5-(1-Hydroxyethylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione and four amino derivatives.

In the structures of 5-(1-hydroxyethylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione, C8H10N2O4, (I), 1,3-dimethyl-5-[1-(propylamino)ethylidene]pyrimidine-2,4,6(1H,3H,5H)-trione, C11H17N3O3, (II), and 5-[1-(2,2-dimethoxyethylamino)ethylidene]-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione, C12H19N3O5, (III), there are no direction-specific intermolecular interactions. The molecules in 5-[1-(benzylamino)ethylidene]-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione, C15H17N3O3, (IV), are linked into chains of edge-fused rings by a combination of one C-H...O hydrogen bond and one C-H...pi(arene) hydrogen bond, while the molecules in 5-(1-hydrazinoethylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione, C8H12N4O3, (V), are linked into a continuous framework structure by three distinct N-H...O hydrogen bonds, each involving a different O-atom acceptor. Each of compounds (I)-(V) contains an intramolecular hydrogen bond, of the O-H...O type in (I) and of the N-H...O type in (II)-(V).