The thermodynamic tendency of a substrate to act as a Lewis acid. Comparative measures of this property are provided by the equilibrium constants for Lewis adduct formation of a series of Lewis acids with a common reference Lewis base.
See also: acceptor number, electrophilicity
PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1135 (https://doi.org/10.1351/pac199466051077)