Silicon tetrachloride

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ImageFileL1 = Silicon tetrachloride.svg|right
ImageFileR1 = Silicon-tetrachloride-3D-vdW.png ImageSizeL1 = 150px
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IUPACName = Silicon tetrachloride
OtherNames = Tetrachlorosilane, silicon (IV) chloride, silicon chloride, UN 1818
Section1 = Chembox Identifiers
CASNo = 10026-04-7
EINECS = 233-054-0
PubChem = 24816
SMILES = [Si] (Cl)(Cl)(Cl)Cl
InChI = 1/Cl4Si/c1-5(2,3)4
Section2 = Chembox Properties
Formula = SiCl₄
MolarMass = 169.90 g/mol
Appearance = Colourless liquid
Density = 1.483 g cm⁻³
MeltingPt = −68.74 °C
BoilingPt = 57.65 °C
Solubility = decomp.
SolubleOther = Chlorinated solvents
VaporPressure = 25.9 kPa at 20 °C
Section3 = Chembox Structure
CrystalStruct = Tetrahedral
Coordination = 4
MolShape =
Section7 = Chembox Hazards
ExternalMSDS = [http://www.physchem.ox.ac.uk/MSDS/SI/silicon_tetrachloride.html MSDS at Oxford University]
MainHazards = Corrosive (C), Harmful (Xn)
RPhrases = R14 R20 R22 R34 R36/37/38
FlashPt = S7 S8 S26
Autoignition =

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 HClWith methanol and ethanol it reacts to give tetramethyl orthosilicate and tetraethyl orthosilicate::SiCl₄ + 4 ROH → Si(OR)₄ + 4 HClAt 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.