5-Bromo­phthalazine hemihydrate

The title compound, C₈H₅BrN₂·0.5H₂O, is a phthalazine derivative synthesized from 3-bromo­benzene-1,2-dicarbaldehyde and hydrazine. The mol­ecule is essentially planar, the deviation from the mean plane of the phthalazine ring being 0.015 (3) Å. The O atom of the solvent water mol­ecule is situated on a twofold rotation axis. In the crystal, O—H...N hydrogen bonds and short N...Br [2.980 (3) Å] contacts lead to the formation of a two-dimensional network parallel to (101).