REACTION BETWEEN TETRAETHYOXYSILANE AND CHLORAL HYDRATE IN ETHANOL - A SI-29 NMR INVESTIGATION

The hydrolysis of tetraethylsilane can be carried out and using chlora l hydrate as the source of water. The first step of the hydrolysis, fo rmation of triethoxysilanol is the rate determining step. The hydrolys is thus resembles that of aectals, ketals and orthoesters. In unbuffer ed media the reaction is sufficiently slow to follow the decrease of S i(OEt)(4), and changes in concentrations of Si(OEt)(3)(OH) and Si(OH)( 4) by Si-29 NMR. The most rapidly formed dimeric species has two OH gr oups on a given Si atom. Formation of oligomers involves one or more h ydrolyzed momoners. In solutions acidified by HCl and containing small amount of water, both hydrolysis and formation of oligomers by conden sation occurs faster. The intermediate Si(OEt)(2)(OH)(2) is also detec ted, indicating that the rate of the first step of hydrolysis increase with increasing acidity more than that of the second step.