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

The title compounds, 6-nitroquinazolin-4(3H)-one (C8H5N3O3; I), 6-aminoquinazolin-4(3H)-one (C8H7N3O; II) and 4-aminoquinazolin-l-ium chloride-4-aminoquinazoline-water (1/1/2), (C8H8N3+center dot Cl-center dot C8H7N3 center dot 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 center dot center dot center dot O interactions. The dimers are connected by weak intermolecular C-H center dot center dot center dot N and C-H center dot center dot center dot O hydrogen bonds, forming a layered structure in the case of I. In the crystal of II, N-H center dot center dot center dot N and C -H center dot center dot center dot 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.