[Mn04 ]/dt = k3[Mn04 J[alkane]h R  The data presented in Table 22 shows that a large primary kinetic isotope effect is observed over a wide range of acidity.  (All of  the oxidation rates for deuterated compounds were corrected for the presence of some protium using the equation of Lewis and Funderbuck; %  =  (k  obs"f  124  V / ( 1 - f ) '>  f = fraction of protium present in compound k , = observed rate for deuterated compound r obs kR  = observed rate for protium analogue.  These results are consistent with a transition state involving one molecule each of oxidant and alkane.  The rate-determining step  clearly involves carbon-hydrogen bond scission, as indicated by the large primary isotope effects.  The cleavage of the carbon-hydrogen bond  could involve either hydride transfer or hydrogen abstraction.  The  statistically corrected 1 ° : 2 ° : 3 ° ratios obtained from the oxidation rates of neopentane, n-pentane, and isopentane were found to be 1:180:3,300.  These ratios are comparable to results obtained for  reactions which are believed to occur by hydrogen-atom abstraction.  - 105 -  Table 21.  Order of Reactants Involved in the Permanganate  Oxidation  of Alkanes in TFA-Water. Substrate Ethane Propane n-Butane n-Pentane Isopentane Neopentane Cyclopentane n-Hexane Cyclohexane Cyclohexane-d;L2 n-Heptane Cycloheptane Cyclooctane  Note:  Order in substrate 1.1 0.6 1.1 1.0 1.0 1.0 1.0 1.1 1.0 1.1 0.9 1.0 1.0 N 1.1 1.0 1.1  Trials  r  Order in h„  129--134 141--148 149--155 163--169 298--304 305--311 285--290 330--336 341--347 192--198 185--191 373--379 408--423  .960 .973 .998 .999 .993 .985 .994 .991 .994 .994 .991 .997 .999  N N N 1.0 1.1  170--177 285--311  .995 .999  0.8 1.0 1.0  v, 322-• 3 3 6 b 337-" 3 5 9 b 185--223b  .991 .999 .997  1.1  360--435  .994  228--233 438--444 469--475  .999 .998 .998  1.1 1.1 0.9 0.8  384--405^ 224--244b 436--459b 466--489b  .990 .997 .999 .996  -  Trials  r  -  -  --  -  -  error in orders are + 5%.  Order with respect to permanganate was in a l l cases 1.00, r = 0.999. b  c  Only those t r i a l s where the solvent was TFA-H^O and T = 2 5 . 0 ° were used. Only those t r i a l s where C,D.. _ was used.  N  Designates order not determined.  1.9  1.6 4  1.3 J  1.0  A  0.7 H  0.4 H  0.1 H 0-1 Figure 17.  1  1  0.5  1  .  1  ,  0.9 1.3 3 + log[alkane] Log k vs. log[alkane] for the oxidation of variety of alkanes.  —  i  1  1.7  - 108 -  Table 2 2 . Kinetic Isotope Effects in the Permanganate Oxidation of Cyclohexane.  k  C6H12/kC6D12  K C  6 12 H  / K C  6 12 D  (corrected) 3 6.12 6.38 6.66 6.74 6.96 7.40 7.70 7.91  5.5 4.8 4.5 4.5 4.4 4.9 6.0 4.1  5.3 4.7 4.3 4.3 4.2 4.7 5.7 4.0  "HR  \ o \ o  6.26 6.93 6.96 6.10^ 7.48  b  1.2 1.0 1.0 2.6 2.3  C  C  C  = 0^Q^s~i kjj)/(l - f)> as discussed  Corrected using the equation in the text. b  For isopentane, k^ Q/^JJ Q = 1.2 (IL^ = - 5 . 9 5 , 7 6 % D) and for n-hexane, k  D O^H 0 =  1  ,  0  ^HR = ~ 6 , 9 3 »  7 2 %  I  n  b o t h  c a s e  s the solvent  was made up from TFA and D 0. 2  c  Solvent system made from CF C0 H and D 0 ( 7 4 % D at 3  7 2 % D at  d  1^ = - 6 . 9 3 , 7 1 % D at  2  2  I L = -6.96).  Solvent system made from CF^CO^ and D 0. 2  = -6.26,  - 109 -  The free-radical bromination ratios for butanes are 1:82:1,600  125  and the chromic acid oxidation ratios for alkanes are 1:110:7,200, both processes taking place by hydrogen-atom abstraction.  34  On the  other hand, the ratios for benzyl chloride solvolysis are 1:100:100,000, 126 and this reaction is known to proceed via carbonium ions to hydride transfer in the present case).  (equivalent  Further, the data obtained  for the oxidation of cycloalkanes in this study are consistent only with processes known to involve hydrogen-atom abstraction (see Tables 23 and 24). * The effect of substituents is illustrated in Figure 19. The p of -2.4 indicates that considerable positive charge develops in the * transition state. The magnitude of p is comparable to that for * 129 solvolysis reactions where carbonium ions are involved (p = -3.0 ), and is considerably larger than that observed for the chromic acid * 130 oxidation of aliphatic alcohols (p = -1.06 ). * 1-31 The values of a used for Figure 19 are those reported by Taft, 132 * some of which were refined by Cohen et a l . The a for R = -Ctt^EO^ * was not available in the literature.  It was estimated using a  = -0.50  for R = -CH^CH^Nu^ and a factor of 2.5 approximated from Taft's data for the attenuation effect of one methylene.  This gives a a  = -1.25  for R = -CH 2 N0 2 . There was no observable salt effect upon the oxidation rate, as shown by the results depicted in Figure 20. Before proposing a mechanism which accounts for a l l of the before mentioned observations i t renains to be determined which of the three possible oxidants are involved in the reaction; namely permanganate ion  - 110 Table 23.  Comparative Reactivities of Methylene Groups in Cycloalkanes Relative to Those in the Corresponding n-Alkane. Reaction  Ratios C  5  C  6  C  7  C  8  T _ 0° T = 49.5°  1.45 1.38  1.47 1.47  2.18 2.02  2.49 2.17  2. Br-, CH3CN,  T = 74.5° T = 125°  1.47 1.31  0.47 0.75  3.24 2.79  8.43 5.56  3. CC1 •  T 74.5° T = 74.5°  1.43 1.75  0.95 0.43  T = 74.5°  1.52  5.0° , TFA-H20, T T = 225.0  2.61  V3  V  CC1 -  CH3CN, CCI4,  3  4. C , H C - , CH.CN, O  D  VII  5. Mnv  =  -  3.53 5.10  0.54  2.39  3.83  0.75  2.8  6.4  _  J =  Reactions 1 to 4 are hydrogen abstraction by the radical shown in the particular solvent. A l l the data for processes 1 to 4 are courtesy of Dr. N Bunce. ^' Reaction 5 is from this study. A l l the ratios were calculated in the following manner; Ratio = k(cyclic)/k(open chain) k(cyclic) = k experimental/number of CH2 groups in ring k(open chain) = k experimental/number of CH2 groups in chain.  Table 24.  Comparative Reactivities of Cycloalkanes• Reactions  Ratios C  5  C  6  a C  7  C  8  1. Cr03,99% CH3C02H,  T = 60°33  1.98  1  6.6  22.4  2. M n V I 1 , TFA-H20,  T = 25°  1.4  1  5.2  14.5  14.0  1  25.3  3.  Acetolysis of tosylates, T = 70° Ratios are  128  k(cycloalkane)/k(cyclohexane).  191  0.8  0.7 A  0.6-4  0.5H CM  0.41  0.31  0.2  0.1  0.2 Molarity of sodium t r i f l u o r o a c e t a t e  0.3  Figure 20. Salt effects on the permanganate oxidation of cycloheptane (IL^ = -5.6, t r i a l s 460-465).  - 113 (MnO^ ), permanganyl ion (MnO^ ), and permanganic acid (HMnO^). Permanganate ion can be excluded as one of the major oxidants since in the highly aqueous region, where i t is the dominant species, very l i t t l e oxidation is observed.  Further, i f permanganate were one of  the major oxidants one would not expect such large rate increases with increased acid content since the concentration of permanganate ion actually decreases as the acid content rises. It has been demonstrated in Section 4.1.2 that the green species generated from permanganate ion at low concentrations of water in the TFA-water system is permanganyl ion (MnC>3+).  The equilibrium constant  for this process showed a small isotope effect i f the medium was made up from CF3C02H and D 2 n (I.e.  less than 100% D) but a large isotope  effect i f the medium was made up from CF^CO^ and D20 (pK (CF3C02H-H20) = -2.13, pK (CF3C02H-D2O) = -2.09, and pK (CF3C02D-D20) = -1.90). . If permanganyl ion is one of the major oxidants these solvent effects predict that i f the oxidation is carried out in CF3C02H-D20 that k(H-D20)/k(H-H20) (H or D designates CF3C02H or CF3C02D) should be greater than one and should increase as the D^O content increases. Further, i f CF3C02D-D20 is used k(D-D20)/k(H-H20) should be appreciably greater than one with a possible maximum value of 1.7 (analog of 0.23, the difference in pK's).  Table 22 l i s t s the solvent isotope  observed and this trend is indeed observed.  effect  This strongly suggests  that permanganyl ion is the major oxidant, which is consistent with * the large negative value of p . It is not possible to directly show the amount of oxidation due to permanganic acid.  However, from the results of aldehyde and alcohol  - 114 oxidation, which are discussed in Sections 4.5 and 4.6, i t appears that permanganic acid is not an effective oxidant of alkanes compared to permanganyl ion. By applying the arguments presented in Section 1.8 to the observation that the alkane oxidation rate shows near unit-order dependence upon h i t is possible to decide which of the two possible R mechanisms best fits the experimental data.  The two possible mechanisms,  those involving permanganic acid and permanganyl cation, are: (a)  HMnO^ as the oxidant, Mn04~  +  H+  HMn04  +  alkane  K  •»  HMn04  *•  r - Kk'[Mn04-] [alkane] f  (b)  , fast  products  M n  .f 4  a l k a n e  , slow  V  / f  Mn0.j+ as the oxidant, MnO ~ 4  +  2H +  + MnO^  +  alkane  -  k"  Mn0 o + 3  *•  +  products  H.O 2  , fast  , slow  r = K'k"[MnO ~ ] [ a l k a n e ] £ _ . - f a 2 +/a u n f . 4 MnO, alkane H H„0 t 4 2 The experimental rate law is r = k „ [ M n O , ] [ a l k a n e ] h . The evaluation consists of seeing which of the two sets of activity coefficients shows medium responses parallel to that shown  - 115 by h n , i . e . the experimental fact that log h vs. log k» has unit R K J slope is tested.  Normally such evaluations are not possible since  the necessary activity coefficients are not known, but i f four assumptions are made the evaluation can be made in this case.  These assumptions are:  (i) The activity coefficients, which are only available for sulfuric acid-water systems, w i l l be assumed to show similar changes in TFAwater solutions; ( i i ) The activity of the proton (a +) w i l l be n a n d n s approximated by fgH+/fg since a^j. = h Q f B H +/f B 0 ' * almost constant over large concentration variations of TFA-water mixtures; ( i i i ) A transition state containing permanganyl ion (MnO^+) and alkane is assumed to have solvation requirements similar to a carbonium ion whereas a transition state containing permanganic acid (HMnO^) and alkane is assumed to have solvation requirements similar to a neutral molecule; (iv) It w i l l be assumed that f., _ - = f „ , ~ - and f ... = ' MnO, CIO, alkane 4 4 benzene For mechanism (a) to be correct the activity quotient which should correlate with H„ is log f_. - _f a.^/f, which becomes & Mn0 R 4 alkane WT t log  -^f^BH+^t^B*  n i s m (b) to be correct the activity 4 2 quotient which should correlate with H_ is log f._ _ - f . . a^/a,, _f. n R ° MnO. alkane tr H„0 t 4 2 2 2 which becomes log ~^f^BH+^aH 0^R+^B* Table 25 contains a l l the F o r  mecna  values of the activity coefficients used and also l i s t the values for the quotients predicted by the two mechanisms along with H  q  and H R for  comparative purposes. It can be seen that only the changes in the quotient from mechanism (b) parallel  the changes in H , the changes of the quotient from  mechanism (a) being closer to changes in H q .  (The changes observed from  - 116 Table 25. Activity Coefficients  i n Sulfuric Acid-Water Mixtures.  Salt or Compound  % H SO. i nH S0 --water solution 4  Triphenylcarbinol''"^ 133 Benzene 2,6-Dichloro-4-nitroanilinel^S 8  l o g  1  0  1  f  B  log f  8  ^-Chloroanilium+PCP"  ROH  f  * log f l o g  Tri (p_-methoxyphenyl)carbonium+PCP" 0  8 l o g  Tetrabutylammonium CIO -  BH+  f  +  1  Functions l o g  H 0 134  a  3  2  2  l o g  3  f  cio "  4  9.6%  19%  29%  40%  50.5%  0.34  0.37  0.73  0.83  0.73  0.14  0.24  0.31  0.36  0.36  0.03  0.07  0.03  0.02  0.04  0.10  0.44  -0.13 0.86  -0.14 -0.40 0.20  -0.32  1.64  2.26  -0.30  -0.39  -0.52 -0.80  -1.18  -0.03  -0.06  -0.12 -0.25  -0.44  4  109  2  ~R H  l 0 g  f  C10 - <|» BH H 0 R B f  f  4  +/a  f  +f  f  -H o  1  f  3  1.90  3.18  4.80  6.60  -0.01  0.61  1.77  3.17  5.26  -0.23  -0.02  0.31  0.98  1.48  1.01  1.70  2.41  3.38  2  C10 - BH+ B  l o g  0.72  /f  0.31  4  PCP , pentacyanopropenide. -  a The activity coefficient of the cations are relative to a standard S + cation, f = f^_/f , S i s the standard cation, tetraethylammonium ion. +  k  +  The activity coefficients of the anion i s relative to the standard cation, f_ = f_«fg+.  - 117 high to low acid content are, A H  R  = 5.88, A H q = 3.07, A mechanism (a) =  1.71, and A mechanism (b) = 5.27.) This evaluation, although made with some assumptions, shows that only the mechanism involving permanganyl ion is consistent with the experimentally observed acid catalysis. The activation parameters listed in Table 26 are comparable to those  f  reported for a wide variety of permanganate oxidations ( A H = 5 to 16 t 135 kcal/mole, A S = -15 to -38 e.u. ). There appears to be a general trend in this data.  As the TFA content increases (larger negative  values) the enthalpy decreases and the entropy becomes more negative. This may be caused by increased solvation of the transition state by TFA.  The ability of TFA to solvate carbonium ion-like species has  . . , . 18,19 been previously noted. The evidence presented in this section, along with the product studies and stoichiometries, are consistent with the following mechanism.  2H+ + MnO ~ 4  * —  Mn0 3 + + R 2 C H 2  Mn0„ + + Ho0 3 2 *  [R 2 C H *  +  HMn0  , fast  3  +  ]  > r a t e determining  [R2CH« + HMn03+]  >  [R2CH-0-Mn02H]  , fast  [R2CH-0-Mn02H]  *  R^HOH + MnV  , fast  2  »  R2CH0H + M n V I 1  >  VII R2CH0H + Mn  >  VII R2C=0 + Mn V 5Mn  >  >  R  C = 0  carboxylic acids carboxylic acids  2+ VII 2Mn + 3Mn  f  a  s  t  , fast , slow , fast  - 118 Table 26.  Activation Parameters  for Permanganate Oxidations in  TFA-Water. Substrate n-Pentane n_-Hexane n-Dodecane Cyclopentane Cyclohexane Cycloheptane Cyclooctane Benzene Toluene  Methanol 3-Pentanol Cyclohexanol Benzyl alcohol 2-Pentanone Cyclohexanone 3-Pentanone Ace tophenone^  Calculated from  t AH  Trials 170--177 211-•218 . 269-•274 350-•357 428--433 450-•457 480-•487 518-•525 749-•753 705-•714 695-•704 741--748 791-•795 850-•857 869-•879 923-•930 931-•937 1024-•1031 1065-•1072 1187-•1196 1246-•1255  7. 52 7. 77 7. 41 7. 02 7. 70 7. 20 6. 80 5. 70 2. 52 4. 13 4. 26 5. 17 3. 18 5. 84 5. 40 3. 58 6. 72 8. 86 6. 34 7. 90 6. 41  7.87 5.74 8.37 7.15 5.24 6.07 7.21 5.57 11.37 10.59 9.43 5.58 12.29 7.75 7.03 8.21 6.86 9.79 11.45 5.64 8.31  kcal/mole ±0.08 ±0.02 +0.08 ±0.05 ±0.07 ±0.02 ±0.08 ±0.09 ±0.1 ±0.1 ±0.08 ±0.08 ±0.08 ±0.1 ±0.1 ±0.04 ±0.2 ±0.2 ±0.06 ±0.03 ±0.03  -AS  t  31.2 35.5 25.0 33.1 36.8 32.9 29.0 40.7 25.2 22.1 25.9 35.5 25.0 33.1 36.1 32.3 27.6 25.3 21.3 40.0 52.0  e.u. ±0.5 ±0.2 ±0.3 ±0.5 ±0.7 ±0.1 ±0.5 ±0.9 ±0.3 ±0.3 ±0.3 ±0:.7 ±0.3 ±0.6 ±0.6 ±0.2 ±1.5 ±0.8 ±0.2 ±0.03 ±0.03  where, rate - k2[Mn0^ ][substrate].  Zero-order data was used,  k was from rate = kfacetophenone].  r .987 .999 .989 .992 .974 .999 .983 .969 .986 .955 .979 .973 .995 .977 .951 .997 .840 .953 .997 .999 .999  - 119 -  The transition state can be cyclic,  R  H—-0^  2  or acyclic  1 N  R2  NJ  ^  n //  T - r H r - " 0=-^Mn +  In the f i r s t case the i n i t i a l product w i l l be the Mn(V) ester and i n the second case a radical and Mn(VI), which would probably quickly recombine to give the Mn(V) ester.  It is not possible at present to  distinguish between these two possibilities. The product studies revealed only minor amounts of alcohols and ketones.  The alcohols can be intermediates in the oxidative sequence  since in a l l cases the alcohol is much more reactive than the alkane. Ketones, however, cannot be free intermediates since they were found to be less reactive than the alkane (see Appendix C).  It is possible  that ketones are formed but that they react with some manganese species of intermediate valency with which they are trapped in a solvent cage. Some previous reports on the reactions of ri-alkanes indicated that 37 38 136 not a l l methylenes are equivalent in reactivity. appears to be the case in this investigation.  '  '  This also  When the products of the  oxidation of n-pentane were analyzed i t was found that a small amount of ketone was formed.  This was actually a mixture of 2-pentanone (66%)  - 120 -  and 3-pentanone (34%).  The kinetic data for the oxidation of these  two ketones indicate that 3-pentanone is six times more reactive to oxidation by permangante than is 2-pentanone.  This fact, along with the  statistical correction of two (2-pentanone can be formed by attack at two positions in pentane but 3-pentanone at only one position), showed that i n i t i a l l y the 3-position in n-pentane is favoured 6:1 over * the 2-position.  Consulting Table 27 i t can be seen that Taft s a  values  indicate that the internal methylenes should differ in reactivity from the methylenes adjacent to the methyl group. * tion process, where p  In the case of this oxida-  = -2.4, the internal methylenes should be  preferentially attacked.  In general the number of most reactive  methylenes can be calculated by n-4, where n is the total number of carbons in the chain. Figure 21 shows that as the alkane chain length increases there is a regular increase in the rate of oxidation.  These experimental  rates, expressed as ratios relative to one of the alkanes, compare favourably only with the number of most reactive methylenes. Tables 28 and 29 contain these comparisons. It appears that the chromic acid oxidation of n-alkanes in acetic acid does not exhibit such selectivity.  The rate data reported by  35 Rocek and Mares  clearly correlate  with the total number of  methylenes  (see Table 30). It can be concluded from this investigation that the oxidation of alkanes by permanganyl ion and micro-organisms are governed by quite different factors.  The biological system is known to attack the  terminal methyl group selectively, possibly because of steric control,  Table 27.  Compound propane n-butane n-pentane n-hexane n-heptane n-octane n-nonane n-decane n-undecane n-dodecane n-tridecane a  *  Calculated-a Values of Individual Carbon Atoms in Some n-Alkanes.'  1 .100 .115 .130 .145 .160 .175 .190 .205 .220 .235 .250  2 0 .100 .115 .130 .145 .160 .175 .190 .205 .220 .235  3 .100 .100 .200 .215 .230 .245 .260 .275 .290 .305 .320  4 .115 .115 .215 .230 .245 .260 .275 .290 .305 .320  5  .130 .130 .230 .245 .260 .275 .290 .305 .320  Carbon number 6 7 8  .145 .145 .245 .260 .275 .290 .305 .320  .160 .160 .260 .275 .290 .305 .320  .175 .175 .275 .290 .305 .320  9  .190 .190 .290 .305 .320  10  11  12  13  .205 .205 .305 .320  .220 .220 .320  .235 .235  .250  * * 131 a was calculated by adding a of the two alkyl segments using Taft s O" values and extrapolated values. * * Note: a values are available only up to alkyl segment length of C^Cn-butyl), a l l other a values of segments longer than C4 were approximated by assuming a constant increase of 0.015 (i.e. C 2 = -0.100, C3 = -0.115, C4 = -0.130, and C5 = -0.145 etc.) The important features of this table are that methylenes next to the methyl groups are always significantly different from the internal methylenes, which are identical to each other.  180  i  i  •  i  5  6  7  Figure 21.  Oxidation rate vs. number of carbon atoms i n n-alkanes.  :  1  8 9 10 No. of carbon atoms i n chain  ,  11  _ _ — p _  12  - 123 -  Table 28.  Relative Ratios of Numbers of Methylenes Present i n n-Alkanes.  Compound  (a) Relative to  (b) Relative to  n-Pentane  n-Hexane  n-Heptane ri-Pentane  n-Hexane n-Heptane  n-Pentane  1.00  0.75  0.60  1.0  0.5  0.33  n-Hexane  1.33  1.00  0.80  2.0  1.0  0.67  n-Heptane  1.67  1.25  1.00  3.0  1.5  1.00  n-Octane  2.00  1.50  1.20  4.0  2.0  1.33  n-Nonane  2.33  1.75  1.40  5.0  2.5  1.67  n-Decane  2.67  2.00  1.60  6.0  3.0  2.00  n_-Undecane  3.00  2.25  1.80  7.0  3.5  2.33  n-Dodecane  3.33  2.50  2.00  8.0  4.0  2.67  n-Tridecane  3.67  2.75 '  2.20  9.0  4.5  3.00  (a)  Ratios of the t o t a l number of methylenes present.  (b)  Ratios of the most reactive methylenes present i n the alkane.  This  number was determined by assuming that the trend shown i n Table 27 continues, i . e . the methylenes next to the methyl group, are less reactive.  This number of methylenes i s given by n-4 (n = t o t a l  number of carbon atoms i n n-alkane).  - 124 Table 29.  Experimental Ratios for n-Alkane Oxidation Rates.  Relative to Compound  n-Pentane  n-Hexane  Predicted Ratios ii-Heptane  Reactive -CH~-  (a) H_ » -7.74, T = 2 5 . 0 ° , [MnO. ] = 4.136 x 10 R H  Total -CH„-  M  n-Pentane  1  0.4  0.4  1.0  1.0  n-Hexane  2.5  1  0.9  2.0  1.3  n-Heptane  2.7  1.1  1.0  3.0  1.7  n-Octane  3.9  1.6  1.5  4.0  2.0  n-Nonane  5.0  2.0  1.9  5.0  2.3  n-Decane  7.1  2.9  2.6  6.0  2.7  n-Undecane  8.6  3.5  3.2  7.0  3.0  n-Dodecane  10.2  4.2  3.8  8.0  3.3  n-Tridecane  14.5  5.9  5.4  9.0  3.7  Ca)  = -8.00, T = 2 5 . 0 ° , [Mn04~] = 4.024 x 10~4 M  n-Pentane  1  0.5  0.4  110  1.0  n-Hexane  1.8  1.0  0.8  2.0  1.3  n-Heptane  2.5  1.3  1.0.  3.0  1.7  n-Octane  3.2  1.7  1.3  4.0  2.0  n-Nonane  4.4  2.4  1.8  5.0  2.3  n-Decane  5.1  2.8  2.1  6.0  2.7  n-Undecane  6.3  3.4  2.5  7.0  3.0  n-Dodecane  7.4  4.0  3.0  8.0  3.3  n-Tridecane  8.0  4.3  3.3  9.0  3.7  - 125 -  Table 30.  Theoretical and Experimental Data f o r the Chromic Acid Oxidation of n-Alkanes .  Compound  C  4 10  C  7 16  C  9 20  C  11 24  C  16 34  C  22 46  H  H  H  H  H  H  9 kxlO M  1 1 s  Ratios  Statistical  Most Reactive CH  2  1.12  1.0  0.39  1.0  0.4  1.0  0.67  2.90  2.59  1.0  2.5  1.0  1.5  1.0  3.90  3.48  1.34  3.5  1.2  2.5  1.66  5.40  4.82  1.86  4.5  1.8  3.5  2.33  8.07  7.20  2.78  7.0  2.8  6.0  4.0  11.14  9.95  3.84  10.0  4.0  9.0  6.0  A l l k i n e t i c data from reference 35. Ratios from the experimental data obtained by d i v i d i n g by either k f o r n-butane or n-heptane. Ratios expected  considering a l l ' methylenes as i n Table 28.  Ratios expected  from most r e a c t i v e methylenes as i n Table 28.  - 126 -  whereas permanganyl ion preferentially attacks the internal methylenes because of electronic effects.  Summary  The data presented for the Mn(VII) oxidation of alkanes is consistent with a mechanism which involves attack by permanganyl ion on the neutral substrate molecule.  In the transition state considerable  positive charge develops on the carbon atom subject to attack.  The  rate-determining step involves hemolytic carbon-hydrogen bond scission.  Not a l l methylenes appear to be equal in their reactivity  towards oxidation by permanganyl ion.  In general the number of  reactive sites for n-alkanes longer than four carbon atoms is given by n-4 (n = number of carbon atoms in the chain).  4.4  Oxidation of Arenes The kinetic data for the oxidation of arenes by permanganate in  TFA-water solutions are tabulated in Appendix C, t r i a l s 490-769 and 1197-1208. The excellent correlation of the time-absorbance data for up to two half-lives of permanganate with the pseudo first-order equation confirms the first-order dependence upon permanganate concentration. The data listed in Table 31 (some of which is depicted in Figures 22 and 23) indicate  that the rate equation contains first-order terms  both in substrate concentration and h . be expressed as;  The general rate equation can  - 127 -  Table 31.  Order of Reactants Involved in the Permanganate Oxidation of Arenes.  Substrate  Benzene  Order in substrate 1.0  Trials  r  h  496--502  0.999 it  Toluene  1.0 1.0 1.1 0.9 1.0 0.8 1.2 1.1 1.1 1.0 0.9  544--550 661--668 551--557 537--543 558--564 565--571 572--578 579--585 586--592 593--599 600--605  0.998 0.995 0.961 0.995 0.989 0.998 0.989 0.984 0.998 0.980  Toluene-dg  1.0  669--676  0.999  Note:  Order i n  Trialsb  r  R 490--536  0.996  0.8 0.7 C 0.7° 0.8 C 0.8 C  537--763 537--571 572--605 606--694 695--763  0.993 0.999 0.998 0.992 0.991  0.9 C  618--736  0.993  1.0 C  Errors in orders are + 5%.  In a l l cases the order of permanganate was 1.00, r = 0.999. Only those t r i a l s where T = 2 5 . 0 ° , Hy) was the co-solvent. The order of h^ was consistently less than one but i f h was used the order was near five with poorer correlation coefficients.  - 130 Figure 24 illustrates that the oxidation rate i s not affected by added salts.  The transition state appears to be achieved from one  molecule of arene and one molecule of oxidant. upon H  The clear dependence  and the observed solvent isotope effects (see Table 32)  indicate, as was the case with alkanes, that permanganyl ion i s the active oxidant.  (The observed rate increases with increased deuterium  content parallel the changes i n the pK for the generation of permanganyl ion.)  Up to this point the arene oxidation appears to be similar to  the alkane oxidation, but the data i n Tables 32 and 33 indicate definite mechanistic differences.  There i s no primary kinetic isotope effect  observed when either toluene-a-d^ or toluene-dg are used i n place of toluene.  Further, there are only very l i t t l e rate differences  observed when the alpha carbon-hydrogen bond i s varied from primary to tertiary.  These data indicate that i n the rate-determining step there  is no carbon-hydrogen bond scission, either on the ring or on the alpha carbon.  Table 33. Comparative Rate Ratios for the Permanganate Oxidation of Toluene, Ethylbenzene, and Cumene. -H  of Medium  3.07 3.18 3.39 3.88 4.44 4.50 4.82 5.39  Toluene:Ethylbenzene:Cumene  1:1.9:1.8 1:1.5:1.3 1:1.7:1.6 1:1.4:1.5 1:1.4:1.4 1:1.3 1:1.3:1.4 1:1.2:1.2  0.9  0.6 -\  0.5 1  0.4  #  sodium perchlorate  ©  sodium t r i f l u o r o a c e t a t e  -I  0.1 Figure 24.  0.2 Molarity of s a l t  0.3 solution  Salt effects on the permanganate oxidation of benzene.  ( T r i a l s 526-533),  0.4  - 132 -  Table 32.  Kinetic Isotope E f f e c t s f o r the Permanganate Oxidation of Arenes.  Substrate  k(D 0)/k(H 0) 2  Toluene/toluene-d o Q  Toluene/toluene-a-d  3  a  2  1.06  2.34  1.11  3.07  0.98  3.39  0.95  3.52  1.00  3.88  1.00  4.42  0.93  4.44  1.01  4.44  0.91  4.50  1.01  4.82  1.03  5.28  0.99  5.29  0.93  5.70  0.94  2.34  1.01  3.52  1.04  4.44  1.10  5.28  Toluene  2.06  4.47  2.23  4.83  Toluene-dg  2.22  4.83  Benzene  1.16  5.67  1.48  5.78  1.14  6.26  1.04  6.96  CF„C0_H-D 0  solvent system.  - 133 -  The product studies and stoichiometrics (see Tables 3 and 5) indicate that considerable r i n g degradation  occurs.  The stoichiometry  of 2.5 i s w e l l above that of 1.2 predicted f o r the oxidation of toluene VII 2+ to benzoic acid (Mn reduced to Mn ). Further, the rate of oxidation of t^-butylbenzene i s comparable to the rate of oxidation of toluene which i s consistent with considerable r i n g attack. The  substituent e f f e c t s on the oxidation of benzene c o r r e l a t e  + best with a values  (see Figure 25).  + The large negative value of p =  -5.2 indicates considerable p o s i t i v e charge development on the r i n g i n the t r a n s i t i o n state. When the oxidation of toluene i s considered  as a sidechain  oxidation the substituent e f f e c t s , depicted i n Figure 26, show random s c a t t e r , but i f the substituted toluenes  are considered  as di-substituted  benzenes undergoing r i n g attack the substituent e f f e c t s are more orderly (see Figure 27).  The c o r r e l a t i o n i n the l a t t e r case i s s t i l l  poor, possibly owing to considerable electron-withdrawing  side-chain oxidation when  substituents such as carboxy or n i t r o are present.  The permanganate oxidation of arenes has several features i n common with e l e c t r o p h i l i c aromatic n i t r a t i o n .  Nitrations i n sulfuric  acid-water medium are known to c o r r e l a t e with  more p r e c i s e l y  73 H + l o g a^ Q, R  and they are known to e x h i b i t no primary isotope  7 A~ 7 6 effects. These features are believed to be due to a mechanism involving r a t e - l i m i t i n g e l e c t r o p h i l i c a t t a c k ^ ^ followed by f a s t 78 4  proton loss to the solvent  to y i e l d the n i t r a t i o n product. I t  appears that a l l the k i n e t i c and supplementary evidence from t h i s i n v e s t i g a t i o n on the permanganate oxidation of arenes i s consistent  3.9  £-CH„0 < 3  r = 0,97 D+  2.6  = -5.21  1, I>-CH3 2, ^-CH 3 CH 2 1  oo° ©  4  3, p-(CH 3 ) 2 CH 4, p-(CH 3 ) 3 C  1.3 CN  CN  60  benzene  0.0  LO  o  0 p-F p-Cl -1.3 m-C02H -2.6 H m-NO,  -3.9  -0.8  Figure 25.  -0.6  -0.4  -0.2  +0.0  0.2  Substituent effectson the permanganate oxidation of benzene. j + m or p designates the particular a value used.  0.4  0.6  Log k„ „+/...,, r,-,x 2 " ° o (.trials 505-517). s  c n c  0.8  P  X  unsubstituted  X  r  =  0.70  X X  m-Cl © m-F  0-  X X  p-Br  1.84  1.3H  O m-C02H  O m-NO,  X  X  © £-00 H  X ©  0.1 Figure 26.  0.2  0.3  0.4  0.5  Substituent effects on the permanganate oxidation of toluene.  0.6 Log  0.7  0.8  vs. a • (Trials 681-694)  2.4  - 137 -  with a mechanism that involves rate-limiting electrophilic aromatic attack by permanganyl ion. A possible scheme which accounts for a l l the observations can be depicted as the following:  (a)  Ring attack, 2H  + MnO.  Mn0  +  3  MnO  H0 2  2  R-<''  +  H  + R\(  R-((  0-MnO„  , fast  H0  , slow  "0-MnO,  JJ-OH + MnO^H + H , fast (Mn ) V  VII  ring degradation products  0H+ Mn  + Mn  2Mn  5Mn  (b)  2+  , fast  , fast  + 3Mn  Side chain attack, (({> = phenyl group) 2H  + MnO. 4  +  Mn0  » T  Mn0 3  o  + c}>-CRH  3  +  2  3  VII  <f)CROH + Mn 2  +  H0 2  , fast  o  [<j)CR + HMn0 ]  , slow  (J)CR0H + Mn  , fast  2  2  [<j>CR + HMn0 ]  +  *  3  V  2  aldehyde or ketone  , fast  - 138  aldehyde  ketone  5Mn  +  +  V  Mn  Mn  -  VII  VII  2Mn  II  +  benzoic acid  »  fast  benzoic acid  »  slow  VII 3Mn  fast  It w i l l be noted that phenol i s proposed as a possible intermediate the r i n g degradation.  There i s no d i r e c t evidence f o r the  in  existence  of phenols i n the reaction mixture since phenols are subject to rapid oxidation even i n aqueous medium but, as i s shown i n Table 5,  the  stoichiometry for the oxidation of phenol shows l e s s permanganate consumed than i n the case of toluene. with phenol being an  This observation  i s consistent  intermediate.  The two separate oxidative pathways proposed for arenes are consistent with the product studies.  It appears that the side chain  oxidation tends to increase as the medium becomes more aqueous.  This  can be ssen by the increases i n the y i e l d of benzoic acid (see Table 3) and the increase of the 1 :2°:3° rate r a t i o s l i s t e d i n Table 33. 0  In the Introduction two  studies on the permanganate oxidation of  arenes i n a c i d i c medium were discussed.  Although neither study  c l e a r l y established the mechanism of the arene oxidation they have  44 features i n common with this i n v e s t i g a t i o n . who  C u l l i s and Ladbury  were the f i r s t to attempt a thorough i n v e s t i g a t i o n of t h i s reaction,  were severely hindered by t h e i r choice of aqueous a c e t i c acid as a reaction medium.  Second order k i n e t i c s were not maintained throughout  the r e a c t i o n , forcing them to use the data from the f i r s t 10% of the reaction to approximate i n i t i a l rates.  (Acetic acid i s also known to  - 139 -  complicate aromatic bromination k i n e t i c s , a problem which disappears when TFA i s substituted f o r a c e t i c acid."''"'")  C u l l i s and Ladbury  observed that there was no e f f e c t of added s a l t s ( i f the s a l t d i d not react with some manganese species) and that there was appreciable r i n g degradation.  The ring degradation and the oxidation rate were  observed to increase when electron-donating substituents were present. A l l of these observations are consistent with the data from this study. They do report one fact which deviates from our observations.  I t was  reported that benzaldehyde could be detected as a reaction product along with benzoic acid from the oxidation of toluene whereas i n t h i s study no evidence could be found f o r benzaldehyde as a product.  However,  consulting Figure 28 i t can be seen that at higher a c i d i t i e s toluene i s more reactive than benzaldehyde.  In f a c t , Figure 28 shows that the  usual order of r e a c t i v i t y towards oxidation (benzaldehyde alcohol > toluene)  becomes inverted.  > benzyl  This appears to be due to r i n g  attack becoming important and the side chain now  acts as a substituent.  The e f f e c t of these groups on ring attack would be expected to produce the order, toluene > benzyl alcohol > benzaldehyde which i s , indeed,  observed. 45  The second more recent study, by Lee and Singer,  concerned  the  a c i d i c permanganate oxidation of jj_-toluenesulfonic acid i n a medium of aqueous p e r c h l o r i c acid.  Although they found that the sulfonate group  caused d r a s t i c mechanistic changes (refer to Section 1.5.2) i n the region where oxidation was  the rate-determining process a rate law of  VII r = k,j[arene] [Mn  ]h  Q  was obeyed.  Clearly the rate dependence upon  acid content i n t h e i r system d i f f e r s from that i n t h i s study.  Since  -  140  PCO  in • rH  o H  .  m •  o  O  O  m •  • O  1y[ Sox  o  •  r-l  m •  i-l  3  CO TH  - 141 -  their mechanism involves substrate protonation and ours does not i t is not surprising that different acid catalyses are observed.  Summary:  The oxidation of arenes tends to proceed mainly via electro-  philic aromatic ring attack by permanganyl ion.  The transition state  formed from the permanganyl ion and arene molecule develops considerable positive charge on the ring.  No ring degradation products could be  isolated although complete oxidation to carbon dioxide does not occur. The evidence presented in this study is consistent with a mechanism involving phenols as intermediates.  4.5  Oxidation of Alcohols The kinetic data for the series of alcohols investigated are  listed in Appendix C, t r i a l s 770-1003. The kinetic experiments of a l l alcohol oxidations required special care to prevent inert trifluoroacetate esters being formed by reaction between alcohol and solvent.  The data in Figure 29 indicate  the magnitude of this interfering reaction.  A l l of the data listed in  the appendix were obtained by a technique which eliminated this effect  (see Section 3.2 for the kinetic procedure).  The excellent f i t of the time-absorbance data with the pseudo first-order rate equation for more than two half-lives of permanganate confirms a first-order dependence upon permanganate.  The data contained  in Table 34 and presented graphically in Figures 30 and 31 indicate a composite rate-law of the following type; -d[Mn0^ ]/dt = k^fMnO^ ][alcohol] h  + klfMnO. ][alcohol]h .  At acidities greater than seven molar TFA h  0.7  0.1 J -r0  Figure 29.  ,  ,  i 1 - i — 1 1 1 Time (min) of use after preparation 10 20 30 40 50 60 Decrease of oxidation rate with age of solution. Methanol in TFA-water.  _ l  1  70  80  - 143 -  Table 34.  Order of Reactants i n the Permanganate  Oxidation of  Alcohols i n TFA-Water.  Substrate  Methanol  2-Pentanol  Order i n substrate 0.8  0.9  r  Trials  Order in h b  r  0.999  0.9  0.994  0.999  1.0  0.999  1.0  0.999  1.0  0.999  0.94  2.1  0.999  3.9  0.999  3.0  0.999  1.0  0.90  0.999  839--842 0.998  858--861 0.8  Benzyl alcohol  4.0 827--830 .  0.9 Cyclohexanol  r  770--773  0.8 3-Pentanol  Order in h o  c  R  0.990  884--887 1.1  0.995  1-Phenylethanol  1.0  0.997  991--994  —  —  2-Phenylethanol  1.1  0.999  995--997  —  —  The order i n permanganate was i n a l l cases 1.00, r = 0.999; Only those t r i a l s where -IL^ > 6.0 are included. Only those t r i a l s where -H^ <5.0 are included. Note:  Error i n orders are + 5%.  3 + log[alcohol] Figure 30.  Log k... vs. log[alcohol] for the oxidation of a v a r i e t y of alcohols.  1.5  0 Figure 31.  1  2  3  4  5  6  Variation of oxidation rate with a c i d i t y for the oxidation of alcohols i n TFA-water.  7  8  -  146 -  governs the observed acid catalysis and this has been demonstrated to be due to oxidation by permanganyl ion.  At lower acidities,  however, the acid catalysis correlates with h Q .  This is clearly  illustrated by the case of benzyl alcohol where i t is possible to measure oxidation rates in the highly aqueous region.  The dependence  upon H q is believed to be due to oxidation by permanganic acid, HMnO^, (refer to Section 4.3, page  115, where i t is demonstrated that  oxidations by permanganic acid should correlate with H ) . Q  Apparently  permanganic acid is a weak oxidant relative to permanganyl ion since i t only functions as an oxidant towards easily oxidizable functional groups such as hydroxyl. Table 35 shows that appreciable kinetic isotope effects are observed when methanol-d^ was used in place of methanol.  This indicates  that the carbon-hydrogen bond is cleaved in the rate-determining step. The carbon-hydrogen bond is probably cleaved homolytically since 1- and 2-phenylethanol  have almost identical oxidation rates.  If a hydride  transfer mechanism were operative as Barter and L i t t l e r ^ have proposed for the oxidation of cyclohexanol in sulfuric acid-water medium, 1-phenylethanol should be oxidized at a much faster rate. (Note: 1-phenylethanol yields exclusively acetophenone but 2-phenylethanol yields phenylacetaldehyde and phenylacetic acid and minute amounts of benzoic acid.) Again there is no effect of added salts upon the oxidation rate (see Figure 32).  The approximate p + for the oxidation of substituted  benzyl alcohol is -1 (trials 884-890).  - 147 Table 35.  Isotope Effects in the Permanganate Oxidation of Alcohols.  Substrate  k(D 2 0)/k(H 2 0) 3  ~\  Benzyl alcohol  0.12  Methanol  3.76 4.38 5.01 6.09 6.59 7.10  1.7  3.5  0.9  10.4 8.3 7.1 10.0 9.1 6.8  Solvent systems made up from CF3C02H-H20 and CF 3 C0 2 H-D 2 0. k^/kp = k 2 (benzyl alcohol)/k 2 (benzyl alcohol-a~d 2 ) • and k^/kp = k2(methanol)/k2(methanol-d^).  The transition state can be considered to result from one molecule of oxidant and one molecule of alcohol, where  some  positive  charge develops on the carbon atom containing the hydroxyl group. Mechanisms consistent with a l l the before mentioned observations, with the product studies of Table 3, and with the stoichiometries of Table 5 can be outlined as follows:  (a)  TFA concentration less than seven molar,  H+  +  HMn04  Mn04~  +  ^  RR^CHOH  [RR COH + H MnO ]  HMn04  *  >•  ,  [RR^OH + H^nO^J  RR C=0  +  MnV  f a s t  i  t  s  o w  t  fast  0.8  0.7-  0.6-  0.5-  0  0 0.4-  0.3-  0.2  0  Figure 32.  0.1  0.2 Molarity of s a l t  Q  sodium perchlorate  ©  sodium t r i f l u o r o a c e t a t e  0.3 solution  Salt effects on the permanganate oxidation of methanol.  ( T r i a l s 812-825).  0.4  - 149 (R=H)aldehyde  ketone  + MnO^  V 5Mn  (b)  + Mn^*'""  *•  2+ 2Mn +  *•  carboxylic acid , fast  carboxylic acids  VII 3Mn  , fast  TFA concentrations more than seven molar,  2H+  +  MnO ~ 4  Mn0 3 +  +  IRRJCOH  +  MnO_+ 3  -<  •  [RR-jCOH +  HMn03+]  >  RR  + Mn0 3 +  V 5Mn  H.O 2  RR^CHOH  (R=H)aldehyde + Mn^**  ketone  +  •  •  *•  2+ 2Mn +  C=0  , fast  HMn03+]  + MnV  carboxylic acid  , slow  , fast  , fast  carboxylic acid VII 3Mn  , fast  The transition states can be depicted as outlined below.  (a)  R  6"+ \  /  R£  n  V------H \  T)H  v~> /^v 0  ~  —MnO.H  - 150 -  (b)  R \r J R  l  L  h  0  -'- Mn0  2  ^OH  Considerable research has been directed towards elucidating the mechanism of the permanganate oxidation of alcohols, but as outlined in the Introduction the emphasis has been on the basic or weakly acidic r e g i o n s . S o m e  of the observations made in this investigation  substantiate previous reports:  (a) substantial primary isotope  effects were observed in the oxidation of cyclohexanol-l-d^;"^ (b) a large number of oxidations show acid catalyses which are governed by  h  q  ; ^ 50,52  ^  su  b s t i t u e n t effects for the oxidation of t r i - and  di-arylcarbinols have negative values of p + indicating positive charge  48 development in the transition state. From the present mechanistic investigation of the oxidation of arenes and alkanes i t became apparent that aromatic ring oxidation differs mechanistically from alkane oxidation.  The oxidant, permanganyl  ion, preferentially degrades aromatic rings via rate-determining electrophilic attack at ring carbon. isotope  This process shows no primary  effect.  Benzyl alcohol is a rather unique substrate which can be used to demonstrate that not only does ring attack proceed with no isotope effect but also that only permanganyl ion is capable of electrophilic ring attack.  Table 36 presents the data for the oxidation of both  benzyl alcohol and benzyl alcohol-a-d 2 .  It can be seen that when side-  chain oxidation is inhibited by the presence of deuterium that the  - 151 Table 36.  Kinetic Isotope Effects in the Oxidation of Benzyl Alcohol  ~\  D  2°'VkDb  d  2 >  k(D 2 0)/k(H 2 0) C  h 2 ,k(D 2 0)/k(H 2 0) d  0.12  3.5  2.6  1.7  1.3  0.87  2.2  1.6  1.8  1.3  2.81  1.1  0.9  1.6  1.2  4.37  0.9  0.9  1.1  1.1  6.46  1.0  1.1  1.0  1.1  7.21  1.3  1.1  1.1  1.0  3  A medium made from CT^CO^H-H^O, k^/k^ = k 2 (benzyl alcohol)/k 2 (benzyl alcohol-ct-d 2 ).  k  A medium made from CF_C0,H-D„0, k^/k_ as defined in (a). Substrate was benzyl alcohol-a-d 2 , k(D20)/k(H20) = k2(medium made from CF2C03H-D20/k2(medium made from CF 2 C0 3 H-H 2 0, k 2 is the oxidation rate of the substrate.  d  Substrate was benzyl alcohol, k(D_0)/k(H„0) as defined i n (c).  - 152 -  solvent isotope effect increases.  This is consistent only with  permanganyl ion being the electrophilic-ring oxidant since the rate changes parallel the pK changes for the generation of permanganyl ion when D^O is substituted for R^O. Further, i t can be seen that as conditions are changed to maximize side chain attack (using R^O and benzyl alcohol) that the primary isotope effect is at a maximum.  This  is in accord with both permanganyl ion and permanganic acid oxidizing the side chain via rate-determining carbon-hydrogen bond scission.  It  w i l l be noted that as the acidity increases the selectivity imposed by deuterium is lost.  This is due to ring attack becoming predominant  when larger amounts of permanganyl ion are generated.  (The solvent  becomes richer in protium as the acidity increases since CF^CO^H was used to prepare the solutions.)  4.6  Oxidation of Aldehydes The data for the oxidation of formaldehyde and benzaldehyde are  presented in Appendix C, t r i a l s 1091-1164. The excellent f i t of the time-absorbance data with the pseudo first-order rate equation for up to two half-lives of permanganate confirms a first-order dependence upon permanganate. illustrates  Figure 33  that the order with respect to substrate was first-order  in both cases.  The order with respect to acidity, as Figure 34  illustrates, was variable, as was also the case for alcohols.  The  resulting rate law can be expressed in a form parallel to that observed for alcohols except that a third term has been added to account for the  - 155 -  participation by permanganate ion.  -d[Mn04~]/dt = k2[aldehyde]lMnOA~] + k3lMn04~][aldehyde]hQ + k'[aldehyde][MnO.~]h  If electron withdrawing substituents are present the oxidation rate decreases (p + = -0.5, t r i a l s 1109-1116).  A solvent isotope  of k(D20)/k(H20) = 1.5 at IL, = -1.86 was observed.  effect  These results  indicate that the transition state resulting from one molecule of oxidant and one of aldehyde develops  some  that permanganyl ion is one of the oxidants.  positive charge and A l l of the evidence is  consistent with mechanisms parallel to those observed for alcohols in the regions where either H or H govern the oxidation. O  4.7  K  Oxidation of Ketones The data for the oxidation of a variety of ketones are contained  in Appendix C, t r i a l s 1004 to 1090 and 1175 to 1255. The order with respect to permanganate was not constant for the series of compounds investigated.  The oxidations of acetone, cyclo-  hexanone, benzophenone,and trifluoroacetophenone were clearly f i r s t order with respect to permanganate for more than two half-lives of permanganate, as the good to excellent f i t s with the pseudo first-order equation indicate.  2,4-Pentanedione and acetophenone were clearly zero  order in permanganate but 3-pentanone was neither zero order nor first order.  2-Pentanone had a considerably better correlation with the  first-order equation but should be considered as a borderline case.  -  156 -  Although the correlations ranged about 0 . 9 9  definite curvature was  observed in a l l plots rather than random scatter about the square line.  least  Figures 3 5 and 3 6 depict typical zero-order and f i r s t -  order plots. The order with respect to substrate (see Table 3 7 and Figure 3 7 ) is first-order in a l l cases where clear dependence upon either the pseudo first-order or the zero-order equation is observed.  2-Pentanone  and 3-pentanone indicate substrate orders in excess of one but this is caused by failure to find a proper equation to treat the time-absorbance data.  The acid dependence is neither upon H q nor upon H , as the data R  in Table 3 7 show. It is known in the chromic acid oxidation of ketones that when enolization becomes rate-determining the order in oxidant changes 137 1 3 8  from f i r s t to zero order.  '  Also, studies by Gero on the enol  content of ketones have established the following order, ranging from highest enol content to the lowest;  2,4-pentanedione »  acetophenone >  139  3-pentanone > cyclohexanone > 2-pentanone > acetone.  In this kinetic  investigation the two ketones which have the largest enol content, according to Gero, are oxidized via zero-order kinetics but those with lower enol contents than 3-pentanone show first-order dependence upon permanganate.  Thus the change observed from first-order to zero-order  in permanganate can be attributed to differences in the degree of enolization. The product studies and the stoichiometrics listed in Tables 3 and 5 indicate that ketones are degraded via carbon-carbon bond cleavage to yield acids.  - 157 1,50  0-30  -4 0  :  ,  .... 0.4  ,  0.8  ,  1.2  ,  1.6  Time (min) Figure 35.  Typical pseudo first-order plot for the oxidation of cyclohexanone. 0.721 to 0.231.  (Trial 1069).  Absorbance changed from  1  2.0  - 158 0.75  0.0 Figure 36.  1  2.0  1  4.0 Time (min)  1  6.0  1  8.0  Typical zero order plot for the oxidation of acetophenone. ( t r i a l 1238).  1  10.0  - 159 -  Table 37.  Order of Reactants i n the Permanganate  Oxidation of  Ketones i n TFA-Water.  Substrate  Acetone  Order of substrate 1.0 1.1  2-Pentanone 2,4-Pentanedione  1.4 1.0  r  0.976 0.993 .990 0.994  Trials  Order i n h^  r  1009--1012 1013--1016 1004--1016  0.5  0.993  1035--1039 1017--1053  0.7  1203--1209 1197--1209  0.1  b  0.996 0.992  1.1  0.988  1077--1080  -  Trifluoroacetophenone  1.1  0.998  1085--1090 1081--1090  0.8  0.999  Acetophenone  1.0  1236--1243 1232--1247  0.8  0.998  1057--1061 1054--1070  0.6  Cyclohexanone 3-Pentanone  Note:  1.1 1.6  0.995 0.999  r  Q  Benzophenone  0.999  Order in h  C  0.97  1179--1186  Error i n orders are + 5%.  First-order i n permanganate except f o r acetophenone and 2,4-pentanedione where the order with respect to permanganate was zero. b  Only those t r i a l s where -H^ > 6.6 and T = 25.0° have been considered. Only those t r i a l s where -H  > 6.0 and T = 25.0° have been considered.  1.50  acetone, YL^ = -9.68 1.25 cyclohexanone, H  R  = -5.64  trifluoroacetophenone, H^. - -5.92  /© ©/  /  /  j  /  benzophenone, H  /  0.50  = -7.42  /  /  /  0.25  /o  / /  / / °  9  V  acetone,  = -8.64  0 0.2  0.5  Figure 37.  Log Y  0.8  1.1  1.4 3 + log[ketone]  1.7  2.0  vs. log[ketone] f o r the oxidation of a v a r i e t y of ketones.  2.3  2.  -  161 -  The oxidation of 2,4-pentanedione, which is extremely fast even in the aqueous region, and the observation that very l i t t l e acid catalysis is observed for this compound (see Table 37) is a consequence of i t readily enolizing and the enol being rapidly oxidized by permanganate ion. The experimental rate law for ketones can be expressed in the following composite form:  -dlMn04~]/dt = ^[ketone] + ^[ketone] [MnO4~]hR  The f i r s t term accounts for the oxidation of the enol by permanganate ion since i t is the predominant oxidant.  The second term accounts for  the degradation of the ketone (in the keto form) by permanganyl ion. A mechanism which accounts for the experimental observations can be expressed as;  ketone  2H  enol  ketone  enol  +  + MnO 4  + MnO  + MnO 4  MnO 3  +  products  3  +  products  »  fast  slow  fast  Using a steady-state approximation for the enol content the following rate law results.  162 -  r = k_ [ketone] [MnO. ]h J  K  H  k k Jketone]lMnO, J -— \ + k 2 lMn0 4 ]  +  Since i t is known that permanganate ion rapidly oxidizes enols i t can be assumed that ko[Mn0. ] »  k  r  k .  The rate equation then reduces to,  E  = -.— [ketone] + k„ [ketone][MnO. ]h D  This derived rate law is similar to the experimental rate law.  The  observed change in order of oxidant can be explained as follows:  If  the ketone does not readily enolize the major oxidative pathway is the degradation of the ketone by permanganyl ion (the first-order case) but i f the ketone readily enolizes then the enol pathway becomes predominant (the zero-order case).  The deviations from either of the  two known acidity functions are probably due to varying degrees of oxidation by a l l three possible oxidants (MnO^ , HMnO^, and MnO^"*") each of which has a different acidity dependence. An alternate mechanism can be proposed which accounts for the experimental facts:  ketone  kE  VII enol + Mn  *  enol 2  •  products  The derived rate law is shown below, which results from the steady-state approximation on enol.  - 163  -  kk.[ketone][Mn ] ii Z VI1  r  =  VTT  k^ + k [ t I n ] V11  2  when kj, »  k [Mn 2  VI1  ],  r =  [ketone] [Mn ] VI1  E when kj, <<k [Mn^**], 2  r = k^[ketone]  This satisfies the change from zero to first-order dependence upon permanganate and this type of rate law has been shown to indeed apply 137  to chromic acid oxidations of ketones.  138  '  But because of the  extremely fast rate for the oxidation of 2,4-pentanedione, which clearly involves enolization, i t can be concluded that k [Mn^**] 2  w i l l always be greater than h^.  (In the highly aqueous region where  the 2,4-pentanedione oxidations were performed permanganate ion, the weakest of the three oxidants, i s the predominant species.)  Thus  whenever the oxidation proceeds via the enol route a zero-order dependence upon permanganate should be observed.  Therefore, this latter  mechanism cannot account for the first-order dependence upon permanganate for some of the ketones. 4.8  Oxidation of Formic Acid The k i n e t i c data f o r the oxidation of formic acid are presented i n  Appendix C, t r i a l s 1165-1174. The excellent c o r r e l a t i o n of the time-absorbance data with: the pseudo f i r s t - o r d e r equation indicates f i r s t - o r d e r dependence upon permanganate.  The order with respect to substrate concentration, as i s  depicted i n Figure 38, i s f i r s t order.  The acid dependence, depicted  - 165 -  in Figure 39, is upon h^ with an order of one.  The resulting rate  law can be expressed as;  -d[Mn0 J/dt = k [Mn0 ][HC0 H]h 4  3  4  2  R  The active oxidant appears to be permanganyl ion, as indicated by the rate dependence upon h . The mechanism of the formic acid oxidation can be expressed as;  HC0 H 2  +  Mn0  +  S l  3  +  [•C0 H + 2  ° » W  [-CC^H + HMnC> ] +  3  fa<?t-  HMn0 ] 3  V  >  C0  2  +  Mn  This scheme i s analogous to that proposed by other researchers.  4.9  63  Oxidation by Permanganate in Benzene After Starks^ showed that permanganate could be used as an  oxidant i n organic solvents such as benzene by phase transfer using quaternary alkyl ammonium cations i t was decided to examine the mechanism of this permanganate oxidation i n benzene. The kinetic data are contained i n Appendix D, t r i a l s 1256-1285. The species present in the benzene layer was identified as a one to one salt of the cation and permanganate ion as i t was possible to isolate this salt in good yields (see Tables 11 and 12 and Section 3.11). This compound can be used to readily oxidize alkenes, alkynes, alcohols, and aldehydes to carboxylic acids.  These oxidations show first-order  3.2  Figure 39.  Log k„ vs. H for the oxidation of formic acid.  -  167 -  dependence upon permanganate ion as the good correlations with the pseudo first-order equation illustrates.  The constancy of the  values in Appendix D confirms a first-order dependence upon substrate concentration.  It was not possible to examine any acid or base  catalysis since such additions resulted in rapid and complete decomposif M V I I tion of Mn .  The effect of substituents, as depicted in Figure 40, shows that electron-withdrawing substituents increase the oxidation rate.  Such  substituent effects, although unusual for an oxidation process, have 140 been observed for some basic permanganate oxidations of arenes. The rate law i s ; -djMnO^ ]/dt = kIsubstrate]TMn04 ] 2  The mechanism of this oxidation can be visualized as the following for  stilbenes;  MnO. 4 H I  + ArCH=CHAr  I  T  Il  —  C-Ar ,  slow  0-MnO,3  H  Ar-C C-Ar 0-Mn03  7  >• Ar-C c  »  •  2ArC02H  ,  fast  The only products detected from the oxidation of tolan, stilbene, benzyl alcohol, and benzaldehyde was benzoic acid.  The yield was  quite low i f based on permanganate consumed and thus the reaction would seem to have very l i t t l e synthetic value.  However, the tetra-  (n-hexyl)ammonium permanganate salt can be isolated and stored without  2.5  2.0  - 169 -  appreciable decomposition and i t is possible that this organic solvent-soluble salt could have some future application.  - 170 -  5.  CONCLUSIONS  The data presented indicate that three manganese(VII) species can be generated in TFA-water.  Their proportions depend upon the  solvent composition and their role as oxidants depends upon the nature of the reductant.  Labile compounds such as aldehydes and enols are  appreciably oxidized by permanganate ion and by permanganic acid.  Some-  what less labile compounds such as alcohols are oxidized mostly by permanganic acid in TFA-water ;solutions less than 7 molar i n TFA. Inert substrates such as ketones (those which do not readily enolize), alkanes, acids, and arenes are oxidized by the more vigorous oxidant permanganyl cation.  In regions more acidic than 7 molar TFA,  regardless of the reductant, permanganyl cation appears to be the major oxidant. The oxidations previously discussed have the following general characteristics. (i) with  Permanganate oxidations in TFA-water solutions that correlate involve permanganyl ion as the oxidant.  (ii) Oxidations in TFA-water solutions that deviate appreciately from H  R  and tend to correlate with H q involve permanganic acid as one  of the.oxidants. ( i i i ) Permanganic acid is not an important oxidant in solutions more acidic than 7 molar TFA.  - 171 "(iv)  Aromatic rings are degraded only by permanganyl cation,  which acts as an electrophile.  The mechanism postulated for these  types of oxidations involves phenolic compounds as intermediates. (v)  Primary kinetic isotope effects are observed only for  oxidations where the major oxidative pathway does not involve aromatic ring attack.  Solvent isotope effects are observed for a wide variety  of substrates and this is due to the~soTvent's effect upon the permanganate ion-permanganyl ion equilibrium. (vi)  The activation parameters change with increased TFA content  showing smaller enthalpy values but larger negative entropy values. This could be indicative of increased solvation of the partially positivelycharged transition state by TFA. (vii) No salt effects were observed for any of the substrates -examined. ( v i i i ) The substituent studies indicate that the substrates examined develop some positive charge in the transition state. (ix)  In a l l cases the rate law showed first-order dependence  upon substrate concentration.  The order with respect to the oxidant  was first-order except when enolizable ketones were the reductants.  In  these cases the order in oxidant was zero. (x)  In a l l cases except arene oxidation the rate-determining  step can be considered to involve homolytic carbon-hydrogen bond cleavage. The following oxidative sequences for arenes and alkanes accommodate a l l of the kinetic results.  Note:  The final inorganic product can be  either manganese(II) ,manganese dioxide, or a mixture of both, depending on the nature of the reductant.  - 172 -  Oxidation of Alkanes RR1CH2 + Mn0 3 +  *  [RR^CH + HMn03+]  [RR-jCH + HMn03+]  [RR CH-0-Mh02+H]  (I) I  or  II  +  (ID  II  *  RRjCHOH + MnV  VII Mn  »  RR^O  RRjCHOH + Mn0 3 +  IRR-JCOH +  »  >  -— k  RR^C^ + Mn0 3 +  enol  +  VII Mn  RR^O  + MnV  [ RR^COH + I^MnO^]  *  [RR1COH + H2Mn04]  RR1C=0  V 2Mn  [RRjCOH + HMn03+]  HMn03+]  RR^HOH + HMn04  +  »  RR^O  + MnV  enol  *•  »  carboxylic acids  carboxylic acids,  - 173 -  (b) > xidation of Arenes (ring attack)  The use of TFA-water medium to perform homogeneous permanganate oxidations of organic substrates appears to have l i t t l e synthetic value since carboxylic acids and unidentifiable degradation products were the only products obtained.  This complication probably  arises from the medium generating the vigorous oxidant, permanganyl ion o  (Mn0 3 + ). The use of tetra(n-hexyl)ammonium permanganate extends the u t i l i t y of permanganate as an oxidant to homogeneous organic systems. Unfortunately this technique makes inefficient use of the oxidant.  - 174 -  SUGGESTIONS FOR FURTHER STUDY  6.  The mechanistic investigation of the oxidation of organic substrates by permanganate in TFA-water medium appears to be complete, but several interesting areas were touched upon which warrant further investigation.  The tetra(n-hexyl)ammonium permanganate salt which is  soluble only in organic solvents could have considerable potential as an oxidant i f a solvent system could be found in which i t is stable. The preliminary kinetic and product analysis indicate that a wide range of functional groups can be oxidized with very l i t t l e aromatic ring degradation. The -mechanism of aromatic nitration should be re-examined in order to explain the presence of phenolic products which could result from electrophilic attack on arenes by the oxygen atoms of the ambident  + nitronium  ion (N0o ).  <  -  175 -  APPENDIX A The tables listed in this appendix present the original spectrophotometry data for the ionization of carbinols in TFA-water solutions.  The acid content is expressed in terms of molarity (M).  The numbers listed were obtained by performing the following calculations. + I R ] = Absorbance observed, corrected for blanks = Abs. [ROH] = Final absorbance of fully ionized carbinol - Abs. Q = [R+]/lROH] pH E  in dilute solutions; used to determine pK^ of the anchor compounds.  The pH values used to determine the average pK^  are marked with an asterisk. pKg+ = H_ + log Q for those solutions which overlapped with the next indicator used.  The  values used to generate the  pK R + of successive indicators are marked with an asterisk. -  denotes the absorbance value used for the fully ionized species.  (Hg) - independent H_ values from the other anchor indicator.  - 176 -  APPENDIX A  4,4',4"-Trimethoxy TPC  M  pH  0.068  1.29  0.072  average p K ^ = +0.92  Abs.  Q  log Q  0.1920  0.429  -0.368*  0.92  1.29  0.1928  0.431  -0.365*  0.92  1.29  0.144  1.28 1.04  0.3012  0.889  -0.051  0.92  0.97  0.140  1.03  0.3042  0.906  -0.043  0.92  0.96  0.270  0.4274  2.011  0.303  0.92  0.62  0.540  0.5450  5.743  0.759  0.92  0.16  0.800  0.6005  15.241  1.183  0.92  -0.26  1.07  0.6266  47.113  1.673  1.31  0.6399" 0.2292  0.410  -0.387*  0.92  1.31  0.2076  0.358  -0.447*  0.92  1.37  0.3410  0.763  -0.118*  0.92  1.04  0.3754  0.909  -0.041*  0.92  0.96  0.256  0.5382  2.153  0.333  0.92  0.59  0.260  0.5080  1.813  0.258  0.92  0.66  0.261  0.5318  2.074  0.317  0.92  0.60  0.270  0.5222  1.962  0.293  0.92  0.63  0.515  0.6950  7.457  0.873  0.92  0.05  0.525  0.6661  5.455  0.737  0.92  0.18  0.770  0.7362  14.158  1.151  0.92  -0.23  1.04  0.7780  76.275  1.292  0.7882  * *  *  0.069  1.30  0.070  1.32  0.130  1.06  0.130  *  1.02  * *  H  -  R  -  - 177 -  APPENDIX A 4-Methyl-4',4"-dimethoxytriphenylcarbinol  pK^+ = -0.28  pH  Abs.  0.069  1.28  0.004  0.006  -2.221  0.069  1.28  0.008  0.012  -1.918  -0.64  0.130  1.01  0.0326  0.051  -1.291  -0.28  1.01 (1.04)  0.0308  0.048  -0.31  1.04 (0.96)  0.0742  0.125  -1.317 -0.905*  -0.25  0.63 (0.60)  0.544  0.1725  0.347  -0.460  0.18 (0.16)  0.796  0.2740  0.692  -0.160  -0.12(-0,26)  1.08  0.3630  1.183  0.073  -0.35  1.33  0.4451  1.981  0.297  -0.58  1.61  0.5088  3.160  0.500  -0.78  1.85  0.5580  4.991  0.698  -0.98  2.11  0.5858  6.974  0.843  -1.12  2.34  0.6159  11.427  1.058  -1.34  2.86  0.6480  29.725  1.473  -1.75  3.10  0.6470  28.377  1.453  -1.71  3.40  0.6680  3.92  0.6698"  M  0.130 0.261  *  * 1.01 0.76*  Q  log Q  * *  - 178 -  APPENDIX A  4,4'-Dimethoxytriphenylitiethyl chloride  M  HR  Abs.  Q  ~ -0.97  log Q  pKR+  \  0.515  0.0356  0.052  -1.284  +0.31  0.770  0.0724  0.112  -0.952  -0.02  1.290  -0.55  0.1840  0.343  -0.464  -1.01  -0.51  1.810  -0.92  0.3567  0.982  -0.008  -1.00  -0.96  2.32  -1.32  0.5032  2.321  0.366  -0.95  -1.34  2.84  -1.70  0.6278  6.809  0.833  -0.97  -1.80  3.32  0.6820  17.947  1.254  -2.22  3.85  0.7111  79.899  1.903  -2.87  4.37  0.7182  4.90  0.7298 0.7200"  - 179 -  APPENDIX A  M  -HR*  Abs.  Q  log Q  -pK R +  -IL,  2.86  1.82  0.0719  0.087  -1.063  2.88  1.75  3.16  2.06  0.1347  0.175  -0.756  2.82  2.05  3.36  2.26  0.2273  0.336  -0.473  2.73  2.34  3.60  0.3708  0.697  -0.157  2.65  3.88  0.4948  1.212  +0.084  2.89  4.46  0.7260  4.102  +0.613  3.42  4.92  0.7850  6.653  +0.823  3.63  5.42  0.8550  17.813  1.251  4.06  5.96  0.8762  32.694  0.9030  - 180 APPENDIX A 4-Methoxytriphenylcarbinol  Abs.  M  2.86 3.34 3.87 4.45 4.87 5.15 5.42 5.44 6.00 6.50 7.00 7.50 8.02 8.55  1.78 2.28 2.88 3.41 3.59 3.79 4.06  not used for p!  0.0305 0.0784 0.1969 0.3770 0.5460 0.6004 0.6482 0.6420 0.6844 0.7093 0.7239 0.7270 0.7352 0.7390 0.7300"  V^~D+  =  ~3.18  Q 0.044 0.121 0.369 1.068 2.967 4.633 7.924 7.133 15.009 34.266  Q  -PV-  -1.360 -0.916 -0.433 0.029 0.472 0.666 0.899 0.853 1.176 1.535  3.14 3.20 3.31 3.39 3.12 3.12 3.16  Log  +  1.82 2.26 2.75 3.21 3.65 3.85 4.08 4.03 4.36  - 181 APPENDIX A 4,4'-Dimethyltriphenylcarbinol  M  *  3.88  Abs.  ^^R+ =  Q  - 3 ,  78  Log Q  0.0720  0.138  -0.860  "HR 2.92  4.44  3.20  0.1404  0.310  -0.509  3.71  3.27  4.73  3.51  0.2039  0.523  -0.282  3.79  3.50  4.96  3.74  0.2681  0.823  -0.085  3.83  3.70  5.23  3.93  0.3419  1.356  0.132  3.80  3.91  5.48  4.07  0.3899  1.910  0.281  3.79  4.06  5.70  0.4552  3.280  0.516  4.30  6.07  0.5170  6.714  0.827  4.61  6.48  0.5461  11.401  1.057  4.84  7.00  0.5800  41.429  1.617  7.53  0.5910  8.10  0.5939  8.57  0.5942 0.5940"  - 182 -  APPENDIX A 4,4 , -Diethoxydiphenylcarbinol  M  * - v  5.47  Abs.  P^R+  =  Q  ""5.77  Log Q  0.0280  0.025  -1.602  -PV  6.00  4.53  0.0586  0.054  -1.269  5.80+  4.50  6.47  4.83  0.1161  0.113  -0.948  5.77  4.82  7.07  0.2105  0.225  -0.648  5.12  7.28  0.2940  0.345  -0.463  5.31  7.47  0.3798  0.495  -0.305  5.47  7.79  0.4830  0.727  -0.138  5.63  8.03  0.5899  1.059  0.025  5.80  8.30  0.6678  1.394  0.144  5.91  8.53  0.7800  2.125  0.327  6.10  8.87  0.8898  3.460  0.539  6.31  9.07  0.9702  5.488  0.739  6.51  9.33  1.008  7.252  0.860  6.63  9.57  1.061  12.337  1.091  6.86  9.83  1.100  24.404  1.369  7.14  10.10  1.113  10.57  1.147"  11.05  1.166  + not used for "P^Hr  -  183  -  APPENDIX A  Triphenylcarbinol  M  *  -V  pK^  =  Abs.  - 6 . 2 5  Q  Log  Q  "HR  7.10  5.14  0.0377  0.066  - 1 . 1 8 1  6.32  5.07  7.57  5.53  0.0794  0.150  -0.825  6.33  5.43  7.80  5.64  0.1206  0.246  - 0 . 6 0 8  6.24  5.64  8.07  5.84  0.1739  0.399  -0.399  6.24  5.85  8.33  5.94  0.2392  0.645  - 0 . 1 9 0  6.14  6.06  8.67  6.20  0.3189  1.095  0.040  6.16  6.29  8.81  0.3771  1.619  0.209  6.46  9.17  0.4549  2.933  0.467  6.72  9.47  0.5112  5.174  0.714  6.96  9.57  0.5478  8.807  0.945  7.20  10.20  0.6039  10.67  0.6178  11.27  0.6101 0.6100"  99.00  1.996  -  184  -  APPENDIX A pIC+ = - 7 . 9 4  4,4',4"-Trichlorotriphenylcarbinol  M  * "HR  Abs.  Q  Log Q  -P*R  +  -HR 6.42  9.13  6.54  0.0273  0.031  - 1 . 5 1 6  9.33  6.72  0.0470  0.054  - 1 . 2 7 0  7.99  6.67  9.53  6.90  0.0815  0.097  - 1 . 0 1 8  7.92  6.93  9.87  7.20  0.1535  0.200  - 0 . 7 0 0  7.91  7.24  10.10  0.2898  0.458  -0.339  7.60  10.27  0.3500  0.612  - 0 . 2 1 3  7.73  10.40  0.4331  0.886  - 0 . 0 5 3  7.89  10.53  0.5578  1.532  0.185  8.13  10.60  0.6400  2.270  0.356  8.30  10.80  0.7114  3.378  0.529  8.47  10.93  0.7760  5.315  0.726  8.67  11.00  0.8030  6.748  0.829  8.77  11.10  0.8458  11.100  1.045  8.99  11.23  0.8660  15.464  1.189  9.13  11.67  0.9120  12.20  0.9220"  12.70  0.9310  - 185 APPENDIX A  4-Nitrotriphenylcarbinol  M  10.57 10.83 11.07 11.37 11.67 11.93 12.20 12.43 12.63 13.03 13.07  -HL*  8.60 8.91  P^R+ 9«56 =-  Abs.  Q  0.0354 0.0428 0.0786 0.0865 0.1554 0.2704 0.3326 0.3753 0.3984 0.4312 0.4320"  0.087 0.110 0.222 0.250 0.551 1.673 3.346 6.619 11.857  Log Q  -1.049 -0.959 -0.653 -0.601 -0.259 0.224 0.525 0.821 1.074  -pK^  9.56 9.56  -IL,  8.51 8.60 8.91 8.96 9.30 9.78 10.09 10.38 10.63  3  Addition of H^SO^ gave no further increase so i t appears to be f u l l y ionized at this point.  - 186 APPENDIX B Oxidation i n H„SO,-ELO  No.  [Substrate] x 10  -H  o  -H  k, x 10 s " 1 3  R  1  k„ M s 2 1  1  r  n-Pentane 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43  3.10 II  3.72  7.49  it  2.325 it  it  1.55 ti it  3.10 ti it  3.50  6.95  2.325 •t ti  1.55 it ti  0.775 it it  3.10 it tt  3.01  5.90  2.325 ti it  1.55 ti it  0.775 II  it  3.10 tt ti it II  ti  2.325 it  it ti  2.53  4.90  17.89 17.97 17.07 11.48 12.77 12.48 7.74 5.07 4.84 5.35 5.98 6.16 4.09 4.52 4.67 1.68 1.41 1.27 0.843 0.801 0.806 1.45 1.45 1.31 0.658 0.610 0.646 0.443 0.418 0.476 0.194 0.183 0.199 0.251 0.289 0.256 0.235 0.284 0.242 0.264 0.248 0.228 0.216  5.76 5.79 5.50 4.94 5.49 5.35 5.00 3.27 3.11 1.73 1.93 1.98 1.76 1.94 2.01 1.08 0.910 0.820 1.09 1.03 1.04 0.467 0.467 0.423 0.283 0.262 0.278 0.286 0.270 0.307 0.251 0.236 0.258 0.0810 0.0930 0.0825 0.0759 0.0915 0.0780 0.113 0.106 0.0979 0.0926  .999  " .990 .980 .999  "  II  .980 .975 .970 .950 .970 .965 .999 it it  ti  .975 .999 .990 .970 .998 .980 .965 .975 .999  "  "  - 187 APPENDIX B No.  [Substrate]  -H  -H^  3-1 x 10 s  -1 -1 k£ M s  x 103 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85  II  it  1.55 II II  0.775 II II  3.10 II  2.19  4.25  II  2.325 II  II  1.55 II II  0.775 II  it "  •i iso-Pentane 3.10 II  3.72  7.49  2.55  4.93  2.325 2.325 1.55  ti  0.775 II  3.10 II  3.01  5.90  2.325 II  1.55  ti  0.775  ti  3.10 II  2.325  it  3.37  6.80  0.214 0.199 0.150 0.144 0.155 0.0719 0.0722 0.0652 0.0900 0.0872 0.0846 0.0852 0.0937 0.0887 0.0710 0.0709 0.0713 0.0423 0.0459 0.0452 0.350 0.340 1.16 1.18 1.36 1.41 0.859 0.876 0.356 0.348 0.78 7.31 3.54 3.60 0.957 1.02 0.151 0.155 11.2 13.1 7.02 5.94  0.0920 0.0855 0.0969 0.0929 0.100 0.0930 0.0934 0.0841 0.0290 0.0282 0.0273 0.0366 0.0402 0.0381 0.0458 0.0457 0.0460 0.0546 0.0592 0.0584 • 0.452 0.440  .999  0.375 0.380 0.586 0.603 0.554 0.565 0.461 0.451 2.18 2.36 1.52 1.54 0.617 0.660 0.195 0.200 3.64 4.24 3.02 2.55  .999  it it it II II  .997 .947 .999  it ti ti it it ti ti it  .997  ti M  .970 .954  tt it II ti it  .990  ti  .999  it it ti ti it  .945 .955 .999  ti ti tt  - 188 APPENDIX B No.  [Substrate] -  -H O  -H_ K  k„ x 103 s" 1 A  k_ M - ^ " 1  r  /  x 10 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128  1.55 V 0.775 " 3.10 " 2.325 " 1.55 " 0.775 " 3.10 2.325 " 1.55 " 0.775 " 3.10 " 2.325 " 1.55 " 0.775 " 3.10 " 2.325 " 1.55  3.78  7.52  3.78  7.52  3.37  6.80  3.19  6.10  11  0.775 " 3.10 " 2.325 " 1.55 " 0.775 "  2.55  4.93  2.61 2.51 0.383 0.432 25.0 24.0 15.8 15.7 4.10 4.34 1.81 1.76 119.0 84.1 84.4 47.1 42.7 7.54 4.27 17.4 16.9 15.1 15.0 5.29 5.83 0.623 0.839 5.84 6.50 4.50 4.34 2.12 2.24 0.890 0.962 1.14 1.22 0.660 0.660 0.643 0.694 0.337 0.346  1.68 1.62 4.95 5.59 8.36 7.75 6.77 6.74 2.64 2.80 2.34 2.77 38.4 36.2 36.3 30.4 27.5 9.74 5.51 5.60 5.44 6.49 6.46 3.41 3.76 0.804 1.08 1.88 2.10 1.93 1.87 1.36 1.44 1.15 1.24 0.367 0.393 0.284 0.284 0.415 0.444 0.435 0.446  .999 .985 .980 .999  .965 .970 .934 .942 .985 .999  .980 .999  .980 .985 .999 II II  .999 " ti  - 189 -  APPENDIX C A l l of the rate data contained in this section have been corrected for blank decomposition.  Some t r i a l s , because of low substrate  concentration, were analyzed by a second-order technique and as such no k^ was reported.  Trials 1197-1255 were analyzed by a zero-order  technique; a l l the rest were calculated by the pseudo first-order method. Unless otherwise stated a l l reactions were performed at 25.0° in a medium of trifluoroacetic acid (TFA) and water.  A l l the alcohol  reactions were carried out immediately after stock solutions were prepared unless otherwise designated.  A l l the tables should be read  in the accepted manner, i . e . Table value = actual rate constant x 10 where x and units are given in the header. Several notations w i l l be found under the heading substrate which mean the following: D20 - a medium of TFA-D20. STFA - designated molar strength of sodium trifluoroacetate added. MP - designated molar strength of potassium perchlorate added. B.Alc. - benzyl alcohol. B.Ald. - benzaldehyde. time - time interval before alcohol solution was used.  - 190 APPENDIX C No.  Substrate  129 130 • 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172  Ethane  8.50 II  II  II  II  it  II  II  II  II  II II  Propionitrile  it  II  Nitroethane  II II  II  Propionic acid  II II  II  Propane  7.08  it  ti  II  ii  II  it  II  II  II  II  II  II  II  II  n-Butane  7.08 tt  II  it  ti  II  it  II  it  II  it  II  it  n-Pentane  7.86 ti  II  6.27  II  II II  ti  •t  it  it  it  it  it  ti  it  II  II  II II  II  31.8°  7.483 it  3.443 it  124.9 II  124.0 it  48.01 II  34.91 ti  17.76 II  44.83 II  39.30 II  34.36 it  33.76 ti  2.787 45.99 it  3.127 it  5.99  it  38.4°  38.0 36.5 42.6 44.0 15.0 15.3 0.305 0.304 0.729 0.705 0.607 0.710 22.2 21.2 13.2 15.2 26.6 23.3 23.9 24.6 45.5 49.1 44.3 47.4 3.35 7.30 6.38 18.6 19.3 0.321 2.28 0.813 13.0 13.9 3.38 3.38 10.3 5.15 4.95 7.29 7.33 18.0 20.5 18.3  II  6.96  it  n  8.680  5.65 7.10 ti  II  k 1 xl0 3 s  3.11 26.47 31.13 15.59  it  II  [S]xl0 3  7.52 II II  it  ti  18.71 8.98 it  13.47  "  6.250 II  7.812  1  k2M-1s  1  4.38 4.21 5.69 5.88 4.35 4.45 0.00244 0.00243 0.00588 0.00569 0.0127 0.0148 0.635 0.606 0.743 0.855 0.594 0.520 0.609 0.627 1.33 1.43 1.31 1.41 1.20 1.59 1.39 5.96 6.17 0.103 0.0976 0.0261 0.836 0.894 0.564 0.564 0.551 0.574 0.552 0.541 0.544 2.87 3.28 2.35  r .999  "  .983 .975 .980 .998 .999  . " "  " " "  - 191 -  APPENDIX C  No.  Substrate  173 n-Pentane 174 it II 175 II 176 II 177 II 178 II 179 180 it II 181 II 182 183 it II 184 185 n-Hexane II 186 187 n 188 it 189 ti 190 tt 191 it 192 ti 193 it 194 it 195 it 196 it 197 it 198 it 199 tt 200 ti 201 it 202 it 203 ti 204 ti 205 it 206 ii 207 ti 208 it 209 it 210 ti 211 it 212 tt 213 ti 214 it 215 it II 216 217. tt  -IL.  19.8° 25.2° 25.4° 14.0° it  7.52 11  it  11  ti 6.70 11  7.74 11  8.00 tt 11  6.42 11  it  11  ti  11  it 6.96  11  14.0°  11  7.30 it 8.26 6.66 ti  4.13 1.983 1.652 13.77 it  7.86 it 6.93  2.754  11  2  7.812 6.250 tt 7.812 ti 7.812 it 15.63 tt 3.12 it tt 13.77 9.91 tt 6.61 ti 3.305  tt it ti  11  D0 it H2O ti 38.5° tt 31.8° 20.0° 25.4°  3  13.77 9.91 it 6.61 tt 3.305  11  25.0° 21.4° 15.6°  [S]xl0  11  11  11 11  7.77 it 11  it it  11  tt  11  11 11  5.509 11  8.263 11  4.132 11  3.443 11  4.132 11  ti  k^xlC^s"  10.3 8.92 10.5 7.56 7.52 3.98 4.02  -  4.93  3.51 3.53 2.64 2.65 1.39 1.39 17.9 11.3 10.6 7.22 7.44 3.23 3.81 13.4 6.40 39.3 12.8 5.99 5.10 37.1 37.0 7.20 9.35 10.8 12.5 45.3 43.6 29.9 19.2 28.0 27.6 19.0  1  lc^V" 1.32 1.43 1.68 0.968 0.963 0.510 0.515 3.88 3.88 20.2 21.3 19.4 0.358 0.354 0.356 0.399 0.400 0.421 0.419 1.30 1.14 1.07 1.09 1.13 0.976 1.15 3.25 3.22 23.8 0.930 0.435 0.370 13.5 13.4 1.31 1.70 1.30 1.52 11.0 10.6 8.68 5.59 6.77 6.67 4.60  1  r  .999  11 11  tt it it it  11  tt it it it tt it  11  ti  11  it  11 11 11 11 11  it  11  11 11  it it  11 11 11 11 11 11  it  11 11 11 11 11 11 11  it it  - 192 -  APPENDIX C  No.  Substrate  218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265  n-Hexane ti  -H_ 13.9°  II  4.132 8.260  8.00  1.380  it  II  tt  ii  n-Heptane II  II  6.82  6.81  12.28 8.84  it it ti  it  it it tt  it  it ti tt II  tt it  n-Octane it  it II  ti  n-Nonane it  ti ti it it tt  n-Decane it ii  ti it  n-Undecane ti II  tt  it  tt  tt  5.89 II  6.42  2.95 12.28  6.66  12.28  ti  25.0° 21.4° 15.6°  it  7.20 it it it  II  ti  3.68  it  II  it  7.86 tt  ti  3  7.77 7.74 ti  II  [S]xl0  tt II  it it  it  7.86 7.74  2.456 7.37  8.00  1.23  it it it  it  it it  7.74  4.928  8.00  1.11  7.86  2.014  7.74  3.021  8.00  0.850  it  it tt ti  it  it it  it  ti tt ti  it  it  tt  7.74  1.847  8.00  0.740  7.74  1.705  8.00  0.680  it  ti ti it it  II  it it  ti it  k xl0 s" 3  1  18.3  -  64.4 68.0 29.2 31.1 18.0 11.3 11.6 6.94 7.40 3.62 6.09 6.18 10.3 4.89 4.21 39.9  --  -  -  -  -  63.3 67.3  --  1  kM 2  1 S  -  1  4.42 9.73 9.28 41.0 35.9 35.3 17.5 18.5 4.28 4.56 1.46 1.28 1.31 1.18 1.26 1.23 0.496 0.504 0.838 0.398 0.343 16.2 10.7 10.2 52.8 50.2 46.8 15.3 14.9 65.7 66.6 60.6 31.4 33.4 19.6 19.1 93.0 91.3 86.3 26.6 28.2 103.0 101.0 107.0 33.8 33.1 131.0 126.0  r  ,999  - 193 APPENDIX C  No.  Substrate  -IL,  266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310  n-Undecane n-Dodecane  8.00 7.86  0.680 1.582  7.41  2.37  it  " tt ti  ti  38.2° it  31.1° 24.9° 19.4° 14.0°  tt ti  7.41 it  it  "  " " "  tt it  tt  0.738  8.00  0.370  ti  5.71 ti it it ti  6.00 tt tt ti tt it II  it tt • ti it it it  "tt  ti  7.74  6.33 tt it  tt  0.630  II  "  1.98 0.40  8.00  tt it  it  it  0.791  it  it  Isopentane  it  7.74 ti  n-Tridecane  [S]xlO  6.64 ti  tt  II  tt ti  15.50 11.16 • ti  7.44 II  3.720 15.50 11.16 it  7.440 ti  3.720 II  15.50 11.16 tt  7.440 tt  3.720 ti  7.751 5.581 it  it ti  3.720  ti  1.860  it  k^lO s  -  85.0 86.8 70.1 79.7 39.9 5.79 4.95 3.69  --3.90  2.11 2.30 1.44 1.67 0.771 7.77 4.19 4.67 2.53 2.95 1.09 1.13 16.6 9.28 10.3 7.03 7.54 3.12 3.86 16.2 9.96 10.6 6.32 7.09 3.45  kM 2  s  124.0 53.7 54.9 29.6 33.6 20.1 14.5 12.4 9.23 39.9 39.1 153.0 138.0 162.0 58.2 54.5 167.0 155.0 164.0 0.257 0.189 0.206 0.193 0.224 0.207 0.502 0.376 0.419 0.339 0.397 0.294 0.382 1.07 0.825 0.922 0.944 1.01 0.839 1.04 2.09 1.79 1.90 1.70 1.91 1.86  r  - 194 -  APPENDIX C  No.  Substrate  -H_  [S]xlQ3  311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354  Isopentane  6.64 6.66  1.860 6.20  "  25.0° 21.2° 15.6° 12.5° H0 2  ti  D2O 11  it  ti  tt  11  5.95  "  it . >  it  it  it  8.96  31.23  it  tt  11  11  50.89 it  it  11  11  35.00  it it  7.52  11  23.09 tt  7.71  11  ti  6.52  19.28  it  it  6.26 it 11  ti 11 11 11  "  11  8.70  11  "  11  34.50  11  ft  7.730 7.730 30.80  8.44 11  Cyclopentane  11 11  it  "  9.282  ti it  4.08 4.80 7.90  Neopentane  11  it  28.91 20.82 11  13.88 it  9.25 11  5.72  19.28  38.6°  7.02  7.71  it  it  31.8° 25.0°  11  11  • 11  tt tt  11 11  9.638 7.71 tt  k xl03s_:L 4.21 17.2 7.91 6.08 3.64 3.19 3.71 3.74 4.17 0.2130 0.483 6.31 6.32 14.1 14.6 15.1 42.5 39.0 44.1 42.9 43.3 43.7 26.4 24.7 18.0 17.5 55.9 48.9 15.7 15.9 11.4 7.91 7.52 5.29 4.99 3.80 3.44 2.47 2.77 30.2 26.6 27.5 17.6 16.4  k^"1*-1 2.26 2.77 1.28 0.981 0.587 0.343 0.400 0.403 0.449 0.0276 0.0624 0.205 0.205 0.408 0.422 0.437 1.36 1.25 1.41 0.843 0.851 0.858 0.755 0.705 a 779 0.757 7.24 6.34 0.813 0.825 0.394 0.380 0.361 0.381 0.360 0.411 0.371 0.128 0.144 3.91 3.46 2.85 2.28 2.12  .999  .997 .999  -  195  -  APPENDIX C  No.  Substrate  355  Cyclopentane  356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393  - R 19.9°  II  14.0° tt  it II II  Cyclohexane  II  tt  it  II  it ti  6.96 it  tt  ti  tt  it  ti  ti  ti  tt  it  it  ti II  it  it  it  it  ti  ti  it  ti  II  ti it  25.0°  tt  21.4°  II  Cyclohexane-d._ it  Cyclohexane  400  tt  Cyclohexane-d.^ Cyclohexane Cyclohexane-d..„  "  401  it  Cyclohexane-d.. 0  "  16.8  1.74  12.2  1.27  11.9  1.23  42.7  2.21  41.2  2.14  ti  ti ti  1.79  0.447  1.77  0.442  2.00  1.01  0.503  it  1.28  ti  8.46  1.41  it  8.26  1.38  10.7  5.40  1.35  5.89  1.47  3.30  1.65  3.20  1.60  8.332  32.7  3.92  5.999 tt  22.2  3.70  22.2  3.70  3.999 n  15.0  3.74  16.4  3.80  7.93  3.97  it  ti 29.17 it 16.66 II  tt II II  16.66 it it 16.66 it  5.22  0.313  5.41  0.185  6.85  0.235  it  it ti ti it it it it ti tt it ti it II  ti it it ti ti II  12.9  0.772  12.5  0.748  it  12.9  0.773  it  13.1  0.789  it  3.00  0.180  ti  5.25  0.315  ti  1.13  0.0678  it  1.10  0.0657  tt  2.62  0.157  it  0.496  0.0298  it  17.3  2.083  34.6  7.70 it  4.166  32.7  II  0.860 0.529  4.166  8.332  30.4  8.81  7.91 it  13.33  4.10  7.60  14.3  II  ti  3.999 ti  16.66 tt  7.40  it  0.412  6.66 ti  6.12 it  .999 it  2.47  60.7  ti  r  it  2.00  .  -1  0.426  8.26  6.38 ti  s  2.55  2.000 tt  it  -1  5.999 it  2.000 it  ti  k2M  it  II  6.74 ti  ti  it  25.0° ti  ,  0.384  3.999  II  -1  3.20  5.999 •t  6.80 it  tt  it  15.6"  ,„3  kjXlO s  8.332  8.332  7.30 it  it  Cyclohexane  399  19.28 ti  it  397 398  6.90 it  II  396  395  it  ti  Cyclohexane Cyclohexane-d-„ II -L^  394  ti  n  3  9.638 it  7.02 it  6.42 it  II  II  [S]xlO  H  4.15 16.6 7.84  11.4  1.37  11.2  0.837  12.9  0.971  ti it it ti it II  - 196 -  APPENDIX C  [SjxlO  No.  Substrate  402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446  Cyclohexane  7.40  Cyclohexane-d- _ II xl Cyclohexane  6.96  ti  II  it  II  II  6.665 tt  13.33 it  it  it  ti  tt  6.77 it  II  1.33 II  it tt  •t it  4.23  II II  ti tt  8.00  it  II  tt  tt  II  6.77  II  it it it  it  tt  ii ii  tt  II  it  II II  II  II  6.93  ti II  it ti II  it II  it II  ti tt  Cycloheptane II  it tt  II  D20 II  38.5° 31.8° 25.3°  it it  7.70 ti  it  II  II  19.9° 13.9°  II II  10.66 it  13.33 16.00 it  24.00 ti  26.66 •t  33.33 9.998 ti  6.665 II  3.333 4.166 4.999 II  4.166 II  6.80  4.46  6.36  11.89 8.562  it it II II  it  II  II  it it  II  it  8.33  II  it  ti  tt  6.90  II  it  3  5.37 5.82  II  II  it  5.708 it  2.854 it  2.975 ti  k xl0 s 3  1  28.4 28.4 2.67 5.36 16.4 16.2 1.01 1.09 2.86 3.38 5.71 5.74 7.41 7.67 9.64 10.8 11.3 15.9 16.4 19.1 18.3 21.5 13.3 14.3 9.77 9.26 39.2 45.2 43.4 44.9 29.1 22.3 13.6 13.1 22.9 23.2 27.7 18.0 18.7 12.2 12.8 6.47 6.48 0.899 2.08  _ 1  kM 2  s  4.26 4.26 0.191 0.402 1.23 1.22 0.755 0.826 0.675 0.799 0.714 0.718 0.695 0.720 0.723 0.674 0.704 0.661 0.684 0.715 0.686 0.649 1.33 1.43 1.47 1.40 11.8 10.8 8.68 8.98 6.98 5.35 1.63 1.58 5.13 5.21 2.33 2.11 2.18 2.14 2.25 2.27 2.27 0.302 0.698  r  .999 "  " " " " "  " "  " "  " " " " "  - 197 -  APPENDIX C  No.  Substrate  447 Cycloheptane " 448 449 450 38.4° ti 451 45.2 31.8° 453 19.9° 454 25.3° it " 455 456 14.0° ti 457 458 459 460 0.36 STFA it it " 461 462 0.28 STFA ti II 463 464 0.07 STFA it ti 465 466 Cyclooctane 467 468 " 469 470 471 472 473 474 475 476 477 478 it 479 480 38.6° it 481 482 31.8° 483 19.9° 484 25.2° ti 485 486 14.0° it 487 488 489 D2O 490 Benzene ti 11 491  ~\  [S]xl0 3  5.82 6.09  2.975 5.946  7.20  2.973  11 11  tt tt ti ti  ti  11  3.716 11  2.973 tt  11  11  it  ti  6.90  7.45  5.58  3.716  11  it  it  11  5.60  it  11  11  5.64  11  11  6.80 11  tt  6.36 11 11  it  2.01 4.012 11  8.024 5.777 11  tt it  3.852  11  1.926  11  •t  11  5.82  2.675  6.09  5.349  6.80  1.377  •t  11  it  11  11  it  11  11  11  11  11  it  11  it  11  11  11  ti  6.90  3.34  5.78  22.28  11  it  it  ti  k1xl03s~1 2.13 7.11 7.43 68.8 67.6 68.7 44.5 41.5 44.3 27.3 27.2 63.4 61.5 2.32 2.38 2.45 2.29 2.15 2.31 30.6 52.9 54.8 57.9 39.1 39.1 26.9 28.0 12.4 12.4 5.75 5.44 20.2 20.5 37.3 38.7 23.1 16.9 19.2 20.0 12.5 12.1 78.6 76.9 26.3 26.7  s 0.717 1.20 1.25 23.1 22.7 18.5 12.0 14.0 14.9 9.19 9.15 8.51 8.26 0.625 0.640 0.660 0.616 0.578 0.623 15.2 13.2 13.7 7.22 6.78 6.78 6.98 7.27 6.45 6.43 2.15 2.03 3.77 3.83 27.9 29.0 17.3 12.7 14.4 15.0 9.38 9.01 23.5 23.0 1.18 1.20  r .999 "  11  "  " " " " " " "  "  " " " " "  "  " "  - 198 -  APPENDIX C i  No.  Substrate  492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536  Benzene  H20  IS]xl0 3  k1xl03s~1  4.80  20.50  5.40  20.50  5.84  5.74  1.52 1.45 6.06 5.97 4.82 4.84 8.45 8.45 11.5 11.1 18.4 54.3 55.0 58.3 40.7 22.3 3.82 5.41 32.0 4.65 16.6 7.36 5.04 4.15 5.90 2.22 20.9 21.1 16.5 9.25 12.4 12.4 9.10 9.55 6.43 6.30 6.68 7.51 7.12 7.25 6.41 6.51 1.44 0.365 0.336  ti  II  it it it it II  ti  6.30 •t  "  6.64 II  Chlorobenzene Fluorobenzene Nitrobenzene Benzoic acid Anisole Benzene Toluene Ethylbenzene Cumene t-Butylbenzene Fluorobenzene Chlorobenzene Benzene  it it ti  4.16 it it ti tt •t  5.64 ti  38.5° II  31.8° 19.9° 25.3° it  13.9° II  "  II  it it ti ti  II  it  0.07 STFA 5.64 II  II  "  0.29 STFA 5.60 II  11  it it  0.048 MP 5.64 0.026 MP 5.60 0.36 STFA 5.58 II  "  5.70  II  ti  4.80 4.08 it  it  it  ti  9.72 it  13.94 tt  20.50 16.20 ti  5.06 17.69 4.80 44.00 32.06 0.35 30.37 16.94 5.88 3.23 2.91 28.78 26.54 20.25 it ti ti it it  20.25 II  10.12 it ti it it II  ti tt  20.25 ti it  1  w~"l -1  k2M  s  0.0741 0.0709 0.296 0.291 0.839 0.843 0.869 0.869 0.822 0.798 0.895 3.35 3.40 11.5 2.30 4.64 0.00868 0.169 91.3 0.0153 0.977 • 1.25 1.56 1.43 0.205 0.0838 1.03 1.04 0.813 0.457 0.610 0.612 0.449 0.472 0.636 0.623 0.660 0.742 0.704 0.716 0.633 0.643 0.0712 0.0180 0.0166  r .999 ti  .998 .999 ti it it tt ti II  it it II II II  it it  .997 .999 it it ti ti II II  it n  it II  it it II  it  .998 .999 II  it it  .997 .999 ti it  .998 .999 ti  - 199 -  APPENDIX C No.  Substrate  537 Toluene 538 " 539 540 " 541 542 543 544 545 " 546 " 547 " 11 548 549 " 550 " 551 " 552 " 553 " 554 " 555 " 556 557 " 558 " 559 560 561 562 " 563 " 564 565 " 566 567 568 569 " 570 571 " 572 " 573 574 575 " 576 " 577 " 578 579 " 580 " 581 "  -H^  [S]xl0 3  kjXlO^"1  2.88  4.24 6.78  0.719 1.39 1.13 1.56 1.46 2.03 2.37 1.70 2.74 2.74 4.22 4.14 4.78 5.41 2.72 4.88 4.72 7.73 7.73 9.58 9.58 3.71 5.95 6.11 8.53 8.28 11.3 12.3 10.9 14.7 15.0 20.6 19.1 27.3 27.6 0.620 1.08 1.07 1.71 1.82 2.56 2.69 1.45 2.79 3.07  M  II  ti  it tt  10.20  II  13.60  ti  3.48 it  it it II II II  3.84 it II  II  II  4.24 6.78 II  10.20 it  13.60 II  4.24 6.78 II  tt it  10.20  II  13.60  it  4.32 ti it  it it II  it  4.84 II  it II II II II  2.90 II  II II  ti ti II  3.42 II  ti  it II  2.12 3.39 II  5.10 it  6.80 it  2.12 3.39 it  5.10 ti  6.80 II  4.24 6.78 II  10.20 it  13.60 II  4.24 6.78 II  k U~ 18~ 1 2  0.170 0.205 0.167 0.153 0.143 0.149 0.174 0.402 0.404 0.404 0.414 0.406 0.351 0.396 0.642 0.721 0.696 0.758 0.758 0.705 0.705 1.78 1.76 1.80 1.67 1.62 1.66 1.81 5.13 4.34 4.42 4.04 3.74 4.01 4.06 0.146 0.160 0.158 0.168 0.178 0.188 0.197 0.341 0.412 0.454  r .999  - 200 -  APPENDIX C  No.  Substrate  582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627  Toluene  [S]xl0 3.42  ?IIi  it it tt  it  II  3.82 II  II  it ii ti ti •t it II  it II it tt it  4.19 II  tt it •t II  ti II ti  it  it it it II  II  m-Toluic acid  it  II  ti II  it  II  II  it  m-Nitrotoluene  II  m-Chlorotoluene  n  •t  Ethylbenzene II  Toluene-d_  II ti  o  II  Toluene-d_ o  Ethylbenzene  it  10.20 II  13.60  it  2.12 3.39 II  5.10  •t II  it  6.80  it  8.846  ti  22.06 II  25.64 II  33.23 II  6.051 II  5.88  it  5.99  II  3.74 6.77  II  II  •2.07  II  4.24 6.78  4.50  II  II  It  ti  n  Toluene  II  2.12 4.24 5.10  4.08  ti  13.60  4.70  it it tt it  p_-Nitrotoluene  tt  6.80  II  tIIt  10.20  4.19  it  II  3  iIIt  iIIt  II  II  II  3.387 II  3.404 II  3.234  T  k^lO s  -1  4.42 4.41 5.77 5.64 2.88 5.23 5.31 6.42 7.93 1.05 1.05 3.39 5.74 5.69 8.37 8.63 10.9 11.3 7.76 14.6 17.0 17.9 22.4 22.9 9.67 10.7 2.73 2.43 1.13 1.26 3.27 4.30 1.46 1.54 1.74 1.70 1.56 1.50 0.952 1.56 1.59 0.797 0.633 0.681 0.601 1.27  , -1 -1 k^A s  r  0.434 .999 0.433 " 0.424 " 0.415 " 0.679 " 0.771 0.783 0.630 0.778 0.772 " 0.772 " 1.60 " 1.69 " 1.68 1.64 1.69 1.60 1.66 3.66 3.44 " 3.34 • " 3.51 " 3.30 3.37 " 2.04 2.08 " 1.09 " 1.04 0.642 " 0.692 0.993 1.11 " 1.38 1.41 2.95 " 2.88 2.60 " 2.50 2.54 2.31 2.34 0.235 0.187 " 0.200 0.177 0.391 " 11  - 201 APPENDIX C  No.  Substrate  628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673  Cumene Toluene  H  3.07 3.39 ti  II  Toluene-d II  it Q  o  Ethylbenzene Cumene II  II  it it ti  3.88  Toluene  it  II  Toluene-dg Ethylbenzene Cumene ti  Toluene Toluene-dg Ethylbenzene Cumene Toluene II  it ti ti it  4.44 ti  it it  4.82 tt ti  Toluene-d II  0  o  it  Ethylbenzene  it  Cumene Toluene  it  II  it it  0  o  tt  5.70  Toluene  ti  it  it  Toluene-d II  it  5.29  Toluene-d it  Q  o  it  4.42  Toluene  it  II  it  ti  it  ti  ti  II  II  it  it  it  II  it  Toluene-d It II  ,~3 -1 , -1 -1 -, 3 kM s [S]xl0 kjXlO s r  "R  II Q  o  it it  ti  ti  tt  II  2  3.235 3.387 it  3.404 tt  3.675 2.588 ti  3.387 II  8.510 2.940 2.588 it  7.114 6.808 5.879 3.235 3.387 ti  3.404 it  2.940 tt  3.235 1.694 ti  1.702 it  0.339 ti  0.340 II  3.387 it  6.775 ti  13.55 it  20.33 tt  3.404 II  6.808 it  13.62  1.24 1.26 1.20 1.28 1.27 2.25 1.58 1.42 2.63 2.58 6.57 3.15 2.91 2.93 13.2 13.5 15.2 8.18 14.4 14.5 14.4 14.3 15.5 15.8 19.1 21.5 23.2 22.7 22.7 11.6 11.6 13.0 12.1 5.40 5.14 10.6 10.9 23.1 23.7 32.1 32.0 5.47 5.61 10.7 10.7 22.4  r  0.382 .999 II 0.372 tt 0.355 it 0.375 ti 0.373 ti 0.611 it 0.609 it 0.554 ti 0.777 ti 0.761 it 0.771 II 1.07 tt 1.12 it 1.13 it 1.86 ti 1.99 it 2.59 it 2.53 it 4.26 tt 4.28 ti 4.23 ti 4.21 ' II 5.27 it 5.37 •t 5.91 ti 12.7 tt 13.7 tt 13.3 it 13.4 it 34.3 ti 34.3 ti 38.3 it 35.6 it 1.59 ti 1.52 it 1.56 it 1.62 ti 1.71 ti 1.75 it 1.58 it 1.57 ti 1.61 ti 1.65 II 1.57 II 1.57 it 1.65  - 202 -  APPENDIX C  No.  Substrate  674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718  Toluene-d  "R H  4.42  0  it II  II  Toluene-d , Q  II  Toluene,  o  it  D0 2  it  D0 2  II  m-Nitrotoluene m-Toluic acid p_-Toluic acid m-Nitrotoluene p_-Bromo toluene  II  it II  tt it II  II  II  m-Bromotoluene  it it ti  II  m-Chlorotoluene it  ti tt  Toluene II  II  it it II II II II II  Toluene tt II  n it tt tt II  ti II II  Toluene-dg Toluene-a-d^ Toluene  tt tt  p_-Nitrotoluene  II  it it  5.40  II  II  4.83  14.7° it  4.26 tt  r  ,  [S]xlO 13.62 20.43 II  4.255 8.510 4.234 8.469 14.69 17.74 25.39 14.69 5.001 II  17.95 it  7.746 II  9.144  H  6.241 II  5.10 it  20.4°  II  it  II  II  II  25.0°  II  II  it  II  II  31.6°  II  II  it  II  II  36.2°  II  II  II  II  • II  15.0° II  4.13 it  5.10 II  II  tt  II  II  II  II  II  II  30.0°  tt  II  II  II  II  35.0°  II  II  II  II  20.0* II  25.0° II  II  2.90 2.34 II  it  3  16.94 5.08 II  II  kjXlO s  , w-1 -1 kM s  22.5 32.8 33.6 42.2 75.2 41.1 79.1 2.19 2.68 1.81 2.60 3.90 4.22 4.75 3.66 24.0 24.0 30.0 30.2 107.0 116.0 4.99 4.72 6.34 5.81 9.30 9.37 12.8 11.7 10.5 12.8 4.83 3.63 5.63 5.89 9.29 9.39 10.5 10.3 9.67 10.2 2.79 0.270 0.307 0.288  1.65 1.61 1.64 9.91 8.83 9.71 9.34 0.149 0.151 0.0714 0.177 0.780 0.844 0.0264 0.0204 3.10 3.10 3.20 3.30 17.1 18.6 0.978 0.926 1.24 1.14 1.82 1.84 2.51 2.30 2.06 2.52 0.947 0.711 1.10 1.16 1.82 1.84 2.06 2.01 1.90 1.99 0.165 0.0532 0.0604 0.0566  ,~3 -1  2  r .999 II II  H II it II II  it II  .995 .999 II  II  .992 .999 II  II II II  II  it it ti tt II  it II II  it II II II II II II II II II II  it II  it II  - 203 -  APPENDIX C  No.  Substrate  -H  719 Toluene-d 720 II o 721 Toluene-a-dII -3 722 Toluene 723 II 724 II 725 II 726 727 Toluene-d 723 II o 729 Toluene-a-d« II 3 730 731 Toluene II 732 733 Toluene-a-d„ II 3 734 735 Toluene-d II o 736 737 Toluene II 738 II 739 II 740 741 Toluene II 742 743 it 744 it II 745 746 it ' 747 tt 748 tt 749 it 750 ti 751 ti 752 it 753 it 754 Toluene 755 it 756 Ethylbenzene II 757 758 Cumene 759 it 760 t-Butylbenzene 761 tt 762 Toluene 763 tt 764 Ethylbenzene 765 ti  3.52  Q  ti tt it II  ti  DoO n  37.4°  it  31.5° 20.0° 25.0°  tt  14.0°  it  37.4° 31.6° 25.0° 19.9° 14.1°  6.77 II  it it tt ti  3.39  5.28  1.69  4.47  6.775  5.17  1.694  tt ti it it it  Q  3  4.44  it it it it ti  Q  [S]xl0  ti tt it  it ti ti it II  it it  2.52  ti n  •t II  3.18  it it ti it it tt ti  5.39 5.39 II  it  it ti ti it it  tt it tt it ti  it it it  ti  4.234  it  1.694  ti  3.388 II  4.234  it  5.081 4.234 5.081 4.23  ti  3.67  it  1.94  ti  1.74  it  4.23  ti  2.20 II  3 -1 k-jXlO s 3.00 3.17 2.91 2.91 2.92 2.96 5.40 5.54 5.25 5.55 5.25 5.23 21.0 20.8 19.0 19.1 20.2 20.2 15.5 15.2 31.7 31.1 22.4 22.0 43.4 28.0 16.1 16.5 19.4 20.1 0.821 0.646 0.462 0.231 0.230 1.73 1.90 2.35 2.29 1.19 1.28 0.786 0.799 85.3 95.6 74.5 70.0  kM 2  -1 -1 s  r  .998 0.450 .999 0.469 0.429 it 0.430 it 0.432 ti 0.437 ti II 1.59 1.63 it 1.55 it 1.64 it 1.55 it 1.54 it 12.4 ti 12.3 ti 11.2 it 11.3 it 12.0 ti 12.0 it II 2.28 2.24 ti 4.69 ' it 4.59 it 13.2 ti 13.0 it 10.3 it 6.59 it 9.47 tt 9.74 ti 5.73 ti 5.93 it 0.194 tt 0.153 it 0.0910 it 0.0545 ti 0.0453 it 0.408 it 0.448 ti II 0.640 0.655 it II 0.611 0.659 ti 0.452 it 0.459 it 20.2 ti 22.6 it 33.9 ti 31.8 ti  - 204 -  APPENDIX C 3  No.  Substrate  -H^  [S]xl0  766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812  Cumene  5.39  1.94  "  1.74  6.34  8.233 16.47 24.70 32.93 164.7  t-Butylbenzene Methanol  Methanol " " " " 11  Methanol  15 min 45 min 75 min 7 min 30 min 60 min  6.34  ir ti  II II  " " 5.64  82.33 II  it  16.47 ti  " "  4.08 5.01  41.17 41.17  "  3.26  "  6.15  82.33 41.17 8.233  "  6.84  8.233  Methanol " " " " Methanol-d4 Methanol " Methanol-d, Methanol Methanol-d " Methanol Methanol-d, Methanol " Methanol-d, Methanol " " Methanol  37.4° 3.18 31.6° 25.0° " 19.8° " 14.1° " 4.38 " 7.10 " 6.09 5.01 " 3.76 " 6.59 " 5.01 D20 " 0.019 MP  " 5.44  it  it  ti  200.1 it •t it ti  88.92 44.46 4.446 8.892 11.13 22.23 44.46 22.23 200.1 100.5 11.12 22.23 35.57 it II II  66.99  3-1 k^lO s 63.7 65.8 50.8 52.4 28.9 53.2 73.9 90.0 76.2 38.2 21.0 53.2 30.3 16.7 11.3 11.0 2.24 8.03 8.33 1.87 1.03 22.3 19.6 90.7 80.5 9.48 7.17 3.80 2.99 1.77 0.891 3.68 72.1 21.2 22.6 4.46 1.24 4.23 0.451 2.35 56.3 12.5 5.87 6.70 7.33 7.06 33.2  -1-1 k2M s 32.8 .999 it 33.9 II 29.2 tt 30.1 it 3.51 ti 3.23 ti 2.99 it 2.73 it 0.463 ti 0.232 it 0.127 ti 0.646 II 0.368 II 0.203 II 0.683 it 0.668 II 0.0545 it 0.195 it 0.202 ti 0.0227 II 0.0249it 2.71 •t 2.38 ti 11.0 II 9.78 it 0.0474 it 0.0359 ti 0.0190 it 0.0149 it 0.00886 ti 0.0100 II 0.0828 it 16.2 it 2.38 it 2.03 ti 0.201 ti 0.0278 it 0.190 it 0.00225 ti 0.0234 ti 5.06 0.559 n it 0.165 it 0.188 ti 0.206 ti 0.199 II 0.499  - 205 -  APPENDIX C  No.  Substrate  —H  [S]xl0  3  R  813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857  Methanol  0.019 MP 0.05 MP II it 0.026 MP II it 0.36 STFA ti II 0.07 STFA II  "  II  0.28 STFA II it  2-Pentanol  5.44 II II  5.40 II  5.38 it 5.44 II  4.08 it 6.15 II  6.84 tt 3.26 II  5.64 it II  it 4.08 II  5.01 it 6.15 6.84 II  38.1° II  "  II  31.0° 19.5° 25.0° it 14.0° II  it II II II  it it  30.64 it  II  "  II  3.26 it 5.01 5.64 ti  3-Pentanol  66.99 n  II  II  5.84 ti II  it II  3  J.  5.40 II  k,xl0 s  II  II  12.26 9.192 6.128 3.064 30.64 II  6.128 II  3.064 •t 30.83 ti 12.33 9.250 6.167 3.083 30.83 II  30.83 II  6.167 3.083 II  6.66 II  8.33 ti it  ti ti  II  II  II  ti  31.7 32.1 35.3 32.2 35.7 31.1 28.3 27.1 29.1 31.3 32.9 1.73 1.71 7.57 7.39 5.51 3.84 2.15 2.96 2.90 9.77 10.2 18.1 17.7 1.90 1.83 7.62 5.72 3.85 2.05 3.11 3.19 7.83 8.00 10.2 17.6 18.3 8.69 9.48 8.24 6.00 6.61 6.91 3.52 3.39  1  k„M s L X  1  0.475 0.481 0.530 0.483 0.535 0.466 0.425 0.406 0.436 0.470 0.493 0.0563 0.0557 0.247 0.603 0.599 0.627 0.700 0.0967 0.0947 1.59 1.67 5.91 5.77 0.0617 0.0594 0.618 0.618 0.625 0.664 0.101 0.104 0.254 0.260 1.65 5.70 5.95 1.30 1.42 0.990 0.720 0.793 0.830 0.422 0.407  .999  -  206  -  APPENDIX C  No.  Substrate  -IL  858  Cyclohexanol  5.64 II  859  II  860  II  861 862 863  3.203  2.76  0.860  6.406  5.58  0.871  9.609  8.49  12.81  0.157  2.44  0.152  it  6.25  0.391  it  6.59  0.411  ti 6.84  6.406  ti 3.203  869  38.0°  5.40  870  38.2°  it  II  871  30.9°  17.30  872  19.4°  it ti  25.0°  874  24.9°  875  13.8°  876  14.0°  877  Benzyl, alcohol  878  10.38  II  it •t  II  II  ti  II  II  II  888 889 890 891 892  it II II  893 894 895 896 897 898 899 900 901 902 903  it II  it 2.87  II  Benzyl alcohol it  II II II II  DJJO  0.606  5.36  0.310  ti  3.60  II  II  4.09  0.279  6.57  0.316  6.67  0.321 0.502 0.539  4.162  2.16  0.519  2.081  1.04  0.499  4.756  0.589  0.124  1.46  0.117  12.56 II  10.41  II  II  5.81  3.37  II  2.79  0.281  6.243  it  II  0.433  5.85  4.35  II  2.33  3.01  8.671  II  3.20  it  it  II  it it II  0.632  0.438  3.28  Benzyl alcohol  10.5  0.542  0.386  II  II  9.37 10.9  0.865 0.784  3.04  1.81  £-Nitro B.Alc. m-Nitro B.Alc.  13.6  0.933  6.94  ti it it  887  8.98  2.76  tt  886  9.69  0.302  20.81  885  27.7  3.34  1.00  884  2.37 8.65  5.22  880  883  2.39  15.2  8.67  tt  882  15.3  2.90  879 881  0.883 0.866  2.52  6.15  "  11.1  it  866  873  s  16.01  it  868  k„M  it  865 867  k.xlO s  4.08 5.01  864  [S]xl0  34.69 II  17.34 II II II II  ti it  1.44  0.114  4.24  0.408  4.14  0.398  5.69  0.547  6.05  0.581  14.5  0.419  15.5  0.446  7.70  0.444  8.00  0.461  9.27  0.535  9.53  0.549  11.4  0.658  11.9  0.685  15.4  0.885  r  - 207 APPENDIX C No.  [S]xl0 3  Substrate  904 Benzyl alcohol II 905 II 906 II 907 it 908 II 909 tt 910 it 911 ti 912 II 913 n 914 II 915 II 916 ti 917 it 918 it 919 it 920 it 921 it 922 ti 923 37.5° II •t 924 II 925 31.4° it 926 20.0° II 927 25.0° II tt 928 ti 929 14.1° it 930 14.1° it 931 37.4° II 932 31.4° it 933 25.0° II it 934 ti 935 20.0° II 936 14.0° II II 937 II 938 / it 939 940 Benzyl alcohol-cv" d 2 ti 941 942 Benzyl alcohol n 943 944 Benzyl alcohol D20 it ti 945 946 Benzyl alcohol-a-d?} DoO II 947 ft 948 Benzyl a l c o h o l - « - d 2  4.09 4.50 it  4.94 ti  5.40 it  5.74 II  6.20 tt  2.35 it  1.71 ti  0.98 it  0.60 0.12 3.58 it  it it II  it it ti  6.72 II II  ti II II II  4.41 II  0.84 it ti II  9.90 tt tt II  2.76  k 1 xl0 3 s  15.5 17.0 II 17.6 10.41 21.5 it 22.0 II 38.8 tt 40.7 3.47 22.9 II 24.3 4.35 96.3 II 95.6 34.69 15.0 it 15.0 II 12.8 II 13.0 17.34 5.79 II 5.67 ti 5.04 it 4.59 27.66 25.5 it 27.5 25.94 18.3 II 10.8 34.55 19.0 it 19.2 II 10.4 it 10.1 0.9104 60.9 0.867 63.9 1.734 125.0 II 119.0 0.867 31.1 1.734 54.9 II 49.8 II 15.3 II 15.3 21.28 2.07 II 1.96 21.68 3.92 it 4.90 it 5.66 II 6.01 21.28 3.63 17.34 13.87  II  34.06  3.58 12.0  1  k2M  s  0.893 1.22 1.22 2.07 2.11 3.73 3.91 6.59 7.00 22.2 22.0 0.433 0.432 0.370 0.375 0.334 0.327 0.291 0.265 0.921 0.994 0.705 0.417 0.550 0.555 0.301 0.293 66.9 73.7 72.0 68.8 35.9 31.7 28.7 0.879 0.880 0.0969 0.0919 0.181 0.226 0.261 0.277 0.171 0.168 0.353  r .999 II  it II II II  it II II II . II II  it tt ti II II  tt it tt ti II  it II  it ti II II  it II  it II II  tt II II II  it it it tt II  tt it ii  - 208 -  APPENDIX C No.  Substrate  -H^  [S]xl0  949 950 951 952 953 954  Benzyl alcohol-a-d2 Benzyl alcohol  2.76  34.06 34.69  955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987  II  II  tt  ti  Benzyl a l c o h o l - a - d „  Z  Benzyl alcohol ti tt II  Y ti  Benzyl alcohol-0t-d o ti z Benzyl alcohol II  tt II  D2O tt  Benzyl alcohol-a-d2, D20 II  11  Benzyl alcohol-a-d2 II  Benzyl alcohol •t ti ti  11  Benzyl alcohol-ot-d-, ii  it  D20 it  Benzyl alcohol-a-d 2 , D20 it  tt  34.06  it  11  0.12 tt it  11  21.28 11  21.68 •t  ti  11  11  11  11  21.28  it  it  6.48 tt it ti  6.44 11  it it  7.24 ti tt  7.18 tt  11  it  Benzyl a l c o h o l - a - d „ it z Benzyl alcohol ti it  2.86  tt  D20  11  it it  11  Benzyl alcohol-a-d2> D20 tt  it ti  Benzyl alcohol-a-d_,  it  11  4.40 ti  11  it  4.34 11  tt it  3  4.26 11  4.34 11  0.867 it  0.851 11  tt tt  0.867 ti ti  11  0.851 11 11 11  0.867 11  it  "  0.851 11  3-1 k-jXlO s  -1 -1 k^M s  12.3 13.3 14.9 16.7 17.0 18.9  0.361 0.384 0.430 0.482 0.491 0.555  19.2 1.12 1.10 4.08 3.74 5.08 4.87 1.84  0.565 0.0528 0.0515 0.188 0.173 0.234 0.225 0.0867  1.91 222.0 218.0 223.0 221.0 48.1 50.0 41.9  0.0899 52.2 51.2 51.5 50.9 55.5 57.6 49.2  43.1 198.0 189.0 241.0 259.0 239.0 238.0 216.0  50.7 233.0 222.0 278.0 298.0 276.0 275.0 254.0  210.0 10.2 10.1 9.44 9.42 10.3 10.1 10.8  247.0 1.20 1.19 1.09 1.09 1.19 1.17 1.27  11.1  1.30  .999 ti  11  it 11 11 11  tt 11 11  it 11 11  it 11 11 11  tt it it ti 11  it it it ti ti 11 11  tt 11 11  it it 11 11  it 11 11  - 209 -  APPENDIX C  No.  988 1-Phenylethanol II 989 II 990 ir 991 it 992 II 993 it 994 995 2-Phenylethanol it 996 ti 997 it 998 II 999 tt 1000 it 1001 ti 1002 tt 1003 1004 Acetone II 1005 tt 1006 II 1007 ti 1008 it 1009 it 1010 ti 1011 it 1012 tt 1013 II 1014 it 1015 tt 1016 1017 2-Pentanone ti 1018 ti 1019 it 1020 it 1021 it 1022 tt 1023 II 1024 tt 1025 it 1026 II 1027 tt 1028 II 1029 ti 1030 it 1031 1032  -, 3 [S]xlO  ,~3 -1 1^x10 s  11.26 7.507 3.754 3.754 15.02 11.26 7.507 7.535 11.30 15.07 15.07 7.535  5.50 12.6 1.47 3.09 12.6 8.88 5.66 6.07 9.15 12.9 1.57 16.1 8.38 116.0 131.0 5.29 1.12 0.162 0.360 0.0384 3.52 2.20 3.53 6.56 5.06 2.58 6.25 13.1 14.1 16.0 24.2 33.0 1.04 3.85 0.528 28.7 25.1 34.6 16.5 16.1 19.1 21.8 9.93 12.0 2.02  r  Substrate 1.85 4.84 2.82 4.16 ti II  it  4.10 ti it  1.85 4.84 4.16 5.70 it  2.82 8.76 6.66 7.42 5.64 9.42 8.64 it  ti ti  9.68 II II II  8.76 it II  38.2° II  31.2" 19.5° 25.0° tt  13.9° 14.0°  6.66 ' 7.42 5.64 9.42 8.86 it  it ti tt tt ti ti  6.33  n  15.07 it  tt  61.27 ti it II  ti  133.5 264.4 392.8 328.9 53.71 133.5 212.3 264.4 22.07 30.90 44.14 33.95 42.45 it  8.49 10.19 II  12.73 16.98 it tt it ti  33.96  k2M  -1 -1 s  r  .999 0.489 " 1.68 0.393 0.823 0.839 0.789 0.754 " 0.805 0.810 " 0.856 0.104 .998 2.14 .999 1.11 " 7.67 8.69 0.351 0.0183 0.00264 .992 0.00588 .998 0.000627 .842 0.0574 .996 0.0165 .995 0.0133 .999 it 0.0167 it 0.0154 0.0480 .997 ti 0.0468 it 0.0615 0.0533 .983 0.726 .999 " 0.783 0.748 0.0307 " 0.0908 0.0124 " 3.38 2.47 3.39 1.30 " 0.946 1.12 1.28 " 0.585 0.704 0.0594  -  210 -  APPENDIX C No.  Substrate  -H_  [SjxlO 3  K  1 0 3 3 2-Pentanone  6.33  1034  7.40  1035  "  1036  "  8.04 11  33.96 11 11  1037  11  24.45 11  1038  11  16.30  1039  "  11  10.87  1040  "  8.92 ti  10.19 tt  6.70 11  1041 1042  "  1043  "  1044  "  1045 1046 1047  1.48  0.174  .995  7.41 11  84.05 11  7.27  0.0864  .999  6.65  0.0791  5.51  0.0817  5.56  0.0825  1052  "  11 ti  1 0 5 4 Cyclohexanone  6.90  1055  "  1056  "  6.24 11  1057  "  1058  "  5.64 it  1071  "  1072 1073  "  1074  "••  1 0 7 5 Benzophenone  0.0903  16.98 it  1.54  0.0904  1.49  0.0879  18.30 ti 11 36.60  16.1  0.880  7.85  0.429  7.99  0.437  11.5  11  0.315 0.314 0.279  11  17.57  5.04  0.287  11.71  3.36  0.287  5.16 11  36.60 11  8.18  0.223  8.55  0.234  D2O  8.07  10.07  35.3  3.50  .996  38.0°  6.34 11  10.98 11  14.0  1.27  .999  13.4  1.22  15.0  0.820  38.2° 31.1°  11  19.4°  11  24.9° 1 1  0.0896  3.07  7.34  1061  1070  3.04  it tt  1069  33.96 11  8.27  "  "  67.38 it  26.35 11  1059  1068  1.01  " "  it  1067  0.225  0.189  "  "  2.45  "  0.0251  1051  1066  0.248  1.61  11  1065  0.290  4.04  8.49 ti  "  "  0.266  7.09  7.90 11  1050  1064  0.387  6.49  10.3  .999  0.0253  11  "  0.0985  1.27  11  "  0.0538  3.35  0.941  "  1063  1.83 13.2  r  2.  1.28  "  1062  k-M^s-1  50.63 it  1049  1060  1  9.59  1048  1053  k,xl03s 1  25.1° 14.0° 11  18.30 11  7.40  "  0.404  n  11  10.5  0.571  11  11  10.3  0.565  11  it  11  11  7.41 11  " "  4.36  0.238  4.39  0.240  11  49.7  2.72  .997  11  49.8  2.72  .999  5.46  0.370  .985  0.836  0.252  .995  1.80  .992  14.77  1076  6.66 n •  1077  7.42  18.01  3.32  32.5  - 211 -  APPENDIX C  No.  Substrate  1078 Benzophenone 1079 it 1080 1081 T r i f l u o r o a c e t o phenone ti 1082 II 108e II 1084 II 1085 it 1086 II 1087 II 1088 it 1089 it 1090 1091 Formaldehyde II 1092 II 1093 II 1094 it 1095 it 1096 II 1097 it 1098 it 1099 it 1100 it 1101 it 1102 it 1103 II 1104 II 1105 1106 Benzaldehyde tt 1107 tt 1108 II 1109 II 1110 1111 j3-Chloro B.ald. 1112 jj-Nitro B.ald. 1113 Benzaldehyde it 1114 1115 m-Methyl B.ald. n 1116 1117 Benzaldehyde tt 1118 it 1119 it 1120 tt 1121  "R H  [S]xl0  3  k xl0 s 3  1  1  kM 2  s  12.61 6.30 9.01 13.45  21.6 11.0 13.5 7.49  1.71 1.74 1.50 0.557  6.62  II  6.74 5.92  20.17 13.45  43.0 45.6 76.7 12.9 11.0 5.60 6.13 2.40 2.70 70.8 73.5 63.3 47.0 45.2 29.2 31.2 20.0 20.3 62.9 67.8 26.1 25.8 15.3 15.9 18.2 7.39 7.34 1.91 1.99 1.63 1.90 3.53 3.40 2.20 2.50 4.10 4.22 28.4 23.0 23.1  3.20 3.39 3.80 0.962 0.815 0.833 0.912 0.714 0.803 38.7 40.2 6.92 7.15 6.87 6.65 7.10 6.83 6.96 17.2 18.6 3.57 3.53 1.40 1.45 2.07 2.09 2.08 1.81 1.88 1.02 0.901 2.08 2.00 1.50 1.71 2.32 2.39 1.71 1.81 1.82  7.42 it it  5.66 II  it  II II II  tt  ti  ti  6.72 it  3.36 ti  4.98  1.83  3.00  9.14 6.58  tt  tt tt II  it II II  II  tt  4.39 ti  2.92 it  4.16  3.65  2.04  7.30  .1.03  10.90  II  II  tt  2.90 2.76 II  1.00 II  2.16 II  it it  it II  it  8.830 3.534 ti  10.60 II  1.606 2.105 1.699 II  2.16  1.468  3.28  1.767  II  tt  1.86 tt ti  II  tt  16.67 12.72 ti  r  .994 .991 .993 .998 II  .999 .996 .997 .995 .999 it it it tt  .998 .999  " "  .994 .992 .999  " "  .996 .997 .999 .997 .999  - 212 APPENDIX C [S]xl0  No. Substrate 1122 Benzaldehyde 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 " 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 II 1149 1150 1151 1152 1153 1154 1155 1156 1157 " 1158 1159 1160 1161 1162 1163 1164 1165 Formic acid 1166 1167  1.86 11 11  ti  1.86 11  D2O 11  it tt  2.33 11  2.79 11  11  4.241 it  10.60 11  7.066 it  3.53 11 11 11  3.53  3.60  3.53  ti  4.09 11  4.50 it  4.94 it  5.40 11  5.75 it  it  it  11  n 11 11 11 11  tt it 11 11  6.20  4.42  2.35  7.07  1.71  6.71  0.9 8  7.07  11  tt it  11  11  11  it  11  0.60  tt  0.12  11  ti it  6.34 11  7.62 11  no TFA  8.482  3.20 11  4.98 5.70 8.42  3  11  it  1.77 11  11 11  7.07 23.9 46.75 46.70  k xl0 s~ 3  1  13.8 14.2 7.35 7.44 20.1 20.4 20.4 20.1 7.71 7.92 8.00 8.10 8.78 8.93 9.60 9.88 10.5 10.7 11.5 11.7 15.9 15.7 18.3 18.6 24.1 25.0 59.9 56.1 16.2 16.6 13.1 12.6 15.1 15.4 14.8 13.6 13.7 13.6 32.1 32.7 54.7 55.9 1.26 0.179 0.387 27.8  1  , -1 -1 k^M s 1.62 1.68 1.73 1.76 1.89 1.92 2.89 2.84 2.19 2.25 2.27 2.29 2.49 2.53 2.72 2.80 2.99 3.02 3.26 3.30 4.52 4.44 5.19 5.26 6.83 7.08 13.5 12.7 2.29 2.34 1.95 1.88 2.13 2.17 2.10 1.93 1.94 1.93 18.2 18.5 30.9 31.6 0.178 0.00747 0.00828 0.582  r .997 .999 11  .997 .999 it  .997 11  .998 .999 11  it  .996 it  ti 11  .997 it  .998 11  .997 11  .996 .995 .997 11  .999 11  .997 .996 .997 11  tt 11  it  .999 .997 .998 .997 11  .999 11  .997 .980 .999 it  - 213 -  APPENDIX C  No.  Substrate  1168 F o r m i c tt 1169 it 1170 ti 1171  1172  acid  [S]xl0  8.42 6.26  46.70 68.42 95.03 45.61 30.41 119.3  ti it  it  it 1173 it 1174 1175 3 - P e n t a n o n e ti 1176 it 1177 it 1178 ti 1179 ti 1180 II 1181 II 1182 it 1183 II 1184 it 1185 tt 1186 ti 1187 ti 1188 it 1189 it .. 1190 tt 1191 ti 1192 II 1193 it 1194 it 1195 it 1196 1197 B e n z e n e , tt 1198 ti 1199 it 1200 it 1201 ti 1202 tt 1203 ti 1204 tt 1205 II 1206 ti 1207 tt 1208 1209 C y c l o h e x a n e , ti 1210 it 1211 ti 1212  ~\  it  8.50 11  6.90 11  7.90 it  7.41 ti 11 11 11 tt tt 11  14.6° 14.8° 20.6°  7.90 it  20.46  9.68  25.58 11  8.53 tt  29.84  11  17.90 11  8.53 it  17.05 11  it  11  11  30.2°  tt  11  ti  11  it  37.6° 37.4° 25.0°  ti  tt  it  11  11  11  it  11  it  D2O  6.96  11  11  H 0  11  tt  it  11  ti  D2O  6.15  11  11  11  H 0  6.26  tt  2  11  D 0  it  5.013 tt  11  5.67  20.50  11  11  11  H2O  5.64  11  it  11  11  D20  6.15  33.32  2  11  H2O tt  it  3  1  ti  n  11  it  k xl0 s~  29.0 2.19 2.98 1,37 0.898 82.9 79.5 3.55 3.73 4.23 3.71 17.4 17.4  11  2  3  it  6.26  11  11  11  9.83 7.80 8.03 2.43 2.57 9.94 9.63 11.9 12.4 15.9 16.7 22.3 21.3 14.0 13.8 139.0 147.0 140.0 133.0 15.1 15.3 13.9 13.7 11.6 11.2 9.89 9.70 7.84 7.78 7.08 6.84  1  k M" s" 1  1  2  0.607 0.0319 0.0314 0.0299 0.0295 0.695 0.666 0.139 0.146 0.496 0.435 0.582 0.584 0.473 0.480 0.436 0.448 0.285 0.301 0.583 0.565 0.698 0.728 0.930 0.979 1.31 1.25 0.819 0.812 27.7 29.3 28.0 26.5 3.01 3.06 2.76 2.74 0.565 0.545 0.482 0.473 0.235 0.234 0.212 0.205  r  .999 11 it it 11 11  .998 .993 it  .991 11  .999 it  11 11 11 11  .992 .993 .994 11 tt ti  .997 it  11  .998 .997 .996 .999 11  11 11  .998 it  11  .997 .999 .994 .997 .995 .999 it  11 it  - 214 APPENDIX C  No.  Substrate  -H  H20 1213 Cyclohexane, ti " 1214 1215 D20 tt 1216 1306 TFAD, D 0 it II 1307 g  No.  Substrate  6.98 ti  6.96 II  6.10 7.48  "HR  1217 2,4-Pentanedione 1.02 1218 1.02 " 1219 2.86 II 1220 1221 -0.05 II " 1222 1223 -0.41 II 1224 it 1225 tt 1226 it 1227 it 1228 it ti 1229 1230 3-Pentanone 6.70 II 1231 1232 7.90 it 1233 " 1234 7.41 ti 1235 II " 1236 II 1237 it 1238 II " 1239 II ti 1240 it 1241 1242 1 4 . 6 ° 7.90 ti 1243 14.8° II " 1244 20.6° II n 1245 II 1246 30.2° II II " 1247 II 1248 37.6°  [S]xlO 16.66 it it II  11.66 8.33  [S]xl0 3 1.75 II II II  3.50 II  1.68 II  2.52 II  3.78 it  5.24 25.58 II  8.53 it  29.84 II  20.46 II  17.90 II  8.53 it  17.05 ti II II II  ti it  k xlO s 27.5 28.9 25.9 25.2 0.00683 0.140  kM s 1.65 1.72 1.55 1.51 0.585 16.8  k-jXlO^ s * k^xlO^s 172.0 172.0 254.0 242.0 246.0 245.0 116.0 117.0 172.0 176.0 259.0 270.0 337.0 5.04 5.08 8.23 6.91 26.2 25.9 13.7 13.5 10.9 10.4 4.58 5.06 17.6 16.2 18.7 18.2 20.2 19.9 23.8  r  984.0 983.0 145.0 138.0 703.0 700.0 691.0 698.0 701.0 697.0 684.0 714.0 643.0 1.97 1.98 9.65 8.10  8.78  8.67 6.71 6.62 6.08 5.81 5.37 5.93 10.3 9.50 11.0 10.7 11.9 11.7 13.9  .999 II II  it it  .997 -1 r .998 II  .997 II  .979 .996 .999 .996 II  .995 .991 .996 .999 .995 .994 .978 .991 .981 .979 .973 .971 .975 .978 .975 .978 .981 .985 .979  .984 .97.8 it  .969  - 215 -  APPENDIX C  No.  Substrate  1249 3-Pentanone 1250 " 1251 " 1252 Acetophenone 1253 " 1254 " 1255 1256 " 1257 1258 " 1259 " 1260 " 1261 " 1262 " 1263 " 1264 " 1265 1266 " 1267 " 1268 1269 1270 " 1271 1272 1273 " 1274 " 1275 "  37.4° 25.0° II  7.90 ti  II  22.7 18.8 1.8.5 1.53 1.74 5.47 5.43 9.38 8.84 3.38 3.21 6.02 6.24 15.2 14.8 2.08 2.18 3.32 3.37 12.4 11.5 8.75 8.78 5.08 5.21 3.96 3.85  ti ti  6.62 6.62 6.74  15.40  II  it II  it it II  it  tt  23.10 ti  7.70 it  15.40 it  38.51 ti  5.92  23.10  6.41  15.40  it  37.6° 37.4° 30.2°  17.05 23.10  ti  it  k 1 xl0 7 Ms  5.66 tt  25.0°  [S]xl0 3  it  ti ti  it ti  30.80 it  tt  it  ti  it  it  20.6°  ti  II  it  ti  II  14.7° 14.8°  it  •t  it  II  1  k2xl05s_:L  r  13.3 11.0 10.8 0.660 0.759 3.55 3.53 4.06 3.83 4.38 4.16 3.91 4.05 3.95 3.85 0.898 0.942 2.16 2.19 4.02 3.75 2.84 2.85 1.65 1.69 1.29 1.25  .969 .980 it  .999 .997 .999 ti  it  .994 .999 ti  it it  .996 .997 .999  "  - 216 -  APPENDIX D Permanganate i n Benzene  No.  Substrate  [S]xl0  3  a  k xl0 s" 3  1  1  w~" 1  1  kM 2  1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305  trans-Stilbene  2.27 3.72  II II  II  II  2.27 1.29  II II  II  4.32  cis-Stilbene  II  II II  3.59  II  II  II  0.884 3.72  trans-Stilbene II  II  41.56  Tolan II  II  p ,p -Dinitro-transstilbene  0.353  m,p'-Dinitro-transstilbene  0.128  1  it  II  ti  : II  p-Nitrb-trans-stilbene 1.687 II  II  II  1.012 II  tt  5.4776  Benzyl alcohol II  Benzaldehyde j>-Nitrobenzyl II  it  alcohol  p_-Nitrobenzaldehyde II  *  ^ 4.542 0.716 II  1.679 II  -1  s  r  1.020 1.641 1.612 1.037 0.591 0.611 0.4065 0.4028 0.3065 0.3129 0.0842 1.616 1.650 0.3257 0.3666 84.90  0.449 0.441 0.433 0.457 0.458 0.474 0.0941 0.0932 0.0854 0.0872 0.0953 0.434 0.444 0.00784 0.00882 240.5  .999  61.99 14.62  175.6 114.2  .998  12.55 16.61 16.51 11.51 11.12 0.661 0.772 8.01 31.2 15.9 15.2 16.1  98.05 9.84 9.79 11.4 11.0 0.121 0.141 1.764 43.5 22.2 9.05 9.61  "  .980 II  .999  .910 .960 .985 .999  A l l rates corrected f o r blank corrections. 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