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Methyltrichlorosilane vapor reacts with water on surfaces to give a thin layer of methylpolysiloxane, which changes the contact angle of the surface to water. This effect arises because of the oriented layer of methyl groups, making a water-repellent film. [ 4 ]
The methylchlorosilanes react with water to produce hydrogen chloride, giving siloxanes. In the case of trimethylsilyl chloride, the hydrolyzed product is hexamethyldisiloxane: 2 ((CH 3) 3 SiCl + H 2 O → [(CH 3) 3 Si] 2 O + 2 HCl. The analogous reaction of dimethyldichlorosilane gives siloxane polymers or rings: n (CH 3) 2 SiCl 2 + n H 2 O ...
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.
Trichlorosilane can cause hazardous chemical reactions with moisture and humidity alone, and should be handled and stored under inert gas. [8] Spills of trichlorosilane may be neutralized using a 1-1 ratio of sodium hydroxide , or a 2-1 ratio of sodium bicarbonate to trichlorosilane. [ 9 ]
Methyltrimethoxysilane is usually prepared from methyltrichlorosilane and methanol: CH 3 SiCl 3 + 3 CH 3 OH → CH 3 Si(OCH 3) 3 + 3 HCl. Alcoholysis of alkylchlorosilanes typically proceeds via an S N 2 mechanism. Inversion of the configuration is favored during nucleophilic attack when displacing good leaving groups, such as chloride. [3]
Trichlorosilane is produced commercially by the reaction of hydrogen chloride with silicon: Si + 3 HCl → HSiCl 3 + H 2. Many alkoxy hydrosilanes are generated by alcoholysis of trichlorosilane. One example is triethoxysilane: HSiCl 3 + 3 EtOH → HSi(OEt) 3 + 3 HCl. Organohydrosilanes can be prepared by partial hydrosilation of silane itself:
The mechanism of the direct synthesis is not known. However, the copper catalyst is essential for the reaction to proceed. In addition to dimethyldichlorosilane, products of this reaction include CH 3 SiCl 3, CH 3 SiHCl 2, and (CH 3) 3 SiCl, which are separated from each other by fractional distillation. The yields and boiling points of these ...
Water-reactive substances [1] are those that spontaneously undergo a chemical reaction with water, often noted as generating flammable gas. [2] Some are highly reducing in nature. [ 3 ] Notable examples include alkali metals , lithium through caesium , and alkaline earth metals , magnesium through barium .