Direct Process Reaction

V. SILICON DIRECT PROCESS REACTIONS WITH REAGENTS OTHER... 

A key report investigated a variety of substrates in their reaction with silicon in an effort to find evidence for silylene intermediates during the silicon direct process reaction. When silicon, copper and methanol were reacted as described above but in the presence of alkenes, alkyldimethoxysilanes and (MeO SiH were formed95-97. The use of allyl propyl ether instead of alkenes gave allyldimethoxysilane, with 38% selectivity. These results and the reaction of silicon with MeCl in the presence of butadiene to give silacyclopent-3-enes indicates intermediate formation of silylenes. 

Detailed investigations into the mechanism of reaction between alkyl halides and metals have concentrated primarily on systems of great practical interest the Grignard reaction, the Direct Process Reaction, and a. few others. Whereas research reported in the preceding section involved solely pure gaseous halides and pure metals as single crystals, mechanistic investigations have involved a much wider variety of substrates and reaction conditions. When a solvent is involved, solvation of the metal product... 

As previously mentioned, the Direct Process Reaction involves the reaction of (2) with silicon at elevated temperatures to form methyl-chlorosilanes (6-9) ... 

At the turn of the century the cost of elemental silicon was 1600/lb. Improvement of reduction conditions allowed this price to fall to 0.10/lb by 1931 and made the use of the element more practical. Elemental silicon is employed as an additive to iron to give silicon-steels, which are more acid resistant, to alloy copper for production of silicon bronzes and as an additive to aluminum or magnesium to improve the strength of these structural materials and provide resistance to corrosion. The use of silicon as a semiconductor had begun by 1940 and after discovery of the direct process reaction became the necessary starting point for the production of silicone polymers103. 

Compared to the Grignard route, the direct process reaction requires only the reduction of silica to silicon and the production of methyl chloride. A form of the overall reaction (related to equation 2) is shown in equation 3. On the basis of this equation there... 

As indicated in Table 8, the direct process reaction provides derivatives with less than four organic groups and, by adjusting the conditions, hydrosilanes (derivatives with SiH... 

TABLE 8. Products in the direct process reaction of silicon... 

Synthetic routes to arylsilanes are quite limited. The high temperatures required for the direct process reaction from aryl chlorides produces undesirable side-reactions and the organometallic route is incompatible with certain functional groups on the aromatic ring. 

The best compilation of data on the direct process reaction can be found in R. J. H. Voorhoeve, Organosilanes Per cursors to Silicones, Elsevier, Amsterdam, 1967. 

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