Configuration
In the context of stereochemistry, the term is restricted to the arrangements of atoms of a molecular entity in space that distinguishes stereoisomers, the isomerism between which is not due to conformation differences.
Conformation
The spatial arrangement of the atoms affording distinction between stereoisomers which can be interconverted by rotations about formally single bonds. Some authorities extend the term to include inversion at trigonal pyramidal centres and other polytopal rearrangements.
Enantiomer
One of a pair of molecular entities which are mirror images of each other and non- superposable.
Diastereoisomerism
Stereoisomerism other than enantiomerism. Diastereoisomers (or diastereomers) are
stereoisomers not related as mirror images. Diastereoisomers are characterised by differences in physical properties, and by some differences in chemical behaviour towards achiral as well as chid reagents.
Racemate
An equimolar mixture of a pair of enantiomers. It does not exhibit optical activity. The chemical name or formula of a racemate is distinguished from those of the enantiomers by the prefix (±)- or rac- (or racem-) or by the symbols RS and SR
meso-Compound
A term for the achiral member(s) of a set of diastereoisomers which also includes one or more chiral members
G. P. Moss, Pure Appl. Chem. 1996, 68, 2193-2222.
