Rate and equilibrium constants for Grignard reaction with alkoxysilanes and ketones

Kinetics of tetraethoxysilane reaction with n-butylmagnesium chloride, specifically solvated with dibutyl ether, diethyl ether, THF, and triethylamine, was studied in toluene. Also isopropylmagnesium chloride, isopropyltriethoxysilane, and diisopropylketone were involved in a similar investigation. The pseudo-first-order rate constants determined at a great excess of these organomagnesium compounds were used for separation of the appropriate equilibrium and rate constants. An advantage of the method consists in preclusion of non-specific solvation effects when effects of donor solvents are considered. In separate experiments, thermodynamic parameters were determined for rate and equilibrium constants, measured for the reaction of tetraethoxysilane with n-butylmagnesium chloride solvated with dibutyl ether in toluene, and also in bulk dibutyl ether. The implication of steric and solvation effects on this reaction is discussed.