Methylchlorosilane

In 1940 Rochow discovered the direct process, also cabed the methylchlorosilane (MCS) process, in which methyl chloride is passed over a bed of sibcon and copper to produce a variety of methylchlorosilanes, including dim ethyl dichi oro sil a n e [75-78-5] (CH2)2SiCl2. Working independently, Mbber made a similar discovery in Germany. Consequently, the process is frequently cabed the Rochow process and sometimes the Rochow-Mbber reaction. 

Direct Process. Passing methyl chloride through a fluidized bed of copper and siUcon yields a mixture of chlorosilanes. The rate of methylchlorosilane (MCS) production and chemical selectivity, as determined by the ratio of dimethydichlorosilane to the other compounds formed, are significantly affected by trace elements in the catalyst bed very pure copper and siUcon gives poor yield and selectivity (22). 

High quahty SAMs of alkyltrichlorosilane derivatives are not simple to produce, mainly because of the need to carefully control the amount of water in solution (126,143,144). Whereas incomplete monolayers are formed in the absence of water (127,128), excess water results in facile polymerization in solution and polysiloxane deposition of the surface (133). Extraction of surface moisture, followed by OTS hydrolysis and subsequent surface adsorption, may be the mechanism of SAM formation (145). A moisture quantity of 0.15 mg/100 mL solvent has been suggested as the optimum condition for the formation of closely packed monolayers. X-ray photoelectron spectroscopy (xps) studies confirm the complete surface reaction of the —SiCl groups, upon the formation of a complete SAM (146). Infrared spectroscopy has been used to provide direct evidence for the hiU hydrolysis of methylchlorosilanes to methylsdanoles at the soHd/gas interface, by surface water on a hydrated siUca (147). 

For both economic and technical reasons, commercial production of such polymers is almost entirely restricted lo the methyl derivatives (and to a lesser extent the phenyl derivatives) and hydrolysis of the various methylchlorosilanes has. accordingly, been much studied. Hydrolysis of MeiSiCl yields triniethylsilanol as a volatile liquid (bp 99 ) it is noticeably more acidic than... 

Cyclohexanone (0.52 g, 5.3 mmol) is added, under a nitrogen atmosphere, to a mixture of dry ethylene glycol (3 mb, 54 mmol) and dry methanol (20 mb). Tri-methylchlorosilane 14 (1.4 mb, 11 mmol) is added and the mixture stirred for 16 h at room temperature. The mixture is neutralized to pH 6 by addition of a 5% solution of sodium methoxide in methanol and the solvent is removed under reduced pressure. The residue is dissolved in 20 mb ether and filtered through 5 g silica gel, which is then washed with 2x10 mb ether. The combined ether eluates are evaporated and the crude residue submitted to flash chromatography on silica gel with ethyl acetate-hexane (1 10) to give 0.63 g (83%) cyclohexanoneethylene ketal 392 [28] (Scheme 5.87). 

Preparation of highly active CuCl catalyst for the direct process of methylchlorosilane production... 

CuCl, especially in a single crystal form, is extensively used as an optical material for its special optical properties. Orel et al. [2] first proposed a new method to obtain CuCl particles by the reduction of Cu with ascorbic acid. Several dispersants were used in the reduction and monodispersed CuCl particles can be obtained by selecting the proper dispersant and reduction conditions. In this work, the above method was used to modify the traditional process of CuCl preparation, namely, by reducing the Cu " with sodium sulfite to obtain the highly active CuCl catalyst to be used in the direct process of methylchlorosilane synthesis. 

Highly active CuCl catalysts for the direct process of methylchlorosilane synthesis were prepared by reducing Cu with a sodium sulfite solution in the presence of dispersing agents. Several well-known dispersants, e.g. SDBS, were used in this study. When SDBS was used, a catalyst in the form of small flakes was obtained that gave the best performance in reactivity, product selectivity and silicon conversion. This provides a convenient way to prepare the CuCl catalyst for use in industrial production. 

We find, as described below, that these methyl + chlorine monolayers are active in forming methylchlorosilanes. Furthermore, studies of samples with and without promoters show changes in activity and selectivity which parallel those found over real catalysts, and the results are beginning to show how these additives influence the catalytic process. 

In this section, we will first demonstrate the formation of methylchlorosilanes from CH3 + a monolayers on CuaSi surfaces. The effects of promoters and the effect of surface segregation on the reaction rate and selectivity are scussed subsequently. 

The evolution of methylchlorosilanes between 450 and 600 K is consistent with the 550 - 600 K typical for the catalytic Rochow Process [3]. It is also reasonably consistent with the evolution of methylchlorosilanes at 500 - 750 K reported by Frank and Falconer for a temperature programmed reaction study of the monolayer remaining on a CuaSi surface after catalytic formation of methylchlorosilanes from CHaCl at higher pressures [5]. Both of these observations suggest that the monolayer formed by methyl and chlorine adsorption on pure CuaSi is similar to that present on active catalysts. For reference, methylchlorosilanes bond quite weakly to tiie surface and desorb at 180 - 220 K. It can thus be concluded that the rate-determining step in the evolution of methylchlorosilanes at 450 - 600 K is a surface reaction rather an product desorption. 

By combining the AES and TPR results, it is found that (20 10)% of the adsorbed methyl groups (assuming that all adsorbed carbon exists as methyl groups at the 180 K adsorption temperature) form methylchlorosilanes, -5% form trimethylsilane, and the remaining 50 - 75% decompose on the surface to deposit... 

The reactions of CH3 radicals and CI2 alone with CujSi have also been investigated. On pure Cu3Si, the dominant silane product from CH3 adsorption is SiH(CH3>3 and the temperature at which the surface is sputtered prior to methyl adsorption has a dramatic effect on the reaction rate (see section 3.3). The CI2 reaction gives SiCU evolution, and the reaction temperature is close to that for methylchlorosilane formation. 

The products from the reaction of CH3 + Q monolayers on the promoted Cu3Si surface are the same as those for pure Cu3Si, but both the absolute rates and the selectivities are significantly different. In experiments analogous to those described in section 3.1, methylchlorosilanes are evolved from the promoted CusSi surface between 300 and 450 K. This temperature is 200 K lower than that from the pure Cu3Si surface. This 200 K difference in reaction temperature corresponds to a difference of six orders of magnitude in rate (if the rates are extrapolated to a common reaction temperature of 500 K assuming standard and equivalent pre exponential factors for the reactions on these two surfaces [10]). 

Figure 2. Comparison of the relative yields of methylchlorosilanes from methyl + chlorine monolayers on Cu3Si and doped CuaSi samples with typical yields for the catalytic Rochow process.

In the case of unpromoted CuaSi surfaces, the effect of this copper enrichment on methylchlorosilane formation appears to be relatively minor. The majority of methylchlorosilanes are evolved at 400 - 650 K as on the unpromoted surface. There is, however, a small yield of methylchlorosilanes with a peak temperature of -370 K. By contrast, for trimethylsilane formation from pure methyl monolayers, copper enrichment by low temperature sputtering shifts the dominant product peak from... 

We have now tried to make new larger cyclosilanes by the reductive dehalogenation of mixtures of methylchlorosilanes and methylchlorodisilanes. After a separation of the reaction product mixture by means of GC/MS, we found some new cyclosilanes (Fig. 1) [12]. 

The Miiller-Rochow-Synthesis [16,17] (direct synthesis of methylchlorosilanes) provides as byproduct a high boiling fraction consisting essentially of 1,1,2-trimethyltrichlorodisilane and 1,2-dimethyltetrachlorodisilane [18]. Starting with these disilanes Wacker-Chemie has developed different ways to produce silicon carbide [19, 21] and silicon carbonitride [22] fibers. 

The existence of SiCl2 as an intermediate was indicated from an experiment in which the volatile product of a Si/CuCl reaction was allowed to react with CH3CI to form methylchlorosilanes. 

Methylchloroisothiazolinone, antimicrobial used in cosmetics, 7 831t Methylchlorosilane(s) (MCS) direct-process residue, 22 552 as silylating agents, 22 697 in TD resin preparation, 22 588 Methylchlorosilane process, 22 548, 549 a-Methylcinnamaldehyde, 3 595... 

The example of the first category is the formation of alkyl- and arylchlorosilanes in the so-called direct process (DP). The process was discovered over 60 years ago by Rochow in the United States, and, independently, by Muller in Germany, and it is still the most important reaction in organosilicon chemistry. In fact, it is at the very basis of the silicone industry, being the primary source of organochlorosilane precursors (mostly methylchlorosilanes, comprising over 90% of the total) in the production of silicone oligomers and polymers. 

Methylbenzene halogen complex of, 3 122 iodine monochloridecomplese, 3 109 Methylchlorosilanes hydrolysis, 42 149-150, 157 pyrolysis products of, 7 356-363 Methylcobalamin, 19 151, 152 Methyl-coenzyme M reductase, 32 323-325 EPR spectra, 32 323, 325 F43 and, 32 323-324 function, 32 324-325 Methyl-CoM reductase, 32 329 Methyl cyanide, osmium carbonyl complexes, reaction, 30 198-201 Methylcyclophosphazene salts, 21 70 synthesis, 21 109... 

The silcone resin is a poly(methylphenylsiloxane) synthesized from methylchlorosilanes and phenylsilanes . Incorporation of phenyl groups Improves the thermal stability of the silicone resin. Epoxldatlon of the resin is most likely accomplished through substitution of the oxlrane ring at varlou phenyl group sites, yeildlng an epoxlde/slloxane ratio near unity. 

Carefulness sometimes can be irrelevant a large number of (organic) chemists store tri methylchlorosilane in the refrigerator ... 

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