Bis(4-chlorobenzoic) anhydride

PreparationTo a flask containing 17.5 gm (0.1 mole) of p-chlorobenzoyl chloride is added 50 ml (0.6 mole) of pyridine and the mixture heated for 5 min on the steam bath. The mixture is poured upon 100 gm of cracked ice and 50 ml of concentrated hydrochloric acid, allowed to warm to room temperature, filtered, the solid washed successively with 15 ml of methanol and 15 ml of dry benzene, and dried to afford 14.2-14.6 gm (96-98%), m.p. 192- 193°C (recrystallized from 250 ml of dry benzene).