Silicon tetrachloride

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Silicon tetrachloride (SiCl₄) is a colourless volatile liquid compound of silicon and chlorine. It is most commonly prepared by reacting chlorine with hot silicon:

Si + 2 Cl₂ → SiCl₄

Silicon tetrachloride has a density of 1.483 g cm₋₃, a melting point of −70 °C, and a boiling point of 57.6 °C. It reacts violently with water, in contrast with carbon tetrachloride. This hydrolysis reaction occurs because the atomic radius of the silicon atom is such that the water molecules can attack it, 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

Other oxidants, strong acids, alcohols, bases, ketones, and aldehydes can also react with SiCl₄ to produce hydrogen chloride. It has corrosive effects on the skin, eyes and lungs.

Silicon tetrachloride is sometimes used as an intermediate in the purification of silicon.

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