Itaconsureanhydrid

synthetischeTo a flask equipped with a 12 mm diameter ground glass adaptor tube bent for downward distillation and joined to a 100 cm condenser is added 200 gm (0.95 mole) of citric acid monohydrate. An ice-cooled flask and a cold trap are connected to the condenser. The flask containing the citric acid is heated rapidly with a wide flame of the Meker burner so that in 12-15 min the distillation at 175-190°C is complete. The distillation is stopped earlier if the vapors in the reaction flask become yellow. Superheating of the citric acid will cause rearrangement to citraconic anhydride. The water is quickly separated from the distillate and the itaconic anhydride layer dried to afford 40-50 gm (37-47%), m.p. 67-68°C. Long time contact of the water with the anhydride causes it to hydrolyze to itaconic acid, m.p. 162-165°C.