Enantiomeri

Enantiomeri are a pair of stereoisomers that are non-superimposable mirror images of each other. They arise in molecules that are chiral, meaning they cannot be overlapped with their mirror image. An enantiomeric pair consists of two structures that share identical connectivity but differ in spatial arrangement at all chiral centers, so that one is the inverse of the other.

In most physical properties they are alike; only optical activity and reactions in a chiral environment distinguish them. Optical activity refers to the rotation of plane-polarized light, with enantiomers that are dextrorotatory (+) or levorotatory (-). In molecules with several stereocenters, the enantiomer has opposite configuration at every stereocenter; e.g., 2R,3S vs 2S,3R. Mes o forms may exist when a molecule has an internal plane of symmetry, in which case the compound is achiral and not enantiomeric.

Separating enantiomers is important in chemistry and pharmacology; methods include enantioselective synthesis, or resolution of a racemate via diastereomeric salt formation or chiral chromatography. In biology, enantiomers can have different interactions with enzymes and receptors, leading to different effects and activities.

The term enantiomeri is used in Italian and other languages; in English the corresponding term is enantiomer.