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. To the solution was added 1,250 ml of acetic anhydride, followed by elevating the temperature gradually up to 90° C. After stirring for 6 hours, the mixture was allowed to stand at room temperature overnight, and then the glacial acetic acid and acetic anhydride were removed by distillation under reduced pressure. The residue, while hot, was poured into 500 ml of ethanol, and the precipitated crystals were collected by filtration. The crystals were heat-refluxed in 380 ml of concentrated hydrochloric acid and 400 ml of water for 2 hours and then allowed to stand for 6 hours under ice-cooling. The precipitated crystals were collected by filtration and washed with a small amount of ethanol to obtain 360 g (73%) of 1,3-dimethylbarbituric acid having a melting point of 124° to 125° C.

Provenance & Evidence