Abstract: | In the title compound systematic name: 6‐amino‐5‐formyl‐3‐methylpyrimidine‐2,4(1H,3H)‐dione], C6H7N3O3, the intramolecular dimensions provide evidence for some polarization of the electronic structure. There is an intramolecular N—H...O hydrogen bond; this and a combination of three intermolecular N—H...O hydrogen bonds generate an almost planar ribbon containing S(6), R22(4), R21(6) and R44(16) rings. These ribbons are linked into sheets by a dipolar carbonyl–carbonyl interaction. The structure was refined as a nonmerohedral twin, with twin fractions 0.7924 (1) and 0.2076 (10). |