Silicon, chloride

Silicon, unlike carbon, does notiorm a very large number of hydrides. A series of covalently bonded volatile hydrides called silanes analogous to the alkane hydrocarbons is known, with the general formula Si H2 + 2- I uf less than ten members of the series have so far been prepared. Mono- and disilanes are more readily prepared by the reaction of the corresponding silicon chloride with lithium aluminium hydride in ether ... 

Silcones are important products of silicon. They may be prepared by hydrolyzing a silicon organic chloride, such as dimethyl silicon chloride. Hydrolysis and condensation of various substituted chlorosilanes can be used to produce a very great number of polymeric products, or silicones, ranging from liquids to hard, glasslike solids with many useful properties. 

Nevertheless Kipping made a number of contributions of value to the modem silicone industry. In 1904 he introduced the use of Grignard reagents for the preparation of chlorosilanes and later discovered the principle of the inter-molecular condensation of the silane diols, the basis of current polymerisation practice. The term silicone was also given by Kipping to the hydrolysis products of the disubstituted silicon chlorides because he at one time considered them as being analogous to the ketones. 

Chemical Designations - Synortyms Silicon chloride Chemical Formula SiCl4. 

Spontaneous explosions have been observed [1] with this dangerously explosive material, especially when pure. A sample at 0°C exploded during removal of traces of benzene under high vacuum [2], A residue containing the tetraazide, silicon chloride triazide and probably silicon dichloride diazide, exploded on standing for 2 or 3 days, possibly owing to hydrazoic acid produced by hydrolysis. 

The formation of oligomeric silicon chlorides SixCly from 1 with Si2Cl6 [1] might be due to base -catalysed decomposition of intermediate Me3Si-SiCl3 (a known compound), which would be the product of an anionic trichlorosilylation of the trimethylsilyl group of silylphosphane 1. 

The surface of silica turns hydrophobic on treatment with organo-silicon chlorides. Water vapor adsorption isotherms measured by Stober (219) showed a very marked decrease in reversible adsorption. Less than 0.3 primary adsorption centers per 100 A remained in the surface after covering with the organosiloxane layer. Similar effects were observed in the adsorption of ammonia. About 2.2 silanol groups per 100 A had not reacted with the trimethylsilyl chloride. Nevertheless, the greater part of these had become unaccessible for water vapor. Apparently, they were hidden underneath a trimethylsilyl umbrella. ... 

Silicochloroform Silicolluoric Acid Silicon Chloride Silicone Fluids Silicon Tetrachloride Silver Acetate Silver Carbonate Silver Fluoride Silver Iodate Silver Monofluoride Silver Nitrate Silver Oxide Silver Sulfate Silvisar 510 Slaked Lime Slow-Curing Asphalt Sodamide Sodium... 

Although some of this is used for the production of ultra-pure silicon for semiconductors and for alloys with iron, aluminum, and magnesium, 98% goes for the production of methyl silicon chlorides ... 

N. Tschischewsky made the nitride by working at 1400°. About 4 per cent, of the silicon volatilizes during the reaction. The product obtained after heating the silicon in nitrogen for an hour is an amorphous, voluminous, white powder which, under the microscope, seems to consist of several different substances. The composition of the final product is dependent on the mode of purification if boiled with potassium hydroxide soln., followed by treatment with hydrofluoric acid, a product containing silicon hemitrinitride mixed with silica is obtained. The silica could not be removed from the nitride. M. Blix and W. Wirbelauer obtained the nitride by heating silicam, Si2N3H, between 1200° and 1400° and H. St. C. Deville and F. Wohler, by the action of ammonia on silicon chloride. 

In order to prevent the decomposition of the higher chlorides of silicon, it is very important that only a small part of the reaction tube should be heated at a time. When the chlorine is first passed through the reaction tube, the temperature of the heating coil is about 250°C. when the reaction is well started, it is lowered to about 150°C. The best rate of flow of chlorine is less than two bubbles per second. Under these conditions, in about 12 or 14 days, all the calcium-silicon will be used up, and about 700 ml. of liquid silicon chlorides will be collected. 

Not surprisingly, an explosion resulted on mixing with silicon chloride . This sprayed unreacted metal, which later ignited, casuing a small fire. [All non-metal halides are likley to react violently, any unreactivity can only be kinetic. - Ed.]... 

Silicon bromide, Si2Br6, 2 98 (See also Silicon tetrabromide) Silicon chlorides, higher, 1 42 Si2Cl6, 1 42 Si,Cl, 1 44... 

This reaction again affords another opportunity for preparing higher silicon chlorides, for example ... 

A similar interpretation may be based upon the results of Schwarz and coworkers580 581>. These authors hydrolyzed higher silicon chlorides and found solid white polymeric compounds in which the original Si-Si framework is retained. An irregular network containing Si-O-Si bond systems is also formed, so that the earlier postulated structural formulas are certainly incorrect. 

Polymeric silicon chlorides One of the first detailed studies of the silicon chlorides was published by Besson and Fournier34) in 1909. The authors found that a compound (SiCl2) was formed during silent electrical discharge in SiHCl3/H2 mixtures. 

---