enantiomeric

Enantiomeric refers to enantiomers, a pair of stereoisomers that are non-superimposable mirror images of each other. Enantiomers arise for molecules that are chiral, meaning they lack an internal plane of symmetry. In achiral environments, enantiomers typically have identical physical properties such as melting point and boiling point, but they differ in how they interact with polarized light and with other chiral substances, including biological systems.

In mixtures containing enantiomers, the concept of enantiomeric excess describes the degree of enantiomeric purity. Enantiomeric excess (ee) is calculated as the absolute difference between the amounts of the two enantiomers divided by the total amount, multiplied by 100 percent. An enantiomeric ratio (er) expresses the relative amounts of the two enantiomers, such as 75:25. A racemic mixture has equal amounts of both enantiomers and an ee of 0 percent, while a pure enantiomer has an ee near 100 percent. Enantiomeric purity is a practical measure used in synthesis and analysis.

Methods for determining and achieving enantiomeric composition include polarimetry, which measures the rotation of plane-polarized light, and chromatographic techniques using chiral stationary phases (such as enantioselective HPLC or GC). Nuclear magnetic resonance with chiral solvating agents and other spectroscopic methods can also assess enantiomeric ratios. In pharmaceuticals and biochemistry, enantiomeric properties are especially important, as different enantiomers can exhibit distinct biological activity and safety profiles.