Oxidation of phenols with chromyl chloride

Abstract

The oxidation of phenols with chromyl chloride gives benzoquinones in yields which depend upon the nature of the substituents on the phenol ring. The reaction when carried out in carbon tetrachloride or carbon disulphide yields a solid intermediate which contains the p-benzoquinone co-ordinated onto the reduced chromium species. This solid has a non-stoicheiometric composition unlike other solid intermediates formed in the Etard reaction. The release of the benzoquinone from the solid intermediate by hydrolysis is a ligand exchange reaction; a similar release can be achieved by using other donor solvents such as pyridine and dioxan.