Preface xi

1 Molecular Orbital Theory 1

1.1 The Atomic Orbitals of a Hydrogen Atom 1

1.2 Molecules made from Hydrogen Atoms 2

1.3 C-H and C-C Bonds 9

1.4 Conjugation-Hückel Theory 22

1.5 Aromaticity 32

1.6 Strained Bonds-Cyclopropanes and Cyclobutanes 39

1.7 Heteronuclear Bonds, C-M, C-X and C=O 42

1.8 The Tau Bond Model 52

1.9 Spectroscopic Methods 53

1.10 Exercises 57

2 The Structures of Organic Molecules 59

2.1 The Effects of Conjugation 59

2.2 Conjugation-Hyperconjugation 69

2.3 The Configurations and Conformations of Molecules 81

2.4 Other Noncovalent Interactions 90

2.5 Exercises 95

3 Chemical Reactions-How Far and How Fast 97

3.1 Factors Affecting the Position of an Equilibrium 97

3.2 The Principle of Hard and Soft Acids and Bases (hsab) 97

3.3 Transition Structures 103

3.4 The Perturbation Theory of Reactivity 104

3.5 The Salem-Klopman Equation 106

3.6 Hard and Soft Nucleophiles and Electrophiles 109

3.7 Other Factors Affecting Chemical Reactivity 110

4 Ionic Reactions-Reactivity 111

4.1 Single Electron Transfer (SET) in Ionic Reactions 111

4.2 Nucleophilicity 114

4.3 Ambident Nucleophiles 121

4.4 Electrophilicity 134

4.5 Ambident Electrophiles 137

4.6 Carbenes 147

4.7 Exercises 151

5 Ionic Reactions-Stereochemistry 153

5.1 The Stereochemistry of the Fundamental Organic Reactions 154

5.2 Diastereoselectivity 167

5.3 Exercises 183

6 Thermal Pericyclic Reactions 185

6.1 The Four Classes of Pericyclic Reactions 186

6.2 Evidence for the Concertedness of Bond Making and Breaking 188

6.3 Symmetry-Allowed and Symmetry-Forbidden Reactions 190

6.4 Explanations for the Woodward-Hoffmann Rules 214

6.5 Secondary Effects 221

6.6 Exercises 270

7 Radical Reactions 275

7.1 Nucleophilic and Electrophilic Radicals 275

7.2 The Abstraction of Hydrogen and Halogen Atoms 277

7.3 The Addition of Radicals to Bonds 279

7.4 Synthetic Applications of the Chemoselectivity of Radicals 286

7.5 Stereochemistry in some Radical Reactions 287

7.6 Ambident Radicals 290

7.7 Radical Coupling 295

7.8 Exercises 296

8 Photochemical Reactions 299

8.1 Photochemical Reactions in General 299

8.2 Photochemical Ionic Reactions 301

8.3 Photochemical Pericyclic Reactions and Related Stepwise Reactions 304

8.4 Photochemically Induced Radical Reactions 321

8.5 Chemiluminescence 323

8.6 Exercises 324

References 327

Index 331

Molecular Orbitals and Organic Chemical Reactions