enancjomery

Enancjomery is the property of certain chemical compounds to exist as two stereoisomers that are mirror images of each other but cannot be superimposed. These mirror-image forms are called enantiomers, and they arise when a molecule is chiral, typically because it contains one or more stereogenic centers with four different substituents.

Enantiomers share many properties in achiral environments, such as molecular formula, mass, and most physical constants. They differ in the way they interact with polarized light, each rotating plane-polarized light by an equal amount in opposite directions. A pure enantiomer is optically active, while a racemic mixture (equal amounts of both enantiomers) is optically inactive. In biological systems, however, enantiomers can behave very differently due to stereoselective interactions with chiral biomolecules like enzymes and receptors, often resulting in distinct pharmacological effects or toxicities.

Nomenclature for enantiomers often uses the Cahn–Ingold–Prelog (R/S) system to designate absolute configuration at stereogenic centers. An enantiomer of a given compound has the opposite configurations at all stereocenters, and thus the two are related as mirror images.

Separation and use of enantiomers are central to fields such as pharmaceuticals and agrochemicals. Enantioselective synthesis aims to produce one preferred enantiomer, while various resolution techniques and chiral chromatography can separate enantiomers from a mixture. Historical work by Louis Pasteur on tartrate salts is frequently cited as the foundational demonstration of enantiomery in chemistry.