axial chirality

https://doi.org/10.1351/goldbook.A00547
Term used to refer to stereoisomerism resulting from the non-planar arrangement of four groups in pairs about a chirality axis. It is exemplified by allenes
abC=C=Ccd
(or
abC=C=Cab
) and by the atropisomerism of ortho-substituted biphenyls. The configuration in molecular entities possessing axial chirality is specified by the stereodescriptors Ra and Sa (or by P or M).
A00547.png
Source:
PAC, 1996, 68, 2193. 'Basic terminology of stereochemistry (IUPAC Recommendations 1996)' on page 2201 (https://doi.org/10.1351/pac199668122193)