Methyl chlorosilane reaction

Calculations have been carried out on the. S n2 reactions between chloride ion and methyl chloride or chlorosilane at several DFT levels of theory up to the OLYP/TZ2P level.102 The OLYP/TZ2P method gave much better (excellent compared with the CCDD(T)/aug-cc-pVQZ level) values than the other density functionals for both the geometry and the energies of the reactant complex and transition state for the methyl chloride reaction and the stable transition complex that forms in the chlorosilane reaction. 

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. 

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. 

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). 

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

Silicon reacts with cuprous chloride autocatalytically to form a solid known as T -phase, which then catalyzes the reaction between silicon and methyl chloride to form methyl chlorosilanes. Mass transfer effects are neglected to illustrate the mechanism of this unique reaction and equations are developed for predicting the final product size distribution. 

Silicon reacts with copper chloride catalytically to form a solid product known as q-phase, which then catalyzes the reaction between silicon and methyl chloride to form methyl chlorosilanes. The formation of the q-phase is a unique example of an autocatalytic solid-solid reaction (we are not aware of any other example of such a reaction). Procedures for determining the kinetics of this reaction and the size distribution of the final products of the second reaction are described in this case study. The most important feature of the study is the unexpected discovery of autocatalysis in a solid-solid reaction, which leads us to the important lesson that one should vigorously pursue any such observation that falls outside the comfort zone of research, for that is where true discoveries lie. This advice is particularly relevant to engineers, since they generally do not accept the unexpected and would prefer to tread on safer ground. 

The separate methyl chlorosilanes behave similarly when they are decomposed thermally (33). As soon as decomposition begins, white vapors appear at the exit of the reaction tube as a result of suction by the circulating pump, and these condense in the receivers at room temperature. Gaseous products appear simultaneously, leading to a slow pressure rise in the apparatus. When the production of gases (H2, CH4) brings the pressure... 

Similar mechanistic considerations may be applied to the formation of SiCl-containing carbosilanes from the three methyl chlorosilanes in the gas phase at 700°C. The 1,3-disilapropanes containing SiCl groups, shown in Table V, are key substances in considering the mechanism of this reaction. As in the case of Si(CH3)4, cleavage of both the Si—C and the C—H... 

In this review the authors have traced the development of the chemistry of compounds containing in their structures alternate Si and C atoms, although in all probability the literature coverage is not complete at all points. The article does not represent an area of research which has been fully explored indeed, in many places the subject is still in its infancy. Thus the high molecular weight compounds formed in the pyrolysis of Si(CH3)4 and the methyl chlorosilanes have scarcely been examined, and the possibilities of further reactions of carbosilanes substituted on the bridge carbon atom are also not completely known. In part the text reports only the experimental material available at the moment and discusses its possible interpretation. Further research will have to provide the final answers. It seems certain in any case that the subject will develop far more in the years ahead. 

By now we have studied experimentally numerous SeI reactions of the electrophilic substitution involving the replacement of protons of =SiOH groups by positively charged fragments of molecules of hydro- and methyl-chlorosilanes, silazanes, alkoxysilanes, organosUoxanes, alkyl borates and phosphates, chlorides and oxochlorides... 

Methyl chlorosilanes, used in the manufacture of a variety of resins, elastomers, and silicone oils, are manufactured by reacting silicon (a solid) with methyl chloride (a gas) in the presence of an alloy Cu3Si (called the 7 -phase) as catalyst. Although strictly a gas-solid reaction, and hence mote appropriate to Chapter 15, we illustrate the procedure here by noting all mass transfer effects and focusing only on the two reactions involved (one homogeneous and the other autocatalytic). 

Another adamantane-type compound is obtained by reaction (9.242). The reactions of methyl-chlorosilanes with LiPH2 and Li2PH lead to a whole series of ring and cage compounds built from P-8i linkages [32]. 

Silicones are made from silicon and methyl chloride in a process known as the direct reaction or direct process. This reaction yields methyl chlorosilanes. They are distilled for purification and the dimethyldichlorosilane is hydrolyzed to give PDMS. This product can be formulated into thousands of different products, which are sold to every major industrial segment. 

The bulkier diphenyl methyl chlorosilane reacted with 0.79 silanol groups per Sii4029 unit of kenyaite [189]. During reaction with an allyl dimethyl chlorosilane, the allyl groups were eliminated, and SiOSi(CH3)2 OH groups were found in the interlaya- space [190]. 

The direct reaction process is also called the Rochow process, and methyl-chlorosilane and phenylchlorosilane have been industrially produced by this process [11]. Copper is used as a catalyst. However, the reaction with the single catalyst of copper is not so fast, and the addition of a metal such as Sb, Cd, Al, Zn and Sn or a mixture accelerates the reaction. For example, with a catalyst containing 94.49 wt % Si, 5.00 wt % Cu, 0.50% Zn and 0.001 % Sn, the selectivity of Me2SiCl2 is 80 mole %. In the reaction with methylchloride, the reaction temperature is preferably 300°C and the conversion of silicon is 90-98% [9]. 

Method of synthesis the direct reaction between silicon metal and methyl chloride in a fluid bed reactor yields a complex mixture of methyl chlorosilanes the chlorosilanes are distilled or purified, and the primary product - dimethyidichlorosilane, (CH3)2SiCl2 - is reacted with water (hydrolysis) to give poly(dimethylsiloxane) oligomers (Me SiOJ. ... 

The most important method of production in use today begins with a chemical reaction between methyl chloride and metallic silicon at about 300 C, catalysed by copper. This produces a mixture of methyl chlorosilanes which have the general formula Si(CH3)xCl4 x. Chlorosilanes have differing boiling points. Unlike the final silicone... 

Methyl chlorosilanes comprise by far the largest volume of silicone precursors but phenylchlorosilanes are also important. One way in which they can be produced is by reaction of chlorobenzene with silicon. Other production processes involve the production of methyl or phenyl chlorosilanes with reactive groups such as vinyl or hydrogen attached to some silicon atoms. 

Miktoarm star terpolymer resulted from the reaction of the methyl-chlorosilanes with a living PI first, then by adding methyltrichlorosilane in a great excess. The living PS is reacted with another function and finally with a small excess of poly(butadiene). In spite of the complexity of the procedure, a well-defined 3- miktoarm pol)maer was obtained [32]. One example is given in Figure 5. 

The direct process is less flexible than the Grignard process and is restricted primarily to the production of the, nevertheless all-important, methyl- and phenyl-chlorosilanes. The main reason for this is that higher alkyl halides than methyl chloride decompose at the reaction temperature and give poor yields of the desired products and also the fact that the copper catalyst is only really effective with methyl chloride. 

Terminal alkynes can be converted readily into alkynylsilanes by reaction of the corresponding alkyne anion or its metalloid equivalent with a suitable chlorosilane (/). The reverse reaction, that of liberation of the alkyne, is quite facile, being effected by several reagent combinations, including hydroxide ion, methanolysis, fluoride anion, silver(i) followed by cyanide anion, and methyl lithium-lithium bromide (2). 

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