ELECTRON FLOW IN ORGANIC CHEMISTR Y Paul H. Scudder
1 BONDING AND ELECTRON DISTRIBUTION 1 2 THE PROCESS OF BOND FORMATION 3 4 3 STABILITY AND REACTIVITY OF INTERMEDIATES 5 6 4 CLASSIFICATION OF ELECTRON SOURCES 7 7 5 CLASSIFICATION OF ELECTRON SINKS. 8 9 6 THE ELECTRON FLOW PATHWAYS 9 9 7 INTERACTION OF ELECTRON SOURCES AND SINKS 13 6 8 DECISIONS, DECISIONS 18 1 9 CHOOSING THE MOST PROBABLE PATH 19 4 10 ONE ELECTRON PROCESSES 24 1 APPENDIX 25 6 HINTS TO PROBLEMS FROM CHAPTERS 7, 8, AND 9 27 9 EXERCISE ANSWERS 28 1 INDEX 353
1 BONDING AND ELECTRON DISTRIBUTION 1 1.1 Introduction 2 1.2 Lewis Structures and Resonance Forms 3 1.3 Curved-Arrow Notation 7 1.4 Nomenclature and Abbreviations 10 1.5 Hybridization and Bonding 12 1.6 Orbital Interaction Diagrams (Supplemental) 1 9 1.7 Conjugation 22 1.8 Molecular Orbital Theory for Acyclic Systems (Supplemental) 24 1.9 Aromaticity, Cyclic Systems 28 2 THE PROCESS OF BOND FORMATION 3 4 2.1 Thermodynamics, Position of Equilibrium 3 5 2.2 Kinetics, Rate of Reaction 3 8 2.3 The Basics of Barriers 4 3 2.4 Orbital Overlap in Bond Formation 44 2.5 Microscopic Reversibility, Stereoelectronics 4 5 2.6 Steric Limitations 4 7 2.7 HOMO-LUMO Interactions 4 7 2.8 Hard and Soft Acid-Base Theory 4 9 2.9 Perturbation of the HOMO and LUMO (Supplemental) 5 2 3 STABILITY AND REACTIVITY OF INTERMEDIATES 5 6 3.1 Ion Stability, Solvation, and Media Effects 5 6 3.2 Ranking of Acids and Bases, the pka Chart 59 3.3 Calculation of Keq for Proton Transfer 6 1 3.4 Carbocation Stability and Trends 6 3 3.5 Ranking of Electron-Donor Groups 6 7 3.6 Carbanion Stability and Trends 68 3.7 Ranking of Electron-Withdrawing Groups 7 0 3.8 Ranking of Leaving Groups 7 1 3.9 The ApKa Rule 72 4 CLASSIFICATION OF ELECTRON SOURCES 7 7 4.1 Generalized Ranking of Electron Sources 7 7 4.2 Nonbonding Electrons 7 8 4.3 Electron-Rich Sigma Bonds 8 1 4.4 Electron-Rich Pi Bonds 8 2 4.5 Simple Pi Bonds 84 4.6 Aromatic Rings 85 4.7 Summary of Generic Electron Sources 86
5 CLASSIFICATION OF ELECTRON SINKS 8 9 5.1 Generalized Ranking of Electron Sinks 89 5.2 Electron-Deficient Species 90 5.3 Weak Single Bonds 9 1 5.4 Polarized Multiple Bonds Without Leaving Groups 92 5.5 Polarized Multiple Bonds With Leaving Groups 94 5.6 Summary of Generic Electron Sinks 96 6 THE ELECTRON FLOW PATHWAYS 9 9 6.1 The Dozen Most Common Pathways 100 6.2 Common Path Combinations 11 2 6.3 Eight Minor Pathways 11 5 6.4 Variations 124 6.5 Common Errors 126 6.6 Major Path Summary 132 7 INTERACTION OF ELECTRON SOURCES AND SINKS 13 6 7.1 Source and Sink Matrix 137 7.2 Detailed Matrix-Cell Discussions 138 7.3 Electrophilic Additions 157 7.4 Rearrangements with Loss of a Leaving Group 166 7.5 Nu-L Reactions 16 7 7.6 Fragmentations 170 7.7 Concerted Six-Electron Pericyclic Reactions 17 1 7.8 Miscellaneous Reactions 174 7.9 Product Matrix Summary 177 8 DECISIONS, DECISIONS 18 1 8.1 Decision Point Recognition 18 1 8.2 Multiple Additions 18 2 8.3 Ionization of Leaving Groups 18 3 8.4 Ambident Nucleophiles 18 3 8.5 Substitution vs. Elimination 186 8.6 Ambident Electrophiles 189 8.7 Intermolecular vs. Intramolecular 190 8.8 Kinetic vs. Thermodynamic Enolate Formation 19 1 9 CHOOSING THE MOST PROBABLE PATH 19 4 9.1 Problem-Solving in General 19 5 9.2 General Mechanistic Cross-Checks 199 9.3 The Path-Selection Process 200 9.4 Reaction Mechanism Strategies 202 9.5 Worked Mechanism Examples 20 3 9.6 Worked Product Prediction Examples 21 9 9.7 Methods for Testing Mechanisms 233
10 ONE-ELECTRON PROCESSES 24 1 10.1 Radical Structure and Stability 24 1 10.2 Charged Radicals 244 10.3 Radical Path Initiation 245 10.4 Paths for Radicals Reacting with Neutrals 246 10.5 Other Radical Paths 247 10.6 Radical Path Combinations 249 10.7 Dissolving Metal Reductions 25 1 10.8 Electron Transfer Catalysis 252 10.9 One-Electron Path Summary 253 APPENDIX (A COLLECTION OF IMPORTANT TOOLS) 25 6 General Bibliography 25 6 Abbreviations Used in This Text 25 7 Functional Group Glossary 25 8 Composite pka Chart 26 1 Bond Strength Table 26 4 The Twelve Generic Electron Sources 265 The Eighteen Generic Electron Sinks 26 5 Flow Charts for the Classification of Electron Sources and Sinks 266 Pathway Summary 267 Substitution vs. Elimination Decision Matrices 27 1 Addition/elimination Energy Surfaces 27 2 Trends Guide 273 Thermodynamics and Kinetics 27 6 Generation of Alternate Paths, Reaction Cubes 276 HINTS TO PROBLEMS FROM CHAPTERS 7, 8, AND 9 27 9 EXERCISE ANSWERS 28 1 INDEX 353