GB591149A - Improvements in or relating to the production of organo-silicon compounds by the grignard reaction - Google Patents

Abstract

Compounds of the formula RxSi(OR1)4-x where R and R1 are the same or different alkyl, aryl or aralkyl groups, and hydrolysis products thereof, are prepared by reacting the corresponding Grignard reagent with a tetra-organo silicate in the presence of a solvent therefor, the amount of solvent present at the end of the reaction being so adjusted that the silicon compound and the resulting magnesium compound formed in the reaction are dispersed in a liquid phase. The liquid reaction product is hydrolyzed and resolved into two immiscible phases by means of a dilute aqueous mineral acid and the organo-silicon compound is recovered from the organic phase. In a particular form of the invention the organic halide used for forming the Grignard reagent may be used in such excess as to act as the solvent medium for the reaction. In example (1) magnesium turnings are stirred into a large excess of dry ether with a portion of p-tolyl bromide, and tetra-ethoxy silicane is added followed by the remainder of the p-tolyl bromide which is added dropwise. The homogeneous product is hydrolyzed by ice and p sulphuric acid and di-p-tolyl silicanol and dehydration and polymerization products thereof are recovered from the ether layer which separates. In example (2) ethyl bromide is slowly added to a mixture of magnesium filings, tetra-ethoxy silicane and dry ether seeded with a small quantity of Grignard reagent, and the product is hydrolyzed and the silicanol separated from the ether layer. In example (3) magnesium and an excess of ethyl bromide are added gradually to a mixture of tetra-ethoxy silicane. In example (4), bromobenzene in excess, tetra-ethoxy silicane and a portion of the magnesium required are mixed and the reaction initiated by adding a trace of a Grignard reagent, after which the remainder of the magnesium is gradually added. The product is hydrolyzed and a brown oil which can be converted to a silicone is then separated from the bromobenzene phase. In example (5) monophenyl tri-ethoxy silicane is obtained from an excess of chlorobenzene, tetra-ethoxy silicane and magnesium. In example (6), ethyl bromide is slowly added to a mixture of magnesium, dry ether and tetra-ethoxy silicane, and the product is hydrolyzed by adding aqueous sulphuric acid. A liquid ethyl silicone is separated from the ethereal layer.