Precision in Stereochemical Terminology

Abstract

Many organic chemists have begun to use the Mislow term stereocenter (or stereogenic atom) as an alternative to the traditional term asymmetric carbon atom and the slightly broader IUPAC term chirality center. But the term stereocenter is defined much more broadly. It includes a wide variety of structures that are neither chirality centers nor asymmetric carbon atoms. The rules that students learn about asymmetric carbon atoms are no longer true when one substitutes the broader term stereocenter. Asymmetric carbon atoms are defined structurally, and students can easily find them to use as a tool to help in understanding the stereochemistry and finding the stereoisomers. In contrast, students must already know which stereoisomers exist to identify the stereocenters. This article recommends that instructors use the precise terms asymmetric carbon atom and chirality center when they apply, and use the broader term stereocenter only when there is a need to include stereogenic atoms that are not chirality centers.