Thionyl Chloride

thionyl chloride [′thī·ən·əl ′klȯr‚īd]

(inorganic chemistry)

SOCl₂A toxic, yellowish to red liquid with a pungent aroma, soluble in benzene, decomposes in water and at 140°C; boils at 79°C; used as a chemical intermediate and catalyst. Also known as sulfur oxychloride; sulfurous oxychloride.

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Thionyl Chloride 

(SOCl₂), a colorless liquid that fumes upon exposure to air. Thionyl chloride is prepared commercially by the direct reaction of S, O₂ and Cl₂ at 180°–200°C (using activated carbon as a catalyst) or by the action of excess SO₂ on CCl ₄in the presence of AlCl₃ at 150°C and pressure of about 4 meganewtons per sq m, or 40 kilograms-force per sq cm. It is used for the preparation of sulfochlorinated polymer derivatives, and also as a chlorinating agent—for example, in the manufacture of dyes and pharmaceuticals.

Thionyl chloride is toxic; it irritates the mucous membranes, causing severe burns.