Silicon tetrachloride water

Monosilicic acid can be prepared from the silicate-acid system, just as from the silicon tetrachloride-water or methyl orthosilicate-water systems [746]. Acetic acid or resin exchangers in the H-form can be added to dilute solutions of sodium silicate. Monosilicic acid is formed by reaction of solid calcium orthosilicate with hydrogen chloride in methanol, according to the equation ... 

Silicon tetrachloride. S1CI4 m.p. — TO C, b.p. 57°C. Colourless liquid (Si plus CI2 followed by distillation). Hydrolyses in moist air or in water. 

Silicon tetrachloride is a colourless liquid, b.p. 216.2 K, and again the molecule has a covalent structure. Silicon tetrachloride is hydrolysed by water ... 

When this reaction has occuiTcd accidentally sufficient hydrogen chloride has been liberated to explosively burst the vessel. The purest form of hydrogen chloride is made by the action of water on silicon tetrachloride ... 

Silicon reacts directly with chlorine to form silicon tetrachloride, SiCl4 (this reaction was introduced in Section 14.17, as one step in the purification of silicon). This compound differs strikingly from CC14 in that it reacts readily with water as a Lewis acid, accepting a lone pair of electrons from H20 ... 

Explain why silicon tetrachloride reacts with water to produce SiQ2 but carbon tetrachloride does not react with water. 

With 29Si NMR spectroscopy we can show that the chlorosilanol-intermediates of the partial hydrolysis of silicon tetrachloride are stable in solution for more than one houn After fast mixing of diluent water to prevent fast reactions at the dropping point we can see with 29Si NMR Cl3SiOH, Cl2Si(OH)2, and ClSi(OH)3 (table 1). 

The vapor pressure at 0° (43 mm.) is generally a sufficient criterion for purity. (The checkers also used infrared spectroscopy and noted a trace of impurity of silicon tetrachloride.) Elemental analysis is readily accomplished by heating a weighed sample at 160° for 18 hours with a slight excess of water in a sealed glass tube. A 15 to 20% excess of water over that required by the equation ... 

Fumed silica is prepared by burning volatile silicon compounds such as silicon tetrachloride. This type of silica contains less than 2% combined water and generally no free water. It reacts readily with hydroxyl groups. The particle size is in the region 5-10 nm. Fumed silicas are not generally used in conventional rubber compounding but find application with silicone rubber. The recognised surface area values for best reinforcement of silicone rubber by an amorphous silica lies between 150-400 m2/g. 

FIGURE 3 2 Solvent extraction efficiencies (EF) as functions of dielectric constants (D), solubility parameters (6), and polarity parameters (P and E -). Solvents studied silicon tetrachloride, carbon disulfide, n pentane. Freon 113, cyclopentane, n-hexane, carbon tetradiloride, diethylether, cyclohexane, isooctane, benzene (reference, EF 100), toluene, trichloroethylene, diethylamine, chloroform, triethylamine, methylene, chloride, tetra-hydrofuran, l,4 dioxane, pyridine, 2 propanol, acetone, ethanol, methanol, dimethyl sulfoxide, and water. Reprinted with permission from Grosjean. ... 

Silicon tetrachloride (SiCy, produced when both silicon and chlorine are combined at high temperatures, is used by the military to produce smoke screens. When released in air, it reacts with the moisture in the atmosphere to produce dense clouds of water vapor. 

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. 

Preparation of Silicon Tetrachloride. To prepare amorphous silicon, mix 2 g of dry quartz sand comminuted in an iron mortar with 3 g of powdered magnesium. Spill the mixture into a refractory test tube, secure it at an angle in a stand, and carefully heat first the entire tube, and then its bottom end more intensively until the mixture ignites. When the reaction ends, break the test tube, extract the product, crush it, and wash it in a fume cupboard, wear eye protection. ) with dilute hydrochloric acid until the flashes of light vanish. Filter off the silicon, wash it on the filter with distilled water, and dry it in the air. 

Water causes immediate and almost quantitative decomposition of sulphur tetrachloride, with formation of hydrochloric and sulphurous acids, the latter standing in the same relation to sulphur tetrachloride as carbonic acid to carbon tetrachloride and silicic acid to silicon tetrachloride ... 

Silicon tetrachloride (20 gms.) is mixed willi clilorhonzono (50 gms.) and four times l.lio volume of dry ether, and a small quantity of acetic ester (I to 2 gms.) added. Tlio Hash is attached to a rollnx condenser, ami then sodium (25 gms.) in small pieces is gradually added. A vigorous reaction follows and the flask should be repeatedly shaken. When the roaoLion is completed, water is added hi remove any nnn.ttii.ekod sodium, and then enough to dissolve the sodium chloride, after which the mixture is extracted with hot. benzene. White crystals separate from the benzene solution, m.p. 22H°. 

Stable at room temperature but decomposes at approximately 400°C. Slowly decomposes in water practically insoluble in alcohol, ether, benzene, chloroform, silicochloroform, and silicon tetrachloride. Decomposes in potassium hydroxide solutions.1... 

Nonmetal Halides. Vigorous or explosive reactions occur with phosphorus tribromide on addition of drops of water,20 phosphorus trichloride, phosphorus pentachloride,21 diselenium dichloride,22 sulfur dichloride, boron tribromide, sulfur dibromide,17 seleninyl bromide,23 phosphoryl chloride, sulfinyl fluoride, silicon tetrachloride, and silicon tetrafluoride.24... 

Both silicon tetrachloride and trichlorosilane are fuming liquids with suffocating odors. They both react with water to give off HC1 vapor. 

A good dehydrating substance for chlorobenzene is silicon tetrachloride, which easily reacts with water in chlorobenzene forming a sediment, sili-cagel. Moisture content in chlorobenzene (as well as in methylchloride and ethylchloride) after dtying should not exceed 0.02%. 

The first rectification stage. From collector 10 the mixture of methyl-chlorosilanes is periodically fed into pressure container 11, from where at 50-65 °C it is sent through heater 12 (by self-flow) onto the feeding plate of rectification tower 13. From the tower the tank liquid (methyltrichloro-silane, dimethyldichlorosilane and tank residue) flows into tank 14, where the temperature of 80-90 °C is maintained, and from there is continously poured into collector 22. After the tower, vapours of the head fraction at a temperature below 58 °C, consisting of the rest of methylchloride, di- and trichlorosilane, dimethylchlorosilane, methyldichlorosilane and the azeotropic mixture of silicon tetrachloride and trimethylchlorosilane are sent into refluxer 15, cooled with water, and into refluxer 16, cooled with salt solution (-15 °C). After that, through cooler 17 the condensate is gathered in receptacle 19. Volatile products, which did not condense in reflux-ers 15 and 16, are sent into condenser 18 cooled with Freon (-50 °C). There they condense and also flow into receptacle 19. As soon as it is accumulated, the condensate is sent from receptacle 19 into collector 20. 

The production of silicon tetrachloride (Fig. 46) comprises the following main stages the condensation of dihydroxydiphenylsilane and water distillation the heterofunctional condensation of the product of stage I with tri-acetoxymethylsilane the flushing of the obtained product with water and the distillation of the solvent. 

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