However, it dissolves in hydrofluoric acid, in which it forms an adduct with water, GaF 3·3H 2O.
Another way of defining Lewis acid, which has been approved by IUPAC is by acknowledging that Lewis acid is a molecular entity which accepts an electron-pair,
and thus reacts with Lewis base in order to form a Lewis adduct.
(2003) demonstrated that the Michael reaction of chalcones as acceptors with various active methylene compounds such as diethyl malonate, nitromethane, cyclohexanone, ethyl acetoacetate and
acetylacetone as donors catalyzed by KF/basic alumina results in Adducts in high yield within a shorter time under ultrasound irradiation.