Silicon tetrachloride
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Silicon tetrachloride | |
---|---|
IUPAC name | Silicon tetrachloride |
Other names | Tetrachlorosilane, silicon (IV) chloride, silicon chloride, UN 1818 |
Identifiers | |
CAS number | [10026-04-7] |
PubChem | |
EINECS number | |
SMILES | [Si](Cl)(Cl)(Cl)Cl |
InChI | 1/Cl4Si/c1-5(2,3)4 |
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 |
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 disclaimer and references |
Silicon tetrachloride is the chemical compound with the formula SiCl4. It was prepared by Jöns Jakob Berzelius in 1823.
[edit] 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
[edit] 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.