5‐(1‐Cyclohexen‐1‐yl)‐1,5‐dimethylbarbituric acid (hexobarbitone): a low‐temperature redetermination

A low‐temperature redetermination of the title compound, C 12 H 16 N 2 O 3 , more commonly known as hexobarbitone, is reported, with significantly improved precision. The crystal packing reveals an infinite hydrogen‐bonded hexobarbitone chain linked by a single N—H·O interaction, an extremely rare motif in barbiturate crystal packing. Unlike some other barbiturate crystal structures, there is no phase transition on cooling to 150 K.