DI CHLOROSILANE

Vinyldialkylsilanes and vinyltrimethylsilane having no chlorine atoms do not undergo alkylation with benzene derivatives in the presenee of aluminum chloride but vinylchlorosilanes react with benzene to give the alkylation products. The reaetivities of vinylchlorosilanes decrease in the following order vinyl(methyl)di-chlorosilane > vinyltrichlorosilane > vinyl(dimethyl)chlorosilane. 

In Section 3 of this chapter it was mentioned that polymers obtained by intermolecular condensation of bifunctional monomers may often be prepared alternatively by an addition polymerization of a cyclic compound having the same composition as the structural unit. Typical examples are shown in Table III. The processes indicated are appropriately regarded as addition polymerizations. Each of these polymers may also be prepared through the condensation of suitable bifunctional monomers. The dimethylsiloxane polymer, for example, may be prepared, as indicated in Table I (p. 45), through the condensation of dimethyl dihydroxysilane formed by hydrolysis of the di-chlorosilane... 

Phenyl and vinyl modified versions of poly(m-carborane-siloxane) were readily prepared using the procedure just described, by introducing the appropriate silane feed into the reaction mix.19 Typically, 1 to 3 mol % di-chloro-methylvinylsilane was added to the di-chlorosilane feed in the syntheses described earlier. The repeat unit of the phenyl modified poly(w-carborane-siloxane) is shown in 5. 

Figure 3. Photocurrent vs. 0+ at +0.5 V vs. SCE from an n-type Si disk deriva-tized with 5 X 10 9 mol/cm2 of ferricenium/ferrocene from (1 j -ferrocenediyl)di-chlorosilane.

Both approaches as well as the Yajima route require the creation of silicon-silicon bonds involving the polycondensation of (di)chlorosilanes by refluxing in toluene or xylene in the presence of sodium. Since metals different from the alkali ones are not reactive or require the use of special conditions, it was decided to investigate a simple and practical electrochemical way, involving the use of an undivided cell, a sacrificial anode, and a constant current density [5]. 

Stock and Somieski271 much later prepared the methylsilanes CH3SiH3 and (CH3)2SiH2 from mono- and di-chlorosilane, respectively, at room temperature. 

Polysilanes have been investigated as the raw materials of new ceramics, photoresist polymers for high resolution lithography, semiconductors, electro-conductive polymers, etc. [46]. Polydimethylsilane is prepared by adding di-chlorosilane to the dispersed minute particles of sodium in toluene solution. 

After separation and purification by distillation, the difimctional compound dimethyl di-chlorosilane is then allowed to react with water tQ form a hydrolyzate, which is a mixture of cyclic and linear polydimethylsiloxanes. The linear components are low-molecular weight hydroxyl (silanol) terminated polymers. 

After polymeri2ation is carried out by blending mono- and difunctional chlorosilanes ia excess water, the siloxanes are separated from the water and neutraH2ed. Ratio of the mono-chain stopper to di-chain extender controls the length of the polymer. Once an equiHbrium mixture of chain lengths is catalyticaHy formed, volatile light ends are removed and the desired product results. 

Thienyllithium has been used for the preparation of triphenyl-2-thienylsilane, 2-thienylsulfinic acid, and di-2-thienylketone by means of reactions with triphenyl chlorosilane, sulfur dioxide, and... 

The transmetalation of trimethylsilylphosphanes with germanium and tin halides is a useful way to prepare compounds with P—Ge and P—Sn bonds by simple chlorosilane elimination. The reverse reaction, i. e. formation of P—Si bonds by chlorosilane cleavage of germyl- and stannylphosphanes has not yet been reported. Recently, we observed that hexachlorodisilane "transsilylates di-r-butyl(trimethyl-silyl)phosphane 1 much faster than tetrachlorosilane to give trichlorosilylphosphane 2 ... 

The reaction of (alkyl)chlorosilanes with a silica surface has been discussed and reviewed in great detail in literature [10], Although 5 different reactions are possible with di-, tri- or tetrachlorosilanes, basically two important surface species are created. The first is a monodentate silyl group, created by the monomolecular reaction of 1 silanol with 1 chlorosilane, according to reaction (A) (cfr. Figure 2). The second surface specie is a bidentate silyl group, created either by a bimolecular reaction (B) or by a consecutive reaction (C). We have reported previously [11] that the surface of MCM-48, prepared by the gemini 16-12-16 surfactant, possesses 0.9 OH/nm2. 

The use of LDMAN as the electron transfer reagent also allows (though a higher temperature of —50 °C is required) the preparation of a di(alkoxy)lithiosilane, (t-BuO)2PhSiLi, from the corresponding chlorosilane45. Alternatively, this compound may be obtained from the chlorosilane by reaction with lithium metal at 0°C96. 

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 horizontal reactor of the rotating drum type (Fig.8) does not have certain drawbacks characteristic of the vertical reactor. Particularly, rotating drums provide for a more thorough mixing of gaseous chlorine derivative with contact mass, because they increase the time of contact between the phases (10 times in comparison with the fluidised layer) consequently, the degree of chlorine derivative also grows. In the production of phenyl-chlorosilanes they create favourable conditions to increase the yield of di-phenyldichlorosilane. 

Once a silica is chosen, a reaction must be run to convert the silanols to surface-attached alkyl groups. This reaction may be accomplished as shown in Figure 6-2b with a mono-, di-, or trimethoxysilane. Each reaction results in a different nonpolar surface, but all are called a C]8 (or ODS) column. When a chlorosilane is used, reaction with a monochlorosilane is preferred to produce a consistent reaction without polymerization. However, not all... 

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