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Dimethyldichlorosilane is a tetrahedral organosilicon compound with the formula Si(CH 3) 2 Cl 2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains. Dimethyldichlorosilane is made on an industrial scale as the principal precursor to dimethylsilicone and polysilane compounds.
In the case of dimethyldichlorosilane, two chlorine atoms are available, so that a reaction with excess water produces a linear chain of ether-like linkages between silicon atoms. As in polyethers , these flexible linkages produce a rubbery polymer, polydimethylsiloxane (PDMS).
The main and most sought-after product is dimethyldichlorosilane: 2 CH 3 Cl + Si → (CH 3) 2 SiCl 2. A variety of other products are obtained, including trimethylsilyl chloride and methyltrichlorosilane. About 1 million tons of organosilicon compounds are prepared annually by this route. The method can also be used for phenyl chlorosilanes. [17]
Dimethyldichlorosilane (Si(CH 3) 2 Cl 2) is a key precursor to cyclic (D 3, D 4, etc.) and linear siloxanes. [5] The main route to siloxane functional group is by hydrolysis of silicon chlorides: 2 R 3 Si−Cl + H 2 O → R 3 Si−O−SiR 3 + 2 HCl. The reaction proceeds via the initial formation of silanols (R 3 Si−OH): R 3 Si−Cl + H 2 O ...
Commercially D 5 is produced from dimethyldichlorosilane. Hydrolysis of the dichloride produces a mixture of cyclic dimethylsiloxanes and polydimethylsiloxane. From this mixture, the cyclic siloxanes including D 5 can be removed by distillation.
Even though dimethyldichlorosilane is usually the major product, if methyltrichlorosilane is needed, the amount of metal catalyst is reduced. [1] Reactions.
Stock and Somieski completed the hydrolysis of dichlorosilane by putting the solution of H 2 SiCl 2 in benzene in brief contact with a large excess of water. [3] [5] A large-scale hydrolysis was done in a mixed ether/alkane solvent system at 0 °C, which gave a mixture of volatile and nonvolatile [H 2 SiO] n.
Dimethyldichlorosilane (Me 2 SiCl 2) is of particular value (precursor to silicones), but trimethylsilyl chloride (Me 3 SiCl) and methyltrichlorosilane (MeSiCl 3) are also valuable. [5]: 371 The mechanism of the direct process is still not well understood, despite much research. Copper plays an important role.