Hydrolysis of chlorosilanes

Mixing trichlorosilane, acetonitrile and diphenylsulphoxide, carried out at 10°C, detonated. This accident was put down to the exothermic addition reaction of the silicon-hydrogen bond on the carbon-nitrogen triple bond of nitrile. Other interpretations are possible for instance, the effect of traces of hydrogen chloride formed by the hydrolysis of chlorosilane on acetonitrile. 

Tetrachlorosilane was added to aqueous ethanol (the presence of water was accidental). There was no proper stirring during this operation, which led to the formation of two liquid layers of compounds that did not react. The very fast and exothermic reaction of the alcoholysis-hydrolysis of chlorosilane started violently and the large compoundion of hydrogen chloride caused the reactor to detonate. 

The monomers for silicone polymer have been silanols which are very unstable compounds and are produced by the hydrolysis of chlorosilanes. Then, they condense intermolecularly to yield silicon polymers. 

The self-organization of polysilanols in the presence of other hydrogen bond acceptors has been studied by several groups.512-516 Several other publications have dealt with the stepwise synthesis of siloxane and siloxanol chains.450,517-522 Recent work on fully condensed siloxane rings and silsesquioxane cages involves the non-aqueous hydrolysis of chlorosilanes - as well as mechanistic and structural studies. 

Polysiloxane fluids and resins are obtained by hydrolysis of chlorosilanes such as dichloro-dimethyl-, dichloromethylphenyl-, and dichlorodiphenylsilanes [Brydson, 1999 Hardman and Torkelson, 1989]. The chlorosilane is hydrolyzed with water to a mixture of chlorohy-droxy and dihydroxysilanes (referred to as silanols), which react with each other by dehydration and dehydrochlorination. The product is an equilibrated mixture of approximately equal... 

Ferric chloride is sometimes an important constituent of the hydrolyzing mixture. The formation of gels during polymerization can be controlled. Patents are in existence covering the hydrolysis of chlorosilanes by pouring their solutions onto the surface of a swirling solution of the active electrolyte. 

We will next deal with the hydrolysis reaction. Traditionally, most industrial processes used to make products containing the siloxane bond, such as silicones and silicates, involve the hydrolysis of chlorosilanes. This causes hydrochloric acid to be produced as a by-product. Hydrochloric acid is, however, an unacceptable by-product in products such as zinc-rich silicate coatings and glasses and glass ceramics made by the sol-gel process. The alternative is to use alkoxysilanes, which when hydrolyzed, have alcohols as a by-product. 

S, N or P. The silicones industry is largely based on the hydrolysis of chlorosilanes, while the formation of silicas is often achieved by hydrolysis of alkoxysilanes. 

Although the details of the mechanism are unclear, the final step in the acid hydrolysis of chlorosilanes 39 is an isomerization involving a l,2-OH/Me3Si exchange to give a range of diols 40, (Scheme 7)149. 

Catalytic Rate Constants k and Activation Parameters for Hydrolysis of Chlorosilanes in Anisole at 20°C... 

The silanization reaction in liquid phase (usually in dry toluene) is technologically more convenient, although it is practically impossible to ensure the complete absence of water in a reaction mixture that leads to hydrolysis of chlorosilanes. Using deuterium exchange, Roumeliotis and Unger [55] analyzed surface silanol concentration before and after the modification with different reagents (Table 3-2). 

Fluoride ion activator can be replaced by hydroxide ion. To avoid hydrolysis of chlorosilanes, a heterogeneous system consisting of powdered sodium hydroxide in benzene was found to be particularly effective [Eq.(21)]. [20]. 

This reaction is analogous to the hydrolysis of chlorosilanes. In both cases, cyclic and linear oligomers are formed if dichlorosilanes are used [1]. Further analogies between hydrolyses and carbodiimidolyses by BTSC were reported for reactions with trichlorosilanes RSiCb (R = H, Cl, Alkyl, Aryl) [2, 3] and other element halides [3 - 6]. A characteristic sol-gel transition was observed ... 

Colloidal silicon dioxide is prepared by the vapor hydrolysis of chlorosilanes, such as silicon tetrachloride, at 1800°C using a hydrogen-oxygen flame. 

Linear siloxanes with SiCl-end groups produced by hydrolysis of chlorosilanes with a sub-.stoichiometric quantity of water... 

TABLE 8. Kinetic orders for the nucleophile-catalysed hydrolysis of chlorosilanes... 

Hydrolysis in the silicones is usually just a special case of the reaction with organic halides. The most important reaction is the preparation of siloxanes by the hydrolysis of chlorosilanes and the subsequent condensation to form the commercially important polysiloxanes (see Chap. 15). Diethyl silane diol, (CjHs)2Si(OH)s, and the corresponding di-n-propyl and di-n-butyl diols have been made by hydrolyzing the dichlorosilanes. The trimethyl and triethyl silicon hydroxides have been prepared by the hydrolysis of complex organic silicon compounds containing the aceto and the amino group, respectively. ... 

Silicon.—The sterochemistry for nucleophilic substitution at silicon has continued to receive detailed study. The hydrolysis of chlorosilanes in weakly polar solvents is catalysed by nucleophiles such as HMPA, DMSO, and DMF. Reaction involves retention of configuration at silicon, with nucleophilic attack by water on a five-co-ordinate silicon species. Stable 1 1 adducts of HMPA and McsSiX have been isolated, which are thought to have the structure... 

Polysiloxanes are inorganic polymeric materials well known under the common name of silicone rubbers or simply silicones. Instead of the classic carbon chain skeleton, these particular class of polymers are based on a chemical bond occurring between sihcon and oxygen (Si—O) similar to that found in silicates. Sihcones are usually prepared from the hydrolysis of chlorosilanes such as dimethyl dichlorosilane that yields a silanol according to the chemical reaction Hsted below ... 

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