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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.Sc , 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 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a 1 • f u 1 f i l m e n t o f t h e r e q u i r e m e n t s f o r a n a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l m a k e i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s m a y b e g r a n t e d b y t h e H e a d o f m y D e p a r t m e n t o r b y h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t b e a l l o w e d w i t h o u t m y w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f Chemistry T h e U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8, C a n a d a Dec. 18, 1972 - i i -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. , slow , fast , fast , fast acids The -mechanism of arene oxidation was shown to proceed via rate-determining 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 - i i i RR1CH2 + Mn03+ * [RR^ CH + HMnC>3+] [RR^ CH + HMn03 ] [RR^H-O-MnC^H] (I) (ID I or (II) ? R^ RCHOH + MnV VTT V I or (II) + Mn > RR^O + 2Mn M n V I 1 RR-CHOH or RR C=0 — >• carboxylic 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 nitrite 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 facil it ies 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, Leila, for encouragement and patience. - vi -TABLE OF CONTENTS Page 1. INTRODUCTION 1 1.1 Motives for the Investigation L 1.2 Properties of the Trifluoroacetic acid-Water Medium 2 1.3 Acidity Functions . 4 1.4 Behaviour of Permanganate in 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 1.6 Permanganate Oxidations in Organic Solvents 16 1.7 Electrophilic Aromatic Nitration 17 1.8 Application of the Zucker-Hammett Hypothesis 18 2. SCOPE OF THE INVESTIGATION 21 3. EXPERIMENTAL 22 3.1 Reagents and Indicators 22 3.2 Kinetic Procedure in Acid-Water Medium 31 3.3 Kinetic Analysis 34 38 3.4 Inorganic Product Study 3.5 Organic Product Studies 39 - v i i -Page 3.5.1 Permanganate Oxidations in TFA-Water 39 3.5.2 Nitration and Nitrosation Products in TFA-Water 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 in TFA-H-0 and TFA-D-0 61 3.11 Permanganate in Benzene 69 4. 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 Generated in TFA-Water Mixtures 87 4.1.3 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 - v i i i -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 Function Indicators for TFA-Water 3 Organic Products from the KMnO^  Oxidations in TFA-Water Medium 4 Nitration and Nitrosation Products 5 Experimental Data for Stoichiometric Determinations for KMnO. Oxidations in TFA-Water 4 6 Determination and Verification of for Trifluoro-acetic acid 7 Cryoscopic Data for Substrates in 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-Ho0 or 4 2 TFA-D20 ' 11 Spectral Properties of Tetra(n-hexyl)ammonium Permanganate in Benzene 12 Properties of Tetra(n-hexyl)ammonium Permanganate ... 13 Permanganate in Benzene, Oxidation Products 14 P KR+ V a l u e s f° r Aryl Carbinols 15 H Function for TFA-H_0 16 Temperature Dependence of pK^ + 17 Thermodynamic Parameters for the Indicators used to Determine H R 18 Activity of Water in Various Media - x -Table Page 19 pK for the Ionization of Permanganate Ion to Permanganyl Ion 96 20 Manganese Reduction Products from KMnO^  Oxidations .. 102 21 Order of Reactants Involved in the Permanganate Oxidation of Alkanes in TFA-Water 105 22 Kinetic Isotope Effects in the Permanganate Oxidation • of Cyclohexane . 108 23 Comparative Reactivities of Methylene Groups in Cyclo-alkanes Relative to those in the Corresponding n-Alkane 110 24 Comparative Reactivities of Cycloalkanes 110 25 Activity Coefficients in Sulfuric Acid-Water Mixtures 116 26 Activation Parameters for Permanganate Oxidations in TFA-Water 118 * 27 Calculated -a Values of Individual Carbon Atoms in 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 in the Permanganate Oxidation of Arenes 127 32 Kinetic Isotope Effects for the Permanganate Oxidation of Arenes 132 33 Comparative Rate Ratios for the Permanganate Oxidation of Toluene, Ethylbenzene, and Cumene 130 34 Order of Reactants in the Permanganate Oxidation of Alcohols in TFA-Water 143 - x i -Table Page 35 Isotope Effects in the Permanganate Oxidation of Alcohols 147 36 Kinetic Isotope Effects in the Oxidation of Benzyl Alcohol 151 37 Order of Reactants in the Permanganate Oxidation of Ketones in TFA-Water 159 - x i i -LIST OF FIGURES Figure Page 1 Freezing point apparatus 49 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 q for the ionization of MnO^  in TFA-water 66 7 Log Q vs. H O for the ionization of MnO^  in trifluoro-acetic acid-d^-deuterium oxide 67 8 Log Q vs. H for the ionization of MnO. in trifluoro-o 4 acetic acid-deuterium oxide 68 9 Spectra of MnO^  with different cations and solvent.. 70 10 Acidity functions in TFA-water 79 + 11 a vs. pK^ for substituted triphenylcarbinols 83 12 Chromic acid oxidation of 2-propanol in TFA-water. Log k 2 vs. H q and 88 13 Particulation of potassium permanganate and sodium acetate in TFA 91 14 Particulation of sodium nitrate and sodium nitrite in TFA 92 15 Spectra of side products (from the nitration of benzene) in acidic and basic media 99 16 Spectra of 1:1 mixture of ortho and para-nitrophenol in acidic and basic media • 100 17 Log vs. loglalkane] for the oxidation of a variety of alkanes 106 - x i i i -Figure Page 18 Log k- vs. H_ for the oxidation of a variety of alkanes 107 19 Substituent effects in the permanganate oxidation of ethane I l l 20 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 134 26 Substituent effects on the permanganate oxidation of toluene 135 27 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 136 28 Log k- vs. for toluene, benzyl alcohol, and benzaldehyde 140 29 Decrease of oxidation rate with age of solution. Methanol in TFA-water 142 30 Log k- vs. log[alcohol] for the oxidation of a variety of alcohols 144 31 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 form-aldehyde and benzaldehyde 153 - xiv -Figure Page 34 Log vs. for the oxidation of formaldehyde and benzaldehyde 154 35 Typical pseudo first-order plot for the oxidation of cyclohexanone 157 36 Typical zero-order plot for the oxidation of acetophenone 153 37 Log k^ vs. loglketone] for the oxidation of a variety of ketones 160 38 Log k^ vs. log[formic acid] for the oxidation of formic acid 164 39 Log k 2 vs. for the oxidation of formic acid 166 40 Substituent effects on the permanganate oxidation of trans-stilbenes in a medium of benzene 168 - X V -ABBREVIATIONS AND SYMBOLS USED IN TEXT a i a c tivity of i t h component c constant of integration AG change i n free energy AH change in enthalpy AS change in entropy DPC diphenylcarbinol f. 1 activity coefficient of i t h component F i mole fraction of i t h component g grams h Planck's constant hr hour H o acidity function defined by protonation of primary anilines HR acidity function defined by ionization of carbinols k Boltzmann constant k n rate constant, n = 0,1,2,3 k,k' proportionality constants kg kilogram °K degrees Kelvin In natural logarithm log base 10 logarithm m molality, moles per 1000 g of solvent M molarity, moles per 1000 ml of solution microliter ml m i l l i l i t e r min minutes - xvi -n number of particles generated n^ number of particles predicted by theory N normality, number of equivalent weights per l i ter 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 tre 1. INTRODUCTION 1.1 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 util izing them as a food source. The i n i t i a l approach of reseachers in this area was to util ize yeasts to profitably up-grade crude oils 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 - sp 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 util ize 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. This information might help elucidate 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 5-7 c wide variety of substrates. 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 8 10 to 10 molar. 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 9 acid with pK = -0.26. r a 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 s-H = -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 anion.^ 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 19 carbonium ion generated from the alkyl group of the ester. 1.3 Acidity Functions In this investigation the 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 wi 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. + K BH + + ArNH^ v ArNH2 + H , Ar5= phenyl group (BH+) (B) KBH+ = aBaH+/aBH+ ' 3 = a c t i v i t l e s - 5 -K B R + = [B] f_aH+/[BH+]f_H4: , f = activity coeficient The definition is then made that hQ = f^a^+/f^^_. This then separates those terms hard to determine from those easily accessible by experimental measurements. pK B R + = -log = -log[B]/lBB+] - log hQ p K B H + = Ho " l 0 g tB1 /1 BH"*"] or H q = pKgj-f + log [ B ] / I B H + ] 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 + H (R+) (ROH) V = aROHaH+/aH_OaR+ - r R O H ] f ROH a H+ / [ R + ] f R+ a H 0 hR = fROHaH+/fR+aH20 a n d \ = hR pK_+ = -log[ROH]/[R+] - l o g h R = pK-+ + log [ROH] /[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. The pK for this indicator can then be calculated. This pK value is used to then determine for stronger mixtures by measuring the new ionization ratio ([B]/[BH+]). Eventually this indicator wi 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. This overlapping process is continued until H 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 „ /fD t l )» B^  2 2 2 c = a constant. This condition must be fulfi l led 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), i .e . -log fB aH+/fBH = "log fB aH+/fBH * T h i S c o n d i t i o n c a n b e tested by checking to see that log [3]/[BH+] vs. H x plots give lines that are parallel for overlapping indicators. If deviations are severe the deviant indicator should not be used. - 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 24 28 29 from purple to light green ^ m a x °^ 8 r e e n species is 458 nm ' ). The cause of this spectral change has not yet been resolved. Symons 25 et al . have suggested from conductivity measurements that the spectral change is due to the following process, KMnO/ + 3H.S0. *• 0oMn0S0_H + H_0+ + K + + 2HS0." 4 2 4 — 3 3 3 4 26 but Royer interpreted similar conductivity measurements and cryoscopic data to be consistent with the reaction, KMnO. + 3H„S0. K + + MnO_+ + H o 0 + + 3HS0." 4 2 4 -«— 3 3 4 27 Stewart has suggested that these interpretations may be reconciled by considering the following equilibrium. 0_Mn0S0oH »• MnO.+ + HSO." 3 3 — 3 4 This spectral change has been observed in partially aqueous media where 28 29 the process is taken to be a protonation. ' H + + MnO." HMnO. 4 - — 4 - 8 -28 Syraons et a l . 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 wi 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 Permanganate Oxidation of Organic Substrates 1.5.1 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. —> [R-C-MnO.H ] —»• R„C-0-MnO„H 3 4 3 4 3 3 R3C-0|Mn03H" + H20 —> R3COH + MnV or R3C40-Mn03H~ —> R 3 C + + MnV (*0-MnO„H 3 or R-C-CH2CH2 —*- R-C~CH2CH2 R J C=0 0 R 0 C=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 (a) The rate law was found to be r = k[alkane][Cr03]hQ. (b) 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, 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 statistical factor for the series of 35 C4H10' C 7 H 16» C9H20' C11H24' C16H34' a n d C22H46* - 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 40-43 44 45 arenes only Cullis and Ladbury and Lee and Singer attempted to study the mechanism of this oxidation in acidic media. Cullis and 44 Ladbury were the first 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 in 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 attempted to clarify the mechanism of arene oxidation. 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. k l p_-toluenesulfonate anion •*• p_-toluenesulfonate k - l + [arene] [arene H ] + VII 2 [arene H ] + Mn *• products Using the steady state approximation on [arene H*"] the following rate law results. k-k-[arene] [MnVI*] r = k_- +.k2[MnV I 1] It was stated that the observed order shift could be explained as follows. VTT VTT If, k_-^> k-fMn ], r = Kk-[arene][Mn] If, k_- <$C k-[Mn V I 1 ] , 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 carbon-40 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 alkali . 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 wi 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 47 of an alkoxlde ion from the alcohol. ' The rate law has the form r = k[alcohol][Mn0 4~][0H~]. ( i i ) The observed salt effects are consistent with a bimolecular transition state resulting from the alkoxide ion and permanganate ion. ( i i i ) Carbon-hydrogen bond cleavage i s involved in the rate-determining step since substantial deuterium isotope effects are observed. These can become exceptionally large in fluorinated alcohols, e.g. k^/k^ = 16 for the oxidation of l-phenyl-2,2,2-t r i f luoroethanol.^ (b) Acidic media (i) In acidic medium the rate accelerations observed with increased acidity are believed to be due to the generation of 48-50 permanganic acid. ( i i ) The rate-determining step involves carbon-hydrogen bond scission. Isotope effects of k^/k^ - 2.4-3.2 are observed for the oxidation of cyclohexanols. In the case of 2-carboxycyclo-hexanols effects of ^/^-p = 7-8 were reported."''* ( i i i ) There was no evidence found for the participation of intermediate oxidation states of manganese in the rate-determining step for the oxidation of benzyl alcohol to benzaldehyde in 52 perchloric acid-water mixtures. (iv) In most cases the rate law follows H « ^ 50,52 xri(p_-tolyl)-48 carbinol was exceptional in that i t followed H . Similar dependence upon H was found for the chromic acid oxidation of K 53 triphenyl carbinol. - 14 -48 (v) Stewart and Banoo found that the permanganate oxidation of d i - and tri-phenyl carbinols involved the ionization of the carbinol to the carbonium ion which then formed a permanganate ester. This ester then decomposed to products possibly via a cyclic process similar 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 their enol form. As such they are rapidly oxidized i n alkaline and acidic m e d i a . U n d e r most conditions permanganate oxidizes double bonds by cis addition to 57 58 yield cis diols, ' but when the medium is gla c i a l acetic acid the 59 major products are a-diketones (yields up to 80%). Enolic double bonds are not always degraded by cis addition since Wiberg and Geer^ have presented evidence to show that the enolate ion generated from acetone reacts by electron transfer i n the following manner. 0~ 0 CH0-C=CH. + MnO ~ s l o w > CH--C-CH • + MnO.2" 3 2 4 3 2 4 The oxidation pathway for acetone can be shown as a attack, with 60 subsequent carbon-carbon bond cleavage, 0 0 0 0 II II II II CH3-C-CH3 — CH3-C-CH20H —* Ct^-C-CHO —+ Cl^-C-CO^ CH3-C02 or ° 2 C - C 0 2 - 15 -or in a more general form for a l l enolizable ketones as; 0 0 H II OH" I Mn V I 1 R-C-CHR- + ' R-C=CR- » RCO-H + R-C=0 or H OH R C=0 - > etc. or H Aldehydes are readily oxidized in any medium, yielding chiefly the respective acid although some carbon-carbon bond cleavage may also occur, presumably via the enol."^ In basic media the reaction is 61 62 believed to go via the aldehyde hydrate anion. ' Wiberg and Geer have shown that only such an intermediate can explain the incorporation 18 62 of 0 from the medium in 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 R-C-H — • R-CHCO-H Z ' I _ 2. OH Jf R_C=C-H »• carbon-carbon bond cleavage products f M V I 1  acidic route: R-CH-C-H — » R-CHCO-H Jf R2C=C-H * carbon-carbon bond cleavage products. 1.5.5 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 -63 6 A solutions is well established. ' 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.^ ^ A substantial solvent isotope effect of k_ Q = 2.7 (pH not 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 64 2 2 Onwood. There is some oxygen transfer from the permanganate to the 18 formic acid during the oxidation, since 0 from permanganate was found in the product, carbon dioxide. As the medium becomes more acidic the rate decreases due to the 6 3 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 50% sulfuric acid and these are believed to be due to formation of permanganyl ion (MnO-+). The oxidation is visualized as successive one-electron transfers according to the following scheme. VII - VI HCO- + Mn * CO-' + Mn , slow T VII VI VI V CO- + Mn or Mn CO. + Mn or Mn , fast 1.6 Permanganate Oxidations in Organic Solvents Recently two methods have been described which extend the use of 69 permanganate as an oxidant into organic solvents. Sam and Simmons - 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. Starks was able to use the method of phase-transfer 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^ wi 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 (N02 +). Because of this possibility some of the features of electrophilic aromatic nitrations wil l be presented. Electrophilic aromatic nitrations are known to follow the 72 73 21 73 function, ' ' more precisely + log a^ Q , carbon-hydrogen bond cleavage does not occur in the rate-determining step since only very small (secondary) isotope effects are observed.^4 ^ The nitration rates show some solvent dependence.^ 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. HN03 + H H20 + N02 , fast N attack, + NO, + (ArHN02+) slow [ArHN02+] ArN02 + H , fast 0 attack, 0-N=0 R-<^^)O-N=0+ H 2O OH + NO. 0-N=0 + H OH + HNO, OH + 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 - 19 -80s. or A-2 mechanism. 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 criteria exceptions were reported thus limiting the ut i l i ty 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). This postulate can be generalized in the following manner: For a general case of a bimolecular reaction k2 A + B • products, k. is rate-determining the measured rate law is r = k-[B][A] where k l = k 2 f A f B / f t ' 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_ R + then f A f f i / f + = a^f . /f_ R + . X X X X This reasoning in itself 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 -—*• X »• products r = kV[Mn04-][S] f f /f 4 (b) Permanganic acid as oxidant. MnO ~ + H + HMnO, 4 4 K+ t k + HMnO^  + S X * products r = KK+k+[Mn04-][S] V f M n O , - f S / f t 4 (c) Permanganyl ion as oxidant MnO " + 2H+ Mn0_+ + Ho0 4 3 2 / M n 0 3 + s 7 ^ x > products r - KK+kf[MnOA-][S] a j + f ^ f / a H f + 4 2 - 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 acid-water. 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. EXPERIMENTAL 3.1 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 disti l lation through a 12" Vigreaux column. It was found that i f the acid was disti l led from small amounts of potassium permanganate, approximately 0.5 g per kg of acid, that the fraction collected between 71.0-71.5° 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 Source Purification method Purity Literature n-Pentane E v.p.c. column 1 >99.8% iso-Pentane E used as received >99.8% n-Hexane M spectral grade >99.8% n-Heptane E dist. 97 .5-98.0° >99.8% n-Octane A used as received 99.5% n-Nonane F dist. 149.5-150.0° 99.5% n-Decane A used as received 99.6% n-Undecane A v.p.c. column 1 99.7% n-Dodecane E dist. 215-216° >99.8% n-Tridecane A used as received >99.5% Cyclopentane A spectral grade U.A.R. >99.8% Cyclohexane E spectral grade U.A.R. >99.8% Cycloheptane A U.A.R. >99.7% Cyclooctane A U.A.R. >99.7% Methanol B spectral grade U.A.R. >99.9% Ethanol F distilled >99.8% 2-Pentanol A v.p.c. column 1 >99.8% 3-Pentanol A it II it >99.8% Formaldehyde F 37.4% standard soln. -2-Pentanone E v.p.c. column 1 >99.8% 3-Pentanone E II II II >99.8% Cyclohexanol E dist. 158.0-158.5° 99.5% Cyclohexanone E dist. 151.0-151.5° 99.8% Acetone E spectral grade U.A.R. >99.8% Formic acid E dist. 101.0-101.5° >99.8% Propionic acid F U.A.R. >99.8% 2,4-Pentanedione E dist. 137.0-138.0° 99.5% Propionitrile E v.p.c. column 1 >99.8% Nitroethane M II tt II >99.8% 1,1,1-Trichloro- F II II II >99.8% ethane Table 1 (Continued) Compound Source Purification method Purity Literature Toluene E dist. 109.0-109.5° >99.8% Ethylbenzene E v.p.c. column 1 >99.8% Cumene E II II ti >99.8% t- Bu ty lb en z ene E II II II >99.8% Benzyl alcohol E dist. 203.0-204.0° >99.8% — Benzaldehyde E dist. 173.5-174.0° >99.8% — Acetophenone E v.p.c. column 1 >99.8% — Trifluoroaceto- K & K II tt ti 99.5% — phenone Benzene F spectral grade U.A.R. >99.8% 1 3 2 ° 8 1 a 8 5 . 2 ° 8 1 b 2 1 0 . 8 5 ° 8 1 c Chlorobenzene E dist. 129.0-130.0° >99.8% Fluorobenzene E dist. 82.5-83.0° >99.8% Nitrobenzene E dist. 207.0-208.0° >99.8% Anisole E dist. 150.0-150.5° >99.8% 155° 81d 2-Phenyl-2-propanol A U.A.R. 99.5% — 2-Phenylethanol A U.A.R. 99.0% — 1-Phenylethanol A U.A.R. 99.5% — p-Bromotoluene E recrystallized >99.8% 1 8 4 ° 8 1 e  1 6 2o81f m-Bromotoluene F dist. 180.0-180.5° >99.8% m-Chlorotoluene K & K dist. 158.0-158.5° >99.8% KMnO 4 B Baker analyzed 99.5% — Ethane M U.A.R. 99.99% — Propane M U.A.R. 99.5% — Butane M U.A.R. 99.5% — neo-Pentane FLUKA U.A.R. 99.92% — Cyclohexane-d^2 MSD U.A.R. 99% D — Methanol-d^ MSD U.A.R. 99% D — Deuterium oxide MSD U.A.R. 99.8% D — Toluene-a-d3 MSD U.A.R. 98% D — Toluene-ds MSD U.A.R. 98% D — H2S04 B U.A.R. 97.4% — Table 1 (Continued) Compound Source Purification Method Purity Literature Benzoic acid E p-Nitrotoluene E m-Nitrotoluene E p-Methylbenzoic acid E m-Methy-benzoic acid E Tetra-n-hexyl-ammonium iodide E m-Nitrobenzyl alcohol E m-Methoxylbenzyl alcohol A p-Chlorobenz-aldehyde E m-Me thylb enz-aldehyde K & K p-Nitrobenz-aldehyde K & K Benzophenone E cis-Stilbene K & K trans-Stilbene F Tolan A p-Nitro-trans-stilbene A p,p'-Dinitro-trans-stilbene A p,m'-Dinitro-trans-stilbene A Sodium nitrate B Sodium nitrite F sublimed recrystallized dist. 230.0-231.0° recrystallized U.A.R. dist. 210.0-212.0° 10 mm dist. 254.0-256.0° recrystallized dist. 201.0-202.0° recrystallized II U.A.R. U.A.R. recrystallized mp 122.0-123.0C mp 50.0-51.0° mp 178-180° mp 11.0-112.0° U.A.R. U.A.R. mp 47.0-48.0° mp 104.0-105.0° mp 48.0-49.0° fp 4-5° mp 121.0-123.0° mp 60.0-62.0° mp 155.0-158.0° mp 296-299° mp 220-221° analar grade 96.6% 1 2- 081g 52o81h 227 ° 181° 8 1 1 lll-113° 8 1 i 175-180° at 3 mm81J 252 o 8 1 k 47°91 201° 8 1 m 106° 8 1 n 49° 81o 5-6°81P 124°81P 6 2 5o81q 155° 8 1 r 288° 8 1 a 2]_y o 81s to Table 1 (Continued) A l l compounds except the last 31 were checked by v.p.c Column 1 - 20% Carbowax 20 M on firebrick - 20' x 3/8" Column 2 - 20% Dionylphthalate on Chromosorb - 20' x 3/8" u. A.R. - used as received E - Eastman Chemical Co. F - Fisher Scientific Co. K & K - K & K Laboratories Ltd. A - Aldrich MSD - Merck, Sharp and Dohme B - J.T. Baker Co. M - Matheson of Canada Ltd. using column 1. > i ho ON I Table 2. IL, Function Indicators for TFA-H-0 No. Compound Experimental Literature mp A log e r max ° mp max log £ Source 1 4,4',4"-Trimethoxy TPC 2 4,4'-Dimethoxy-4"-methyl TPC 3 4,4'-Dime thoxy TPMCL 4 4,4',4"-Trimethyl-TPC 5 4-Methoxy TPC 6 4,4'-Dimethyl TPC 7 4,4'-Diethoxy DPC 8 Triphenylcarbinol 9 4,4',4"-Trichloro TPC 10 4-Nitro TPC 81.0-82 .0° 480 5.04 81.0-82.0 74.0-76.0° 72 .0-74.0° 78 .0-78.5° 56 .0-57 .0° 487 427 111.0-113.0° 495 91.0-92 .5° 410 446 469 394 506 163.0-164.0° 425 91.0-93 .0° 403 460 96.5-98 .0° 436 388 4.93 4.67 4.88 4.56 4.97 4.82 4.38 451 4.81 5.22 4.60 4.60 502 4.51 4.47 ,21 485 478 21 82 5.02 4.94 21 82 500 21 5.47 21 94.0' ,83 452 21 5.03 21 60.0 8 2 . 0 ° 8 5 7 5 . 0 ° 8 6 75.5-76.5 82,84 476 21 4.75 21 .87 80.0' •88 456 505 87 87 -4.44 87 5.10 89 1 6 4 - 1 6 5 ° 8 1 t 431 2 1,425 8 2 4.60 2 1 ,4.64 8 2 404 2 1,410 8 2 4.60 2 1 ,4.63 8 2 21 9 3 . 5 - 9 4 . 0 ° 9 0 4652 1 9 5 . 5 - 9 7 . 0 ° 9 1 4542 1 5.01" synthesized synthesized Aidrich lab stock | N lab stock i lab stock lab stock lab stock lab stock lab stock Table 2. (Continued) 3 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 for the respective carbonium ion generated A l l compounds were checked by NMR for substituent identity TPC = triphenylcarbinol TPMCL = triphenylmethyl chloride DPC = diphenylcarbinol 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 distil late 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 disti l led 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. The ether layer was recovered and flash evaporated. 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 in i t i a l deuterium content of the lithium aluminum deuteride was 96.8%. - 30 -4,4',4"-Trimethoxytriphenylcarbinol: The method outlined by Baeyer 92 93 and Villiger was used with minor modifications from Vogel. To a Grignard solution prepared from 0.10 moles of magnesium turnings and 0.10 moles of 4-bromoanisole in 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 distil led and then dissolved in hot n-heptane. Recovery of the desired product was extremely difficult 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 ° , literature mp 8 1 . 0 - 8 2 . 0 ° . 2 1 - 31 -4,4'-Dimethoxy-4" - methyltriphenylcarbinol: This compound was prepared in a similar manner to that described for 4,4',4"-trimethoxytriphenyl-carbinol with the exception that 4-bromotoluene was used to prepare the Grignard reagent. Similar purification problems were also encountered. 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 in 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. Both machines were equipped with thermostated cel l compartments. A l l kinetic experiments except where noted were performed at 2 5 . 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 cel 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 M. The kinetic -4 concentration was then 4.0 x 10 M which gave an in i t i a l absorbance of 0.9. 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 esterifica-tion. 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 air. The solution was then stirred at a moderate rate by means of the magnetic stirrer for a time not exceeding two minutes. The stirring time depended upon the amount of dissolved gas desired. The connecting hose was removed and the volumetric flask was restoppered and reweighed. The weight gain was taken as the amount of gas uptake. 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 acid-water. 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 wi 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 94 developed by the author. The basic kinetic equations used vrere derived from the general rate equation (1) in the following manner. [0 x] = [Mn04 ]. [S] = [substrate] h = applicable acidity function T = temperature °K k_ = Boltzmann's constant h = Planck's constant c = constant of integration n,m, and 1 are powers (1) -d[o„]/dt = k3[ox]n[s]V x In the pseudo-order approach h, S and T are kept constant which reduces equation 1 to equation 2. (2) -d[ox]/dt = k-[ox] n wher e k- = k - t s A 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. These are solved below. - 35 -when n = 0: -d[0 ]/dt = k 1 x o (3) -d[0x] = kQdt Integration of equation 3 yields equation 4. (4) [0 ] = k t + c x o When [0x] is plotted against time the slope is the desired rate constant, k . ' o when n = 1: -d[ox]/dt = (5) - d I O x 1 / I O x ] = k l d t Integration of equation 5 yields equation 6. (6) -ln[0 ] = k nt + c x 1 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 = Absorbance (e = molar extinction coefficient). In the case where n = 0 the - 36 -slope is then equal to but in the case where n = 1 the slope is s t i l l since ln[0 1 = In Abs. - In z and In e is a constant which 1 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 1 = k 2 [Sj m , k 2 = k 3 h 1 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 fits the experimental data. k 2 = k.h 1 = ^/[sf log k 2 = 1 l o g h + l o g ^ 3 or in the more familiar form -log k_ = 1 H + c 2 x where the slope of the -log k2 vs H x plot gives the order of the reaction with respect to h . r x The activation parameters were obtained in the usual manner by - 37 -95 converting the Wynne-Jones Eyring equation into a linear form. -AG+/RT k 2 = (k T/h).e AG+ = AH1" - TAS1* ASt/R -AH+/RT k2 = (kT/h)-e 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 trials 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 x]/dt = k 2IO xJ t.IS] t - 38 -^ t * t S ] o - TJ « ° x ] o " l°* ]t> • d [ ° x ] t dt - k 2 t V t ( [ s ] o - n t V o + i 4 [ ° x ] t ) -d[o x] t (7) [0 J x o 2^ 4 IVt> = k-dt Equation 7 can be readily integrated since i t is of type ^ — dx (a+bx) 1 . a+bx 96 Q In to give equation 8. , [s ] , [0 ] . (8) \ l n (ToV - TJ WT + _ 7 ) = k 2 t + c In actual practice absorbance was used instead of [0 1 . This v x t conversion was readily made by Beer's law, ^ x l t = A/e. 3.4 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 volati l i ty Table 3. Products of KMnO. Oxidations in TFA-Water Medium Substrate wt.a -H^ % Recovered0 Products wt. % d Method n-Pentane 2.5 7.5 40% 2- Pentanol 3.2 7.5 89% 3- Pentanol 3.3 7.5 90% 2- Pentanone 3.3 7.5 94% 3- Pentanone 3.3 7.5 90% Cyclohexane 3.1 7.5 83% Cyclohexanol 3.9 7.5 95% Cyclohexanone 4.0 7.5 89% Toluene 3.5 4.5 95% Toluene 3.5 7.5 82% 2-Pentanone - 66% 1 3-Pentanone - 34% 1 Propionic acid — — 2 2-Pentanone — - 3 Propionic acid - — 2 3-Pentanone — - 3 Propionic acid - — 2 Propionic acid - - 2 Propionic acid - - 2 Cyclohexanol *y0.01 5% 4 Cyclohexanone M).01 5% 4 Adipic acid 0.2 90% 5 Cyclohexanone ^0.03 4% 4 Adipic acid 0.35 91% 5 Tar 0.03 5% Adipic acid 0.5 90% 5 Tar 0.05 10% Benzoic acid .25 - 6 Benzoic acid .05 — 6 Table 3 (Continued) Substrate ^ a wt. -H b % Recovered Products wt. % d Method Benzyl alcohol 4.2 4.5 91% Benzoic acid .3 - 6 Benzaldehyde 4.2 4.5 93% Benzoic acid .4 - 6 Acetophenone 4.1 7.5 92% Benzoic acid .2 - 6 1-Phenylethanol 4.1 5.0 95% Acetophenone .4 100% 7 2-Phenylethanol 4.1 5.0 93% Phenylacetaldehyde (trace) 8 Phenylacetic acid .1 99% 9 in i t i a l amount of substrate added in grams; b c acidity of reaction medium; based on total materials I (products and reactants) recovered; 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. Identified by retention times on chromosorb 101 and Carbowax 20 M columns against known samples. Cyclohexanol existed as the trifluoroacetate ester. 5. Isolated, then purified by recrystallization, mp = 145-148 6. Isolated, the purified by sublimation, mp = 121-122°, literature mp = 122 literature mp = 149-150c 81q 81u 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 Identified by NMR. 81v literature mp = 76° . 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. Only propionic acid could be collected. 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 nitrite . 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 stirrer. 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. See Section 4.1.3 for further discussion and also reference 79. - 44 -Table\4. Nitration and Nitrosation Products. Reactants % Recovered % Converted Products % of Product Detection Method Phenol and NaN03 - black tar 3 - -Toluene NaN03 and 97 \ 9 5 p-nitrotoluene 31.7 p_-nitrotoluene 67.0 Tfi-nitrotoluene 1.3 phenols <.05 1 1 1 2 Benzene NaNC"3 and 100 100 nitrobenzene 100.0 phenols <.05 1 2 Toluene NaN02 and 98 1-2 nitrotoluenes VL-2 1 Benzene NaN02 and 97 2-3 nitrobenzene ^2-3 1 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 162° , 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 TFA-water 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 M in potassium iodide and 2% in sodium bicarbonate. The liberated iodine was titrated with a -4 2 x 10 M standardized sodium thiosulfate solution to a starch end point. These experimental values are tabulated in Table 5. 3.7 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. Previous 26 attempts to identify the species in sulfuric acid had not been 25 27 conclusive. ' 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. a — b Compound R_ Moles substrate Moles Mn04 Difference Y/X applied = X x 10 7 x 10 7 in x 10 7 = Y Blank Trial Isopentane -8. 42 5.15 9. 49 3.95 5.54 1.08 n-Pentane II 2.60 9. 37 8.36 1.01 0.39 n-Hexane II 2.30 9. 67 8.09 1.58 0.68 n-Heptane II 1.36 9. 43 8.15 1.28 0.94 n-Heptane II 2.72 9. 37 6.45 2.92 1.08 n-Octane II 2.46 9. 49 6.08 3.41 1.39 n-Nonane II 1.67 9. 49 6.42 3.07 1.85 n-Decane II 1.54 9. 25 6.05 3.20 2.08 n-Undecane ti 1.40 9. 31 5.99 3.32 2.33 n-Dodecane II 0.88 9. 31 6.57 2.74 3.13 n-Tridecane II 0.82 9. 37 6.51 2.86 3.45 Cyclopentane -7. 82 4.82 9. 67 6.69 2.98 0.62 Cyclohexane II 4.17 9. 40 6.72 2.68 0.64 Cycloheptane II 3.72 9. 12 6.69 2.43 0.65 Cyclooctane II 2.23 9. 25 6.99 2.26 1.01 Methanol II 5.56 10. 10 5.90 4.20 0.76 Methanol -6. 70 5.56 11. 07 9.91 1.16 0.21 Ethanol -7. 90 5.13 9. 37 6.99 2.38 0.46 2-Pentanol II 2.76 9. 12 8.09 1.03 0.37 3-Pentanol ti 5.55 9. 37 6.69 2.68 0.48 Cyclohexanol -7. 82 1.92 10. 46 9.61 0.85 0.44 Cyclohexanol II 5.77 9. 37 7.24 1.95 0.34 Formaldehyde II 5.27 10. 28 5.23 5.05 0.96 Cyclohexanone II 3.05 9. 82 8.18 1.64 0.54 Benzene -6. 70 . 3.37 11. 07 3.89 7.18 2.13 Benzene -7. 50 1.13 7. 53 4.52 3.00 2.67 Phenol II 0.611 6. 86 5.47 1.40 2.28 Toluene ti 0.941 6. 86 4.98 1.88 2.00 Toluene -6. 70 2.82 11. 01 2.92 8.09 2.86 Toluene -3. 65 8.47 10. 89 2.07 8.82 1.04 Ethylbenzene -7. 50 0.817 7. 47 5.89 1.58 2.35 Ethylbenzene -6. 70 1.63' 11. 56 6.08 5.48 3.33 Cumene it 1.44 11. 19 6.45 4.74 3.33 Cumene -7. 50 0.719 7. 95 6.13 1.82 2.53 t-Butylbenzene -7. 50 0.646 7. 59 6.07 1.52 2.35 _t-Butylbenzene -6. 70 1.29 11. 37 7.06 4.31 3.33 Benzyl alcohol -2. 30 14.5 9. 79 2.25 7.54 0.52 Benzyl alcohol -3. 65 8.67 10. 97 2.92 8.05 0.96 Benzyl alcohol -6. 70 2.89 11. 19 4.32 6.87 2.38 Benzaldehyde -2. 30 14.7 9. 73 2.37 7.36 0.50 - 47 -Table 5. (Continued) Compound Moles substrate applied = X x 107 Moles x 107 Blank MnO ~ 4 in Trial Difference'3 x 107 = Y Y/X Benzaldehyde -2.30 7.36 10.73 4.22 6.51 0.88 Benzaldehyde -3.65 8.83 11.86 4.44 7.42 0.84 Benzaldehyde -6.70 2.94 11.13 5.96 5.17 1.75 1-Phenylethanol -3.65 4.97 11.31 9.85 1.46 0.29 1-Phenylethanol -7.50 0.834 7.77 6.98 0.79 0.95 2-Phenyle thanol -7.50 0.837 7.71 5.22 2.49 2.97 2-Phenylethanol -3.65 7.54 11.50 3.95 7.55 1.0 Acetophenone -8.42 5.13 9.12 4.44 4.68 0.91 C-H C-OH 0.40 C-H -> C=0 0.80 C-H ->- CO-H 1.20 C-OH -*- C=0 0.40 C-OH -> C02H 0.80 C=0 + C02H 0.40 R2CH2 •> 2RC02H 2.40 acidity of the TFA-H-0 medium in which the reaction took place. the moles of MnO^  used up according to the data. - 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 in 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. The solution was completed frozen to degas i t and then remelted. 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 ° . For pure TFA the reproducibility was + 0 .005 ° . 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 H Function for TFA-Water K — — — — — — — — — — — — When the in i t i a l kinetic oxidation data were analyzed i t was found that the order with respect to hQ was extremely high, in excess of five. It became apparent that this was not the proper function. The 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 25° . 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. For this purpose indicators 1 and 2 (see Table 2) were used. 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 Molality AT Kf=AT/m substrate = m Determination Benzene 0.02250 0.7329 3.94 5.38 4.00 5.46 3.96 5.40 3.99 5.44 4.08 5.57 4.00 5.46 Kf=5.45+0.02 m =AT/K£ x f n=m /m x b n o Verification Toluene 0.01882 0.6130 3.46 0.6349 1.04 1.0 Sodium 0.001533 0.04993 0.835 0.1532 3.07 3.0 acetate 0.001102 0.03589 0.580 0.1064 2.96 3.0 II 0.000625 0.02035 0.330 0.06052 2.98 3.0 II 0.000244 0.00794 0.140 0.02796 3.42 3.0 II 0.000244 0.00794 0.148 0.02569 3.23 3.0 II 0.000138 0.00450 0.085 0.01559 3.46 3.0 0.080 0.01468 3.26 3.0 0.075 0.01376 3.06 3.0 is the molal freezing point depression constant, n is the number of particles predicted theoretically. - 52 -Table 7. Cryoscopic Data for Substrates in Trifluoroacetic Acid • Substrate Moles added Molality AT mx=AT/Kf n=m / i X = m Water 0.01665 0.5423 3.41 0.6257 1.15 ti 0.00555 0.1808 1.28 0.2349 1.30 II 0.01665 0.5423 3.65 0.6697 1.23 II 0.01110 0.3619 2.37 0.6349 1.20 KMnO. 0.001179 0.03840 0.63 0.1156 3.01 it 4 0.0009430 0.03072 0.60 0.1101 3.58 II 0.0008464 0.02757 0.56 0.1028 3.73 ti 0.0006348 0.02068 0.39 0.0716 3.46 it 0.0004945 0.01611 0.33 0.0606 3.76 it 0.0002781 0.009059 0.22 0.0404 4.46 ti 0.0003122 0.009912 0.16 0.0294 4.25 it 0.0006356 0.02070 0.37 0.0679 3.28 i i 0.0001948 0.006345 0.17 0.0312 4.92 ti 0.0001429 0.004650 0.13 0.0239 5.14 II 0.0001215 0.003958 0.11 0.0202 5.10 Triphenyl- 0.0007547 0.02458 0.46 0.08441 3.43 carbinol 0.0004380 0.01427 0.26 0.04771 3.34 it 0.0001984 0.006463 0.135 0.02477 3.69 it it it 0.140 0.02569 3.83 Sodium 0.001271 0.04141 0.575 0.1053 2.55 nitrate 0.000475 0.01548 0.28 0.05138 3.32 ti 0.000377 0.01226 0.205 0.0376 3.14 i i 0.000233 0.07604 0.142 0.0261 3.42 it it ti 0.165 0.0303 3.98 it 0.000168 0.005461 0.105 0.0193 3.53 II it tt 0.110 0.0202 3.69 ti 0.000113 0.003675 0.090 0.0165 4.49 it tt it 0.095 0.0174 4.74 Sodium 0.001401 0.04563 1.02 0.1872 4.10 nitrite tt it 1.03 0.1890 4.14 0.0009384 0.03057 0.73 0.1339 4.38 ti it 0.75 0.1376 4.50 0.0007304 0.02379 0.575 0.1055 4.43 " it it 0.60 0.1101 4.62 0.0003567 0.01167 0.270 0.04954 4.26 it ti 0.275 0.05046 4.34 0.0001471 0.004792 0.110 0.02018 4.21 it it 0.120 0.02202 4.59 1.65 - 54 -12 Since the H function established by Randies and Tedder was o J 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 > ROH + H z or lRQH] a f f f f R 0 H l R + ] a H 2 0 V log - log -M- + log ROH [R ] "H20 • iR+ i . u H+ ROH _u . let h = r T — then IL = -log h R aH 20 fR+ 1 1 R u . „ , , [ROH] IL = -log \ + + log 1 1 * [R +] v a . 1 [ROH] H,, = pK +^ + log * * [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 in 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. But for pure solvent a = 1 .'. 1 = kpQ or k = 1/p so the equation takes the familiar form a_^  = P^/P o « We did not have the necessary equipment to measure the vapour pressure at 25° 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 in 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. The a^ _ could be then approximated in. the following manner; 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 = 1 = kp ' o r o but, p = k*F = k* ro o then, kk' = 1 therefore, a^ = It must be remembered that these values of a^ _ are only approximate since isothermal conditions did not exist. The values obtained are presented in Table 9. Figure 4 presents the vapour-liquid equilibrium data. - 58 -Figure 3. Vapour-liquid equilibrium study apparatus. - 59 -Table 9. Vapour-Liquid Equilibrium Data for the TFA-Water System. Boiling N of N of F„ * in F u * in Log F "2 2 point liquid vapour liquid vapour vapour 71.0 13.0 13.0, 0 0 -79.2 12.40 12.70 0.254 0.169 -.772 88.1 12.0 12.80 0.346 0.130 -.886 96.0 11.65 12.80 0.410 0.130 -.886 99.9 11.30 12.45 0.466 0.250 -.620 103.7 10.60 11.60 0.556 0.416 -.381 104.7 10.30 10.70 0.585 0.547 -.262 104.9 10.00 9.60 0.614 0.652 -.186 104.5 9.70 8.60 0.641 0.720 -.143 103.5 9.00 7.00 0.693 0.800 -.097 102.3 8.40 5.80 0.731 0.852 -.070 101.8 7.80 5.15 0.765 0.875 -.058 101.3 7.35 4.00 0.785 0.893 -.049 101.0 7.00 3.95 0.800 0.910 -.041 100.8 6.55 3.55 0.821 0.921 -.036 100.65 6.20 3.50 0.837 0.922 -.035 100.35 5.65 3.15 0.858 0.932 -.031 100.15 5.00 2.80 0.881 0.941 -.026 100.0 4.20 2.40 0.905 0.951 -.022 99.4 3.30 2.00 0.928 0.960 -.018 99.6 2.30 1.50 0.953 0.971 -.013 99.3 1.30 0.80 0.975 0.986 -.006 98.0 0 0 1.0 1.0 0.0 F designates mole fraction of water present in solution or vapour. - 60 -110.0 - - i 1 1 1 . 1 0.0 2.6 5.2 7.8 10.4 13.0 Molarity Figure 4. Phase diagram of TFA-water mixtures. - 6 1 -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. The equilibrium between the green species ( A = 458 nm, E m a x - 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 decomp-osition 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. Then the pK = H when x log([green species]/[MnO^ ]) = 0. - 62 -Table 10. Protonation Data for MnO. in Mediums 4 of TFA-H-0 or D-0. ~\ -H o x=Absorbance Abs. F - Abs. = y Q = y/x log Q H-0 - set #1 10.92 3.06 0.0325 0.7696 23.680 1.374 10.80 3.01 0.0449 0.7572 16.864 1.227 10.58 2.90 0.0573 0.7448 12.998 1.114 10.49 2.85 0.0777 0.7244 9.323 0.970 10.24 2.76 0.1098 0.6923 6.305 0.800 10.02 2.57 0.1869 0.1652 3.292 0.517 9.90 2.50 0.2602 0.5419 2.083 0.319 9.60 2.26 0.3585 0.4436 1.237 0.093 9.36 2.06 0.4689 0.3332 0.711 -0.148 9.19 1.95 0.5459 0.2562 0.469 -0.329 8.80 1.80 0.6213 0.1808 0.291 -0.536 8.55 1.65 0.6631 0.1390 0.210 -0.679 8.23 1.46 0.7053 0.0968 0.137 -0.863 7.82 1.31 0.7281 0.0740 0.102 -0.993 7.62 1.22 0.7543 0.0478 0.063 -1.198 6.96 1.00 0.7701 0.0320 0.042 -1.381 6.22 0.8066 Abs. F = 0.8021 5.88 0.7982 H-0 - set #2 10.26 2.78 0.1092 0.8018 7.343 0.866 10.14 2.66 0.1609 0.7501 4.662 0.669 9.94 2.52 0.2286 0.6824 2.985 0.475 9.71 2.35 0.3120 0.5990 1.920 0.283 9.42 2.09 0.4100 0.5010 1.222 0.081 9.30 2.02 0.5710 0.3400 0.595 -0.225 8.96 1.82 0.6370 0.2740 0.431 -0.366 8.58 1.67 0.6840 0.2270 0.332 -0.479 8.32 1.50 0.7410 0.1700 0.229 -0.639 7.56 1.21 0.8310 0.0800 0.096 -1.017 7.02 1.02 0.8900 0.0210 0.024 -1.627 6.18 0.9110 Abs. F = 0.9110 D-O-CF 3C02H 10.92 3.06 0.0406 0.7818 19.26 1.285 10.51 2.88 0.0600 0.7624 12.71 1.104 10.09 2.63 0.1139 0.7063 6.096 0.785 9.72 2.36 0.2324 0.5900 2.539 0.405 9.50 2.18 0.3544 0.4680 1.321 0.121 9.34 2.03 0.4634 0.3590 0.7747 -0.111 9.12 1.92 0.5628 0.2596 0.461 -0.336 - 63 -Table 10 (Continued) • H _ -H R o x=Absorbance Abs. F - Abs. = y Q = y/x log Q ^O (continued) 8.76 1.74 0.6263 0.1961 0.3131 -0.504 8.07 1.44 0.7195 0.1029 0.1430 -0.845 7.44 1.18 0.7678 0.0546 0.071 -1.148 6.90 0.99 0.7949 0.0275 0.035 -1.461 6.12 0.8236 Abs. F = 0.8224 5.78 0.8212 l20 14.6° 9.90 2.50 0.2682 0.5536 2.069 0.315 9.36 2.06 0.4850 0.3368 0.6944 -0.158 8.80 1.80 0.6409 0.1809 0.2818 -0.549 8.23 1.46 0.7133 0.1085 0.1521 -0.818 5.88 0.8218 Abs. F = 0.8218 [20 20.0° 9.90 2.50 0.2685 0.5363 1.997 0.301 9.36 2.06 0.4659 0.3389 0.7274 -0.138 8.80 1.80 0.6254 0.1794 0.2869 -0.542 8.23 1.46 0.6979 0.1069 0.1532 -0.815 5.88 0.8048 Abs. F = 0.8048 l20 25.0° 9.90 2.50 0.2557 0.5425 2.122 0.327 9.36 2.06 0.4612 0.3370 0.7307 -0.136 8.80 1.80 0.6151 0.1831 0.2977 -0.526 8.23 1,46 0.7025 0.0957 0.1362 -0.866 5.88 0.7982 Abs. F = 0.7982 I20 30.5° 9.90 2.50 0.2488 0.5521 2.219 0.346 9.36 2.06 0.4530 0.3479 0.768 -0.115 8.80 1.80 0.6144 0.1863 0.304 -0.518 8.23 1.46 0.7023 0.0986 0.140 -0.853 5.88 0.8009 - 64 -T a b l e a u (Continued) -IL, —H x=Absorbance Abs. F - Abs. = y Q = y/x log Q H20 35.3° 9.90 2.50 0.2226 0.5683 2.553 0.407 9.36 2.06 0.4168 ^. 0.3768 0.897 -0.047 8.80 1.80 0.6053 ^ 0.1856 0.307 -0.513 8.23 1.46 0.6629 _0.1280 0.193 -0.714 5.88 0.7909 D20-CF „C0„D 3 2 10.06 2.61 0.0501 0.4749 9.479 0.977 9.45 2.11 0.1732 0.3518 2.031 0.308 9.34 2.04 0.1955 0.3295 1.685 0.227 8.96 .1.84 0.2856 0.2394 0.838 -0.077 8.39 1.55 0.3572 0.1678 0.470 -0.328 8.06 1.38 0.3729 0.1521 0.408 -0.389 7.80 1.30 0.4174 0.1076 0.258 -0.589 7.44 1.15 0.4355 0.0895 0.206 -0.687 7.06 1.03 0.5292 636 0.5048 5.66 0.5338 4.92 0.5559 Abs. V. => 0.5250 - 65 -1.40 1.05 0.70-0.35 0.0 -\ -0.35--0.701 -1.051 •1.40. r = 0.983 slope = 0.74 pK = -9.29 O 6.9 © / 7.7 / © © © / © © 0 V o © / © 8.5 9.3 10.0 -H R 10.9 Figure 5. Log 0 vs. HR for the ionization of MnO^  in TFA-water, (Data set #1, Table 10). - 66 -1.40 1.05 i 0.70 H 0.35 H 0.0 -0.35 -i -0.70 i -1.05 -1.40 set #1 r = 0.995 slope = 1.32 DK = -2.13 set #2 r = 0.994 slope = 1.27 pK = -2.10 1.0 1.4 1.8 2.2 2.6 -H 3.0 Figure 6. Log Q vs. for the ionization of MnO^  in TFA-water. ( © data set #1, © data set #2, Table 10). - 67 -0.95 ., o Figure 7. Log Q vs. H q for the ionization of MnO^  in trifluoroacetic acid-cL-deuterium oxide. 1.34 - 68 -0.64 I 0.29 4 -0.06 --0.41 -0.76 i - l . l l i 2.60 3.00 in trifluoroacetic 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. - 69 -3.11 Permanganate In Benzene It has been reported that permanganate anion can be extracted into benzene by using salts containing large alkylammonium cations.^ 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 ists 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. However, i t could be purified in the following manner. 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 ists 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~ 560 530 A nm 500 Figure 9. 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 1,322. 548 2,286. 527.5 2,340. 507.5 1,771. 490 1,150. 473 831. lb 571 1,306. 548 2,289. 527.5 2,337. 507.5 1,737. 490 1,121. 473 722. 2 565 1,810. 546 3,130. 525 3,170. 508 2,330. 3 546 2,380. 526 2,400. 1 - Tetra (n-hexyl)ammonium permanganate at two different concentrations a - 8.134 x 10 - 5 M; b - 5.0672 x 10 - 4 M. 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 analysis 3: calculated - C, 60.86%; H, 11.07%; N, 2.96%. experimental - C, 57.42%; H, 10.63%; N, 2.73%. Stability: several weeks i f dry and stored in the dark. Solubility: Solvent Solubility Stability Half l i f e Water N — — Cyclohexane SS d o>5 min n-Hexane N — — n-Heptane N — — Diethyl ether S d ^5 min Acetone vs d ^1 hr Carbon tetrachloride s d ^2-3 hr Dioxane s d 'v-l min Benzene vs.. d M.2 hr Elemental analysis on the sample after four successive benzene recoveries. This i s not intended as proof of composition but is to indicate the purity of the sample. N - not soluble SS - slightly soluble, pale purple color VS - very soluble S - soluble, purple i n color I. >-- >ot opaque d - 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 kinetic analyses were performed using the before mentioned pseudo first-order 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 tetra (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 . After the reaction had been allowed to proceed for 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 sulfate, and evaporated to reduce the volume. The remaining aqueous solution was acidified to pH < 3 by the addition of sulfuric acid, saturated with sodium chloride and then extracted with three 50 ml portions of ether to recover acidic products. The basic extracts were analyzed by v.p.c. and acidic products were recovered by evaporating to dryness, after checking by v.p.c. for v o l a t i l e acidic products. In a l l four cases the only product detected was benzoic acid, and i n low yield as shown in Table 13. - 74 -Table 13. Permanganate i n Benzene Oxidation Products. Substrate I n i t i a l Unchanged Products Recovered % Yield wt. wt. wt. 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 total materials recovered, results i n brackets based on material loss and products. - 75 -4. RESULTS AND DISCUSSION 4.1 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 for Aryl Carbinols, Indicator 3 CFoC0oH- HC10.- H„S0.- HoS0.-3 2 4 QI 2 4 H20 H 20, 1 0 0 CH 3C0 2H 8 7 H20 Ref. 100, Ref. 102 1. 4,4',4"-Tri- +0.92 +0.82 - +0.82 +0.82 methoxy TPC 2. 4,4'-Dimethoxy- -0.28 - -4"-methyl TPC 3. 4,4*-Dimethoxy -0.97b -1.14 - -1.24 -0.89 TPC 4. 4,4',4"-Tri- -2.81 - - -3.563 methyl TPC 5. 4-Methoxy TPC -3.18 -3.59 -3.23 -3.40 -3.20 6. 4,4'-Dimethyl -3.78 - -4.39 TPC 7. 4,4'-Dimethoxy -5.77 - - -5.71 -5.66 DPCC 8. Triphenyl- -6.25 -6.89 -6.65 -6.63 -6.44 carbinol (TPC) 9. 4,4*,4"-Tri- -7.94 -8.01 - -7.74 -7.43 chloro TPC 10. 4-Nitro TPC -9.58 -9.76 - -9.15 -9.44 CF,C0„H- HC1- H-SO.-3 2 i n - 2 4 H 20l2 H 2 0 1 0 3 H 20l4 £-Nitroaniline 1.11 1.03 o-Nitroaniline -0.13 -0.29 -0.25 4-Chloro-2- -0.94 -1.03 -0.97 nitroaniline a b c TPC - triphenylcarbinol; DPC - diphenylcarbinol. 4,4'-Dimethoxytriphenylmethyl chloride used. Comparative values are for 4,4'-dimethoxy DPC. - 77 -region of very low acid concentration where one expects to find good agreement. (Examination of Table 14 indicates that pK of indicators show some variation when the solvent system i s changed.) For this reason and because of the poor overlap of indicators 1 and 3, indicator 2 was synthesized and used in the determination of H_. With two indicators having measurable ionizations i n the accessible pH region (indicators 1 and 2) i t was f e l t that the new function would satisfactorily t i e into the pH scale. Although indicator 3 i s an alkyl chloride, not a carbinol, such changes are known to have no effect on the H_. f unction. ^ » 8 7 Values of H_ for the TFA-water medium are li s t e d i n Table 15 and graphically depicted in 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 indicators using the equations described i n Sections 1.3 and 3.8, i.e. H = K pKD4. - log[R+]/[ROH]. Figure 10 also shows the H and J ' functions K O O for TFA-water. The H q function originally derived by Randies and 12 Tedder i s extrapolated to 100% TFA (dotted line) using the value of 13 18 H Q = -3.03 reported by Hyman and Garber. Eaborn et a l . reported slightly different values of H q in this region. Their results (designa-ted by • ) passed through a maximum value. The J ' function, depicted in Figure 10, w i l l be discussed shortly. When i t was attempted to extend R- past 100% TFA by the addition of trifluoroacetic anhydride i t was observed that very l i t t l e change occurred in the ionization of 4-nitrotriphenylcarbinol 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. H„ Function for TFA-H.O. Molarity ~\ Molarity - y Molarity ~\ 0.068 -1.29 3.34 2.26 8.53 6.10 0.069 -1.31 3.36 2.34 8.67 6.29 0.070 -1.37 3.60 2.65 8.81 6.46 0.072 -1.29 3.85 2.87 8.87 6.31 0.130 -0.96,-1.04 3.87 2.75 9.07 6.51 0.130 -1.01,-1.04 3.88 2.92,2.89 9.17 6.72 0.140 -0.96 4.44 3.27 9.33 6.67,6.63 0.144 -0.97 4.45 3.21 9.47 6.96 0.256 -0.59 4.46 3.42 9.53 6.93 0.260 -0.66 4.73 3.50 9.57 7.20,6.86 0.261 -0.63,-0.60 4.87 3.65 9.83 7.14 0.270 -0.62 4.92 3.63 9.87 7.24 0.515 -0.05,-0.31 4.96 3.70 10.10 7.60 0.525 -0.18 5.15 3.85 10.27 7.73 0.540 -0.16 5.23 3.91 10.40 7.89 0.544 -0.18 5.42 4.08,4.06 10.53 8.13 0.770 0.23,0.02 5.44 4.03 10.57 8.51 0.796 0.12 5.48 4.06 10.60 8.30 0.800 0.26 5.70 4.30 10.80 8.47 1.08 0.35 6.00 4.36,4.50 10.83 8.60 1.29 0.51 6.07 4.61 10.93 8.67 1.33 0.58 6.47 4.82 11.00 '8.77 1.61 0.78 6.48 4.84 11.07 8.91 1.81 0.96 7.07 5.12 11.10 8.99 1.85 0.98 7.10 5.07 11.23 9.13 2.11 1.12 7.28 5.31 11.37 8.96 2.32 1.34 7.47 5.47 11.67 9.30 2.34 1.34 7.57 5.43 11.93 9.78 2.84 1.80 7.79 5.63 12.20 10.09 2.86 1.75,1.75 7.80 5.64 12.43 10.38 2.86 1.82 8.03 5.80 12.63 10.63 3.10 1.71 8.07 5.85 3.16 2.05 8.30 5.91 3.32 2.22 8.33 6.06 10.8 Molarity of TFA-Water Figure 10. Acidity functions in 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. This ester was identified by N.M.R. and I.R. spectroscopy. Similar behaviour was observed when 4,4'-dimethyldiphenylcarbinol was used. The 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 pKR+ values from this study were correlated with Brown's o*+ values*^ deviations were found for those indicators with resonance-interaction substituents, as is illustrated in Figure 11. When the a + 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 considera-tions. In order for these substituents to exert their f u l l influence in stabilizing the carbonium ton the rings with the substituents must become co-planar. 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. T a b l e 1 6 . T e m p e r a t u r e Dependence o f p K - + . I n d i c a t o r N o . 1 4 . 8 ° 1 5 . 2 ° 1 9 . 6 ° 2 0 . 6 ° 2 5 . 0 ° 2 9 . 8 ° 3 0 . 7 ° 3 0 . 8 ° 3 5 . 7 0 ° 3 6 . 0 ° 3 6 . 8 ° 1 0 .91 0 . 9 2 0 . 9 2 0 . 9 3 0 . 9 5 2 - 0 . 3 3 - 0 . 3 0 - 0 . 2 8 - 0 . 2 2 - 0 . 2 3 3 - 1 . 0 5 - 0 . 9 9 - 0 . 9 7 - 0 . 9 4 - 0 . 8 6 4 - 2 . 8 9 - 2 . 8 2 - 2 . 8 1 - 2 . 7 5 - 2 . 7 1 5 - 3 . 2 6 - 3 . 2 2 - 3 . 1 8 - 3 . 1 5 - 3 . 1 2 6 - 3 . 8 3 - 3 . 7 9 - 3 . 7 8 - 3 . 7 6 - 3 . 7 4 7 - " . 7 5 - 5 . 7 6 - 5 . 7 7 - 5 . 7 6 - 5 . 7 8 8 - 6 . 1 9 - 6 . 2 2 - 6 . 2 5 - 6 . 3 0 - 6 . 3 3 9 - 7 . 9 1 - 7 . 9 2 - 7 . 9 4 - 8 . 0 0 - 8 . 0 4 10 - 9 . 5 8 - 9 . 5 8 - 9 . 5 8 - 9 . 5 8 - 9 . 6 2 oo - 82 -Table 17. Thermodynamic Parameters for the Ionization Equilibria of the Indicators Used to Determine H_. Indicator no. AH° kcal/mole AS° e.u. a r This Ref.102 This Ref.102 study study 1 -0.64 -2.49 -6.40 -12.10 0.850 2 -2.24 - -6.27 - 0.960 3 -3.42 -5.68 -7.07 -14.95 0.980 4 -3.44 - -1.28 - 0.980 5 -2.59 -6.48 5.91 -7.10 0.999 6 -1.56 - 12.1 - 0.999 7 +0.44 - 27.8 - 0.800 8 +2.24 -3.41 37.8 18.0 0.973 9 +2.53 -2.49 44.9 25.6 0.955 10 +0.61 +0.87 45.9 46.1 0.560 r, the correlation coefficient is for this study. AH and AS were calculated from the equation, , 1 AH AS _ _ _ 1 0 8 V = T T303R " 2303R ' = g a S c o n s t a n t + \ + + R + H-0 -~—* ROH + H [R0H][H+]/[R+][H-0] 1 0 . 8 8 . 8 i 6.8 4.8 J i 2 . 8 0 . 8 - 1 . 2 mono, p - N 0 o — / - 0 . 8 fi) t r i , p-Cl unsubstituted t r i P-CH. d i , p-CH-O and p-CH, Figure 1 1 . a + vs. pK_ f o r substituted 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 is the large difference between H q and IL^ , larger in fact than that observed for any other acidic medium previously studied. Most inorganic acids have relatively small values of dH^/dHQ (< 2) compared to that observed for TFA-water (> 5). Only one previous investigation, by Stewart and Mathews showed a similar trend. The formic acid-water system was found to have dIL,/dHo > 3. Possibly two factors can account for the differences between H Q and HR. It can be shown that PL. = H q + log Q + log f B f R+/ f B H+ f R 0 H (derived from H q = -log a ^ / f ^ and H R = -log a H + f R m / ^ R + > • 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 is actually smaller than those observed for inorganic - 85 -Table 18. Activity of Water i n Various Media. Acid molarity CF 3C0 2H a HC1 1 0 9 I^SC^ 1 0 9 0.5 - 0.008 0.008 1.0 0.005 0.017 0.018 1.5 0.007 0.027 0.030 2.0 0.012 0.039 0.043 2.5 0.015 0.053 0.063 3.0 0.017 0.070 0.085 3.5 0.019 0.087 0.111 4.0 0.020 0.107 0.142 4.5 0.023 0.130 0.176 5.0 0.026 0.155 0.219 5.5 0.031 0.181 0.267 6.0 0.036 0.211 0.320 6.5 0.039 0.244 0.377 7.0 0.042 0.279 0.439 7.5 0.053 0.318 0.510 8.0 0.061 0.358 0.587 8.5 0.074 0.399 0.670 9.0 0.095 0.444 0.761 9.5 0.125 0.490 0.859 10.0 0.191 0.539 0.968 10.5 0.320 0.591 1.082 11.0 0.500 11.5 0.800 12.0 0.886 12.5 0.770 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 acid-108 water mixtures by Boyd and the.. allow one to estimate the value of log f_fR+/fBH+^ROH* T ^ e 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 gn+f ROH^ becoming increasingly negative <, as the TFA content increases. 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 correlate 21 72 112 113 well with II-, giving close to unit slopes 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. Figure 12 shows how their data correlate with H q and IL^ . 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 ~ + H + HCrO." 4 4 HCr04 + R2CHOH — R 2 C H - 0 - C r 0 3 + H^ O or R2CH-0-Cr03H + OH k2 IV R2CH-0-Cr03 > R2C=0 + Cr , 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 Q = 5 O 1 1 4 O - . "7 £ 115 . _ . „ , „ 116 -5.9, 3-pentanone at -7.6, and acetophenone at -6.5. 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 28 29 aqueous perchloric acid and aqueous sulfuric acid, 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 + + MnO." * HMnO. 4 4 2H+ + MnO " » Mn0_+ + Ho0 4 >« 3 2 2HA + MnO. 0-MnA + H.O + A 4 3 2 It was observed that the green species generated in neat TFA was - 90 -25 spectrally identical to that generated in sulfuric acid 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 + KMnO. »• CF-CO.H + K + + MnO ~ n=2 3 2 4 3 2 4 2. CF„C0oH + KMnO. - CF_C0 ~ + K + + HMnO. , n=3 3 2 4 3 2 4 3. 2CF3C02H + KMnO^  >• 2CF3C02~ + K^ O + K + + Mn0 3 +, n=5 4. 2CF3C02H + 2KMn04 • 2CF3C02~ + H20 + 2K+ + M n ^ , n=6/2=3 5. 2CFoC0oH + KMnO, 0„Mn0C0CFo + K + + H„0 + CF0CO n=4 3 2 4 3 3 2 3 2 (b) Sodium Nitrate 6. CF3C02H + NaN03 » CY^CO^ + Na+ + N03~, n=2 7. CF3C02H + NaN03 • C F 3 C 0 2 ~ + N a + + M ° 3 » n = 3 8. 2CF3C02H + NaN03 > 2CF3C02~ + Na+ + H20 + N0 2 + , n=5 (c) Sodium Nitrite + 3 ~ ~ 2 ~ • — • — 3 ^ 2 a . . .~ 2 9. CF„C0„H + NaN0o > CF^ CO^H + Na + NO^  , n=2 10. CF3C02H + NaN02 *• CF3C02~ + Na+ + HN02, n=3 6 1 1 J i 1 i : 1 1 1 1 I 0 5 10 15 20 25 30 35 40 Molality x 10 Figure 13. Particulation of potassium permanganate and sodium acetate in TFA. 6 1 i 1 : i 1 1 1 12 18 24 „ 30 36 42 48 Molality x 10 Figure 14. Particulation of sodium nitrate and sodium n i t r i t e in TFA. - 93 -11. 2CF3C02H + NaN02 2CF 3C0 2~ + Na + + H20 + N0+, n=5 (d) Sodium Acetate 12. NaOCOCH3 + CF^C^H CH 3C0 2H + Na + CF 3C0 2~, n=3 (e) Triphenylcarbinol 13. (})3COH + CF3C02H ct3COH + CF 3C0 2H , n=l 14. t()3COH + CF3C02H <|)3COH2 + CF 3C0 2" , n=2 15. <j>3COH + CF3C02H 4)3C + H20 + CF 3C0 2 , n=3 (f) Water 16. H20 + CF 3C0 2H H20 + CF 3C0 2H , n=l 17. H20 + CF 3C0 2H H30 + CF 3C0 2 , n=2 (g) Benzene or Toluene 18. Arene + CF3CC"2H Arene + CF^O^H , n=l (n refers to the number of particles formed when the above reactions proceed completely to the right. Experimentally n for water has a value close to 1.2 indicating partial protonation, see Table 7). The various reaction p o s s i b i l i t i e s for permangante have different values of n. The experimental determination of n=5 suggests that Mn0 3 + 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 five. The generation of nitronium ion and nitrosonium ion via 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 in 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 nitric acid would be generated since i t is a much stronger acid than TFA. (The H q value of 100% nitric acid is -6.3 1 1 7 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 nitrite was dissolved in TFA nitrosonium ions were detected by an absorption at X = 260 nm, e = 2,200. The reported J max max spectrum of nitrosonium ion in perchloric acid has X = 260 nm, r 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 26 from 3.0 to 5.1 depending upon the concentrations used. Royer also - 95 -reported similar variations of n. The values of n near five at concentra--3 -3 tions less than 6 x 10 molal (9 x 10 molar) are consistent only with scheme 3. The reaction shown by scheme 5, ester formation, is not consistent with the experimental data nor with evidence from analogous systems. 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 distinguish between them. The changes recorded i n n with concentration changes are not due to variations i n K^. The value of for TFA, which was determined by using benzene as a solute with an assumed value of n = 1, was verified 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 theoretical values. It can be concluded that i n TFA the green species generated from permanganate is 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 reversibly generated from permanganate by varying the acid content of TFA-water mixtures. The pK values for this process in a variety of solvents and at a variety of temperatures are lis t e d In Table 19. As was shown in Section 3.10 the ionization correlated best with H q. The pK of -2.12 i s very similar to that reported for perchloric acid-water solutions, where 28 pK = -2.25. It should also be noted that i f a deuterated system i s used that the ionization i s half completed at lower acid concentrations. It 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^ H R units H units o -pK c Slope r -pK c 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, 14.6° 9.52 0.68 0.991 2.23 1.12 0.995 II II > 20.0° 9.52 0.67 0.994 2.23 1.10 0.994 II II » 25.0° 9.49 0.71 0.997 2.21 1.17 0.997 ti II > 30.5° 9.47 0.72 0.997 2.20 1.17 0.997 II ti » 35.3° 9.39 0.69 0.985 2.14 1.13 0.986 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[Mn04"]/[Mn03+]. 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 in 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 -in TFA-water solutions and that their proportions depend upon the amount of TFA. They are; permanganate ion (MnO^  ), confirmed by i t s characteristic spectrum, permanganyl ion (MnO^+), confirmed by the cryoscopic data, and permanganic acid (HMnO^), possibly present in small amounts as a result of the following equilibria. MnO* + H„0 —*• H + + HMnO. 3 2 •* 4 or MnO " + H + * HMnO. 4 4 4.1.3 Nitration and Nitrosation 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 nitrate. The nitronium ions thus generated were used to achieve aromatic nitrations in excellent yields as the data i n Table 4 i l l u s t r a t e . The distribution of products from the nitration of toluene was found to be 31.7% para, 67.0% ortho and 1.3% meta, quite similar to the results 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 electrophile to attack benzene or toluene. It 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. It has been previously reported that such complex formation readily occurs between 121 nitrosonium ions and aromatic rings without further reaction occurring. It was suspected that some phenolic products were formed during - 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 1 2 2 nitr ic acid. 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-0N0+ ArH-ONO+ > ArONO + H + ArONO + H20 > ArOH + HN02 ArOH + N0 2 + > nitrophenol + H + 4.2 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 ' 360 340 320 300 280 X nm Figure 15. Spectra of side products (from the nitration of benzene) i n acidic and basic media. - 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 wil 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 IV N (Mn •* Mn ). note: n = m + £ + 2 (a) Alkanes VII 5C H. + 12Mn —» 5C H„ ^.OH —-> 5C H. 0 > n 2n+2 n 2n+l n 2n 5CmH2m+lC02H + 5 C 1 H 2 £ + 1 C 0 2 H + i m ^ + (b) Alcohols VII 5C H„ ..OH + 8Mn >• 5C H„ 0 > 5C H. ,-,C0„H + n 2n+l n 2n m 2m+l 2 5 C 1 H 2 ^ + 1 C ° 2 H + 8 M n 2 + (c) Ketones VII 2+ 5C H. 0 + 4Mn —> 5C H. ...CO-H + 5C,H o 0,-C0.H + 4Mn n 2n m 2m+l 2 1 21+1 2 (d) Aldehydes 5C H, 0 + 4MnV I 1 > 5C .H„ .CO.H + 4Mn2+ n 2n n-l 2n-l 2 - 102 -Table 20. Manganese Reduction Products from KMnO, Oxidations. Reductant % Mn % Mn0„ Reductant % Mn % MnO H„ = -6.00 Toluene 98 2 Cyclopentane 57 43 Benzene 64 36 Cyclohexane 57 43 Ethylbenzene 98 2 Cycloheptane 56 44 Cumene 98 2 Cyclooctane 62 38 t-Butylbenzene 95 5 Cyclohexanol 57 43 Methanol 47 53 Cyclohexanone 56 44 2-Pentanol 38 62 Acetophenone 56 44 3-Pentanol 42 58 2-Pentanone 30 70 Benzyl alcohol 76 24 3-Pentanone 30 70 Benzaldehyde 73 27 Formaldehyde 49 51 1-Phenylethanol 79 21 Acetone DNR DNR 2-Phenylethanol 79 21 2-Phenyl-2-pro- 80 20 Benzyl alcohol panol 67 33 = -8.00 Benzaldehyde 71 29 1-Phenylethanol 63 37 n-Pentane 50 50 2-Phenylethanol 87 13 n-Hexane 50 50 2-Phenyl-2- 80 20 n-Heptane 50 50 propanol n-Octane 49 51 n-Nonane 49 51 n-Decane 49 51 n-Undecane 44 56 n-Dodecane 42 58 n-Tridecane 38 62 Benzene 96 4 Isopentane 74 26 DNR - did not react sufficiently. - 103 -(e) Arenes Arene + 2.5Mn These outlines are a l l consistent with the experimentally determined stoichiometries listed in Table 5. 4.3 Oxidation of Alkanes Initially a sulfuric acid-water medium was considered as a possible solvent system to investigate the homogeneous oxidation of alkanes by permanganate. Appendix B l ists the data obtained using this solvent system. 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 first 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 2+ decomposition products + 2.5Mn - 104 -equation (see Section 3.3 for the equation) confirms a first order dependence upon permanganate (refer to correlation coefficients of the alkane trials) . 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]hR 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 124 presence of some protium using the equation of Lewis and Funderbuck; % = ( k obs" f V / ( 1- f )'> f = fraction of protium present in compound k , = observed rate for deuterated compound obs r 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 Order in Trials r Order in Trials r substrate h„ Ethane 1.1 129--134 .960 N Propane 0.6 141--148 .973 N -n-Butane 1.1 149--155 .998 N -n-Pentane 1.0 163--169 .999 1.0 170--177 .995 Isopentane 1.0 298--304 .993 1.1 285--311 .999 1.0 305--311 .985 -1.0 285--290 .994 v, -Neopentane 1.1 330--336 .991 0.8 322-• 3 3 6 b .991 Cyclopentane 1.0 341--347 .994 1.0 337-" 3 5 9 b .999 n-Hexane 1.1 192--198 .994 1.0 185--223b .997 0.9 185--191 .991 -Cyclohexane 1.0 373--379 .997 1.1 360--435 .994 1.0 408--423 .999 -Cyclohexane-d;L2 N - 1.1 384--405^  .990 n-Heptane 1.1 228--233 .999 1.1 224--244b .997 Cycloheptane 1.0 438--444 .998 0.9 436--459b .999 Cyclooctane 1.1 469--475 .998 0.8 466--489b .996 Note: error in orders are + 5%. Order with respect to permanganate was in a l l cases 1.00, r = 0.999. b Only those trials where the solvent was TFA-H^O and T = 25.0° were used. c Only those trials 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 1 1 1 . 1 , — i 1 0-1 0.5 0.9 1.3 1.7 3 + log[alkane] Figure 17. Log k vs. log[alkane] for the oxidation of variety of alkanes. - 108 -Table 22. Kinetic Isotope Effects in the Permanganate Oxidation of Cyclohexane. b c d k C 6 H 1 2 / k C 6 D 1 2 K C 6 H 1 2 / K C 6 D 1 2 (corrected)3 6.12 5.3 5.5 6.38 4.7 4.8 6.66 4.3 4.5 6.74 4.3 4.5 6.96 4.2 4.4 7.40 4.7 4.9 7.70 5.7 6.0 7.91 4.0 4.1 "HR \ o \ o  b 6.26 C 1.2 6. 9 3 C 1.0 6.96 C 1.0 6.10^ 2.6 7.48 2.3 Corrected using the equation = 0^Q^s~i kjj)/(l-f)> as discussed in the text. For isopentane, k^ Q/^JJ Q = 1.2 (IL^ = - 5 . 9 5 , 76% D) and for n-hexane, kD 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 20. Solvent system made from CF 3C0 2H and D 20 ( 7 4 % D at = - 6 . 2 6 , 72% D at 1^  = -6 . 9 3 , 71% D at I L = - 6 . 9 6 ) . Solvent system made from CF^CO^ and D 20. - 109 -125 The free-radical bromination ratios for butanes are 1:82:1,600 34 and the chromic acid oxidation ratios for alkanes are 1:110:7,200, both processes taking place by hydrogen-atom abstraction. 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 (equivalent to hydride transfer in the present case). 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 = -CH2N02. 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 Cyclo-alkanes Relative to Those in the Corresponding n-Alkane. Reaction Ratios C5 C6 C7 C8 T _ 0° 1.45 1.47 2.18 2.49 T = 49.5° 1.38 1.47 2.02 2.17 T = 74.5° 1.47 0.47 3.24 8.43 T = 125° 1.31 0.75 2.79 5.56 T = 74.5° 1.43 0.95 _ 3.53 T = 74.5° 1.75 0.43 - 5.10 T = 74.5° 1.52 0.54 2.39 3.83 T = 25.0° 2.61 0.75 2.8 6.4 V 3 V 2. Br-, CH3CN, 3. CC1 • CH3CN, CC1 3- CCI4, 4. C,H C - , CH.CN, O D J VII 5. Mnv , TFA-H20, T = 25.0 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 C5 Ratios C6 a C7 C8 1. Cr03,99% CH3C02H, T = 6 0 ° 3 3 1.98 1 6.6 22.4 2. M n V I 1 , TFA-H20, T = 25° 1.4 1 5.2 14.5 3. 128 Acetolysis of tosylates, T = 70° 14.0 1 25.3 191 Ratios are k(cycloalkane)/k(cyclohexane). 0.8 0.7 A 0.6-4 0.5H C M 0.41 0.31 0.2 0.1 0.2 0.3 Molarity of sodium trifluoroacetate 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 ists the solvent isotope effect observed and this trend is indeed observed. 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 + K •» HMn04 , fast HMn04 + alkane *• products , slow r - Kk'[Mn04-] [alkane] f M n . f a l k a n e V / f 4 (b) Mn0.j+ as the oxidant, MnO ~ + 2H+ - Mn0o+ + H.O , fast 4 3 2 + k" MnO^  + alkane *• products , slow r = K'k"[MnO ~] [a lkane]£_ . - f a2+/au n f . 4 MnO, alkane H H„0 t 4 2 The experimental rate law is r = k„ [MnO,] [a lkane]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, wi l l be assumed to show similar changes in TFA-water solutions; (ii) The activity of the proton (a +) wi l l be n approximated by fgH+/fg since a j^. = hQfBH+/fB a n d n 0 ' * s 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 wi 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 R & M n 0 4 alkane WT t log -^f^BH+^t^B* F o r m e c n a 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 2 2 4 2 which becomes log ~^f^BH+^aH 0^R+^B* Table 25 contains a l l the 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 in Sulfuric Acid-Water Mixtures. Salt or Compound % H2 SO. in 4 H2S04--water solution 9.6% 19% 29% 40% 50.5% Triphenylcarbinol''"^8 133 Benzene l o g fROH l o g f* log f B 0.34 0.14 0.37 0.24 0.73 0.31 0.83 0.36 0.73 0.36 2,6-Dichloro-4-nitro-anilinel^S 0.03 0.07 0.03 -0.14 -0.40 Tri (p_-methoxyphenyl)-carbonium+PCP" 1 0 8 log f 0.02 0.04 -0.13 0.20 -0.32 ^-Chloroanilium+PCP" 1 0 8 l o g fBH+ 0.10 0.44 0.86 1.64 2.26 Tetrabutylammonium+ CIO - 1 3 3 l o g fcio 4" -0.30 -0.39 -0.52 -0.80 -1.18 Functions 109 l o g aH20 134 ~HR l 0 g fC10 4- f<|» fBH + / aH 20 fR + fB l o g fC10 -fBH+/fB -H 1 3 4 o -0.03 -0.06 -0.12 -0.25 -0.44 0.72 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 0.31 1.01 1.70 2.41 3.38 PCP-, pentacyanopropenide. a The activity coefficient of the cations are relative to a standard S + cation, f + = f^_/f +, S is the standard cation, tetraethylammonium ion. k The activity coefficients of the anion is 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 ~ * Mn0„ + + Ho0 , fast 4 — 3 2 Mn03+ + R 2 C H2 * [R2 C H* + H M n 0 3 + ] > r a t e determining [R2CH« + HMn03+] > [R2CH-0-Mn02H] , fast [R2CH-0-Mn02H] * R^HOH + MnV , fast R2CH0H + M n V I 1 >  R 2 C = 0 »  f a s t VII R2CH0H + Mn > carboxylic acids , fast VII R2C=0 + Mn > carboxylic acids , slow V 2+ VII 5Mn > 2Mn + 3Mn , fast - 118 -Table 26. Activation Parameters for Permanganate Oxidations in TFA-Water. Substrate Trials t AH kcal/mole t -AS e.u. r n-Pentane 170--177 7. 52 7.87 ±0.08 31.2 ±0.5 .987 n_-Hexane 211-•218 . 7. 77 5.74 ±0.02 35.5 ±0.2 .999 n-Dodecane 269-•274 7. 41 8.37 +0.08 25.0 ±0.3 .989 Cyclopentane 350-•357 7. 02 7.15 ±0.05 33.1 ±0.5 .992 Cyclohexane 428--433 7. 70 5.24 ±0.07 36.8 ±0.7 .974 Cycloheptane 450-•457 7. 20 6.07 ±0.02 32.9 ±0 .1 .999 Cyclooctane 480-•487 6. 80 7.21 ±0.08 29.0 ±0.5 .983 Benzene 518-•525 5. 70 5.57 ±0.09 40.7 ±0.9 .969 Toluene 749-•753 2. 52 11.37 ±0 .1 25.2 ±0 .3 .986 705-•714 4. 13 10.59 ±0 .1 22.1 ±0.3 .955 695-•704 4. 26 9.43 ±0.08 25.9 ±0.3 .979 741--748 5. 17 5.58 ±0.08 35.5 ±0:.7 .973 Methanol 791-•795 3. 18 12.29 ±0.08 25.0 ±0.3 .995 3-Pentanol 850-•857 5. 84 7.75 ±0 .1 33.1 ±0.6 .977 Cyclohexanol 869-•879 5. 40 7.03 ±0 .1 36.1 ±0.6 .951 Benzyl alcohol 923-•930 3. 58 8.21 ±0.04 32.3 ±0.2 .997 931-•937 6. 72 6.86 ±0.2 27.6 ±1.5 .840 2-Pentanone 1024-•1031 8. 86 9.79 ±0.2 25.3 ±0.8 .953 Cyclohexanone 1065-•1072 6. 34 11.45 ±0.06 21.3 ±0.2 .997 3-Pentanone 1187-•1196 7. 90 5.64 ±0.03 40.0 ±0.03 .999 Ace tophenone^ 1246-•1255 6. 41 8.31 ±0.03 52.0 ±0.03 .999 Calculated from where, rate - k2[Mn0^ ][substrate]. Zero-order data was used, k was from rate = kfacetophenone]. - 119 -The transition state can be cyclic, R2 H—-0^ or acyclic 1 N N J ^ n // T - r H r - " 0=-^Mn + R2 In the first case the in i t i a l product wi l l be the Mn(V) ester and in 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. ' ' This also appears to be the case in this investigation. 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 in i t ia l ly 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. In the case of this oxida-* tion process, where p = -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. Calculated-a Values of Individual Carbon Atoms in Some n-Alkanes.' Carbon number 13 Compound 1 2 3 4 5 6 7 8 9 10 11 12 propane .100 0 .100 n-butane .115 .100 .100 .115 n-pentane .130 .115 .200 .115 .130 n-hexane .145 .130 .215 .215 .130 .145 n-heptane .160 .145 .230 .230 .230 .145 .160 n-octane .175 .160 .245 .245 .245 .245 .160 .175 n-nonane .190 .175 .260 .260 .260 .260 .260 .175 .190 n-decane .205 .190 .275 .275 .275 .275 .275 .275 .190 .205 n-undecane .220 .205 .290 .290 .290 .290 .290 .290 .290 .205 .220 n-dodecane .235 .220 .305 .305 .305 .305 .305 .305 .305 .305 .220 .235 n-tridecane .250 .235 .320 .320 .320 .320 .320 .320 .320 .320 .320 .235 .250 a * * * 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 1 , _ _ — p _ 5 6 7 8 9 10 11 12 No. of carbon atoms in chain Figure 21. Oxidation rate vs. number of carbon atoms i n n-alkanes. - 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 total number of methylenes present. (b) Ratios of the most reactive methylenes present in 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 = total number of carbon atoms in n-alkane). - 124 -Table 29. Experimental Ratios for n-Alkane Oxidation Rates. Relative to Predicted Ratios Compound n-Pentane n-Hexane ii-Heptane Reactive -CH~- Total -CH„-(a) H_ » -7.74, T = 2 5 . 0 ° , [MnO. ] = 4.136 x 10 M R H 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 for the Chromic Acid Oxidation of n-Alkanes . 9 1 1 Most Compound kxlO M s Ratios S t a t i s t i c a l Reactive CH2 C4 H10 1.12 1.0 0.39 1.0 0.4 1.0 0.67 C7 H16 2.90 2.59 1.0 2.5 1.0 1.5 1.0 C9 H20 3.90 3.48 1.34 3.5 1.2 2.5 1.66 C11 H24 5.40 4.82 1.86 4.5 1.8 3.5 2.33 C16 H34 8.07 7.20 2.78 7.0 2.8 6.0 4.0 C22 H46 11.14 9.95 3.84 10.0 4.0 9.0 6.0 A l l kinetic data from reference 35. Ratios from the experimental data obtained by dividing by either k for n-butane or n-heptane. Ratios expected considering a l l ' methylenes as in Table 28. Ratios expected from most reactive 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, trials 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 . The general rate equation can be expressed as; - 127 -Table 31. Order of Reactants Involved in the Permanganate Oxidation of Arenes. Substrate Order in Trials substrate r Order in hR Trials b r Benzene 1.0 496--502 0.999 1.0 490--536 0.996 Toluene 1.0 544--550 it 0.8C 537--763 0.993 1.0 661--668 0.998 0.7C 537--571 0.999 1.1 551--557 0.995 0 . 7 ° 572--605 0.998 0.9 537--543 0.961 0.8C 606--694 0.992 1.0 558--564 0.995 0.8C 695--763 0.991 0.8 565--571 0.989 1.2 572--578 0.998 1.1 579--585 0.989 1.1 586--592 0.984 1.0 593--599 0.998 0.9 600--605 0.980 Toluene-dg 1.0 669--676 0.999 0.9C 618--736 0.993 Note: Errors in orders are + 5%. In a l l cases the order of permanganate was 1.00, r = 0.999. Only those trials 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 is not affected by added salts. The transition state appears to be achieved from one molecule of arene and one molecule of oxidant. The clear dependence upon H and the observed solvent isotope effects (see Table 32) indicate, as was the case with alkanes, that permanganyl ion is the active oxidant. (The observed rate increases with increased deuterium content parallel the changes in 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 in Tables 32 and 33 indicate definite mechanistic differences. There is no primary kinetic isotope effect observed when either toluene-a-d^ or toluene-dg are used in place of toluene. Further, there are only very l i t t l e rate differences observed when the alpha carbon-hydrogen bond is varied from primary to tertiary. These data indicate that in 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 Toluene:Ethylbenzene:Cumene 3.07 1:1.9:1.8 3.18 1:1.5:1.3 3.39 1:1.7:1.6 3.88 1:1.4:1.5 4.44 1:1.4:1.4 4.50 1:1.3 4.82 1:1.3:1.4 5.39 1:1.2:1.2 0.9 0.6 -\ 0.5 1 # sodium perchlorate © sodium trifluoroacetate 0.4 -I 0.1 Figure 24. 0.2 0.3 Molarity of salt solution Salt effects on the permanganate oxidation of benzene. (Trials 526-533), 0.4 - 132 -Table 32. Kinetic Isotope Effects for the Permanganate Oxidation of Arenes. Substrate k(D 20)/k(H 20) a Toluene/toluene-d Q 1.06 2.34 o 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 Toluene/toluene-a-d 3 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 ring degradation occurs. The stoichiometry of 2.5 i s well above that of 1.2 predicted for 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 ring attack. The substituent effects on the oxidation of benzene correlate + + best with a values (see Figure 25). The large negative value of p = -5.2 indicates considerable positive charge development on the ring in the transition state. When the oxidation of toluene i s considered as a sidechain oxidation the substituent effects, depicted in Figure 26, show random scatter, but i f the substituted toluenes are considered as di-substituted benzenes undergoing ring attack the substituent effects are more orderly (see Figure 27). The correlation i n the latter case i s s t i l l poor, possibly owing to considerable side-chain oxidation when electron-withdrawing substituents such as carboxy or nitro are present. The permanganate oxidation of arenes has several features i n common with electrophilic aromatic nitration. Nitrations in sulfuric acid-water medium are known to correlate with more precisely 73 H R + l o g a^ Q, and they are known to exhibit no primary isotope 7 A~ 7 6 effects. These features are believed to be due to a mechanism involving rate-limiting electrophilic attack^ 4 ^ followed by fast 78 proton loss to the solvent to yield the nitration product. It appears that a l l the kinetic and supplementary evidence from this investigation on the permanganate oxidation of arenes i s consistent CN C N 60 o 3.9 2.6 1.3 0.0 -1.3 -2.6 H -3.9 £-CH„0 < 3 -0.8 -0.6 1 o o ° © 4 1, I>-CH3 2, ^-CH3CH2 3, p-(CH3)2CH 4, p-(CH3)3C benzene 0 p-F p-Cl r = 0,97 D + = -5.21 m-C02H -0.4 -0.2 + 0.0 0.2 0.4 0.6 LO m-NO, 0.8 Figure 25. Substituent effectson the permanganate oxidation of benzene. Log k„ „ + / . . . , , c n c r,-,x j + 2 " s ° o (.trials 505-517). m or p designates the particular a value used. P unsubstituted X 1.84 1.3H X X X m-Cl X 0-© m-F X p-Br O m-C02H © £-00 H r = 0.70 X O m-NO, X X © 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Figure 26. Substituent effects on the permanganate oxidation of toluene. Log 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. Mn03 + H20 , fast MnO R-<'' + "0-MnO, , slow H20 + R\( H 0-MnO„ R-(( JJ-OH + MnO^ H + H , fast (MnV) 0H+ Mn VII ring degradation products + Mn 2 + , fast 5Mn 2Mn + 3Mn , fast (b) Side chain attack, (({> = phenyl group) 2H+ + MnO. » Mn0o+ + Ho0 4 T 3 2 , fast Mn03 + c}>-CR2H [<j)CR2 + HMn03 ] , slow [<j>CR2 + HMn03+] * (J)CR20H + MnV , fast <f)CR2OH + Mn VII aldehyde or ketone , fast - 138 -aldehyde + Mn VII benzoic acid fast » ketone + Mn VII benzoic acid slow » 5Mn V 2Mn II + 3Mn VII fast It w i l l be noted that phenol is proposed as a possible intermediate i n the ring degradation. There i s no direct evidence for the existence of phenols in the reaction mixture since phenols are subject to rapid oxidation even in aqueous medium but, as is shown in Table 5, the stoichiometry for the oxidation of phenol shows less permanganate consumed than in the case of toluene. This observation i s consistent with phenol being an 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 yield of benzoic acid (see Table 3) and the increase of the 10:2°:3° rate ratios lis t e d in Table 33. In the Introduction two studies on the permanganate oxidation of arenes in acidic medium were discussed. Although neither study clearly established the mechanism of the arene oxidation they have 44 features in common with this investigation. Cullis and Ladbury who were the f i r s t to attempt a thorough investigation of this reaction, were severely hindered by their choice of aqueous acetic acid as a reaction medium. Second order kinetics were not maintained throughout the reaction, 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 kinetics, a problem which disappears when TFA is substituted for acetic acid."''"'") Cullis and Ladbury observed that there was no effect of added salts ( i f the salt did not react with some manganese species) and that there was appreciable ring 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. It was reported that benzaldehyde could be detected as a reaction product along with benzoic acid from the oxidation of toluene whereas in this study no evidence could be found for benzaldehyde as a product. However, consulting Figure 28 i t can be seen that at higher acidities toluene is more reactive than benzaldehyde. In fact, Figure 28 shows that the usual order of reactivity towards oxidation (benzaldehyde > benzyl alcohol > toluene) becomes inverted. This appears to be due to ring attack becoming important and the side chain now acts as a substituent. The effect 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 acidic permanganate oxidation of jj_-toluenesulfonic acid in a medium of aqueous perchloric acid. Although they found that the sulfonate group caused drastic mechanistic changes (refer to Section 1.5.2) in 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 in their system differs from that i n this study. Since - 140 -PCO i n o m o m o m 3 • . • • • • • CO rH H O O O r-l i- l TH 1y[ Sox - 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, trials 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 f^MnO^ ][alcohol] h + klfMnO. ][alcohol]h . At acidities greater than seven molar TFA h 0.7 0.1 J , , _ l -r- i 1 - i — 1 1 1 1 0 10 20 30 40 50 60 70 80 Time (min) of use after preparation Figure 29. Decrease of oxidation rate with age of solution. Methanol in TFA-water. - 143 -Table 34. Order of Reactants in the Permanganate Oxidation of Alcohols in TFA-Water. Substrate Order i n r substrate Trials Order in h Rb r Order in h c o r Methanol 0.8 0.999 770--773 0.9 0.994 4.0 0.94 2-Pentanol 0.9 0.999 827--830 . 0.8 0.999 2.1 0.999 3-Pentanol 1.0 0.999 839--842 0.9 0.998 3.9 0.999 Cyclohexanol 1.0 0.999 858--861 0.8 0.990 3.0 0.999 Benzyl alcohol 1.0 0.999 884--887 1.1 0.995 1.0 0.90 1-Phenylethanol 1.0 0.997 991--994 — — 2-Phenylethanol 1.1 0.999 995--997 — — The order in permanganate was in 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 variety of alcohols. 1.5 0 1 2 3 4 5 6 7 8 Figure 31. Variation of oxidation rate with acidity for the oxidation of alcohols in TFA-water. - 1 4 6 -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(D20)/k(H20)3 Benzyl alcohol 0.12 1.7 3.5 Methanol 3.76 10.4 4.38 8.3 5.01 0.9 7.1 6.09 10.0 6.59 9.1 7.10 6.8 Solvent systems made up from CF3C02H-H20 and CF3C02H-D20. k^/kp = k2(benzyl alcohol)/k2(benzyl alcohol-a~d2) • 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 + + Mn04~ ^ HMn04 , f a s t HMn04 + RR^ CHOH * [RR^OH + H^nO^J t s i o w [RR COH + H MnO ] >• RR C=0 + MnV t f a s t 0.8 0.7-0.6-0.5-0.4-0.3-0.2 0 0 Q sodium perchlorate © sodium trifluoroacetate 0 0.1 0.2 0.3 0.4 Molarity of salt solution Figure 32. Salt effects on the permanganate oxidation of methanol. (Trials 812-825). - 149 -(R=H)aldehyde + Mn *^'"" *• carboxylic acid , fast ketone + MnO^ *• carboxylic acids V 2+ VII 5Mn 2Mn + 3Mn , fast (b) TFA concentrations more than seven molar, 2H+ + MnO ~ MnO_+ + H.O , fast 4 -< 3 2 Mn03 + + RR^ CHOH • [RR-jCOH + HMn03+] , slow IRRJCOH + HMn03+] > RR C=0 + MnV , fast (R=H)aldehyde + Mn^** • carboxylic acid , fast ketone + Mn03 + *• carboxylic acid V 2+ VII 5Mn • 2Mn + 3Mn , fast The transition states can be depicted as outlined below. (a) R 6"+ \ n v~> /^v V - - - - - - H 0 —MnO.H / \ ~ R£ T)H - 150 -(b) R \ r J L h 0 -'- Mn02 R l O^H 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 ^ s u b s t i tuent 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. This process shows no primary isotope 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-d2. 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 ~\ D2°'VkDb d 2 > k(D20)/k(H20)C h 2,k(D 20)/k(H 20)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)/k2(benzyl alcohol-ct-d2). k A medium made from CF_C0,H-D„0, k^/k_ as defined in (a). Substrate was benzyl alcohol-a-d2, k(D20)/k(H20) = k2(medium made from CF2C03H-D20/k2(medium made from CF2C03H-H20, k 2 is the oxidation rate of the substrate. d Substrate was benzyl alcohol, k(D_0)/k(H„0) as defined in (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 wi 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, trials 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. Figure 33 illustrates 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, trials 1109-1116). A solvent isotope effect of k(D20)/k(H20) = 1.5 at IL, = -1.86 was observed. These results indicate that the transition state resulting from one molecule of oxidant and one of aldehyde develops some positive charge and that permanganyl ion is one of the oxidants. 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 K 4.7 Oxidation of Ketones The data for the oxidation of a variety of ketones are contained in Appendix C, trials 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 first-order with respect to permanganate for more than two half-lives of permanganate, as the good to excellent fits 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. - 1 5 6 -Although the correlations ranged about 0 . 9 9 definite curvature was observed in a l l plots rather than random scatter about the least square line. Figures 3 5 and 3 6 depict typical zero-order and first-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 R , as the data 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 1 3 7 1 3 8 from first 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 > 1 3 9 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 : , , , , 1 0 .... 0.4 0.8 1.2 1.6 2.0 Time (min) Figure 35. Typical pseudo first-order plot for the oxidation of cyclohexanone. (Trial 1069). Absorbance changed from 0.721 to 0.231. - 158 -0.75 1 1 1 1 1 0.0 2.0 4.0 6.0 8.0 10.0 Time (min) Figure 36. Typical zero order plot for the oxidation of acetophenone. (trial 1238). - 159 -Table 37. Order of Reactants in the Permanganate Oxidation of Ketones in TFA-Water. Substrate Order of r Trials Order r Order r substrate in h^ in h Q Acetone 1. 0 0.976 1009--1012 1. 1 0.993 1013--1016 1004--1016 0.5 0.993 2-Pentanone 1. 4 .990 1035--1039 1017--1053 0.7b 0.996 2,4-Pentanedione 1. 0 0.994 1203--1209 1197--1209 0.1 0.992 Benzophenone 1. 1 0.988 1077--1080 -Trifluoroaceto- 1. 1 0.998 1085--1090 phenone 1081--1090 0.8 0.999 Acetophenone 1. 0 0.999 1236--1243 1232--1247 0.8 0.998 Cyclohexanone 1. 1 0.995 1057--1061 1054--1070 0.6C 0.97 3-Pentanone 1. 6 0.999 1179--1186 Note: Error in orders are + 5%. First-order in permanganate except for acetophenone and 2,4-pentane-dione 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 1.25 0.50 0.25 0 acetone, YL^ = -9.68 cyclohexanone, H R = -5.64 trifluoroacetophenone, H^ . - -5.92 /© ©/ / / /o 9 j / benzophenone, H = -7.42 / / / / / / / ° V / acetone, = -8.64 0.2 0.5 0.8 1.1 1.4 1.7 2.0 2.3 2. 3 + log[ketone] Figure 37. Log Y vs. log[ketone] for the oxidation of a variety of ketones. - 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 first 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 enol 2H + MnO MnO + fast 4 3 » ketone + MnO + products slow 3 enol + MnO + products fast 4 Using a steady-state approximation for the enol content the following rate law results. 162 -k k Jketone]lMnO, J r = k_ [ketone] [MnO. ]h + - — J H K \ + k2lMn04 ] Since i t is known that permanganate ion rapidly oxidizes enols i t can be assumed that ko[Mn0. ] » k . The rate equation then reduces to, k E r = -.— [ketone] + k„ [ketone][MnO. ]hD 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: k E ketone * enol VII 2 enol + Mn • products The derived rate law is shown below, which results from the steady-state approximation on enol. - 163 -kk.[ketone][Mn V I 1] i i Z r = VTT k^ + k 2[tIn V 1 1] when kj, » k 2[Mn V I 1], r = [ketone] [MnVI1] E when kj, <<k2[Mn^**], 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 137 138 to chromic acid oxidations of ketones. ' But because of the extremely fast rate for the oxidation of 2,4-pentanedione, which clearly involves enolization, i t can be concluded that k2[Mn^**] will 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, is 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 kinetic data for the oxidation of formic acid are presented i n Appendix C, t r i a l s 1165-1174. The excellent correlation of the time-absorbance data with: the pseudo first-order equation indicates first-order dependence upon permanganate. The order with respect to substrate concentration, as is 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[Mn04 J/dt = k3[Mn04 ][HC02H]hR 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; HC02H + Mn03+ S l ° W » [-CC^ H + HMnC>3+] + fa<?t- V [•C02H + HMn03] > C02 + Mn 63 This scheme is analogous to that proposed by other researchers. 4.9 Oxidation by Permanganate in Benzene After Starks^ showed that permanganate could be used as an oxidant in 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 in benzene. The kinetic data are contained in Appendix D, trials 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 decomposi-f 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 = k2Isubstrate]TMn04 ] The mechanism of this oxidation can be visualized as the following for stilbenes; MnO. + ArCH=CHAr >• Ar-C C-Ar , slow 4 l — 7 T c I 0-MnO, 3 H H I I Ar-C C-Ar » • 2ArC02H , fast 0-Mn03 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 in 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) Permanganate oxidations in TFA-water solutions that correlate with 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 positively-charged transition state by TFA. (vii) No salt effects were observed for any of the substrates -examined. (viii) 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 + Mn03+ * [RR^ CH + HMn03+] [RR-jCH + HMn03+] [RR CH-0-Mh02+H] (I) (ID I or II * RRjCHOH + MnV VII V II + Mn » R R ^ O + 2Mn RRjCHOH + Mn03+ » [RRjCOH + HMn03+] IRR-JCOH + HMn03+] > RR^O + MnV RR^HOH + HMn04 * [ RR^ COH + I^ MnO ]^ [RR1COH + H2Mn04] » RR^O + MnV RR1C=0 -— k enol RR^C^ + Mn03+ *• carboxylic acids VII enol + Mn » 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 (Mn03+). The use of tetra(n-hexyl)ammonium permanganate extends the ut i l i ty of permanganate as an oxidant to homogeneous organic systems. Unfortunately this technique makes inefficient use of the oxidant. - 174 -6. SUGGESTIONS FOR FURTHER STUDY 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 pKR + 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 average pK^ = +0.92 M pH Abs. Q log Q HR 0.068 * 1.29 0.1920 0.429 -0.368* 0.92 1.29 0.072 * 1.28 0.1928 0.431 -0.365* 0.92 1.29 0.144 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" 0.069 * 1.30 0.2292 0.410 -0.387* 0.92 1.31 0.070 * 1.32 0.2076 0.358 -0.447* 0.92 1.37 0.130 * 1.06 0.3410 0.763 -0.118* 0.92 1.04 0.130 * 1.02 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 - 177 -APPENDIX A 4-Methyl-4',4"-dimethoxytriphenylcarbinol pK^+ = -0.28 M pH Abs. Q log Q 0.069 1.28 0.004 0.006 -2.221 0.069 1.28 0.008 0.012 -1.918 -0.64 * * (1.04) 0.130 1.01 0.0326 0.051 -1.291 -0.28 1.01 0.130 * 1.01 0.0308 0.048 * -1.317 -0.31 1.04 (0.96) 0.261 0.76* 0.0742 0.125 -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" - 178 -APPENDIX A 4,4'-Dimethoxytriphenylitiethyl chloride ~ -0.97 M HR Abs. Q 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 - H R * 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 V^~D+ = ~3.18 M Abs. Q Log Q -PV-2.86 1.78 0.0305 0.044 -1.360 3.14 1.82 3.34 2.28 0.0784 0.121 -0.916 3.20 2.26 3.87 2.88 0.1969 0.369 -0.433 3.31 2.75 4.45 3.41 0.3770 1.068 0.029 3.39+ 3.21 -4.87 3.59 0.5460 2.967 0.472 3.12 3.65 5.15 3.79 0.6004 4.633 0.666 3.12 3.85 5.42 4.06 0.6482 7.924 0.899 3.16 4.08 5.44 0.6420 7.133 0.853 4.03 6.00 0.6844 15.009 1.176 4.36 6.50 0.7093 34.266 1.535 7.00 0.7239 7.50 0.7270 8.02 0.7352 8.55 0.7390 0.7300" not used for p! - 181 -APPENDIX A 4,4'-Dimethyltriphenylcarbinol ^^R+ = - 3 , 7 8 M * Abs. Q Log Q " H R 3.88 0.0720 0.138 -0.860 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 P ^ R + = ""5.77 M * - v Abs. Q Log Q -PV 5.47 0.0280 0.025 -1.602 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 Triphenylcarbinol - 1 8 3 -APPENDIX A pK^ = - 6 . 2 5 M * -V Abs. Q Log Q " H R 7 . 1 0 5 . 1 4 0 . 0 3 7 7 0 . 0 6 6 - 1 . 1 8 1 6 . 3 2 5 . 0 7 7 . 5 7 5 . 5 3 0 . 0 7 9 4 0 . 1 5 0 - 0 . 8 2 5 6 . 3 3 5 . 4 3 7 . 8 0 5 . 6 4 0 . 1 2 0 6 0 . 2 4 6 - 0 . 6 0 8 6 . 2 4 5 . 6 4 8 . 0 7 5 . 8 4 0 . 1 7 3 9 0 . 3 9 9 - 0 . 3 9 9 6 . 2 4 5 . 8 5 8 . 3 3 5 . 9 4 0 . 2 3 9 2 0 . 6 4 5 - 0 . 1 9 0 6 . 1 4 6 . 0 6 8 . 6 7 6 . 2 0 0 . 3 1 8 9 1 . 0 9 5 0 . 0 4 0 6 . 1 6 6 . 2 9 8 . 8 1 0 . 3 7 7 1 1 . 6 1 9 0 . 2 0 9 6 . 4 6 9 . 1 7 0 . 4 5 4 9 2 . 9 3 3 0 . 4 6 7 6 . 7 2 9 . 4 7 0 . 5 1 1 2 5 . 1 7 4 0 . 7 1 4 6 . 9 6 9 . 5 7 0 . 5 4 7 8 8 . 8 0 7 0 . 9 4 5 7 . 2 0 1 0 . 2 0 0 . 6 0 3 9 9 9 . 0 0 1 . 9 9 6 1 0 . 6 7 0 . 6 1 7 8 1 1 . 2 7 0 . 6 1 0 1 0 . 6 1 0 0 " - 1 8 4 -APPENDIX A 4,4',4"-Trichlorotriphenylcarbinol pIC+ = - 7 . 9 4 M * " H R Abs. Q Log Q -P*R+ - H R 9 . 1 3 6 . 5 4 0 . 0 2 7 3 0 . 0 3 1 - 1 . 5 1 6 6 . 4 2 9 . 3 3 6 . 7 2 0 . 0 4 7 0 0 . 0 5 4 - 1 . 2 7 0 7 . 9 9 6 . 6 7 9 . 5 3 6 . 9 0 0 . 0 8 1 5 0 . 0 9 7 - 1 . 0 1 8 7 . 9 2 6 . 9 3 9 . 8 7 7 . 2 0 0 . 1 5 3 5 0 . 2 0 0 - 0 . 7 0 0 7 . 9 1 7 . 2 4 1 0 . 1 0 0 . 2 8 9 8 0 . 4 5 8 - 0 . 3 3 9 7 . 6 0 1 0 . 2 7 0 . 3 5 0 0 0 . 6 1 2 - 0 . 2 1 3 7 . 7 3 1 0 . 4 0 0 . 4 3 3 1 0 . 8 8 6 - 0 . 0 5 3 7 . 8 9 1 0 . 5 3 0 . 5 5 7 8 1 . 5 3 2 0 . 1 8 5 8 . 1 3 1 0 . 6 0 0 . 6 4 0 0 2 . 2 7 0 0 . 3 5 6 8 . 3 0 1 0 . 8 0 0 . 7 1 1 4 3 . 3 7 8 0 . 5 2 9 8 . 4 7 1 0 . 9 3 0 . 7 7 6 0 5 . 3 1 5 0 . 7 2 6 8 . 6 7 1 1 . 0 0 0 . 8 0 3 0 6 . 7 4 8 0 . 8 2 9 8 . 7 7 1 1 . 1 0 0 . 8 4 5 8 1 1 . 1 0 0 1 . 0 4 5 8 . 9 9 1 1 . 2 3 0 . 8 6 6 0 1 5 . 4 6 4 1 . 1 8 9 9 . 1 3 1 1 . 6 7 0 . 9 1 2 0 1 2 . 2 0 0 . 9 2 2 0 " 1 2 . 7 0 0 . 9 3 1 0 - 185 -APPENDIX A 4-Nitrotriphenylcarbinol P^R+ = -9«56 M - H L * Abs. Q Log Q -pK^ -IL, 10.57 0.0354 0.087 -1.049 8.51 10.83 8.60 0.0428 0.110 -0.959 9.56 8.60 11.07 8.91 0.0786 0.222 -0.653 9.56 8.91 11.37 0.0865 0.250 -0.601 8.96 11.67 0.1554 0.551 -0.259 9.30 11.93 0.2704 1.673 0.224 9.78 12.20 0.3326 3.346 0.525 10.09 12.43 0.3753 6.619 0.821 10.38 12.63 0.3984 11.857 1.074 10.63 13.03 0.4312 13.07 0.4320" 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 in H„SO,-ELO No. [Substrate] -H -H k, x 10 3 s" 1 k„ M 1 s 1 r - o R 1 2 x 10 n-Pentane 1 3.10 3.72 7.49 17.89 5.76 .999 2 II 17.97 5.79 3 it 17.07 5.50 4 2.325 11.48 4.94 5 it 12.77 5.49 6 it 12.48 5.35 " 7 1.55 7.74 5.00 8 ti 5.07 3.27 .990 9 it 4.84 3.11 .980 10 3.10 3.50 6.95 5.35 1.73 .999 11 ti 5.98 1.93 " 12 it 6.16 1.98 13 2.325 4.09 1.76 14 •t 4.52 1.94 15 ti 4.67 2.01 II 16 1.55 1.68 1.08 .980 17 it 1.41 0.910 .975 18 ti 1.27 0.820 .970 19 0.775 0.843 1.09 .950 20 it 0.801 1.03 .970 21 it 0.806 1.04 .965 22 3.10 3.01 5.90 1.45 0.467 .999 23 it 1.45 0.467 it 24 tt 1.31 0.423 it 25 2.325 0.658 0.283 ti 26 ti 0.610 0.262 .975 27 it 0.646 0.278 .999 28 1.55 0.443 0.286 .990 29 ti 0.418 0.270 .970 30 it 0.476 0.307 .998 31 0.775 0.194 0.251 .980 32 II 0.183 0.236 .965 33 it 0.199 0.258 .975 34 3.10 2.53 4.90 0.251 0.0810 .999 35 tt 0.289 0.0930 " 36 ti 0.256 0.0825 37 it 0.235 0.0759 38 II 0.284 0.0915 39 ti 0.242 0.0780 " 40 2.325 0.264 0.113 41 it 0.248 0.106 42 it 0.228 0.0979 43 ti 0.216 0.0926 - 187 -APPENDIX B 3 - 1 -1 -1 No. [Substrate] -H -H^ x 10 s k £ M s x 103 44 II 0.214 0.0920 .999 45 it 0.199 0.0855 it 46 1.55 0.150 0.0969 it 47 II 0.144 0.0929 it 48 II 0.155 0.100 II 49 0.775 0.0719 0.0930 II 50 II 0.0722 0.0934 .997 51 II 0.0652 0.0841 .947 52 3.10 2.19 4.25 0.0900 0.0290 .999 53 II 0.0872 0.0282 it 54 II 0.0846 0.0273 ti 55 2.325 0.0852 0.0366 ti 56 II 0.0937 0.0402 it 57 II 0.0887 0.0381 it 58 1.55 0.0710 0.0458 ti 59 II 0.0709 0.0457 ti 60 II 0.0713 0.0460 it 61 0.775 0.0423 0.0546 .997 62 II 0.0459 0.0592 ti 63 it 0.0452 0.0584 • M 64 " 3.72 7.49 0.350 0.452 .970 65 •i iso-Pentane 0.340 0.440 .954 66 3.10 2.55 4.93 1.16 0.375 .999 67 II 1.18 0.380 tt 68 2.325 1.36 0.586 it 69 2.325 1.41 0.603 II 70 1.55 0.859 0.554 ti 71 ti 0.876 0.565 it 72 0.775 0.356 0.461 .990 73 II 0.348 0.451 ti 74 3.10 3.01 5.90 0.78 2.18 .999 75 II 7.31 2.36 it 76 2.325 3.54 1.52 it 77 II 3.60 1.54 ti 78 1.55 0.957 0.617 ti 79 ti 1.02 0.660 it 80 0.775 0.151 0.195 .945 81 ti 0.155 0.200 .955 82 3.10 3.37 6.80 11.2 3.64 .999 83 II 13.1 4.24 ti 84 2.325 7.02 3.02 ti 85 it 5.94 2.55 tt - 188 -APPENDIX B No. [Substrate] -H -H_ k„ x 103 s"1 k_ M - ^ " 1 r - O K A / x 10 86 1.55 2.61 1.68 .999 87 V 2.51 1.62 88 0.775 0.383 4.95 .985 89 " 0.432 5.59 .980 90 3.10 3.78 7.52 25.0 8.36 .999 91 " 24.0 7.75 92 2.325 15.8 6.77 93 " 15.7 6.74 94 1.55 4.10 2.64 .965 95 " 4.34 2.80 .970 96 0.775 1.81 2.34 .934 97 " 1.76 2.77 .942 98 3.10 3.78 7.52 119.0 38.4 .985 99 2.325 84.1 36.2 .999 100 " 84.4 36.3 101 1.55 47.1 30.4 102 " 42.7 27.5 103 0.775 7.54 9.74 104 " 4.27 5.51 .980 105 3.10 3.37 6.80 17.4 5.60 .999 106 " 16.9 5.44 107 2.325 15.1 6.49 108 " 15.0 6.46 109 1.55 5.29 3.41 110 " 5.83 3.76 111 0.775 0.623 0.804 .980 112 " 0.839 1.08 .985 113 3.10 3.19 6.10 5.84 1.88 .999 114 " 6.50 2.10 115 2.325 4.50 1.93 116 " 4.34 1.87 117 1.55 2.12 1.36 118 11 2.24 1.44 119 0.775 0.890 1.15 120 " 0.962 1.24 121 3.10 2.55 4.93 1.14 0.367 .999 122 " 1.22 0.393 " 123 2.325 0.660 0.284 124 " 0.660 0.284 ti 125 1.55 0.643 0.415 126 " 0.694 0.444 127 0.775 0.337 0.435 128 " 0.346 0.446 II II - 189 -APPENDIX C A l l of the rate data contained in this section have been corrected for blank decomposition. Some trials , 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 wil 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 [S]xl03 k 1xl0 3s 1 k 2 M - 1 s 1 r 129 Ethane 8.50 8.680 38.0 4.38 .999 130 • II II II 36.5 4.21 131 II II 7.483 42.6 5.69 132 it II it 44.0 5.88 133 II II 3.443 15.0 4.35 134 II II it 15.3 4.45 " 135 Propionitrile II 124.9 0.305 0.00244 .983 136 II it II 0.304 0.00243 .975 137 Nitroethane II 124.0 0.729 0.00588 .980 138 II II it 0.705 0.00569 .998 139 Propionic acid II 48.01 0.607 0.0127 .999 140 II II II 0.710 0.0148 . " 141 Propane 7.08 34.91 22.2 0.635 142 it ti ti 21.2 0.606 143 II i i 17.76 13.2 0.743 " 144 II it II 15.2 0.855 145 II II 44.83 26.6 0.594 146 II II II 23.3 0.520 147 II II 39.30 23.9 0.609 148 II II II 24.6 0.627 149 n-Butane 7.08 34.36 45.5 1.33 150 II tt it 49.1 1.43 151 it ti 33.76 44.3 1.31 152 II it ti 47.4 1.41 153 II it 2.787 3.35 1.20 " 154 II it 45.99 7.30 1.59 155 II it it 6.38 1.39 " 156 n-Pentane 7.86 3.127 18.6 5.96 157 II ti it 19.3 6.17 158 II 6.27 3.11 0.321 0.103 " 159 II it 26.47 2.28 0.0976 160 II 5.65 31.13 0.813 0.0261 161 II 7.10 15.59 13.0 0.836 162 ti ti it 13.9 0.894 163 II 6.96 5.99 3.38 0.564 164 •t it ti 3.38 0.564 165 it it 18.71 10.3 0.551 166 it it 8.98 5.15 0.574 167 it it it 4.95 0.552 168 ti it 13.47 7.29 0.541 169 II II " 7.33 0.544 170 n 38.4° 7.52 6.250 18.0 2.87 171 II II II II 20.5 3.28 172 II 31.8° II 7.812 18.3 2.35 - 191 -APPENDIX C No. Substrate -IL. [S]xl0 3 k^xlC^s" 1 lc^V"1 r 173 n-Pentane 19.8° 7.52 7.812 10.3 1.32 .999 174 it 25.2° 11 6.250 8.92 1.43 11 175 II 25.4° it tt 10.5 1.68 11 176 II 14.0° 11 7.812 7.56 0.968 tt 177 II it ti ti 7.52 0.963 it 178 II 6.70 7.812 3.98 0.510 it 179 II 11 it 4.02 0.515 it 180 it 7.74 15.63 - 3.88 11 181 II 11 tt - 3.88 tt 182 II 8.00 3.12 - 20.2 it 183 it tt it - 21.3 it 184 II 11 tt - 19.4 it 185 n-Hexane 6.42 13.77 4.93 0.358 tt 186 II 11 9.91 3.51 0.354 it 187 n it tt 3.53 0.356 11 188 it 11 6.61 2.64 0.399 ti 189 ti ti ti 2.65 0.400 11 190 tt 11 3.305 1.39 0.421 it 191 it it 11 1.39 0.419 11 192 ti 6.96 13.77 17.9 1.30 11 193 it 11 9.91 11.3 1.14 11 194 it 11 it 10.6 1.07 11 195 it tt 6.61 7.22 1.09 11 196 it it tt 7.44 1.13 it 197 it ti 3.305 3.23 0.976 11 198 it 11 11 3.81 1.15 11 199 tt 7.30 4.13 13.4 3.25 11 200 ti it 1.983 6.40 3.22 it 201 it 8.26 1.652 39.3 23.8 it 202 it 25.0° 6.66 13.77 12.8 0.930 11 203 ti 21.4° ti it 5.99 0.435 11 204 ti 15.6° 11 11 5.10 0.370 11 205 it 7.86 2.754 37.1 13.5 11 206 ii it 11 37.0 13.4 11 207 ti D20 6.93 5.509 7.20 1.31 11 208 it it 11 11 9.35 1.70 it 209 it H2O 11 8.263 10.8 1.30 11 210 ti ti 11 11 12.5 1.52 11 211 it 38.5° 7.77 4.132 45.3 11.0 11 212 tt tt it 11 43.6 10.6 11 213 ti 31.8° 11 3.443 29.9 8.68 11 214 it 20.0° it 11 19.2 5.59 11 215 it 25.4° it 4.132 28.0 6.77 11 216 II 11 11 11 27.6 6.67 it 217. tt 14.0° tt ti 19.0 4.60 it - 192 -APPENDIX C No. Substrate -H_ [S]xl0 3 k 1 x l 0 3 s " 1 k2M 1 S - 1 r 218 n-Hexane 13.9° 7.77 4.132 18.3 4.42 219 ti 7.74 8.260 - 9.73 220 II ti it - 9.28 221 II 8.00 1.380 - 41.0 222 II it ti - 35.9 223 tt ii it - 35.3 224 n-Heptane II 7.86 3.68 64.4 17.5 225 tt it 68.0 18.5 226 ti 7.20 6.82 29.2 4.28 227 II it tt 31.1 4.56 228 II 6.81 12.28 18.0 1.46 229 II it 8.84 11.3 1.28 230 it it tt 11.6 1.31 231 it it 5.89 6.94 1.18 232 ti it II 7.40 1.26 233 it it 2.95 3.62 1.23 234 it 6.42 12.28 6.09 0.496 235 tt ti it 6.18 0.504 236 25.0° 6.66 12.28 10.3 0.838 237 21.4° tt it 4.89 0.398 238 15.6° II it 4.21 0.343 239 it 7.86 2.456 39.9 16.2 240 ti 7.74 7.37 - 10.7 241 tt it it - 10.2 242 II 8.00 1.23 - 52.8 243 tt it it - 50.2 244 it it it - 46.8 245 n-Octane 7.74 4.928 - 15.3 246 it it it - 14.9 247 it 8.00 1.11 - 65.7 248 II it ti - 66.6 249 ti tt tt - 60.6 250 n-Nonane 7.86 2.014 63.3 31.4 251 it ti ti 67.3 33.4 252 ti 7.74 3.021 - 19.6 253 ti it it - 19.1 254 it 8.00 0.850 - 93.0 255 it it it - 91.3 256 tt it tt - 86.3 257 n-Decane 7.74 1.847 - 26.6 258 it it II - 28.2 259 ii 8.00 0.740 - 103.0 260 ti ti it - 101.0 261 it ti it - 107.0 262 n-Undecane 7.74 1.705 - 33.8 263 ti it ti - 33.1 264 II 8.00 0.680 - 131.0 265 tt it it - 126.0 ,999 - 193 -APPENDIX C No. Substrate -IL, [S]xlO k ^ l O s k2M s r 266 n-Undecane 8.00 0.680 - 124.0 267 n-Dodecane 7.86 1.582 85.0 53.7 268 ti it 86.8 54.9 269 38.2° 7.41 2.37 70.1 29.6 270 it it tt it 79.7 33.6 271 31.1° ti 1.98 39.9 20.1 272 24.9° 7.41 0.40 5.79 14.5 273 19.4° it tt 4.95 12.4 274 " 14.0° it ti 3.69 9.23 275 7.74 0.791 - 39.9 276 tt it tt - 39.1 277 ti 8.00 0.630 - 153.0 278 ti it - 138.0 279 it tt - 162.0 280 n-Tridecane 7.74 0.738 - 58.2 281 ti II - 54.5 282 8.00 0.370 - 167.0 283 tt tt - 155.0 284 it ti - 164.0 285 Isopentane 5.71 15.50 3.90 0.257 286 ti 11.16 2.11 0.189 287 it • ti 2.30 0.206 288 it 7.44 1.44 0.193 289 it ti II 1.67 0.224 290 II 3.720 0.771 0.207 291 6.00 15.50 7.77 0.502 292 " tt 11.16 4.19 0.376 293 tt it 4.67 0.419 294 ti 7.440 2.53 0.339 295 " tt ti 2.95 0.397 296 it 3.720 1.09 0.294 297 II II 1.13 0.382 298 6.33 15.50 16.6 1.07 299 it 11.16 9.28 0.825 300 tt tt • tt 10.3 0.922 301 it ti 7.440 7.03 0.944 302 " it tt 7.54 1.01 303 it 3.720 3.12 0.839 304 it ti 3.86 1.04 305 " 6.64 7.751 16.2 2.09 306 tt ti 5.581 9.96 1.79 307 " tt it 10.6 1.90 308 it 3.720 6.32 1.70 309 " ti it 7.09 1.91 310 ti 1.860 3.45 1.86 - 194 -APPENDIX C No. Substrate -H_ [S]xlQ3 k x l 0 3 s _ : L k ^ " 1 * - 1 311 Isopentane 6.64 1.860 4.21 2.26 312 25.0° 6.66 6.20 17 .2 2.77 313 21.2° it 11 7.91 1.28 314 15.6° it ti 6.08 0.981 315 12.5° tt 11 3.64 0.587 316 " H20 5.95 9.282 3.19 0.343 317 ti ti 11 3.71 0.400 318 D2O it 11 3.74 0.403 319 11 it .> it 4.17 0.449 320 4.08 7.730 0.2130 0.0276 321 " 4.80 7.730 0.483 0.0624 322 Neopentane 7.90 30.80 6.31 0.205 323 it 11 6.32 0.205 324 8.44 34.50 14.1 0.408 325 11 11 14.6 0.422 326 it it 15.1 0.437 327 8.96 31.23 42.5 1.36 328 it tt 39.0 1.25 329 11 11 44.1 1.41 330 8.70 50.89 42.9 0.843 331 " 11 it 43.3 0.851 332 it 11 43.7 0.858 333 11 35.00 26.4 0.755 334 11 11 24.7 0.705 335 it 23.09 18 .0 a 779 336 it tt 17.5 0.757 337 Cyclopentane 7.52 7.71 55.9 7.24 338 11 ti 48.9 6.34 339 ft 6.52 19.28 15.7 0.813 340 it it 15.9 0.825 341 6.26 28.91 11.4 0.394 342 it 20.82 7.91 0.380 343 11 11 7.52 0.361 344 ti 13.88 5.29 0.381 345 11 it 4.99 0.360 346 11 9.25 3.80 0.411 347 11 11 3.44 0.371 348 5.72 19.28 2.47 0.128 349 " 11 11 2.77 0.144 350 38.6° 7.02 7.71 30.2 3.91 351 it it 11 26.6 3.46 352 " 31.8° 11 9.638 27.5 2.85 353 25.0° tt 7.71 17.6 2.28 354 • 11 tt tt 16.4 2.12 .999 .997 .999 - 1 9 5 -APPENDIX C 3 , „ 3 - 1 , - 1 - 1 N o . Substrate -HR [S]xlO kjXlO s k2M s r 3 5 5 Cyclopentane 1 9 . 9 ° 7 . 0 2 9 . 6 3 8 1 6 . 8 1 . 7 4 . 9 9 9 3 5 6 II 1 4 . 0 ° it it 1 2 . 2 1 . 2 7 it 3 5 7 it tt ti it 1 1 . 9 1 . 2 3 it 3 5 8 II 6 . 9 0 1 9 . 2 8 4 2 . 7 2 . 2 1 ti 3 5 9 II it ti 4 1 . 2 2 . 1 4 ti 3 6 0 Cyclohexane 6 . 4 2 8 . 3 3 2 3 . 2 0 0 . 3 8 4 it 3 6 1 II it 5 . 9 9 9 2 . 5 5 0 . 4 2 6 it 3 6 2 n ti it 2 . 4 7 0 . 4 1 2 ti 3 6 3 II it 3 . 9 9 9 1 . 7 9 0 . 4 4 7 ti 3 6 4 II tt ti 1 . 7 7 0 . 4 4 2 it 3 6 5 it II 2 . 0 0 1 . 0 1 0 . 5 0 3 it 3 6 6 it 6 . 9 6 8 . 3 3 2 1 0 . 7 1 . 2 8 ti 3 6 7 ti it 5 . 9 9 9 8 . 4 6 1 . 4 1 it 3 6 8 tt ti •t 8 . 2 6 1 . 3 8 it 3 6 9 tt it 3 . 9 9 9 5 . 4 0 1 . 3 5 ti 3 7 0 ti ti II 5 . 8 9 1 . 4 7 ti 3 7 1 ti tt 2 . 0 0 0 3 . 3 0 1 . 6 5 it 3 7 2 it it it 3 . 2 0 1 . 6 0 it 3 7 3 ti 7 . 3 0 8 . 3 3 2 3 2 . 7 3 . 9 2 it 3 7 4 it it 5 . 9 9 9 2 2 . 2 3 . 7 0 it 3 7 5 II it tt 2 2 . 2 3 . 7 0 ti 3 7 6 it it 3 . 9 9 9 1 5 . 0 3 . 7 4 tt 3 7 7 it ti n 1 6 . 4 4 . 1 0 it 3 7 8 ti it 2 . 0 0 0 7 . 6 0 3 . 8 0 ti 3 7 9 ti II tt 7 . 9 3 3 . 9 7 it 3 8 0 ti 8 . 2 6 2 . 0 0 6 0 . 7 3 0 . 4 II 3 8 1 it 2 5 . 0 ° 6 . 6 6 1 6 . 6 6 1 4 . 3 0 . 8 6 0 ti 3 8 2 tt 2 1 . 4 ° ti tt 8 . 8 1 0 . 5 2 9 it 3 8 3 II 1 5 . 6 " it ti 5 . 2 2 0 . 3 1 3 it 384 Cyclohexane-d._ it 2 5 . 0 ° II 2 9 . 1 7 5 . 4 1 0 . 1 8 5 ti 3 8 5 ti ti it 6 . 8 5 0 . 2 3 5 ti 3 8 6 Cyclohexane 6 . 8 0 1 6 . 6 6 1 2 . 9 0 . 7 7 2 II 3 8 7 tt it II 1 2 . 5 0 . 7 4 8 it 3 8 8 tt 6 . 7 4 tt 1 2 . 9 0 . 7 7 3 it 3 8 9 ti ti II 1 3 . 1 0 . 7 8 9 it 3 9 0 Cyclohexane-d.^ Cyclohexane it II 3 . 0 0 0 . 1 8 0 ti 3 9 1 6 . 3 8 . 1 6 . 6 6 5 . 2 5 0 . 3 1 5 ti 3 9 2 Cyclohexane-d..„ II " ti it 1 . 1 3 0 . 0 6 7 8 it 3 9 3 ti it 1 . 1 0 0 . 0 6 5 7 tt 3 9 4 Cyclohexane 6 . 1 2 1 6 . 6 6 2 . 6 2 0 . 1 5 7 it 3 9 5 Cyclohexane-d-„ II -L^  it it 0 . 4 9 6 0 . 0 2 9 8 it 3 9 6 7 . 9 1 4 . 1 6 6 1 7 . 3 4 . 1 5 ti 3 9 7 Cyclohexane it 2 . 0 8 3 3 4 . 6 1 6 . 6 it 3 9 8 it 7 . 7 0 4 . 1 6 6 3 2 . 7 7 . 8 4 it 3 9 9 Cyclohexane-d.. 0 it " it 8 . 3 3 2 1 1 . 4 1 . 3 7 ti 4 0 0 7 . 4 0 1 3 . 3 3 1 1 . 2 0 . 8 3 7 it 4 0 1 it II II 1 2 . 9 0 . 9 7 1 II - 196 -APPENDIX C No. Substrate [SjxlO 3 k 1 x l 0 3 s _ 1 k2M s r 402 Cyclohexane 7.40 6.665 28.4 4.26 .999 403 II ti tt 28.4 4.26 404 Cyclohexane-d- _ 6.96 13.33 2.67 0.191 " 405 II xl it it 5.36 0.402 406 Cyclohexane it it 16.4 1.23 407 II ti tt 16.2 1.22 408 II 6.77 1.33 1.01 0.755 409 II it II 1.09 0.826 410 it •t 4.23 2.86 0.675 411 tt it tt 3.38 0.799 412 II ti 8.00 5.71 0.714 413 II tt it 5.74 0.718 414 it II 10.66 7.41 0.695 415 tt tt it 7.67 0.720 " 416 II 6.77 13.33 9.64 0.723 " 417 II it 16.00 10.8 0.674 418 II it it 11.3 0.704 " 419 II it 24.00 15.9 0.661 " 420 it tt ti 16.4 0.684 421 ii tt 26.66 19.1 0.715 422 ii II •t 18.3 0.686 " 423 II it 33.33 21.5 0.649 424 II 6.93 9.998 13.3 1.33 425 ti II ti 14.3 1.43 426 II D20 it 6.665 9.77 1.47 " 427 it II it II 9.26 1.40 428 ti 38.5° 7.70 3.333 39.2 11.8 " 429 II 31.8° ti 4.166 45.2 10.8 430 it 25.3° it 4.999 43.4 8.68 431 II II II II 44.9 8.98 432 it 19.9° II 4.166 29.1 6.98 433 II 13.9° II II 22.3 5.35 434 ti 6.90 8.33 13.6 1.63 435 tt II II 13.1 1.58 " 436 Cycloheptane 6.80 4.46 22.9 5.13 " 437 II it II 23.2 5.21 438 it 6.36 11.89 27.7 2.33 439 tt it 8.562 18.0 2.11 440 II II it 18.7 2.18 " 441 it II 5.708 12.2 2.14 " 442 it II it 12.8 2.25 443 II it 2.854 6.47 2.27 " 444 it it it 6.48 2.27 " 445 II 5.37 2.975 0.899 0.302 " 446 ti 5.82 ti 2.08 0.698 - 197 -APPENDIX C No. Substrate ~\ [S]xl03 k 1xl0 3s~ 1 s r 447 Cycloheptane 5.82 2.975 2.13 0.717 .999 448 " 6.09 5.946 7.11 1.20 " 449 11 ti 7.43 1.25 450 38.4° 7.20 2.973 68.8 23.1 451 ti 11 11 67.6 22.7 45.2 31.8° tt 3.716 68.7 18.5 11 453 19.9° tt 11 44.5 12.0 454 25.3° ti 2.973 41.5 14.0 " 455 " it ti tt 44.3 14.9 456 14.0° 11 11 27.3 9.19 457 ti it ti 27.2 9.15 458 6.90 7.45 63.4 8.51 " 459 11 it 61.5 8.26 460 0.36 STFA 5.58 3.716 2.32 0.625 " 461 " it it it 11 2.38 0.640 " 462 0.28 STFA 5.60 it 2.45 0.660 " 463 ti II 11 11 2.29 0.616 " 464 0.07 STFA 5.64 11 2.15 0.578 465 it ti 11 it 2.31 0.623 " 466 Cyclooctane 6.80 2.01 30.6 15.2 467 11 4.012 52.9 13.2 " 468 tt 11 54.8 13.7 469 " 6.36 8.024 57.9 7.22 470 11 5.777 39.1 6.78 471 11 11 39.1 6.78 " 472 tt 3.852 26.9 6.98 473 it •t 28.0 7.27 474 11 1.926 12.4 6.45 475 11 11 12.4 6.43 " 476 5.82 2.675 5.75 2.15 " 477 •t 11 5.44 2.03 478 6.09 5.349 20.2 3.77 " 479 it 11 11 20.5 3.83 480 38.6° 6.80 1.377 37.3 27.9 " 481 it it it 38.7 29.0 482 31.8° 11 11 23.1 17.3 " 483 19.9° 11 11 16.9 12.7 484 25.2° 11 it 19.2 14.4 485 ti 11 it 20.0 15.0 486 14.0° 11 11 12.5 9.38 " 487 it 11 ti 12.1 9.01 488 6.90 3.34 78.6 23.5 489 11 it 76.9 23.0 490 Benzene D2O 5.78 22.28 26.3 1.18 " 491 ti 11 it ti 26.7 1.20 " - 198 -APPENDIX C i No. Substrate IS]xl0 3 k 1xl0 3s~ 1 1 w~"l -1 k2M s r 492 Benzene H20 4.80 20.50 1.52 0.0741 .999 493 ti it 1.45 0.0709 ti 494 5.40 20.50 6.06 0.296 .998 495 II it 5.97 0.291 .999 496 5.84 5.74 4.82 0.839 ti 497 it ti 4.84 0.843 it 498 it 9.72 8.45 0.869 it 499 it it 8.45 0.869 tt 500 it 13.94 11.5 0.822 ti 501 II tt 11.1 0.798 II 502 ti 20.50 18.4 0.895 it 503 6.30 16.20 54.3 3.35 it 504 " •t ti 55.0 3.40 II 505 6.64 5.06 58.3 11.5 II 506 Chlorobenzene II 17.69 40.7 2.30 II 507 Fluorobenzene it 4.80 22.3 4.64 it 508 Nitrobenzene it 44.00 3.82 0.00868 it 509 Benzoic acid ti 32.06 5.41 0.169 .997 510 Anisole 4.16 0.35 32.0 91.3 .999 511 Benzene it 30.37 4.65 0.0153 it 512 Toluene it 16.94 16.6 0.977 • it 513 Ethylbenzene ti 5.88 7.36 1.25 ti 514 Cumene tt 3.23 5.04 1.56 ti 515 t-Butylbenzene •t 2.91 4.15 1.43 II 516 Fluorobenzene 5.64 28.78 5.90 0.205 II 517 Chlorobenzene ti 26.54 2.22 0.0838 it 518 Benzene 38.5° 5.70 20.25 20.9 1.03 n 519 II it it 21.1 1.04 it 520 31.8° it ti 16.5 0.813 II 521 19.9° II ti 9.25 0.457 it 522 25.3° it it 12.4 0.610 it 523 it it it 12.4 0.612 II 524 13.9° ti 20.25 9.10 0.449 it 525 II ti II 9.55 0.472 .998 526 " 0.048 MP 5.64 10.12 6.43 0.636 .999 527 0.026 MP 5.60 it 6.30 0.623 II 528 0.36 STFA 5.58 ti 6.68 0.660 it 529 II II it it 7.51 0.742 it 530 0.07 STFA 5.64 it 7.12 0.704 .997 531 " II II " II 7.25 0.716 .999 532 0.29 STFA 5.60 ti 6.41 0.633 ti 533 II II ti tt 6.51 0.643 it 534 4.80 20.25 1.44 0.0712 .998 535 4.08 ti 0.365 0.0180 .999 536 11 it it 0.336 0.0166 ti - 199 -APPENDIX C No. Substrate -H^ [S]xl03 k j X l O ^ " 1 k2U~ 18~ 1 r 537 Toluene 2.88 4.24 0.719 0.170 538 " M 6.78 1.39 0.205 539 II ti 1.13 0.167 540 " it 10.20 1.56 0.153 541 tt II 1.46 0.143 542 II 13.60 2.03 0.149 543 ti II 2.37 0.174 544 3.48 4.24 1.70 0.402 545 " it 6.78 2.74 0.404 546 " it II 2.74 0.404 547 " it 10.20 4.22 0.414 548 11 II it 4.14 0.406 549 " II 13.60 4.78 0.351 550 " II II 5.41 0.396 551 " 3.84 4.24 2.72 0.642 552 " it 6.78 4.88 0.721 553 " II II 4.72 0.696 554 " tt 10.20 7.73 0.758 555 " it it 7.73 0.758 556 II 13.60 9.58 0.705 557 " it II 9.58 0.705 558 " 4.32 2.12 3.71 1.78 559 ti 3.39 5.95 1.76 560 it II 6.11 1.80 561 it 5.10 8.53 1.67 562 " it it 8.28 1.62 563 " II 6.80 11.3 1.66 564 it it 12.3 1.81 565 " 4.84 2.12 10.9 5.13 566 II 3.39 14.7 4.34 567 it it 15.0 4.42 568 II 5.10 20.6 4.04 569 " II ti 19.1 3.74 570 II 6.80 27.3 4.01 571 " II II 27.6 4.06 572 " 2.90 4.24 0.620 0.146 573 II 6.78 1.08 0.160 574 II II 1.07 0.158 575 " II 10.20 1.71 0.168 576 " ti it 1.82 0.178 577 " ti 13.60 2.56 0.188 578 II II 2.69 0.197 579 " 3.42 4.24 1.45 0.341 580 " II 6.78 2.79 0.412 581 " ti II 3.07 0.454 .999 - 200 -APPENDIX C 3 T -1 , -1 -1 No. Substrate [S]xl0 k ^ l O s k^A s r 582 Toluene 3.42 10.20 4.42 0.434 .999 583 ?i it tt 4.41 0.433 " 584 II it 13.60 5.77 0.424 " 585 it tt II 5.64 0.415 " 586 II 3.82 4.24 2.88 0.679 " 587 II II 6.78 5.23 0.771 588 it it it 5.31 0.783 589 ii II 10.20 6.42 0.630 590 ti it II 7.93 0.778 591 ti tt 13.60 1.05 0.772 " 592 •t it it 1.05 0.772 " 593 it 4.19 2.12 3.39 1.60 " 594 II II 3.39 5.74 1.69 " 595 tt ti II 5.69 1.68 596 it II 5.10 8.37 1.64 597 •t ti •t 8.63 1.69 598 II 4.19 6.80 10.9 1.60 599 it it II 11.3 1.66 600 II 4.70 2.12 7.76 3.66 601 it II 4.24 14.6 3.44 " 602 it it 5.10 17.0 3.34 • " 603 it it it 17.9 3.51 " 604 II tt 6.80 22.4 3.30 605 tt it it 22.9 3.37 " 606 II 4.08 8.846 9.67 2.04 607 ti it ti 10.7 2.08 " 608 p_-Nitrotoluene II 22.06 2.73 1.09 " 609 II ti II 2.43 1.04 610 m-Toluic acid II 25.64 1.13 0.642 " 611 it II II 1.26 0.692 612 m-Nitrotoluene II 33.23 3.27 0.993 613 II it II 4.30 1.11 " 614 m-Chlorotoluene n 6.051 1.46 1.38 615 •t ti II 1.54 1.41 616 Ethylbenzene 4.50 5.88 1.74 2.95 " 617 II II II 1.70 2.88 618 Toluene-d_ II o it 5.99 1.56 2.60 " 619 II II 1.50 2.50 11 620 ti II 3.74 0.952 2.54 621 Toluene n 6.77 1.56 2.31 622 II II II 1.59 2.34 623 II •2.07 3.387 0.797 0.235 624 II it II 0.633 0.187 " 625 Toluene-d_ It o II 3.404 0.681 0.200 626 it II 0.601 0.177 627 Ethylbenzene II 3.234 1.27 0.391 " - 201 -APPENDIX C r -, 3 ,~3 -1 , -1 -1 No. Substrate "HR [S]xl0 kjXlO s k2M s r 628 Cumene 3.07 3.235 1.24 0.382 .999 629 Toluene 3.39 3.387 1.26 0.372 II 630 II ti it 1.20 0.355 tt 631 Toluene-d Q II o it 3.404 1.28 0.375 it 632 II tt 1.27 0.373 ti 633 Ethylbenzene it 3.675 2.25 0.611 ti 634 Cumene it 2.588 1.58 0.609 it 635 II ti ti 1.42 0.554 it 636 Toluene 3.88 3.387 2.63 0.777 ti 637 II it II 2.58 0.761 ti 638 Toluene-dg Ethylbenzene it 8.510 6.57 0.771 it 639 ti 2.940 3.15 1.07 II 640 Cumene ti 2.588 2.91 1.12 tt 641 ti it it 2.93 1.13 it 642 Toluene 4.44 7.114 13.2 1.86 it 643 Toluene-dg Ethylbenzene ti 6.808 13.5 1.99 ti 644 it 5.879 15.2 2.59 it 645 Cumene it 3.235 8.18 2.53 it 646 Toluene 4.82 3.387 14.4 4.26 it 647 II tt ti 14.5 4.28 tt 648 Toluene-d 0 II o ti 3.404 14.4 4.23 ti 649 it it 14.3 4.21 ' ti 650 Ethylbenzene it 2.940 15.5 5.27 II 651 II it tt 15.8 5.37 it 652 Cumene it 3.235 19.1 5.91 •t 653 Toluene 5.29 1.694 21.5 12.7 ti 654 it ti 23.2 13.7 tt 655 Toluene-d 0 it o it 1.702 22.7 13.3 tt 656 tt it 22.7 13.4 it 657 Toluene 5.70 0.339 11.6 34.3 it 658 it ti ti 11.6 34.3 ti 659 Toluene-d Q II o it 0.340 13.0 38.3 ti 660 it II 12.1 35.6 it 661 Toluene 4.42 3.387 5.40 1.59 it 662 II it it 5.14 1.52 ti 663 it ti 6.775 10.6 1.56 it 664 it ti ti 10.9 1.62 it 665 ti II 13.55 23.1 1.71 ti 666 II it it 23.7 1.75 ti 667 it it 20.33 32.1 1.58 it 668 II it tt 32.0 1.57 it 669 Toluene-d Q It o II 3.404 5.47 1.61 ti 670 it II 5.61 1.65 ti 671 II it 6.808 10.7 1.57 II 672 ti ti it 10.7 1.57 II 673 tt II 13.62 22.4 1.65 it - 202 -APPENDIX C r , 3 ,~3 -1 , w-1 -1 No. Substrate "HR [S]xlO kjXlO s k2M s r 674 Toluene-d0 4.42 13.62 22.5 1.65 .999 675 it 20.43 32.8 1.61 II 676 II II II 33.6 1.64 II 677 Toluene-dQ, II o D20 4.83 4.255 42.2 9.91 H 678 it it 8.510 75.2 8.83 II 679 Toluene, D20 it 4.234 41.1 9.71 it 680 it II tt 8.469 79.1 9.34 II 681 m-Nitrotoluene 5.40 14.69 2.19 0.149 II 682 m-Toluic acid tt 17.74 2.68 0.151 it 683 p_-Toluic acid II 25.39 1.81 0.0714 II 684 m-Nitrotoluene it 14.69 2.60 0.177 .995 685 p_-Bromo toluene II 5.001 3.90 0.780 .999 686 II tt II 4.22 0.844 II 687 p_-Nitrotoluene it 17.95 4.75 0.0264 II 688 II II it 3.66 0.0204 .992 689 m-Bromotoluene II 7.746 24.0 3.10 .999 690 II it II 24.0 3.10 II 691 m-Chlorotoluene it 9.144 30.0 3.20 II 692 it ti H 30.2 3.30 II 693 Toluene ti 6.241 107.0 17.1 II 694 II tt II 116.0 18.6 695 II 14.7° 4.26 5.10 4.99 0.978 II 696 II it tt it 4.72 0.926 it 697 II 20.4° II it 6.34 1.24 it 698 it II II II 5.81 1.14 ti 699 it 25.0° II II 9.30 1.82 tt 700 II it II II 9.37 1.84 II 701 II 31.6° II II 12.8 2.51 it 702 II it II II 11.7 2.30 II 703 II 36.2° II II 10.5 2.06 II 704 II • II II II 12.8 2.52 it 705 Toluene 15.0° 4.13 5.10 4.83 0.947 II 706 tt II it II 3.63 0.711 II 707 II 20.0* II tt 5.63 1.10 II 708 n II II II 5.89 1.16 II 709 it 25.0° II II 9.29 1.82 II 710 tt II II II 9.39 1.84 II 711 tt 30.0° tt II 10.5 2.06 II 712 II II II II 10.3 2.01 II 713 ti 35.0° II II 9.67 1.90 II 714 II II II II 10.2 1.99 II 715 II 2.90 16.94 2.79 0.165 it 716 Toluene-dg Toluene-a-d^ 2.34 5.08 0.270 0.0532 II 717 II II 0.307 0.0604 it 718 Toluene it II 0.288 0.0566 II - 203 -APPENDIX C 3 3 -1 -1 -1 No. Substrate -H [S]xl0 k-jXlO s k2M s r 719 Toluene-dQ II o 3.52 6.77 3.00 0.450 .998 720 ti II 3.17 0.469 .999 721 Toluene-a-d- tt it 2.91 0.429 it 722 II -3 it it 2.91 0.430 it 723 Toluene II tt 2.92 0.432 ti 724 II ti ti 2.96 0.437 ti 725 II 4.44 3.39 5.40 1.59 II 726 II it it 5.54 1.63 it 727 Toluene-dQ II o it ti 5.25 1.55 it 723 it ti 5.55 1.64 it 729 Toluene-a-d« it it 5.25 1.55 it 730 II 3 ti it 5.23 1.54 it 731 Toluene 5.28 1.69 21.0 12.4 ti 732 II tt tt 20.8 12.3 ti 733 Toluene-a-d„ ti it 19.0 11.2 it 734 II 3 it tt 19.1 11.3 it 735 Toluene-dQ II o it it 20.2 12.0 ti 736 it ti 20.2 12.0 it 737 Toluene 4.47 6.775 15.5 2.28 II 738 II ti it 15.2 2.24 ti 739 II DoO tt it 31.7 4.69 ' it 740 II n it it 31.1 4.59 it 741 Toluene 37.4° 5.17 1.694 22.4 13.2 ti 742 II it it ti 22.0 13.0 it 743 it 31.5° ti 4.234 43.4 10.3 it 744 it 20.0° ti it 28.0 6.59 it 745 II 25.0° it 1.694 16.1 9.47 tt 746 it ' tt II ti 16.5 9.74 ti 747 tt 14.0° it 3.388 19.4 5.73 ti 748 tt it it II 20.1 5.93 it 749 it 37.4° 2.52 4.234 0.821 0.194 tt 750 ti 31.6° ti it 0.646 0.153 it 751 ti 25.0° n 5.081 0.462 0.0910 it 752 it 19.9° •t 4.234 0.231 0.0545 ti 753 it 14.1° II 5.081 0.230 0.0453 it 754 Toluene 3.18 4.23 1.73 0.408 it 755 it it ti 1.90 0.448 ti 756 Ethylbenzene it 3.67 2.35 0.640 II 757 II ti it 2.29 0.655 it 758 Cumene it 1.94 1.19 0.611 II 759 it it ti 1.28 0.659 ti 760 t-Butylbenzene tt 1.74 0.786 0.452 it 761 tt ti it 0.799 0.459 it 762 Toluene 5.39 4.23 85.3 20.2 ti 763 tt 5.39 ti 95.6 22.6 it 764 Ethylbenzene II 2.20 74.5 33.9 ti 765 ti it II 70.0 31.8 ti - 204 -APPENDIX C 3 3-1 -1-1 No. Substrate -H^ [S]xl0 k^ lO s k2M s 766 Cumene 5.39 767 768 t-Butylbenzene " 769 770 Methanol 6.34 771 772 773 774 Methanol 15 min 6.34 775 " 45 min 776 " 75 min 777 " 7 min 778 " 30 min " 779 11 60 min " 780 Methanol 5.64 781 782 " 4.08 783 " 5.01 784 785 " 3.26 786 787 " 6.15 788 789 " 6.84 790 791 Methanol 37.4° 3.18 792 " 31 .6° 793 " 25.0° " 794 " 19.8° " 795 " 14 .1° " 796 Methanol-d4 4.38 797 Methanol " 798 " 7.10 799 Methanol-d, " 800 Methanol 6.09 801 Methanol-d 802 " 5.01 803 Methanol " 804 Methanol-d, 3.76 805 Methanol " 806 " 6.59 807 Methanol-d, " 808 Methanol 5.01 809 810 " D20 " 811 " " 812 Methanol 0.019 MP 5.44 1.94 63.7 32.8 .999 ir 65.8 33.9 it 1.74 50.8 29.2 II ti 52.4 30.1 tt 8.233 28.9 3.51 it 16.47 53.2 3.23 ti 24.70 73.9 2.99 ti 32.93 90.0 2.73 it 164.7 76.2 0.463 it II 38.2 0.232 ti II 21.0 0.127 it 82.33 53.2 0.646 ti II 30.3 0.368 II it 16.7 0.203 II 16.47 11.3 0.683 II ti 11.0 0.668 it 41.17 2.24 0.0545 II 41.17 8.03 0.195 it it 8.33 0.202 it 82.33 1.87 0.0227 ti 41.17 1.03 0.0249- II 8.233 22.3 2.71 it it 19.6 2.38 •t 8.233 90.7 11.0 ti ti 80.5 9.78 II 200.1 9.48 0.0474 it it 7.17 0.0359 it •t 3.80 0.0190 ti it 2.99 0.0149 it ti 1.77 0.00886 it 88.92 0.891 0.0100 ti 44.46 3.68 0.0828 II 4.446 72.1 16.2 it 8.892 21.2 2.38 it 11.13 22.6 2.03 it 22.23 4.46 0.201 ti 44.46 1.24 0.0278 ti 22.23 4.23 0.190 it 200.1 0.451 0.00225 it 100.5 2.35 0.0234 ti 11.12 56.3 5.06 ti 22.23 12.5 0.559 n 35.57 5.87 0.165 it it 6.70 0.188 it II 7.33 0.206 ti II 7.06 0.199 ti 66.99 33.2 0.499 II - 205 -APPENDIX C No. Substrate —H [S]xl0 3 k,xl0 3s 1 k„M Xs 1 R J. L 813 Methanol 0.019 MP 5.44 66.99 31.7 0.475 814 0.05 MP II n 32.1 0.481 815 II it II II 35.3 0.530 816 0.026 MP 5.40 it 32.2 0.483 817 II it II II 35.7 0.535 818 0.36 STFA 5.38 II 31.1 0.466 819 ti II it II 28.3 0.425 820 0.07 STFA 5.44 it 27.1 0.406 821 II II II it 29.1 0.436 822 " 0.28 STFA 5.40 II 31.3 0.470 823 II it II II 32.9 0.493 824 2-Pentanol 3.26 30.64 1.73 0.0563 825 it it 1.71 0.0557 826 5.01 II 7.57 0.247 827 5.64 12.26 7.39 0.603 828 II 9.192 5.51 0.599 829 ti 6.128 3.84 0.627 830 II 3.064 2.15 0.700 831 4.08 30.64 2.96 0.0967 832 it II 2.90 0.0947 833 6.15 6.128 9.77 1.59 834 II II 10.2 1.67 835 6.84 3.064 18.1 5.91 836 tt •t 17.7 5.77 837 3-Pentanol 3.26 30.83 1.90 0.0617 838 II ti 1.83 0.0594 839 5.64 12.33 7.62 0.618 840 it 9.250 5.72 0.618 841 II 6.167 3.85 0.625 842 it 3.083 2.05 0.664 843 4.08 30.83 3.11 0.101 844 II II 3.19 0.104 845 5.01 30.83 7.83 0.254 846 " it II 8.00 0.260 847 6.15 6.167 10.2 1.65 848 6.84 3.083 17.6 5.70 849 II II 18.3 5.95 850 38.1° 5.84 6.66 8.69 1.30 851 II ti II 9.48 1.42 852 31.0° II 8.33 8.24 0.990 853 " 19.5° it ti 6.00 0.720 854 25.0° II it 6.61 0.793 855 it ti II 6.91 0.830 856 14.0° ti ti 3.52 0.422 857 II II II II 3.39 0.407 .999 - 206 -APPENDIX C No. Substrate -IL [S]xl0 k.xlO s k„M s r 858 Cyclohexanol 5.64 3.203 2.76 0.860 859 II 6.406 5.58 0.871 860 II 9.609 8.49 0.883 861 II 12.81 11.1 0.866 862 4.08 1 6 . 0 1 2.52 0.157 863 it it 2.44 0.152 864 5.01 it 6.25 0.391 865 it it 6.59 0.411 866 6.15 6.406 15.3 2.39 867 ti ti 15.2 2.37 868 6.84 3.203 27.7 8.65 869 38.0° 5.40 10.38 9.69 0.933 870 38.2° it II 8.98 0.865 871 3 0 . 9 ° it 17.30 13.6 0.784 872 19.4° ti II 9.37 0.542 873 " 2 5 . 0 ° it II 10.9 0.632 874 2 4 . 9 ° •t II 10.5 0.606 8 7 5 1 3 . 8 ° II ti 5.36 0.310 876 1 4 . 0 ° II II 5.22 0.302 877 Benzyl, alcohol 2.90 8.67 3.34 0.386 878 2.76 6.94 3.04 0.438 879 tt it 3.01 0.433 880 1.00 20.81 5.85 0.281 881 tt ti 5.81 0.279 882 1.81 it 6.57 0.316 883 II it 6.67 0.321 884 3.28 8.671 4.35 0.502 885 it 6.243 3.37 0.539 886 II 4.162 2.16 0.519 887 II 2.081 1.04 0.499 888 £-Nitro B.Alc. it 4.756 0.589 0.124 889 m-Nitro B.Alc. II 1 2 . 5 6 1.46 0.117 890 II it II 1.44 0.114 891 Benzyl alcohol 2.87 10. 4 1 4.24 0.408 892 II II II 4.14 0.398 893 Benzyl alcohol DJJO II it 5.69 0.547 894 it II II 6.05 0.581 895 II 2.33 34.69 14.5 0.419 896 II II II 15.5 0.446 897 II 2.79 17.34 7.70 0.444 898 II II II 8.00 0.461 899 it 3.20 II 9.27 0.535 9 0 0 it II II 9.53 0.549 901 ti 3.60 II 11.4 0.658 902 II II ti 11.9 0.685 903 it 4.09 it 15.4 0.885 - 207 -APPENDIX C No. Substrate [S]xl03 k 1xl0 3s 1 k2M s r 904 Benzyl alcohol 4.09 17.34 15.5 0.893 .999 905 II 4.50 13.87 17.0 1.22 II 906 II it II 17.6 1.22 it 907 II 4.94 10.41 21.5 2.07 II 908 it ti it 22.0 2.11 II 909 II 5.40 II 38.8 3.73 II 910 tt it tt 40.7 3.91 it 911 it 5.74 3.47 22.9 6.59 II 912 ti II II 24.3 7.00 II 913 II 6.20 4.35 96.3 22.2 II 914 n tt II 95.6 22.0 . II 915 II 2.35 34.69 15.0 0.433 II 916 II it it 15.0 0.432 it 917 ti 1.71 II 12.8 0.370 tt 918 it ti II 13.0 0.375 ti 919 it 0.98 17.34 5.79 0.334 II 920 it it II 5.67 0.327 II 921 it 0.60 ti 5.04 0.291 tt 922 it 0.12 it 4.59 0.265 it 923 ti 37.5° 3.58 27.66 25.5 0.921 tt 924 II •t it it 27.5 0.994 ti 925 II 31.4° it 25.94 18.3 0.705 II 926 it 20.0° it II 10.8 0.417 it 927 II 25.0° II 34.55 19.0 0.550 II 928 II tt it it 19.2 0.555 it 929 ti 14.1° it II 10.4 0.301 ti 930 it 14.1° ti it 10.1 0.293 II 931 it 37.4° 6.72 0.9104 60.9 66.9 II 932 II 31.4° II 0.867 63.9 73.7 it 933 it 25 . 0 ° II 1.734 125.0 72.0 II 934 II it ti II 119.0 68.8 it 935 ti 20.0° II 0.867 31.1 35.9 II 936 II 14.0° II 1.734 54.9 31.7 II 937 II II II II 49.8 28.7 tt 938 II 4.41 II 15.3 0.879 II 939 it / II II 15.3 0.880 II 940 Benzyl alcohol-cv "d2 0.84 21.28 2.07 0.0969 II 941 ti it II 1.96 0.0919 it 942 Benzyl alcohol ti 21.68 3.92 0.181 it 943 n II it 4.90 0.226 it 944 Benzyl alcohol D20 9.90 it 5.66 0.261 tt 945 it ti tt II 6.01 0.277 II 946 Benzyl alcohol-a-d?} tt 21.28 3.63 0.171 tt DoO 947 II ft II II 3.58 0.168 it 948 Benzyl a lcohol-«-d2 2.76 34.06 12.0 0.353 ii - 208 -APPENDIX C 3 3-1 -1 -1 No. Substrate -H^ [S]xl0 k-jXlO s k^ M s 949 Benzyl alcohol-a-d2 2.76 34.06 12.3 0.361 .999 950 Benzyl alcohol 11 34.69 13.3 0.384 ti 951 II it 11 14.9 0.430 11 952 II 2.86 it 16.7 0.482 it 953 tt ti it 17.0 0.491 11 954 Benzyl alcohol-a-d_, tt 34.06 18.9 0.555 11 955 ti it 11 19.2 0.565 11 956 Benzyl a lcohol-a-d„ 0.12 21.28 1.12 0.0528 tt 957 it Z tt 11 1.10 0.0515 11 958 Benzyl alcohol it 21.68 4.08 0.188 11 959 ti 11 •t 3.74 0.173 it 960 tt Y ti 11 5.08 0.234 11 961 II 11 11 4.87 0.225 11 962 Benzyl alcohol-a-d2> 11 21.28 1.84 0.0867 it D20 11 963 tt ti it it 1.91 0.0899 964 Benzyl alcohol-0t-do 6.48 4.26 222.0 52.2 11 965 ti z tt 11 218.0 51.2 11 966 Benzyl alcohol it 4.34 223.0 51.5 tt 967 II ti 11 221.0 50.9 it 968 tt D2O 6.44 0.867 48.1 55.5 it 969 II tt 11 it 50.0 57.6 ti 970 Benzyl alcohol-a-d2, it 0.851 41.9 49.2 11 D20 it 971 II 11 it 11 43.1 50.7 972 Benzyl alcohol-a-d2 7.24 tt 198.0 233.0 it 973 II ti tt 189.0 222.0 it 974 Benzyl alcohol tt 0.867 241.0 278.0 ti 975 •t tt ti 259.0 298.0 ti 976 ti D20 7.18 ti 239.0 276.0 11 977 ti 11 tt 11 238.0 275.0 11 978 Benzyl alcohol-ot-d-, 11 0.851 216.0 254.0 tt 979 ii it 11 210.0 247.0 11 980 Benzyl a lcohol-a-d„ 4.40 11 10.2 1.20 11 981 it - z ti 11 10.1 1.19 it 982 Benzyl alcohol 11 0.867 9.44 1.09 it 983 ti it 11 9.42 1.09 11 984 it D20 4.34 it 10.3 1.19 11 985 it it 11 " 10.1 1.17 it 986 Benzyl alcohol-a-d2, tt 0.851 10.8 1.27 11 D20 11 987 it 11 it 11 11.1 1.30 - 209 -APPENDIX C r -, 3 ,~3 -1 -1 -1 No. Substrate [S]xlO 1^ x10 s k2M s r 988 1-Phenylethanol II 1.85 11.26 5.50 0.489 .999 989 4.84 7.507 12.6 1.68 " 990 II 2.82 3.754 1.47 0.393 991 ir 4.16 3.754 3.09 0.823 992 it ti 15.02 12.6 0.839 993 II II 11.26 8.88 0.789 994 it it 7.507 5.66 0.754 995 2-Phenylethanol it 4.10 7.535 6.07 0.805 " 996 ti 11.30 9.15 0.810 997 ti it 15.07 12.9 0.856 " 998 it 1.85 15.07 1.57 0.104 .998 999 II 4.84 7.535 16.1 2.14 .999 1000 tt 4.16 n 8.38 1.11 1001 it 5.70 15.07 116.0 7.67 " 1002 ti it it 131.0 8.69 1003 tt 2.82 tt 5.29 0.351 1004 Acetone 8.76 61.27 1.12 0.0183 1005 II 6.66 ti 0.162 0.00264 .992 1006 tt 7.42 it 0.360 0.00588 .998 1007 II 5.64 II 0.0384 0.000627 .842 1008 ti 9.42 ti 3.52 0.0574 .996 1009 it 8.64 133.5 2.20 0.0165 .995 1010 it it 264.4 3.53 0.0133 .999 1011 ti ti 392.8 6.56 0.0167 it 1012 it ti 328.9 5.06 0.0154 it 1013 tt 9.68 53.71 2.58 0.0480 .997 1014 II II 133.5 6.25 0.0468 ti 1015 it II 212.3 13.1 0.0615 it 1016 tt II 264.4 14.1 0.0533 .983 1017 2-Pentanone 8.76 22.07 16.0 0.726 .999 1018 ti it 30.90 24.2 0.783 " 1019 ti II 44.14 33.0 0.748 1020 it 6.66 ' 33.95 1.04 0.0307 1021 it 7.42 42.45 3.85 0.0908 " 1022 it 5.64 it 0.528 0.0124 1023 tt 9.42 8.49 28.7 3.38 " 1024 II 38.2° 8.86 10.19 25.1 2.47 1025 tt II it II 34.6 3.39 1026 it 31.2" it 12.73 16.5 1.30 1027 II 19.5° ti 16.98 16.1 0.946 " 1028 tt 25.0° tt it 19.1 1.12 1029 II tt tt tt 21.8 1.28 1030 ti 13.9° ti it 9.93 0.585 " 1031 it 14.0° ti ti 12.0 0.704 1032 6.33 33.96 2.02 0.0594 - 210 -APPENDIX C No. Substrate -H_ [SjxlO3 k , x l 0 3 s 1 k - M ^ s - 1 r K 1 2. 1 0 3 3 2-Pentanone 6 . 3 3 3 3 . 9 6 1 . 8 3 0 . 0 5 3 8 . 9 9 9 1 0 3 4 7 . 4 0 11 3 . 3 5 0 . 0 9 8 5 1 0 3 5 " 8 . 0 4 11 1 3 . 2 0 . 3 8 7 1 0 3 6 " 11 2 4 . 4 5 6 . 4 9 0 . 2 6 6 1 0 3 7 11 11 7 . 0 9 0 . 2 9 0 " 1 0 3 8 11 1 6 . 3 0 4 . 0 4 0 . 2 4 8 1 0 3 9 " 11 1 0 . 8 7 2 . 4 5 0 . 2 2 5 1 0 4 0 " 8 . 9 2 1 0 . 1 9 1 0 . 3 1 . 0 1 1 0 4 1 ti tt 9 . 5 9 0 . 9 4 1 1 0 4 2 " 6 . 7 0 5 0 . 6 3 1 . 2 8 0 . 0 2 5 3 1 0 4 3 " 11 it 1 . 2 7 0 . 0 2 5 1 " 1 0 4 4 " 7 . 9 0 8 . 4 9 1 . 6 1 0 . 1 8 9 " 1 0 4 5 11 ti 1 . 4 8 0 . 1 7 4 . 9 9 5 1 0 4 6 7 . 4 1 8 4 . 0 5 7 . 2 7 0 . 0 8 6 4 . 9 9 9 1 0 4 7 11 11 6 . 6 5 0 . 0 7 9 1 1 0 4 8 " 11 6 7 . 3 8 5 . 5 1 0 . 0 8 1 7 1 0 4 9 " 11 it 5 . 5 6 0 . 0 8 2 5 1 0 5 0 " 11 3 3 . 9 6 3 . 0 4 0 . 0 8 9 6 0 . 0 9 0 3 1 0 5 1 " it 11 3 . 0 7 1 0 5 2 " 11 1 6 . 9 8 1 . 5 4 0 . 0 9 0 4 1 0 5 3 ti it 1 . 4 9 0 . 0 8 7 9 11 1 0 5 4 Cyclohexanone 6 . 9 0 1 8 . 3 0 1 6 . 1 0 . 8 8 0 1 0 5 5 " 6 . 2 4 ti 7 . 8 5 0 . 4 2 9 1 0 5 6 " 11 11 7 . 9 9 0 . 4 3 7 1 0 5 7 " 5 . 6 4 3 6 . 6 0 1 1 . 5 0 . 3 1 5 1 0 5 8 " it 2 6 . 3 5 8 . 2 7 0 . 3 1 4 1 0 5 9 it 11 7 . 3 4 0 . 2 7 9 1 0 6 0 " 11 1 7 . 5 7 5 . 0 4 0 . 2 8 7 " 1 0 6 1 tt 1 1 . 7 1 3 . 3 6 0 . 2 8 7 " 1 0 6 2 " 5 . 1 6 3 6 . 6 0 8 . 1 8 0 . 2 2 3 1 0 6 3 " 11 11 8 . 5 5 0 . 2 3 4 " 1 0 6 4 " D2O 8 . 0 7 1 0 . 0 7 3 5 . 3 3 . 5 0 . 9 9 6 1 0 6 5 3 8 . 0 ° 6 . 3 4 1 0 . 9 8 1 4 . 0 1 . 2 7 . 9 9 9 1 0 6 6 " 3 8 . 2 ° 11 11 1 3 . 4 1 . 2 2 1 0 6 7 3 1 . 1 ° 11 1 8 . 3 0 1 5 . 0 0 . 8 2 0 1 0 6 8 " 1 9 . 4 ° 11 11 7 . 4 0 0 . 4 0 4 1 0 6 9 2 4 . 9 ° n 11 1 0 . 5 0 . 5 7 1 1 0 7 0 " 2 5 . 1 ° 11 11 1 0 . 3 0 . 5 6 5 1 0 7 1 1 1 1 4 . 0 ° 11 it 4 . 3 6 0 . 2 3 8 1 0 7 2 11 11 11 4 . 3 9 0 . 2 4 0 1 0 7 3 " 7 . 4 1 11 4 9 . 7 2 . 7 2 . 9 9 7 1 0 7 4 "•• 11 11 4 9 . 8 2 . 7 2 . 9 9 9 1 0 7 5 Benzophenone 6 . 6 6 1 4 . 7 7 5 . 4 6 0 . 3 7 0 . 9 8 5 1 0 7 6 n • 3 . 3 2 0 . 8 3 6 0 . 2 5 2 . 9 9 5 1 0 7 7 7 . 4 2 1 8 . 0 1 3 2 . 5 1 . 8 0 . 9 9 2 - 211 -APPENDIX C No. Substrate " HR [S]xl03 k 1xl0 3s 1 k2M s r 1078 Benzophenone 7.42 12.61 21.6 1.71 .994 1079 it 6.30 11.0 1.74 .991 1080 it it 9.01 13.5 1.50 .993 1081 Trifluoroaceto- 5.66 13.45 7.49 0.557 .998 phenone 1082 ti 6.62 II 43.0 3.20 II 108e II II ti 45.6 3.39 .999 1084 II 6.74 20.17 76.7 3.80 .996 1085 II 5.92 13.45 12.9 0.962 .997 1086 it it ti 11.0 0.815 .995 1087 II II 6.72 5.60 0.833 .999 1088 II II it 6.13 0.912 it 1089 it II 3.36 2.40 0.714 it 1090 it tt ti 2.70 0.803 it 1091 Formaldehyde 4.98 1.83 70.8 38.7 tt 1092 II tt II 73.5 40.2 .998 1093 II 3.00 9.14 63.3 6.92 .999 1094 II tt 6.58 47.0 7.15 1095 it tt tt 45.2 6.87 1096 it II 4.39 29.2 6.65 1097 II it ti 31.2 7.10 1098 it II 2.92 20.0 6.83 1099 it II it 20.3 6.96 1100 it 4.16 3.65 62.9 17.2 1101 it II it 67.8 18.6 1102 it 2.04 7.30 26.1 3.57 1103 it II II 25.8 3.53 1104 II .1.03 10.90 15.3 1.40 " 1105 II tt it 15.9 1.45 1106 Benzaldehyde 2.90 8.830 18.2 2.07 1107 tt 2.76 3.534 7.39 2.09 " 1108 tt II ti 7.34 2.08 .994 1109 II 1.00 10.60 1.91 1.81 - .992 1110 II II II 1.99 1.88 .999 1111 j3-Chloro B.ald. 2.16 1.606 1.63 1.02 1112 jj-Nitro B.ald. II 2.105 1.90 0.901 1113 Benzaldehyde it 1.699 3.53 2.08 1114 it it II 3.40 2.00 " 1115 m-Methyl B.ald. 2.16 1.468 2.20 1.50 1116 n II II 2.50 1.71 " 1117 Benzaldehyde 3.28 1.767 4.10 2.32 .996 1118 tt tt tt 4.22 2.39 .997 1119 it 1.86 16.67 28.4 1.71 .999 1120 it tt 12.72 23.0 1.81 .997 1121 tt ti ti 23.1 1.82 .999 - 212 -APPENDIX C No. Substrate [S]xl03 k 1xl0 3s~ 1 , -1 -1 k^ M s r 1122 Benzaldehyde 1.86 8.482 13.8 1.62 .997 1123 11 11 14.2 1.68 .999 1124 11 4.241 7.35 1.73 11 1125 ti it 7.44 1.76 .997 1126 1.86 10.60 20.1 1.89 .999 1127 11 11 20.4 1.92 it 1128 D2O it 7.066 20.4 2.89 .997 1129 11 tt it 20.1 2.84 11 1130 2.33 3.53 7.71 2.19 .998 1131 11 11 7.92 2.25 .999 1132 2.79 11 8.00 2.27 11 1133 11 11 8.10 2.29 it 1134 3.20 3.53 8.78 2.49 .996 1135 11 it 8.93 2.53 it 1136 3.60 3.53 9.60 2.72 ti 1137 ti it 9.88 2.80 11 1138 " 4.09 11 10.5 2.99 .997 1139 11 n 10.7 3.02 it 1140 4.50 11 11.5 3.26 .998 1141 it 11 11.7 3.30 11 1142 4.94 11 15.9 4.52 .997 1143 it 11 15.7 4.44 11 1144 5.40 tt 18.3 5.19 .996 1145 11 it 18.6 5.26 .995 1146 5.75 11 24.1 6.83 .997 1147 it 11 25.0 7.08 11 1148 6.20 4.42 59.9 13.5 .999 1149 II 11 11 56.1 12.7 11 1150 2.35 7.07 16.2 2.29 .997 1151 tt 11 16.6 2.34 .996 1152 1.71 6.71 13.1 1.95 .997 1153 it it 12.6 1.88 11 1154 0.9 8 7.07 15.1 2.13 tt 1155 11 11 15.4 2.17 11 1156 0.60 tt 14.8 2.10 it 1157 " ti 11 13.6 1.93 .999 1158 0.12 11 13.7 1.94 .997 1159 it it 13.6 1.93 .998 1160 6.34 1.77 32.1 18.2 .997 1161 11 11 32.7 18.5 11 1162 7.62 11 54.7 30.9 .999 1163 11 11 55.9 31.6 11 1164 no TFA 7.07 1.26 0.178 .997 1165 Formic acid 4.98 23.9 0.179 0.00747 .980 1166 5.70 46.75 0.387 0.00828 .999 1167 8.42 46.70 27.8 0.582 it - 213 -APPENDIX C N o . S u b s t r a t e ~\ [ S ] x l 03 k 1 x l 0 3 s ~ 1 k 2 M " 1 s " 1 r 1168 F o r m i c a c i d 8 . 4 2 4 6 . 7 0 2 9 . 0 0 . 6 0 7 .999 1169 tt 6 . 2 6 6 8 . 4 2 2 . 1 9 0 . 0 3 1 9 11 1170 it ti 9 5 . 0 3 2 . 9 8 0 . 0 3 1 4 it 1171 ti it 4 5 . 6 1 1 ,37 0 . 0 2 9 9 it 1172 it it 3 0 . 4 1 0 . 8 9 8 0 . 0 2 9 5 11 1173 it 8 . 5 0 1 1 9 . 3 8 2 . 9 0 . 6 9 5 11 1174 it 11 n 7 9 . 5 0 . 6 6 6 . 9 9 8 1175 3 - P e n t a n o n e 6 . 9 0 2 5 . 5 8 3 . 5 5 0 . 1 3 9 . 9 9 3 1176 ti 11 11 3 . 7 3 0 . 1 4 6 it 1177 it 7 . 9 0 8 . 5 3 4 . 2 3 0 . 4 9 6 . 9 9 1 1178 it it tt 3 . 7 1 0 . 4 3 5 11 1179 ti 7 . 4 1 2 9 . 8 4 1 7 . 4 0 . 5 8 2 . 9 9 9 1180 ti ti ti 1 7 . 4 0 . 5 8 4 it 1181 II 11 2 0 . 4 6 9.68 0 . 4 7 3 11 1182 II 11 11 9 . 8 3 0 . 4 8 0 11 1183 it 11 1 7 . 9 0 7 . 8 0 0 . 4 3 6 11 1184 II tt 11 8 . 0 3 0 . 4 4 8 11 1185 it tt 8 . 5 3 2 . 4 3 0 . 2 8 5 . 9 9 2 1186 tt 11 it 2 . 5 7 0 . 3 0 1 . 9 9 3 1187 ti 1 4 . 6 ° 7 . 9 0 1 7 . 0 5 9 . 9 4 0 . 5 8 3 .994 1188 ti 1 4 . 8 ° it 11 9 . 6 3 0 . 5 6 5 11 1189 it 2 0 . 6 ° 11 11 1 1 . 9 0 . 6 9 8 tt 1190 it .. it 11 11 1 2 . 4 0 . 7 2 8 ti 1191 tt 3 0 . 2 ° tt 11 1 5 . 9 0 . 9 3 0 .997 1192 ti ti 11 it 1 6 . 7 0 . 9 7 9 it 1193 II 3 7 . 6 ° ti tt 2 2 . 3 1 .31 11 1194 it 3 7 . 4 ° it 11 2 1 . 3 1 .25 . 9 9 8 1195 it 2 5 . 0 ° 11 11 1 4 . 0 0 . 8 1 9 .997 1196 it it 11 it 1 3 . 8 0 . 8 1 2 . 996 1197 B e n z e n e , D2O 6 . 9 6 5 . 0 1 3 1 3 9 . 0 2 7 . 7 .999 1198 tt 11 11 tt 1 4 7 . 0 2 9 . 3 11 1199 ti H 2 0 11 tt 1 4 0 . 0 2 8 . 0 11 1200 it it 11 ti 1 3 3 . 0 2 6 . 5 11 1201 it D2O 6 . 1 5 11 1 5 . 1 3 . 0 1 . 9 9 8 1202 ti it 11 11 1 5 . 3 3 . 0 6 it 1203 tt H 2 0 6 . 2 6 tt 1 3 . 9 2 . 7 6 11 1204 ti 11 it 11 1 3 . 7 2 . 7 4 . 9 9 7 1205 tt D 2 0 5 . 6 7 2 0 . 5 0 1 1 . 6 0 . 5 6 5 . 9 9 9 1206 II 11 11 11 1 1 . 2 0 . 5 4 5 .994 1207 ti H2O 5 . 6 4 11 9 . 8 9 0 . 4 8 2 .997 1208 tt it 11 11 9 . 7 0 0 . 4 7 3 . 9 9 5 1209 C y c l o h e x a n e , D20 6 . 1 5 3 3 . 3 2 7 .84 0 . 2 3 5 . 9 9 9 1210 ti 11 it it 7 . 7 8 0 . 2 3 4 it 1211 it H2O 6 . 2 6 11 7 . 0 8 0 . 2 1 2 11 1212 ti tt 11 11 6 . 8 4 0 . 2 0 5 it - 214 -APPENDIX C No. Substrate -H [S]xlO k xlO s k M s r 1213 Cyclohexane, H20 ti 6.98 16.66 27.5 1.65 .999 1214 " ti it 28.9 1.72 II 1215 D20 6.96 it 25.9 1.55 II 1216 tt II II 25.2 1.51 it 1306 TFAD, D g 0 6.10 11.66 0.00683 0.585 it 1307 it II 7.48 8.33 0.140 16.8 .997 No. Substrate "HR [S]xl03 k-jXlO^ s * k^xlO^s -1 r 1217 2,4-Pentanedione 1.02 1.75 172.0 984.0 .998 1218 1.02 II 172.0 983.0 II 1219 " 2.86 II 254.0 145.0 .997 1220 II II 242.0 138.0 II 1221 -0.05 3.50 246.0 703.0 .979 1222 " II II 245.0 700.0 .996 1223 -0.41 1.68 116.0 691.0 .999 1224 II II 117.0 698.0 .996 1225 it 2.52 172.0 701.0 II 1226 tt II 176.0 697.0 .995 1227 it 3.78 259.0 684.0 .991 1228 it it 270.0 714.0 .996 1229 it ti 5.24 337.0 643.0 .999 1230 3-Pentanone 6.70 25.58 5.04 1.97 .995 1231 II II 5.08 1.98 .994 1232 7.90 8.53 8.23 9.65 .978 1233 it it 6.91 8.10 .991 1234 " 7.41 29.84 26.2 8.78 .981 1235 ti II 25.9 8.67 .979 1236 " II 20.46 13.7 6.71 .973 1237 II II 13.5 6.62 .971 1238 it 17.90 10.9 6.08 .975 1239 " II II 10.4 5.81 .978 1240 ti II 8.53 4.58 5.37 .975 1241 it it 5.06 5.93 .978 1242 14.6° 7.90 17.05 17.6 10.3 .981 1243 14.8° ti ti 16.2 9.50 .985 1244 " 20.6° II II 18.7 11.0 .979 1245 II n II 18.2 10.7 .984 1246 30.2° II II 20.2 11.9 .97.8 1247 " II II ti 19.9 11.7 it 1248 37.6° II it 23.8 13.9 .969 - 215 -APPENDIX C No. Substrate [S]xl03 k1xl07Ms 1 k 2 xl0 5 s _ : L r 1249 3-Pentanone 37.4° 7.90 17.05 22.7 13.3 .969 1250 " 25.0° ti ti 18.8 11.0 .980 1251 " II II ti 1.8.5 10.8 it 1252 Acetophenone 5.66 23.10 1.53 0.660 .999 1253 " tt it 1.74 0.759 .997 1254 " 6.62 15.40 5.47 3.55 .999 1255 6.62 tt 5.43 3.53 ti 1256 " 6.74 23.10 9.38 4.06 it 1257 ti ti 8.84 3.83 .994 1258 " II 7.70 3.38 4.38 .999 1259 " it it 3.21 4.16 ti 1260 " II 15.40 6.02 3.91 it 1261 " it it 6.24 4.05 it 1262 " it 38.51 15.2 3.95 .996 1263 " II ti 14.8 3.85 .997 1264 " 5.92 23.10 2.08 0.898 .999 1265 it it 2.18 0.942 1266 " 25.0° 6.41 15.40 3.32 2.16 1267 " it it ti 3.37 2.19 1268 37.6° ti 30.80 12.4 4.02 1269 37.4° ti it 11.5 3.75 1270 " 30.2° tt it 8.75 2.84 1271 ti it it 8.78 2.85 1272 20.6° ti II 5.08 1.65 1273 " it ti II 5.21 1.69 1274 " 14.7° it •t 3.96 1.29 1275 " 14.8° it II 3.85 1.25 " - 216 -APPENDIX D a Permanganate in Benzene No. Substrate [S]xl0 3 k 1 x l 0 3 s " 1 1 w~" 1 -1 k2M s r 1276 trans-Stilbene 2.27 1.020 0.449 .999 1277 II 3.72 1.641 0.441 1278 II II 1.612 0.433 " 1279 II 2.27 1.037 0.457 1280 II 1.29 0.591 0.458 1281 II II 0.611 0.474 1282 cis-Stilbene 4.32 0.4065 0.0941 1283 II II 0.4028 0.0932 1284 II 3.59 0.3065 0.0854 1285 II II 0.3129 0.0872 1286 II 0.884 0.0842 0.0953 1287 trans-Stilbene 3.72 1.616 0.434 1288 II II 1.650 0.444 1289 Tolan 41.56 0.3257 0.00784 1290 II II 0.3666 0.00882 1291 p ,p 1-Dinitro-trans- 0.353 84.90 240.5 .980 stilbene 1292 it II 61.99 175.6 .998 1293 m,p'-Dinitro-trans- 0.128 14.62 114.2 II stilbene 1294 ti : II 12.55 98.05 .999 1295 p-Nitrb-trans-stilbene 1.687 16.61 9.84 1296 II II 16.51 9.79 1297 II 1.012 11.51 11.4 1298 tt II 11.12 11.0 1299 Benzyl alcohol 5.4776 0.661 0.121 1300 II it 0.772 0.141 1301 Benzaldehyde ^ 4.542 8.01 1.764 1302 j>-Nitrobenzyl alcohol 0.716 31.2 43.5 .910 1303 II * II 15.9 22.2 .960 1304 p_-Nitrobenzaldehyde 1.679 15.2 9.05 .985 1305 II II 16.1 9.61 .999 A l l rates corrected for blank corrections. 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