In stereochemistry, cryptochirality is a special case of chirality in which a molecule is chiral but its specific rotation is non-measurable. The underlying reason for the lack of rotation is the specific electronic properties of the molecule. The term was introduced by Kurt Mislow in 1977.
For example, the alkane 5-ethyl-5-propylundecane found in certain species of Phaseolus vulgaris is chiral at its central quaternary carbon, but neither enantiomeric form has any observable optical rotation:
It is still possible to distinguish between the two enantiomers by using them in asymmetric synthesis of another chemical whose stereochemical nature can be measured. For example, the Soai reaction of 2-(3,3-dimethylbut-1-ynyl)pyrimidine-5-carbaldehyde with diisopropylzinc performed in the presence of 5-ethyl-5-propylundecane forms a secondary alcohol with a high enantiomeric excess based on the major enantiomer of the alkane that was used.
Even a slight enantiomeric excess of the alkane is rapidly amplified due to the autocatalytic nature of this reaction.
The term is also used to describe a situation where an enantiomeric excess lies far below the observational horizon, but is still relevant, e.g. in highly enantiosensitive, self-amplifying reactions.