Crystal structures of 6-nitroquinazolin-4(3H)-one, 6-aminoquinazolin-4(3H)-one and 4-aminoquinazoline hemihydrochloride dihydrate

The title compounds, 6-nitroquinazolin-4(3 H )-one (C 8 H 5 N 3 O 3 ; I ), 6-aminoquinazolin-4(3 H )-one (C 8 H 7 N 3 O; II ) and 4-aminoquinazolin-1-ium chloride–4-aminoquinazoline–water (1/1/2), (C 8 H 8 N 3 + ·Cl − ·C 8 H 7 N 3 ·2H 2 O; III ) were synthesized and their structures were determined by single-crystal X-ray analysis. In the crystals of I and II , the quinazoline molecules form hydrogen-bonded dimers via N—H...O interactions. The dimers are connected by weak intermolecular C—H...N and C—H...O hydrogen bonds, forming a layered structure in the case of I . In the crystal of II , N—H...N and C—H...O interactions link the dimers into a three-dimensional network structure. The asymmetric unit of III consists of two quinazoline molecules, one of which is protonated, a chloride ion, and two water molecules. The chloride anion and the water molecules form hydrogen-bonded chains consisting of fused five-membered rings. The protonated and unprotonated quinazolin molecules are linked to the chloride ions and water molecules of the chain by their amino groups.