Enantiomer

In chemistry, an enantiomer (/ɪˈnæntiəmər, ɛ-, -tioʊ-/ə-NAN-tee-ə-mər; from Greek ἐνάντιος (enántios), meaning "opposite", and μέρος (méros), meaning "part"), also known as an optical isomer, is one of two stereoisomers that are mirror images of each other that are non-superposable (not identical), much as one's left and right hands are the same except for being reversed along one axis (the hands cannot be made to appear identical simply by reorientation). Organic compounds that contain a chiral carbon atom usually have two non-superposable structures. These two structures are mirror images of each other and are, thus, commonly called enantiomorphs (enantio = opposite ; morph = form), hence this structural property is now commonly referred to as enantiomerism.

Enantiopure compounds refer to samples having, within the limits of detection, molecules of only one chirality.

When present in a symmetric environment, enantiomers have identical chemical and physical properties except for their ability to rotate plane-polarized light (+/−) by equal amounts but in opposite directions (although the polarized light can be considered an asymmetric medium). They are sometimes called optical isomers for this reason. A mixture of equal parts of an optically active isomer and its enantiomer is termed racemic and has zero net rotation of plane-polarized light because the positive rotation of each (+) form is exactly counteracted by the negative rotation of a (−) one.

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