The
Cahn–Ingold–Prelog priority rules,
CIP system or
CIP conventions (after the scientists;
Robert Sidney Cahn,
Christopher Kelk Ingold and
Vladimir Prelog) are a set of rules used in
organic chemistry to name the
stereoisomers of a molecule. A molecule may contain any number of
stereocenters and any number of
double bonds, and each gives rise to two possible configurations. The purpose of the CIP system is to assign an R or S descriptor to each stereocenter and an E or Z descriptor to each double bond so that the configuration of the entire molecule can be specified uniquely by including the descriptors in its systematic name.