The Partial Hydrolysis of Ethyltriethoxysilane

Abstract

Appreciable yields of distillable liquids result from the acid-catalyzed reaction of three molar equivalents of water with ethyltriethoxysilane in benzene solution. The major components are polycyclic polysiloxanes that contain free silanol groups and residual ethoxyl groups. Lower yields are obtained in ethanol solution with an acid catalyst, and only gels are obtained with an alkaline catalyst. If smaller amounts of water are used, the major products are first less highly cyclic, and finally predominantly straight-chain polysiloxanes. Several ethoxy-substituted linear and monocyclic polysiloxanes were isolated. Co-hydrolysis of equimolar mixtures of ethyltriethoxysilane and ethyltrichlorosilane gives products similar in physical properties to those derived from the trialkoxysilane alone, but with much less residual ethoxyl and silanol. A sublimable high-melting solid obtained in small amounts was identified as octa-(ethylsilsesquioxane), (C2H5SiO1.5)8- A lower melting solid frequently present in even smaller amounts was identified as hexa-(ethylsilsesquioxane), (C2H5.SiO1.5)6. © 1955, American Chemical Society. All rights reserved.