Theoretical Study of Hydrolysis and Condensation of Silicon Alkoxides

The two title reactions were investigated by means of ab initio molecular orbital calculations. Under neutral conditions, the hydrolysis of methylmethoxydihydroxysilane was examined, and the water-trimer cluster was found to be a reactant for ready bond interchange. The condensation of methyltrihydroxysilane was caused by the participation of the water dimer. Two of the observed reactions involved a front-side nucleophilic attack to the silicon center or a similar mechanism. Acid- and base-promoted hydrolyses were also examined, and their enhanced reactivities were ascribed to the stability of the silyl cation and a hypervalent intermediate, respectively.