定义Definition
氯化亚砜 SOCl₂（亚硫酰氯）是无色至淡黄色的发烟液体，沸点约 76 °C。它是常用的氯化试剂，能把醇转化为氯代烃、把羧酸转化为酰氯。由于副产物 SO₂ 和 HCl 都是气体，会自行逸出，产物容易提纯。
Thionyl chloride, SOCl₂, is a colourless to pale yellow fuming liquid boiling at about 76 °C. It is a common chlorinating agent that converts alcohols into chloroalkanes and carboxylic acids into acyl chlorides. Because both by-products, SO₂ and HCl, are gases that escape, the product is easy to purify.
主要反应Main reactions
与醇：ROH + SOCl₂ → RCl + SO₂ + HCl；与羧酸：RCOOH + SOCl₂ → RCOCl + SO₂ + HCl；遇水剧烈水解：SOCl₂ + H₂O → SO₂ + 2HCl。因此必须在干燥条件下使用，并在通风橱中操作。
With alcohols: ROH + SOCl₂ → RCl + SO₂ + HCl; with carboxylic acids: RCOOH + SOCl₂ → RCOCl + SO₂ + HCl; with water it hydrolyses vigorously: SOCl₂ + H₂O → SO₂ + 2HCl. It must be used dry and in a fume cupboard.
与磷的氯化物比较Compared with phosphorus chlorides
PCl₅ 和 PCl₃ 也能完成同样的转化，但副产物 POCl₃ 或 H₃PO₃ 需要分离；SOCl₂ 的气态副产物使后处理更简单。
PCl₅ and PCl₃ do the same conversions, but their by-products, POCl₃ or H₃PO₃, must be separated; SOCl₂'s gaseous by-products make the work-up simpler.
化学性质Chemical properties
与乙醇反应：C₂H₅OH + SOCl₂ → C₂H₅Cl + SO₂ + HCl
With ethanol: C₂H₅OH + SOCl₂ → C₂H₅Cl + SO₂ + HCl
水解：SOCl₂ + H₂O → SO₂ + 2HCl
Hydrolysis: SOCl₂ + H₂O → SO₂ + 2HCl