Methyltriacetoxysilane: Methyltrichlorosilane with Acetic Acid, Then Acetic Anhydride

Methyltriacetoxysilane is the cross-linker that makes acetoxy silicone cure in moist air. This route (Horn et al., Hüls, US 5,817,854, 1998) swaps the chlorine on methyltrichlorosilane for acetate in two steps. First acetic acid replaces about half of it, and the hydrogen chloride escapes. Then acetic anhydride replaces the rest, and the acetyl chloride that forms is distilled off. From 700 g of the chlorosilane the patent got 985 g of product. Hydrogen chloride and acetyl chloride are corrosive: fume hood. The picture: our diagram.