Silicon tetrachloride synthesis

Denmark SE, Eklov BM (2008) Neutral and cationic phophoramide adducts of silicon tetrachloride synthesis and characterization of their solution and solid-state structures. ChemEur J 14 234-239... 

Aminolysis of the corresponding halides is the preferred method for the synthesis of dialkylamino derivatives of boron,1 silicon,2 germanium,3 phosphorus,4 arsenic,5 and sulfur.6 (Dialkylamino) chlorosilanes are prepared stepwise by the reaction of silicon tetrachloride with dialkylamines. This method may be utilized equally well for the conversion of alkyl- or aryl-substituted halides [e.g., (CH3) SiCl4. ] or of oxide and sulfide halides (e.g., POCl3 or PSC13) to the corresponding dialkylamino compounds. 

The 1980s saw major developments in secondary synthesis and modification chemistry of zeolites. SUicon-enriched frameworks of over a dozen zeolites were described using methods of (i) thermochemical modification (prolonged steaming) with or without subsequent acid extraction, (ii) mild aqueous ammonium fluorosilicate chemistry, (iii) high-temperature treatment with silicon tetrachloride and (iv) low-temperature treatment with fluorine gas. Similarly, framework metal substitution using mild aqueous ammonium fluorometaUate chemistry was reported to incorporate iron, titanium, chromium and tin into zeolite frameworks by secondary synthesis techniques. 

Methyltrichlorosilane is produced by the Grignard reaction of silicon tetrachloride and methylmagnesium chloride (structure 17.24). Dimethyldichlorosilane, used in the synthesis of polydimethylsiloxane, is obtained by the reaction of methylmagnesium chloride and methyltrichlorosilane (structure 17.25). 

The traditional synthesis of miinchnones involves the cyclodehydration of N-acylamino acids usually with acetic anhydride or another acid anhydride. Potts and Yao (3) were apparently the first to employ dicyclohexylcarbodiimide (DCC) to generate mesoionic heterocycles, including miinchnones. Subsequently, Anderson and Heider (4) discovered that miinchnones can be formed by the cyclodehydration of N-acylamino acids using Ai-ethyl-Ai -dimethylaminopropylcarbodiimide (EDC) or silicon tetrachloride. The advantage of EDC over DCC is that the urea byproduct is water soluble and easily removed, in contrast to dicyclohexylurea formed from DCC. Although the authors conclude that the traditional Huisgen method of acetic anhydride is still the method of choice, these two newer methods are important alternatives. Some examples from the work of Anderson and Heider are shown. The in situ generated miinchnones (not shown) were trapped either with dimethyl acetylenedicarboxylate (DMAD) or ethyl propiolate. 

Silicon tetrafluoride, for laboratory use, can be obtained from fluorosilicic acid1 or by thermolysis at 450-600°C of barium or disodium hexafluorosilicate.2 3 However, the most conventional synthesis of pure silicon tetrafluoride is by fluorination of silicon tetrachloride with sodium fluoride in acetonitrile.4... 

Gas-Phase Synthesis. A gas-phase synthesis route to making fine, pure SiC having controllable properties has been described (78,79). Methane was used as a carbon source if required, and the plasma decomposition of three feedstocks, silicon tetrachloride [10026-04-7], SiQ dimethyldichlorosilane, and methyltrichlorosilane [75-79-6], CH Cl Si, into fine SiC powders was investigated. 

Uses. The most important commercial use for benzonitrile is the synthesis of benzoguanamine, which is a derivative of melamine and is used in protective coatings and molding resins (see Amino RESINS Cyanamides). Other uses for benzonitrile are as an additive in nickel-plating baths, for separating naphthalene and alkylnaphthalenes from nonaromatics by azeotropic distillation (qv), as a jet-fuel additive, in cotton bleaching baths, as a drying additive for acrylic fibers, and in the removal of titanium tetrachloride and vanadium oxychloride from silicon tetrachloride. 

Thus, the direct synthesis of phenylchlorosilanes produces a complex mixture, which, apart from phenyltrichlorosilane, diphenyldichlorosilane, phenyldichlorosilane and triphenylchlorosilane, also contains silicon tetrachloride, trichlorosilane, benzene, solid products (diphenyl and carbon) and a gaseous product (hydrogen). It also forms high-boiling polyolefines, which are part of tank residue and can deposit on contact mass, reducing its activity. It should be kept in mind that the production of phenylchlorosilanes requires silicon with a minimal impurity of aluminum, because the aluminum chloride formed contributes to the detachment of the phenyl group from phenylchlorosilanes at higher temperature. The harmful effect of aluminum chloride is counteracted by the addition of metal salts to contact mass, which form a nonvolatile and nonreactive complex with aluminum chloride. 

C (intermediate), containing a mixture of trichlorosilane and silicon tetrachloride. It can be used for phenylchlorosilane synthesis by high-temperature condensation. 

Temperature has a profound effect on the direct synthesis of trichlorosi-lane. 280-320 °C are optimal when temperature is raised above 320 °C, the content of silicon tetrachloride in reaction products is increased if the temperature falls below 280 °C, the amount of dichlorosilane and polychlorosilanes grows. The synthesis of trichlorosilane is negatively affected by moisture that is why it is necessary to dry raw stock and equipment thoroughly. 

In this case, similarly to the vinyltrichlorosilane case, in the conditions of synthesis (600-640 °C) there is a secondary reaction of reduction, which forms silicon tetrachloride and benzene. However, if the process is conducted in the presence of an initiator (5% of diazomethane), it is possible to reduce the temperature down to 500-550 °C. Then the secondary reaction proceeds very slowly, which increases the yield of phenyltrichlorosilane by 1.5 times. To suppress the reduction process, one can also add... 

The main raw stock for the synthesis of tetraalkoxy- and tetraaroxysi-lanes is silicon tetrachloride thus, below we consider the methods of its preparation. 

These results led Schumb and Sailer to devise a two-stage synthesis 6 which allows a much better control. The sodium first is allowed to react with a halide such as chlorobenzene in a solvent to yield phenyl sodium. After the heat of this reaction is dissipated, the phenyl sodium is mixed with the silicon halide in solution, and a milder reaction ensues. In this way hexaphenyldisilane was made from hexachlorodisilane, and hexaphenyldisiloxane from hexachlorodisiloxane. Moreover, phenyltrichlorosilane was made by the action of less than one equivalent of sodium phenyl on silicon tetrachloride. The use of a separately prepared sodium alkyl in this way provides the same degree of control as in a Grignard synthesis, and the reactions indeed are very similar. Organolithium compounds probably could be used in the same way. 

Of the other methods for preparing organosilicon compounds, the Grignard and direct methods have been selected for further consideration here. This is not to say that the Wurtz synthesis and the meta-thetical reactions of silicon tetrachloride with alkyls of zinc and mer-... 

As in other preparative methods for organosilicon compounds, the direct synthesis produces a mixture of methylchlorosilanes rather than the single compound shown in equation 3. Besides dimethyl-dichlorosilane, the mixture usually contains silicon tetrachloride, tri-chlorosilane, methyltrichlorosilane, methyldichlorosilane, trimethyl-chlorosilane, and even silicon tetramethyl. Under proper conditions, dimethyldichlorosilane is the principal product. Of the other compounds, methyltrichlorosilane usually is next in abundance this substance finds use in the cross-linked methyl silicone resins, or it can be methylated further by the Grignard method to increase the yield of dimethyldichlorosilane. There is no way of recycling it in the direct process, and so supplemental operations are required for the conversion. The interconversion of this and the other minor products of the direct synthesis, involving the exchange of methyl and chlorine groups as desired, has been a special study in itself.10... 

Shtetter synthesis. The process of forming chloroalkyl compounds of silicon by absorbing unsaturated hydrocarbons in silicon tetrachloride under pressure and with the aid of metallic chlorides or oxychlorides as catalysts. The method was patented by I. I. Shtetter in 1935. 

PEPTIDE SYNTHESIS Diphenylphosphoryl azide. N-Ethoxycarbonyl-2-ethoxy-l,3-di-hydroquinoline. o-Nitrophenylsulfenyl chloride. 2-Picolyl chloride hydrochloride. Silicon tetrachloride. Triphenylpbosphine. Triphcnylphosphinc-Carbon tetrachloride. Triphcnyl phosphite. 

Silane, germane, and stannane can be synthesized by the reduction of a variety of silicon, germanium, or tin compounds with active metal hydrides. The general method described below, involving the lithium hydroaluminate (LiAlHi) reduction of silicon tetrachloride and tin (IV) chloride, is convenient for the eflficient preparation of 1-50 mmoles of silane and stannane. The method is easily adapted to the synthesis of the deuterio compounds, i.e., silane-d4, germane-dt, and stannane-d4, by... 

Summary The synthesis of trichlorosilane (TCS) from silicon and HCl produces considerable amounts of less desired chlorosilanes by side reactions, especially silicon tetrachloride (STC). The results of this paper support the view that the undesired STC is formed from TCS in a consecutive reaction, which is probably catalyzed by Si impurities and which is preferred at low space velocity and high temperatures. It seems that TCS selectivity losses are due to regions or spots in the industrial reactor with such conditions. XPS surface concentrations of Si impurities dramatically change with the proceeding synthesis reaction because of the mobility of the impurity species and do not correlate with results of Si bulk analysis. 

Non-chlorine methods that are based on obtaining basic organic compounds of silicon fr om artificial amorphous silica have many stages and are ineffective, as they use the silica obtained by hydrolysis of tetraalkoxysilane or silicon tetrachloride. So it became necessary to find methods of SOC synthesis based on natural amorphous silica. Such methods are currently being developed by some authors [1-3]. 

Organosilicon compounds can be prepared by reaction of silicon halides with other organometallic compounds. The first such synthesis (1865) was that by Friedel and Crafts270 who heated silicon tetrachloride with dimethyl-zinc in a sealed tube at 200° ... 

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