26th International Congress of Pure and Applied Chemistry, Volume 4: Organic Chemistry is a collection of session lectures presented at the 26th International Congress of Pure and Applied Chemistry, held in Tokyo, Japan on September 4-10, 1977. This volume is composed of six chapters and starts with a discussion of the problems related to the understanding orders of nucleophilic reactivity. The succeeding chapters deal with the synthetic approaches to the pentagonal dodecahedrane and several designs and concepts in natural product synthesis. These topics are followed by the examination of the full structures of tissue culture adducts formed from polyaromatic hydrocarbons and nucleic acids. The final chapters describe the biosynthesis of aspulvinone metabolites from Aspergillus terreus and a mathematical model for the deductive solution of chemical problems using computer programs. This book is intended for organic chemists, researchers, and students.