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	24816
EINECS number	233-054-0
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, ε_r, 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.