The hydrolysis of n‐amyltriethoxysilane and phenyltriethoxysilane

Abstract n‐Amyltriethoxysilane and phenyltriethoxysilane were hydrolyzed in organic solvents in the presence of acidic or basic catalysts. The bulky substituents allow relatively large amounts of low‐molecular‐weight partial hydrolysis products to be isolated and stabilize the silanol functions present against further condensation. Cyclic ethoxypolysiloxanols in the molecular weight range 500–1000 are principal products of acid catalyzed hydrolysis. More extensive condensation occurs under alkaline conditions. Relatively high yields of low‐polymeric silsesquioxanes (octamers and possibly hexamers) are then obtained. The major product obtained from phenyltriethoxysilane, when hydrolyzed in a ketone solvent with a quaternary base as catalyst, is an amorphous high polymer virtually free of functional groups. In inert solvents in the presence of traces of catalyst a very facile rearrangement occurs, giving the octamer (and possibly the hexamer) in very high yield.