Phosphorus oxychloride (molecular formula: POCl3), also known as phosphoryl chloride, phosphorus oxychloride and phosphorus oxychloride, is an industrial chemical raw material and a colorless and transparent liquid. It has a pungent odor. Smoke violently in humid air. Relative density 1.67. Melting point: 1.25 ℃. Boiling point 105.1 ℃. It decomposes in water and ethanol to form phosphoric acid and hydrogen chloride. When a large amount of water is poured suddenly, a violent reaction can occur. POCl3 reacts with water and alcohol to form phosphoric acid or phosphate ester, such as o = PCl3 + 3H2O → o = P (OH) 3 + 3hcl. If alcohol replaces water in the reaction, the product is trialkyl phosphate. Such reactions are often carried out in pyridine or amine to absorb the generated HCl and promote the reaction. Under the catalysis of Lewis acid such as manganese chloride, POCl3 is co heated with excess phenol (aroh) to obtain triaryl phosphate. For example, when reacting with phenol: 3c6h5oh + o = PCl3 → o = P (oc6h5) 3 + 3hcl, phosphorus oxychloride is a Lewis base and will form adducts with many Lewis acids. For example, the adduct (POCl3 · AlCl3) formed by the reaction with titanium tetrachloride: cl3p + - O − + TiCl4 → cl3p + - O - − TiCl4 and aluminum chloride is very stable, so POCl3 is also used to remove AlCl3 from the product of Friedel Crafts reaction. In the presence of AlCl3, POCl3 reacts with hydrogen bromide to form pobr3. In industry, it is prepared by the reaction of phosphorus trichloride with oxygen or phosphorus pentoxide. It is mainly used to produce phosphate esters, such as trimethylbenzene phosphate.