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| Silicon tetrachloride | |
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| IUPAC name | Silicon tetrachloride |
| Other names | Tetrachlorosilane, silicon (IV) chloride, silicon chloride, UN 1818 |
| Identifiers | |
| CAS number | 10026-04-7 |
| PubChem | |
| EINECS number | |
| SMILES |
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| InChI |
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| Properties | |
| Molecular formula | SiCl4 |
| Molar mass | 169.90 g/mol |
| Appearance | Colourless liquid |
| Density | 1.483 g cm−3 |
| Melting point |
−68.74 °C |
| Boiling point |
57.65 °C |
| Solubility in water | decomp. |
| Solubility | Chlorinated solvents |
| Vapor pressure | 25.9 kPa at 20 °C |
| Structure | |
| Crystal structure | Tetrahedral |
| Coordination geometry |
4 |
| Hazards | |
| MSDS | External MSDS |
| MSDS | MSDS at Oxford University |
| Main hazards | Corrosive (C), Harmful (Xn) |
| R-phrases | R14 R20 R22 R34 R36/37/38 |
| Flash point | S7 S8 S26 |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Silicon tetrachloride is the chemical compound with the formula SiCl4. It was prepared by Jöns Jakob Berzelius in 1823.
Chemistry
This colourless volatile liquid compound is prepared by the treatment of silicon with chlorine:
- Si + 2 Cl2 → SiCl4
It reacts readily with water, in contrast with carbon tetrachloride. The differing rates of hydrolysis are attributed to the greater atomic radius of the silicon atom, whereas carbon has a smaller atomic radius so the chlorine atoms effectively shield the carbon from attack. In water, the following reaction occurs:
- SiCl4 + 2 H2O → SiO2 + 4 HCl
With methanol and ethanol it reacts to give tetramethyl orthosilicate and tetraethyl orthosilicate:
- SiCl4 + 4 ROH → Si(OR)4 + 4 HCl
At higher temperatures homologues of silicon tetrachloride can be prepared by the reaction:
- Si + SiCl4 → Si2Cl6 + homologues
Uses
Silicon tetrachloride is sometimes used as an intermediate in the manufacture of extremely pure silicon, since it has a boiling point convenient for purification by repeated fractional distillation; it can be reduced to silicon by hydrogen gas, or hydrolysed to SiO2 as a precursor for extremely pure synthetic fused silica. Very pure silicon is used in large amounts in the semiconductor industry, and also in the production of photovoltaic cells. Reports of silicon tetrachloride pollution in China have been associated with the increased demand for photovoltaic cells that has been stimulated by subsidy programs. (http://www.washingtonpost.com/wp-dyn/content/article/2008/03/08/AR2008030802595.html)
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- This page was last modified on 22 October 2008, at 22:05.
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