pseudochiral

Pseudochiral is a term used in stereochemistry to describe systems that exhibit chiral properties in certain respects without possessing a conventional stereogenic element in their static structure. It is often applied to molecules in which apparent chirality arises from restricted rotation, conformational locking, or environments that create non-equivalent spatial relationships among otherwise identical substituents.

Contexts and interpretations

Two common contexts are recognized. First, pseudochirality due to conformational constraints occurs when a molecule contains two substituents that are chemically identical but occupy non-equivalent positions because the geometry is fixed. This can give rise to chiral-like behavior despite the absence of a true stereocenter. Second, in dynamic or ensemble situations, rapid interconversion between conformers or enantiomeric forms can be slowed by interactions or by a rigid framework, leading to observable chiral effects on certain timescales or in specific environments.

Observations and caution

Pseudochiral systems may display optical activity or enantioselective interactions, but their chirality is not guaranteed by a permanent stereogenic element. The term is not always used consistently across literature; some authors reserve it for particular constructs such as pseudoasymmetric centers or sigma-chiral arrangements, while others use it more broadly to describe any chiral-like behavior in nominally achiral molecules.

See also

Chirality, Optical activity, Pseudoasymmetry, Dynamic chirality. Etymology: pseudo- meaning false, chiral from Greek cheir (hand).