Mol-ecules of the title compound, C14H18N2O3 [systematic name: 5-allyl-5-(hex-3-yn-2-yl)-1-methylpyrimidine-2,4,6(1H,3H,5H)-trione in the (RbSh )/(SbRh ) racemic form], are connected by mutual N-H⋯O=C hydrogen bonds in which the carbonyl group at the 2-position of the pyrimidine-trione ring is employed. These inter-actions result in an inversion dimer which displays a central R 2 (2)(8) ring motif. This dimer is topologically distinct from that of the previously reported (SbRh ) form, which is, however, also based on an R 2 (2)(8) motif. The methyl group at the 1-position of the pyrimidine-trione ring in the title structure is disordered over two sets of sites in a 0.57 (2):0.43 (2) ratio.
Keywords: anaesthetic; barbiturate; crystal structure; hydrogen bonding.