CHEMICAL KINETICS

EDITED BY

C.H. BAMFORD

M.A., Ph.D., Sc.D. (Cantab.), F.R.I.C., F.R.S. Campbell-Brown Professor of Industrial Chemistry,

Uniuersity of Liverpool

AND

C.F.H. TIPPER

Ph.D. (Bristol), D.Sc. (Edinburgh) Senior Lecturer in Physical Chemistry,

University of Liverpool

VOLUME 16

LIQUID-PHASE OXIDATION

WSSSKUH

ELSEVIER SCIENTIFIC PUBLISHING COMPANY AMSTERDAM — OXFORD — NEW YORK

1980

Contents

Preface vii

Chapter 1 (T. Mill and D.G. Hendry)

Kinetics and mechanisms of free radical oxidation of alkanes and olefins in the liquid phase 1 1. Introduction 1 2. Historical basis of oxidation kinetics 1 3. The elementary rate steps in oxidation 3

3.1 Oxidation of cyclohexene. The hydroperoxide chain 3 3.2 Oxidation of styrene. The peroxy radical addition mechanism 5 3.3 The oxidation of isobutane. Competition among alkylperoxy and

alkoxy radical chains and olefin formation 6 3.4 Oxidation of cumene (isopropylbenzene). The role of alkoxy radicals . 8 3.5 n-Butane. Oxidation at secondary and primary C—H bonds 10 3.6 2,4-Dimethylpentane. Intramolecular oxidation 11

4. Elementary rate steps. Absolute rate coefficients 13 4.1 Measurement of absolute rate coefficients 13

4.1.1 Overall kinetics of oxygen consumption 14 4.1.2 Evaluation of ftt independent of kp 16 4.1.3 Measurement of kt and fep dependently 19 4.1.4 Evaluation of kp using added hydroperoxide 24

4.2 The reaction of carbon radicals with oxygen 25 4.2.1 Formation of peroxy radicals 25 4.2.2 Olefin formation 27

4.3 Propagation 32 4.3.1 Hydrogen atom transfer to R 0 2 ' radicals 32 4.3.2 Addition of RO2' radicals to carbon double bonds: formation of

di- and polyperoxides 40 4.3.3 Intramolecular H-atom transfer to peroxy radicals 42 4.3.4 Ring closures of peroxy radicals 45 4.3.5 H-Atom transfer to alkoxy radicals 47 4.3.6 Absolute rate coefficients and Parameters for C—C cleavage of

alkoxy radicals (RO') 52 4.3.7 Intramolecular H-atom transfer by RO* 53

4.4 Peroxy radical interactions 55 4.4.1 Chemistry of R02 - radical interactions 55 4.4.2 Structure—reactivity relationships in radical interactions 57 4.4.3 Thermochemistry of radical interactions 57 4.4.4 Absolute rate coefficients for termination 59

5. Special features of initiation 61 5.1 Autocatalysis 62

6. Co-oxidation 64 6.1 Kinetic relations 64

6.2 Reactivity ratios, rx and r2 67 6.3 Evaluation of the cross-termination parameter, 0 69

7. Inhibition of oxidation 70 7.1 Chemistry of inhibition 70 7.2 Kinetics of inhibition by phenols and amines 72 7.3 Rate coefficients and Parameters for inhibition 74 7.4 Synergetic effects of phenols 76 7.5 Inhibition by metal complexes , 77

8. Photooxidations involving singlet molecular oxygen ( ' 0 2 ) 77 8.1 Introduction 77 8.2 Chemistry of photooxidations with ' 0 2 78 8.3 Kinetic relations and rate coefficients 81

References 83

Chapter 2 (L. Sajus and I. Seree de Roch)

The liquid phase oxidation of aldehydes 89 1. Introduction 89

1.1 Analytical aspects 90 1.2 Operational techniques 90 1.3 Oxidation products 91

2. Oxidation of normal saturated aldehydes 94 2.1 Oxidation of n-decanal 94 2.2 Oxidation of acetaldehyde 96 2.3 Oxidation of heptaldehyde 101 2.4 Oxidation of n-butanal 102

3. Oxidation of unsaturated aldehydes 103 3.1 Oxidation of 2-butenal 103 3.2 Oxidation of acrolein and methacrolein 104

4. Oxidation of benzaldehyde 108 4.1 Autoxidation of benzaldehyde alone 108

4.1.1 Photochemical oxidation 108 4.1.2 Thermal oxidation 109 4.1.3 Catalytic oxidation 111

4.2 Co-oxidation of substituted benzaldehydes 112 4.3 Benzaldehyde—olefin co-oxidation in benzene Solution 113 4.4 Co-oxidation of benzaldehyde with cyclohexanone 115 4.5 Direct determination of kinetic coefficients 115

5. Catalytic aldehyde oxidation without a chain mechanism 118 6. Conclusions 118

References 122

Chapter 3 (E.T. Denisov)

The oxidation of alcohols, ketones, ethers, esters, and acids in Solution 125 1. Introduction 125 2. Oxidation of alcohols 125

2.1 The kinetics and products of alcohol oxidation 125 2.1.1 Primary alcohols 125 2.1.2 Secondary alcohols 126

2.2 Chain mechanism of alcohol oxidation 128 2.3 The formation of free radicals in alcohol oxidation 132

2.3.1 Generation of chains 132 2.3.2 Decomposition of hydrogen peroxide to free radicals 132 2.3.3 Mechanism of cyclohexanol oxidation 134

2.4 Photo-oxidation and radiation-induced oxidation of alcohols 135 2.4.1 Photo-oxidation 135 2.4.2 Radiation-induced oxidation 137 2.4.3 Oxidation with ozone 139

2.5 Inhibitors of alcohol oxidation 139 2.5.1 Mechanism of reaction of alcohol peroxy radicals with phenols

and aromatic amines 139 2.5.2 Regeneration of aromatic amines in alcohol oxidation 141 2.5.3 Inhibition of alcohol oxidation by quinones 143 2.5.4 Chemiluminescence in oxidations inhibited by aromatic amines

in the presence of alcohols 143 2.6 Negative catalysis in alcohol oxidation 145

2.6.1 Negative redox catalysis 145 2.6.2 Inhibition by bases 147

2.7 Catalysis in the oxidation of alcohols 148 2.7.1 Catalysis by transition metals 148 2.7.2 Catalysis by bromide ions 149 2.7.3 Catalysis by hydrogen ions 149 2.7.4 Oxidation of alcohols with palladium salts 151 2.7.5 Oxidation of alcohols in the presence of heterogeneous catalysts 151

2.8 Oxidation of alcohols in basic solvents 151 2.9 Co-oxidation of alcohols and aromatics 153

3. Oxidation of ketones 154 3.1 The products of ketone oxidation 154

3.1.1 Acetone 154 3.1.2 Methyl ethyl ketone and other aliphatic ketones 155 3.1.3 Cyclohexanone 155 3.1.4 Other ketones 156 3.1.5 a-Ketohydroperoxide 157 3.1.6 The formation of acids by the oxidation of ketones 157

3.2 Elementary Steps of ketone oxidation 158 3.2.1 Chain propagation 158 3.2.2 Chain termination 162 3.2.3 Generation of chains 163 3.2.4 Degenerate chain branching 163

3.3 Formation of free radicals by reactions of ketones with hydroperox-ides 164

3.4 Oxidation of ketones in the presence of acids and bases 167 3.5 Oxidation of ketones with ozone 168

4. Oxidation of ethers 169 4.1 Oxidation products 169

4.1.1 Aliphatic ethers 169 4.1.2 Cyclic ethers 170 4.1.3 Ethers of benzyl alcohol 170

4.2 The chain mechanism of ether oxidation 171 5. Oxidation of acids 173

5.1 Oxidative decarboxylation of acids 173 5.2 Oxidation of acids 175

ö. Oxidation of esters 177 6.1 The products of ester oxidation 177 6.2 The chain mechanism of ester oxidation 177

7. Oxidation of phenols 181 7.1 Oxidation of phenols in hydrocarbon Solutions 181

7.2 Oxidation of phenols in polar Solutions 182 7.3 Catalytic oxidation of phenols 183

8. The role of hydrogen bonds in oxidation 184 8.1 Hydrogen bonding and the formation of free radicals , 184 8.2 Formation of hydrogen bonds with and abstraction of hydrogen

atoms from O—H and N—H bonds 186 8.3 Hydrogen bonding with peroxy radicals 188

9. Reactions of peroxy radicals with polyfunctional molecules 191 References 195

Chapter 4 (D.L. Trimm)

The liquid phase oxidation of sulphur, nitrogen, and chlorine Compounds 205 1. Introduction 205 2. Autoxidation of organic Compounds containing nitrogen 205

2.1 Co-oxidation with hydrocarbons 205 2.1.1. Inhibition by complex formation 206 2.1.2. Inhibition by hydrogen abstraction 208

2.2 Factors affecting inhibitor efficiency 213 2.2.1 Electron-directing and steric effects: solvents 213 2.2.2 Oxidation—reduction Potentials 216

2.3 Autoxidation of nitrogen-containing Compounds 216 3. Autoxidation of organic Compounds containing sulphur 222

3.1 Co-oxidation with hydrocarbons 222 3.2 Autoxidation of sulphur-containing Substrates in the absence of other

hydrocarbon free radical chain reactions 228 3.3 Metal catalysis 231 3.4 Reactions of sulphoxide products 236

4. Autoxidation of organic Compounds containing chlorine 238 References 244

Index 249