Diphenylacetic acid anhydride

synthetischeTo a flask containing 50 gm (0.236 mole) of diphenylacetic acid is added 50 gm (0.49 mole) of acetic anhydride and the solution refluxed for 2 hr. The excess acetic anhydride is removed by distillation and the thick brown liquid residue is treated with ether to cause crystallization of the anhydride product. The crystals are filtered, washed with cold ether, and dried to afford 43-44 gm (90-92%), m.p. 98°C. The product can also be distilled at 182°C (3.0 mm Hg).