Methyl chlorosilane

Many chlorine compounds, including methyl chlorosilanes, such as ClSi(CH2)3, Cl2Si(CH3)2, Cl3Si(CH3) tetrachlorosilane [10026-04-7] SiCl chlorine, CI2 and carbon tetrachloride, CCl, can completely react with molecular surface hydroxyl groups to form hydrochloric acid (40), which then desorbs from the gel body in a temperature range of 400—800°C, where the pores are still interconnected. Carbon tetrachloride can yield complete dehydration of ultrapure gel—siUca optical components (3,23). 

Figure 1. Relative rates of methyl chlorosilane formation from a methyl + chlorine monolayer on a CusSi surface. The Cu3Si surface was prepared by ion bombardment at 330 K, and a 1 1 ratio of methyl groups and chlorine atoms were reacted in these studies.

METHANESULFONIC ACID METHYL MERCAPTAN METHYL CHLOROSILANE METHYLAMINE METHYL SILANE TETRANITROMETHANE CARBON MONOXIDE CARBONYL SULFIDE CARBON DIOXIDE CARBON DISULFIDE BROMOTRIFLUOROETHYLENE... 

The uses of methyl chloride are as follows methyl chlorosilanes as intermediates for silicones (82%), methyl cellulose (6%), agricultural chemicals (4%), quaternary amines (4%), and butyl rubber (2%). 

The use pattern for methyl chloride in the United States in 1992 and 1995 was (%) methyl chlorosilanes used as intermediates for silicones, 80 methyl cellulose manufacture, 6 quaternary ammonium compounds, 5 agricultural chemicals, 5 butyl rubber production, 2 and miscellaneous, 2 (Anon., 1992, 1995). 

A crystalline silsesquioxane, octamethyloctasilsesquioxane, was first isolated by Scott (65) among the cracking products of mixed methyl-chlorosilane hydrolyzates. Its molecular weight was not established until some years later (75). This highly symmetrical octamer does not melt below 450° but is readily sublimable in a good vacuum at much lower temperatures. 

Sivtsova, E. V., Kogan, V. B., Ogorodnikov, S. K. Application of gas-liquid chromatography for the selection of stationary phase for use in analysing methyl-chlorosilane mixtures. Zh. Prikl. Khim. (Leningrad) 38, 2609 (1965). — Anal. 

The high vapour pressure of the (methyl)chlorosilanes allows a vapour-phase reaction. Moreover, these reactions are usually performed on amorphous silica with a high surface area, which is very suitable for a detailed study of the surface species by means of FTIR, XPS and NMR. 

Vapour-phase reactions with (methyl)chlorosilanes... 

The reactions between (methyl)chlorosilanes and the surface of silica have been investigated by many researchers, primarily because of the utility of these reagents as coupling agents in polymer chemistry and as surface deactivating agents in chromatography. 

This conclusion is not surprising. Also (methyl)chlorosilanes do not react with the silica surface at room temperature. Reaction temperatures > 473 K are required to achieve noticeable reaction. The boiling point of octadecyltrichlorosilane is 433 K. It would be very interesting to see what happens at reflux temperature. 

The first rectification stage. From collector 10 the mixture of methyl-chlorosilanes is periodically fed into pressure container 11, from where at 50-65 °C it is sent through heater 12 (by self-flow) onto the feeding plate of rectification tower 13. From the tower the tank liquid (methyltrichloro-silane, dimethyldichlorosilane and tank residue) flows into tank 14, where the temperature of 80-90 °C is maintained, and from there is continously poured into collector 22. After the tower, vapours of the head fraction at a temperature below 58 °C, consisting of the rest of methylchloride, di- and trichlorosilane, dimethylchlorosilane, methyldichlorosilane and the azeotropic mixture of silicon tetrachloride and trimethylchlorosilane are sent into refluxer 15, cooled with water, and into refluxer 16, cooled with salt solution (-15 °C). After that, through cooler 17 the condensate is gathered in receptacle 19. Volatile products, which did not condense in reflux-ers 15 and 16, are sent into condenser 18 cooled with Freon (-50 °C). There they condense and also flow into receptacle 19. As soon as it is accumulated, the condensate is sent from receptacle 19 into collector 20. 

The most important monomers (> 95 % by weight) for silicone synthesis are the methyl chlorosilanes. Next to them are the phenyl chlorosilanes, methyl phenyl chlor-osilanes, methyltrifluoropropyl chlorosilanes, and a variety of silanes containing organic functional groups such as hydroxyl, amine, epoxy, acrylate and carboxyl which are responsible for the different products. 

The halogen methyl-chlorosilanes were prepared by photochlorination or photobromination of methylchlorosilanes. The compounds... 

Thus the function of the copper catalyst in the synthesis of methyl-chlorosilanes seems to be to transport the free methyl groups and to prolong their life in the form of copper methyl, and also to transfer the chlorine from methyl chloride to silicon. It is probable that copper acts similarly in the reaction of other hydrocarbon halides with silicon, and that similar metals also may undergo the same cycle of reactions. 

These considerations seem to rule out the Shtetter synthesis, for this method produces trichlorosilanes with chlorine atoms in the organic groups. Processes for converting these into ethyl- or methyl-chlorosilanes have not been published supposedly such conversions would have to be extremely simple if the combined procedures are to retain an advantage over the Grignard and direct methods. As such methods of conversion are lacking, the Shtetter synthesis probably will reach commercial importance only after further research has demonstrated how use may be made of its interesting products. 

A direct correlation of the activation energy and velocity constant with 7( C— H) for the reaction of methyl radicals with [Me4M] (M = Si, Ge, Sn, Pb) has been found (40). A similar correlation exists for methyl-chlorosilanes (44). The solvent dependence of 7( C— H) for [Me2Pb(acac)2] has been interpreted in terms of the amount of positive charge on the central metal atom (7). 

In addition to the basic strength of catalysts the acceptor strength of chlorosilanes is important for the hydrogenation course. With the increasing number of methyl groups (instead of Cl atoms) the silane reactivity decreases (Table 2). This tendency seems to be associated with the decreasing Lewis-acid strength of methyl chlorosilanes. 

A common feature of all these compounds is their tetrahedral structure at the silicon atom which is bound to four oxygen neighbors. A tremendous breakthrough in the history of silicon-based polymers has been achieved by the invention of the Direct Process by Muller and Rochow resulting in the industrial production of methyl chlorosilanes with hydrolytically stable Si-C bonds besides very reactive Si-Cl bonds which serve as building units for a wide variety of polydimethyl siloxanes including silicon fluids, resins, and elastomers. 

Since Me3SiCI does not show any reduction wave at more positive potentials than -3.0 V vs SCE [6] in contrast with phenylchlorosilanes, it acts as the electrophile in the cross-coupling of phenyl(methyl)-chlorosilanes with Me3SiCl. Eq. 7 and Table 1 summarize the results ... 

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

Methylsilicon triisocyanate and dimethysilicon diisocyanate can be prepared from the appropriate methyl-chlorosilane and a 10% theoretical excess of the inorganic cyanate with the same equipment and procedure as employed in the synthesis of silicon tetraisocyanate. With... 

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