Reactivity of inorganic α-nucleophiles in acyl group transfer processes in water and surfactant micelles: I. Systems based on organic complexes of tribromide anion

Resumo

Systems based on organic complexes of tribromide anion generate upon dissolution in water nucleophile–oxidant couple HOBr/BrO^– and accelerate hydrolysis of ethyl 4-nitrophenyl ethylphosphonate, diethyl 4-nitrophenyl phosphate, and 4-nitrophenyl p-toluenesulfonate by a factor of 15–90 in the presence of cationic surfactant micelles. As in water, hypobromite ion in surfactant micelles acts as α-nucleophile, and the magnitude of the α-effect almost does not change in going from water to micelles. Micellar effects of surfactants are determined by the nucleophilicity of hypobromite ion in surfactant micelles and by solubilization of the substrate and BrO^–, which largely depend on the counterion concentration in the micelle surface layer. The main factor responsible for the observed acceleration is increased reactant concentration in the micellar pseudophase.