Nucleophilic cleavage of the silicon–oxygen bond: acid-catalysed hydrolysis of tributylphenoxysilanes in aqueous organic solvents

Abstract

The kinetics of acid-catalysed hydrolysis of tributylphenoxysilanes have been studied in aqueous dioxan, aqueous propan-2-ol, and aqueous acetonitrile. In aqueous dioxan, when allowance has been made for changes of acidity functions with solvent composition, the hydrolysis is shown to be at least second-order in water. Substituent effects are consistent with a mechanism involving fast protonation of the phenoxysilane followed by rate-limiting hydrolysis of the protonated species. The similarity of rates of hydrolysis in each solvent indicates that solvation differences between initial and transition states are either small or constant.