Main Page | See live article | Alphabetical index Properties General Name Silane Chemical formula SiH4 Appearance Colourless gas Physical Formula weight 32.1 amu Melting point 88 K (-185 °C) Boiling point 161 K (-112 °C) Density 0.7 ×103 kg/m3 (liquid) Solubility insoluble Thermochemistry ΔfH0gas ? kJ/mol ΔfH0liquid ? kJ/mol ΔfH0solid -1615 kJ/mol S0gas, 1 bar ? J/mol·K S0liquid, 1 bar ? J/mol·K S0solid 283 J/mol·K Safety Ingestion Relatively low toxicity, but avoid exposure where possible. Inhalation Relatively low toxicity: may cause coughing, hyperventilation. Skin Irritant, may cause redness and swelling. Eyes As for skin, may cause irritation. More info Hazardous Chemical Database SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references Silane is a chemical compound with chemical formula SiH4. It is the silicon analog of methane. At room temperature, silane is presumed to be a pyrophoric gas -- it spontaneously undergoes combustion in air without the need for external ignition. However, there is a school of thought which says that silane is stable and that it is the natural formation of larger silanes during production which causes its pyrophoricity. Above 420°C, silane decomposes into silicon and hydrogen; it can therefore be used in the chemical vapor deposition of silicon. More generally, a silane is any silicon analog of an alkane hydrocarbon. Silanes consist of a chain of silicon atoms covalently bound to hydrogen atoms. The general formula of a silane is SinH2n+2. Silanes tend to be less stable than their carbon analogs because the Si-Si bond has a strength slightly lower than the C-C bond. Oxygen decomposes silanes easily, because the silicon-oxygen bond is quite stable. There exists a regular nomenclature for silanes. Each silane's name is the word silane preceded by a numerical prefix (di, tri, tetra, etc.) for the number of silicon atoms in the molecule. Thus Si2H6 is disilane, Si3H8 is trisilane, and so forth. There is no prefix for one; SiH4 is simply silane. Silanes can also be named like any other inorganic compound; in this naming system, silane is named silicon tetrahydride. However, with longer silanes, this becomes cumbersome. A cyclosilane is a silane in a ring, just as a cycloalkane is an alkane in a ring. Branched silanes are possible. The radical SiH3- is names silyl, Si2H5- is disilanyl etc. If we have trisilane with a silyl group attached to the middle silicon, we have silyltrisilane. It parallels alkanes. Silanes can also take the same functional groups as alkanes, OH to make a silanol. There is (at least in principle) a silicon analogue for all carbon alkanes. Production Industrially, silane is produced from metallurgical grade silicon in a two-step process. In the first step, powdered silicon is reacted with hydrchloric acid at about 300°C to produce trichlorosilane, HSiCl3, along with hydrogen gas, according to the chemical equation Si + 3 HCl → HSiCl3 + H2 The trichlorosilane is then boiled on a resinous bed containing a catalyst which promotes its disproportionation to silane and silicon tetrachloride according to the chemical equation 4 HSiCl3 → SiH4 + 3 SiCl4 The most commonly used catalysts for this process are metal halides, particularly aluminum chloride. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.