Organochlorosilanes reactions with

A convenient synthesis of organochlorosilanes from organosilanes is achieved by reaction with inorganic chlorides of Hg, Pt, V, Cr, Mo, Pd, Se, Bi, Fe, Sn, Cu, and even C. The last compounds, tin tetrachloride, copper(II) chloride, and, under catalytic conditions, carbon tetrachloride (117,118), are most widely used. 

Selectivity of contact mass. Since the most important products in the synthesis of organochlorosilanes are diorganodichlorosilanes, it is natural that the increase of their yield receives much attention. The selective formation of diorganodichlorosilanes when organic chlorine derivatives interact with contact mass is connected with the purity of the reactants, silicon above all. High yield of dimethyldichlorosilane in the direct synthesis of methylchlorosilanes largely depends on the presence of noticeable quantities of aluminum in contact mass. The yield of dimethyldichlorosilane in the presence of aluminum as a rule decreases due to the formation of trimethylchlorosilane in the reaction with pure (semiconductor) silicon in the presence of copper trimethylchlorosilane is virtually not formed. 

The direct process can also be applied to produce further organochlorosilanes e.g. the reaction with ethyl chloride yields ethylchlorosilanes16 but with lower selectivity toward the dialkyldichlorosilane (equation 11). 

Thousands of papers and patents have appeared on the direct synthesis of organochlorosilanes since 1940 when Rochow reported the direct reaction.4 These results are comprehensively accounted for in a number of earlier reviews and books.3 8 The purpose of this review is to describe the recent developing trend of the direct reaction of elemental silicon with activated or unactivated alkyl chlorides, in particular, emphasizing direct reactions with a mixture of hydrogen chloride and activated alkyl chlorides such as polychlorinated methanes, silylmethyl chlorides and dichlorides, allyl chloride, etc. 

Silica can be drastically altered by reaction with organochlorosilanes or organoalkoxysilanes giving Si—O—Si—R linkages with the surface. The attachment of hydrocarbon chains to silica produces a non-polar surface suitable for reversed-phase chromatography where mixtures of water and organic solvents are used as eluents. The most popular material is octadecyl-silica (ODS-silica) which contains C g chains, but materials with Cj, C, Cg, and C22 chains are also available. 

Subsequent reactions with organochlorosilanes and 1,2-dichlorotetramethyldisilane yielded hypersilyltelluro-substituted silanes and disilanes (see Scheme 1). 

Metal-fragment substituted silanols are known to be stable towards self-condensation due to the strongly reduced acidity of the Si-OFI proton [2], However, these species show ready reaction with organochlorosilanes RsSiCl, which gives access to metallo-siloxanes [2], constituting attractive models for transition metal complexes anchored on silica surfaces. 

However, the facile isolation of metallo-silanols allows controlled condensation reactions with organochlorosilanes in the presence of an auxiliary base leading to transition metal substituted oligosiloxanes which can be considered as model compounds for silica-immobilized catalytic systems (Eq. 2a). 

Compared to the Wurtz method, electrochemical reduction with alkaline-earth metals is a milder alternative coupling reaction with the corresponding organochlorosilane. The silanes that can react with Mg are not preferred for this approach. Regardless of this limitation, the electrochemical method is applicable to phenyl-containing chlorosilane because Mg and Mg-Cu are not reactive when in contact with water and air. The water- and/or air-sensitive reactions are not welcome for technical reasons. 

Figure 4.3 Synthesis of onoaeric and polymeric siloxane bonded phases by reaction of organochlorosilanes with silica gel under different conditions.

First preparations were made by Schlenk eta/.546 who synthesized Si2 6 by the reaction of Siip3Cl with sodium. Kipping381 prepared the first mixed-substituent disilanes by reaction of the corresponding organochlorosilanes with sodium, but was not able to separate the optical isomers. Kraus and Nelson391 obtained Si2 et6 by this method. 

The process of the direct synthesis of organochlorosilanes is heterophase. However, it differs from many other heterophase processes in that solid silicon mixed with the catalyst is one of the parent components and is thus constantly spent during synthesis. It means that, as the reaction products form, the amount of the solid phase continually decreases. At the same time, the ratio of silicon and catalyst in contact mass also changes, until silicon is spent completely, which naturally impairs the conditions of the reaction. That is why there are several requirements to the construction of contact apparatuses for the effective direct synthesis of alkyl- and aiyl-chlorosilanes. So, the contact apparatus should provide for ... 

The reaction is conducted in the autoclave apparatus at 240-300 °C and 1.5-20 MPa in the presence of a catalyst. The reaction can be catalysed by Lewis acids, for example, A1CI3, BCI3 or B(OH)3, amounting to 0.1-5%. The yield of target products is 20-40%, because the main reaction is accompanied by the secondary disproportioning of organochlorosilanes. This technique is convenient for the preparation of organochlorosilanes with various radicals attached to the silicon atom. 

It is more practical to chlorinate organochlorosilanes with the help of initiators. The use of radical initiators (the dinitrile of 2,2 -azobis(isobutyric) acid, etc.) allows to carry out the chlorination reaction in the dark. This chlorination method is known in the literature as the dark technique. 

A toluene solution of organochlorosilane mixture is sent from weight batch box 7 into jet mixer (hydroejector) 3 with a certain amount of water. The consumption of the components is monitored by rotameters. The reaction of hydrolytic cocondensation takes place in the mixing chamber of hydroejector 3. To complete the hydrolytic cocondensation, the reactive mixture is sent into tower 2, from where the mixture is poured into Florentine flask 4. There the products of hydrolytic cocondensation and hydrochloric acid split. 

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