Chirales

Chirales is a term used to describe objects or substances that exhibit chirality, a property in which an object cannot be superimposed onto its mirror image. In chemistry, chirality refers to the non-superposability that leads to pairs of mirror-image forms called enantiomers. Although the standard English terminology uses “chirality” and “chiral” as the noun and adjective, some languages or contexts may use a plural or noun form related to “chirales” to refer to chiral substances or to chirality itself.

A central feature of chirality is the existence of stereoisomers that are non-superimposable mirror images. Enantiomers have nearly identical chemical compositions and most physical properties, but they can rotate plane-polarized light in opposite directions and interact differently with chiral environments, such as biological systems or chiral solvents. The degree of excess of one enantiomer in a mixture is called the enantiomeric excess.

Chirality often arises from stereogenic centers, commonly a tetrahedral carbon atom attached to four different substituents. Other forms of chirality include axial, planar, and helical chirality, which do not require a stereogenic carbon.

Applications and implications include enantioselective synthesis, resolution of racemic mixtures, and the importance of chirality in pharmaceuticals, agrochemicals, and biology. The biological activity of many compounds depends on their chirality, as enzymes and receptors are themselves chiral and can distinguish between enantiomers.

Techniques to determine or analyze chirality include measuring optical rotation, circular dichroism, chiral chromatography, and X-ray crystallography with anomalous dispersion, as well as nuclear magnetic resonance with chiral shift reagents.