A best-seller for the advanced physical organic chemistry course, the text uses organic mechanisms as the focal point for examining current research. The third edition also has an expanded discussion of electron transfer processes, including application of valence-bond configuration interaction and treatment of energy surface crossings in photochemical processes; improved treatment of chemically induced dynamic nuclear polarization (CIDNP); and a new appendix to Chapter 9 on electron spin resonance (ESR). The expanded discussion of molecular orbital theory includes an introduction to perturbation molecular orbital (PMO), and the material on nucleophilic substitution, photochemistry, and radicals has been extensively revised. End-of-chapter problems ranging in difficulty encourage further investigation of reactions. Appendices include transition state thermodynamics and isotrope effects.