A new scheme for investigating geometric and stereoisomeric features in stereochemistry

The concept of RS-stereoisomers is proposed as an intermediate concept between enantiomers and stereoisomers. Stereoisograms developed for examining relationships between RS-stereoisomers contain three kinds of relationships (enantiomeric, RS-diastereomeric, and holantimeric relationships). Because these relationships correspond to three attributes (chirality, RS-stereogenicity, and sclerality), a quadruplet of RS-stereoisomers can be regarded as an equivalence class. The intermediacy of such RS-stereoisomeric relationships provides a paradigm shift from the conventional terminology of stereochemistry to a new terminology based on the concept of RS-stereoisomers. In addition, the recognition of a quadruplet of RS-stereoisomers as an equivalence class provides another paradigm shift on the basis of such equivalence classes. For example, the basis of the Cahn–Ingold–Prelog system for generating RS-descriptors is changed from the stereogenicity of conventional stereochemistry to the RS-stereogenicity specified by stereoisograms.