ELECTRON FLOW IN ORGANIC CHEMISTR Y. Paul H. Scudder

Transcription

1 ELECTRON FLOW IN ORGANIC CHEMISTR Y Paul H. Scudder

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3 1 BONDING AND ELECTRON DISTRIBUTION 1 2 THE PROCESS OF BOND FORMATION STABILITY AND REACTIVITY OF INTERMEDIATES CLASSIFICATION OF ELECTRON SOURCES CLASSIFICATION OF ELECTRON SINKS THE ELECTRON FLOW PATHWAYS INTERACTION OF ELECTRON SOURCES AND SINKS DECISIONS, DECISIONS CHOOSING THE MOST PROBABLE PATH ONE ELECTRON PROCESSES 24 1 APPENDIX 25 6 HINTS TO PROBLEMS FROM CHAPTERS 7, 8, AND EXERCISE ANSWERS 28 1 INDEX 353

4 1 BONDING AND ELECTRON DISTRIBUTION Introduction Lewis Structures and Resonance Forms Curved-Arrow Notation Nomenclature and Abbreviations Hybridization and Bonding Orbital Interaction Diagrams (Supplemental) Conjugation Molecular Orbital Theory for Acyclic Systems (Supplemental) Aromaticity, Cyclic Systems 28 2 THE PROCESS OF BOND FORMATION Thermodynamics, Position of Equilibrium Kinetics, Rate of Reaction The Basics of Barriers Orbital Overlap in Bond Formation Microscopic Reversibility, Stereoelectronics Steric Limitations HOMO-LUMO Interactions Hard and Soft Acid-Base Theory Perturbation of the HOMO and LUMO (Supplemental) STABILITY AND REACTIVITY OF INTERMEDIATES Ion Stability, Solvation, and Media Effects Ranking of Acids and Bases, the pka Chart Calculation of Keq for Proton Transfer Carbocation Stability and Trends Ranking of Electron-Donor Groups Carbanion Stability and Trends Ranking of Electron-Withdrawing Groups Ranking of Leaving Groups The ApKa Rule 72 4 CLASSIFICATION OF ELECTRON SOURCES Generalized Ranking of Electron Sources Nonbonding Electrons Electron-Rich Sigma Bonds Electron-Rich Pi Bonds Simple Pi Bonds Aromatic Rings Summary of Generic Electron Sources 86

5 5 CLASSIFICATION OF ELECTRON SINKS Generalized Ranking of Electron Sinks Electron-Deficient Species Weak Single Bonds Polarized Multiple Bonds Without Leaving Groups Polarized Multiple Bonds With Leaving Groups Summary of Generic Electron Sinks 96 6 THE ELECTRON FLOW PATHWAYS The Dozen Most Common Pathways Common Path Combinations Eight Minor Pathways Variations Common Errors Major Path Summary INTERACTION OF ELECTRON SOURCES AND SINKS Source and Sink Matrix Detailed Matrix-Cell Discussions Electrophilic Additions Rearrangements with Loss of a Leaving Group Nu-L Reactions Fragmentations Concerted Six-Electron Pericyclic Reactions Miscellaneous Reactions Product Matrix Summary DECISIONS, DECISIONS Decision Point Recognition Multiple Additions Ionization of Leaving Groups Ambident Nucleophiles Substitution vs. Elimination Ambident Electrophiles Intermolecular vs. Intramolecular Kinetic vs. Thermodynamic Enolate Formation CHOOSING THE MOST PROBABLE PATH Problem-Solving in General General Mechanistic Cross-Checks The Path-Selection Process Reaction Mechanism Strategies Worked Mechanism Examples Worked Product Prediction Examples Methods for Testing Mechanisms 233

6 10 ONE-ELECTRON PROCESSES Radical Structure and Stability Charged Radicals Radical Path Initiation Paths for Radicals Reacting with Neutrals Other Radical Paths Radical Path Combinations Dissolving Metal Reductions Electron Transfer Catalysis 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 EXERCISE ANSWERS 28 1 INDEX 353