Heterogeneous reactions : VII. Further studies on the heterogeneous gas/solid reactions of solid alkoxide bases with vaporized chloromethyldimethylhalosilanes

The results of the heterogeneous gas/solid reactions of chloromethyldimethylchloro (and fluoro)silane with solid lithium, sodium and potassium methoxide in the temperature range from 80–160°C are presented and discussed. Reaction with lithium methoxide serves as a clean, efficient high yield synthesis of chloromethyldimethylmethoxysilane without the complicating factors of side products or solvent to separate. The reactions of both the sodium and potassium methoxides lead to the displacement of halogen from silicon and to the displacement of the chloromethyl group. New evidence for the mechanism of the latter reaction is presented. With the potassium compound methylethyldimethoxysilane also is formed and carbene, sila-olefin addition mechanism is suggested. Surprisingly, lithium t-buthoxide did not react with the chlorosilane but did react with the fluorosilane to produce chloromethyldimethyl-t-butoxysilane in high purity and excellent yield. The reaction with potassium t-butoxide was more complicated, giving substitution for halogen and the chloromethyl group at silicon as well as t-butyl ether.