text: The industrial route to acetyl chloride involves the reaction of acetic anhydride with hydrogen chloride: 
  Propionyl chloride is produced by chlorination of propionic acid with phosgene:
  Benzoyl chloride is produced by the partial hydrolysis of benzotrichloride:
  Similarly, benzotrichlorides react with carboxylic acids to the acid chloride. This conversion is practiced for the reaction of 1,4-bis(trichloromethyl)benzene to give terephthaloyl chloride: