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-(benzylaminoethylidene)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).