RSnomenklatuuri

RSnomenklatuuri is the Finnish term for the R/S nomenclature system used to describe the absolute configuration of stereogenic centers in organic molecules. The system is based on the Cahn‑Ingold‑Prelog priority rules, which assign a priority ranking to the substituents attached to a chiral center. From the assigned priorities, one of two arrangements is chosen as the reference configuration: the one in which the lowest priority group (usually numbered four) points away from the observer is designated as the (R) state, while the opposite arrangement is labelled (S). The letters R (rectus) and S (sinister) are Latin words meaning “right” and “left,” respectively, and reflect the direction in which a viewer would observe the arrangement of substituents.

The R/S system was introduced in the 1950s by Robert S. Newmann and further developed by the International Union of Pure and Applied Chemistry (IUPAC). It became a standard part of organic chemistry and medicinal chemistry, allowing chemists to unambiguously specify the stereochemistry required for the synthesis of optically active compounds. In practice, the R/S designations are added to the names of molecules, for example (R)-2-butanol or (S)-2-methyl-3-buten-2-ol, and are required in IUPAC names.

In the context of Finnish chemistry literature, RSnomenklatuuri is widely taught in university courses and used in scientific publications. It is often accompanied by the description of other stereochemical notations such as E/Z for double bonds and D/L for enantiomers, providing a comprehensive framework for describing the spatial arrangement of atoms in complex molecules.