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26-452: Methyltrichlorosilane results from the direct process of chloromethane with elemental silicon in the presence of a copper catalyst, usually at a temperature of at least 250   °C. While this reaction is the standard in industrial silicone production and is nearly identical to the first direct synthesis of methyltrichlorosilane, the overall process is inefficient with respect to methyltrichlorosilane. Even though dimethyldichlorosilane

52-679: A Si-Si backbone. For example, dodecamethylcyclohexasilane can be prepared in this way: 6 ( CH 3 ) 2 SiCl 2 + 12 M ⟶ [ ( CH 3 ) 2 Si ] 6 + 12 MCl   ( M = Na , K ) {\displaystyle {\ce {6 (CH3)2SiCl2 + 12 M -> [(CH3)2Si]6 + 12 MCl}}\ {\ce {(M = Na, K)}}} The reaction also produces polydimethylsilane and decamethylpentasilane. Diverse types of dichlorosilane precursors, such as Ph 2 SiCl 2 , can be added to adjust

78-502: A chemist from General Electric, and Richard Müller , working independently in Germany, found an alternate synthesis of dimethyldichlorosilane that allowed it to be produced on an industrial scale. This Direct Synthesis, or Direct process , which is used in today’s industry, involves the reaction of elemental silicon with methyl chloride in the presence of a copper catalyst. Rochow's synthesis involved passing methyl chloride through

104-565: A heated tube packed with ground silicon and copper(I) chloride . The current industrial method places finely ground silicon in a fluidized bed reactor at about 300 °C. The catalyst is applied as Cu 2 O . Methyl chloride is then passed through the reactor to produce mainly dimethyldichlorosilane. 2 CH 3 Cl + Si ⟶ ( CH 3 ) 2 SiCl 2 {\displaystyle {\ce {2 CH3Cl + Si -> (CH3)2SiCl2}}} The mechanism of

130-429: A highly crosslinked material called poly(methylsilyne) : The reaction illustrates the susceptibility of silicon halides to reductive coupling. Poly(methylsilyne) is soluble in organic solvents, and can be applied to surfaces before being pyrolyzed to give the ceramic material, silicon carbide . One use for methyltrichlorosilane is in the production of methyl silicone resins (highly crosslinked polymers). Because of

156-854: 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. The first organosilicon compounds were reported in 1863 by Charles Friedel and James Crafts who synthesized tetraethylsilane from diethylzinc and silicon tetrachloride . However, major progress in organosilicon chemistry did not occur until Frederick Kipping and his students began experimenting with diorganodichlorosilanes ( R 2 SiCl 2 ) that were prepared by reacting silicon tetrachloride with Grignard reagents . Unfortunately, this method suffered from many experimental problems. In

182-808: Is easily hydrolyzed, it cannot be handled in air. One method used to overcome this problem is to convert it to a less reactive bis(dimethylamino)silane. ( CH 3 ) 2 SiCl 2 + 4 HN ( CH 3 ) 2 ⟶ ( CH 3 ) 2 Si [ N ( CH 3 ) 2 ] 2 + 2 H 2 N ( CH 3 ) 2 Cl {\displaystyle {\ce {(CH3)2SiCl2 + 4 HN(CH3)2 -> (CH3)2Si[N(CH3)2]2 + 2H2N(CH3)2Cl}}} Another benefit to changing dimethyldichlorosilane to its bis(dimethylamino)silane counterpart

208-401: Is of particular value (precursor to silicones ), but trimethylsilyl chloride (Me 3 SiCl) and methyltrichlorosilane (MeSiCl 3 ) are also valuable. The mechanism of the direct process is still not well understood, despite much research. Copper plays an important role. The copper and silicon form intermetallics with the approximate composition Cu 3 Si. This intermediate facilitates

234-459: Is produced annually using this process. Few companies actually carry out the Rochow process, because of the complex technology and high capital requirements. Since the silicon is crushed prior to reaction in a fluidized bed , the companies practicing this technology are referred to as silicon crushers . The relevant reactions are (Me = CH 3 ): Dimethyldichlorosilane (Me 2 SiCl 2 )

260-523: Is purified by fractional distillation . Although the boiling points of the various chloromethylsilanes are similar (Me 2 SiCl 2 : 70   °C, MeSiCl 3 : 66   °C, Me 3 SiCl: 57   °C, MeHSiCl 2 : 41   °C, Me 2 HSiCl: 35   °C), the distillation utilizes columns with high separating capacities, connected in series. The purity of the products crucially affects the production of siloxane polymers, otherwise chain branching arises. Dimethyldichlorosilane Dimethyldichlorosilane

286-1035: Is that it forms an exactly alternating polymer when combined with a disilanol comonomer. n   ( CH 3 ) 2 Si [ N ( CH 3 ) 2 ] 2 + n   HO ( CH 2 ) 2 SiRSi ( CH 2 ) 2 OH ⟶ [ ( CH 3 ) 2 SiO ( CH 2 ) 2 SiRSi ( CH 2 ) 2 O ] n + 2 n   HN ( CH 3 ) 2 {\displaystyle n\ {\ce {(CH3)2Si[N(CH3)2]2}}+n\ {\ce {HO(CH2)2SiRSi(CH2)2OH -> [(CH3)2SiO(CH2)2SiRSi(CH2)2O]}}_{n}+2n\ {\ce {HN(CH3)2}}} Sodium–potassium alloy can be used to polymerize dimethyldichlorosilane, producing polysilane chains with

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312-686: Is the most common technology for preparing organosilicon compounds on an industrial scale. It was first reported independently by Eugene G. Rochow and Richard Müller in the 1940s. The process involves copper-catalyzed reactions of alkyl halides with elemental silicon, which take place in a fluidized bed reactor . Although theoretically possible with any alkyl halide, the best results in terms of selectivity and yield occur with chloromethane (CH 3 Cl). Typical conditions are 300   °C and 2–5   bar. These conditions allow for 90–98% conversion for silicon and 30–90% for chloromethane. Approximately 1.4 Mton of dimethyldichlorosilane (Me 2 SiCl 2 )

338-429: Is used as a reagent in silicon carbide epitaxy to introduce chloride in the gas phase. Chloride is used to reduce the tendency of silicon to react in the gas phase and thus to increase the growth rate of the process. Methyltrichlorosilane is an alternative to HCl gas or to trichlorosilane . Direct process The direct process , also called the direct synthesis , Rochow process , and Müller-Rochow process

364-474: Is usually the major product, if methyltrichlorosilane is needed, the amount of metal catalyst is reduced. Methyltrichlorosilane undergoes hydrolysis, shown in idealized form here: The silanol is unstable and will eventually condense to give a polymer network: Methyltrichlorosilane undergoes alcoholysis (reaction with alcohol) to give alkoxysilanes. Methanol converts it to trimethoxymethylsilane : Reduction of methyltrichlorosilane with alkali metals forms

390-497: The 1930s, the demand for silicones increased due to the need for better insulators for electric motors and sealing materials for aircraft engines, and with it the need for a more efficient synthesis of dimethyldichlorosilane. To solve the problem, General Electric , Corning Glass Works , and Dow Chemical Company began a partnership that ultimately became the Dow Corning Company. During 1941–1942, Eugene G. Rochow ,

416-657: The contact angle of the surface to water. This effect arises because of the oriented layer of methyl groups, making a water-repellent film. Filter paper treated with methyltrichlorosilane allows organic solvents to pass through, but not water. Another benefit of such water-repellent films is that the polymers formed are stable: one of the only ways to remove the siloxane film is by acid strong enough to dissolve silicone. A combination of methyltrichlorosilane and sodium iodide can be used to cleave carbon-oxygen bonds such as methyl ethers. Esters and lactones can also be cleaved with methyltrichlorosilane and sodium iodide to give

442-420: The corresponding carboxylic acids . Acetals convert to carbonyl compounds. Thus, methyltrichlorosilane can be used to remove acetal protecting groups from carbonyl compounds under mild conditions. Methyltrichlorosilane and sodium iodide can be used as a means of converting alcohols to their corresponding iodides ; however, this reaction does not work as well with primary alcohols. Methyltrichlorosilane

468-455: The direct process should be dichlorodimethylsilane, Me 2 SiCl 2 . However, many other products are formed. Unlike most reactions, this distribution is actually desirable because the product isolation is very efficient. Each methylchlorosilane has specific and often substantial applications. Me 2 SiCl 2 is the most useful. It is the precursor for the majority of silicon products produced on an industrial scale. The other products are used in

494-531: 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 products are shown in the following chart. Dimethyldichlorosilane hydrolyzes to form linear and cyclic silicones , compounds containing Si-O backbones. The length of

520-603: The formation of the Si-Cl and Si-Me bonds. It is proposed that close proximity of the Si-Cl to a copper-chloromethane "adduct" allows for formation of the Me-SiCl units. Transfer of a second chloromethane allows for the release of the Me 2 SiCl 2 . Thus, copper is oxidized from the zero oxidation state and then reduced to regenerate the catalyst. The chain reaction can be terminated in many ways. These termination processes give rise to

546-641: The hydrolysis of dimethoxydimethylsilanes is slower, it is advantageous when the hydrochloric acid byproduct is unwanted: n   ( CH 3 ) 2 Si ( OCH 3 ) 2 + n   H 2 O ⟶ [ ( CH 3 ) 2 SiO ] n + 2 n   CH 3 OH {\displaystyle n\ {\ce {(CH3)2Si(OCH3)2}}+n\ {\ce {H2O -> [(CH3)2SiO]}}_{n}+2n\ {\ce {CH3OH}}} Because dimethyldichlorosilane

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572-490: The other products that are seen in the reaction. For example, combining two Si-Cl groups gives the SiCl 2 group, which undergoes Cu-catalyzed reaction with MeCl to give MeSiCl 3 . In addition to copper, the catalyst optimally contains promoter metals that facilitate the reaction. Among the many promoter metals, zinc, tin, antimony, magnesium, calcium, bismuth, arsenic, and cadmium have been mentioned. The major product for

598-403: The preparation of siloxane polymers as well as specialized applications. Dichlorodimethylsilane is the major product of the reaction, as is expected, being obtained in about 70–90% yield. The next most abundant product is methyltrichlorosilane (MeSiCl 3 ), at 5–15% of the total. Other products include Me 3 SiCl (2–4%), MeHSiCl 2 (1–4%), and Me 2 HSiCl (0.1–0.5%). The Me 2 SiCl 2

624-494: The properties of the polymer. In organic synthesis it (together with its close relative diphenyldichlorosilane ) is used as a protecting group for gem -diols . The main purpose of dimethyldichlorosilane is for use in the synthesis of silicones , an industry that was valued at more than $ 10 billion per year in 2005. It is also employed in the production of polysilanes, which in turn are precursors to silicon carbide . In practical uses, dichlorodimethylsilane can be used as

650-2043: The resulting polymer is dependent on the concentration of chain ending groups that are added to the reaction mixture. The rate of the reaction is determined by the transfer of reagents across the aqueous-organic phase boundary; therefore, the reaction is most efficient under turbulent conditions. The reaction medium can be varied further to maximize the yield of a specific product. n   ( CH 3 ) 2 SiCl 2   + n   H 2 O   ⟶ [ Si ( CH 3 ) 2 O ] n + 2 n   HCl m   ( CH 3 ) 2 SiCl 2   +   ( m + 1 )   H 2 O   ⟶     HO [ Si ( CH 3 ) 2 O ] m H   +   2 m   HCl {\displaystyle {\begin{alignedat}{4}n\ {\ce {(CH3)2SiCl2}}\ +&&n\ {\ce {H2O}}\ \longrightarrow &&{\ce {[Si(CH3)2O]}}_{n}\quad \,+&&2n\ {\ce {HCl}}\\m\ {\ce {(CH3)2SiCl2}}\ +&&\ (m\!+\!1)\ {\ce {H2O}}\ \longrightarrow &&\ \ {\ce {HO[Si(CH3)2O]}}_{m}{\ce {H}}\ +&&\ 2m\ {\ce {HCl}}\end{alignedat}}} Dimethyldichlorosilane reacts with methanol to produce dimethoxydimethylsilanes. ( CH 3 ) 2 SiCl 2 + 2 CH 3 OH ⟶ ( CH 3 ) 2 Si ( OCH 3 ) 2 + 2 HCl {\displaystyle {\ce {(CH3)2SiCl2 + 2CH3OH -> (CH3)2Si(OCH3)2 + 2 HCl}}} Although

676-448: The stability of the cross-linked polymers resulting from condensation, the resin is stable to 550   °C in a vacuum, making it an ideal material for electrical insulation at high temperatures. These resins can be used to coat computer chips or other electronic parts since they both repel water and provide thermal isolation. Methyltrichlorosilane vapor reacts with water on surfaces to give a thin layer of methylpolysiloxane, which changes

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