Basic Principles of the CIP‐System and Proposals for a Revision

Abstract “From Configurational Notation of Stereoisomers to the Conceptual Basis of Stereochemistry” is the title of a lecture [V. Prelog, ACS Symp. Ser. No. 12 (1975) 179] in which the chronologically and alphabetically third member of the CIP‐triumvirate discusses the history of the CIP‐system. The experience accumulated in the meantime, particularly the efforts to teach computers to use the system as described in 1966 by Cahn, Ingold and Prelog, has shown that certain of its aspects must be more strictly formulated and others modified. Questions dealing with stereoisomers (and stereotopicity), which previously have been treated predominantly in a pragmatic manner, are now discussed in a systematic way.