Malonic Acid → Dimethylbarbituric acid

Participants

Reaction Steps

In 600 ml of glacial acetic acid were dissolved 276 g (3.14 mol) of 1,3-dimethylurea and 376 g (3.62 mol) of malonic acid at 60° to 70° C. Then, 1,250 ml of acetic anhydride was added thereto, and the temperature was gradually elevated up to 90° C. After stirring for 6 hours, the mixture was left to stand at room temperature overnight. The glacial acetic acid and acetic anhydride were removed by distillation under reduced pressure, and the residue, while hot, was poured into 500 ml of ethanol. The thus precipitated crystals were collected by filtration and heatrefluxed in 380 ml of concentrated hydrochloric acid and 400 ml of water for 2 hours, and then ice-cooled for 6 hours. The precipitated crystals were separated by filtration and washed with a small amount of ethanol to obtain 360 g of 1,3-dimethylbarbituric acid.

Provenance & Evidence