2,3,4-Trihy­droxy­benzoic acid 0.25-hydrate

The asymmetric unit of the title compound, C(7)H(6)O(5)·0.25H(2)O, contains two mol­ecules of 2,3,4-trihy­droxy­benzoic acid, with similar conformations, and one water mol­ecule which lies on a twofold rotation axis. Both acid mol­ecules are essentially planar [maximum r.m.s deviations = 0.0324 (2) and 0.0542 (3) Å for the two acid molecules]. The mol­ecular conformations are stabilized by intra­molecular O(phenol)—H⋯O(carbox­yl/phenol) inter­actions. A cyclic inter­molecular association is formed between the two acid and one water mol­ecule [graph set R (3) (3)(12)] involving O—H⋯O hydrogen bonds. The two acid mol­ecules are further linked through a cyclic R (2) (2)(8) carb­oxy­lic acid hydrogen-bonding association, which together with inter­molecular O—H⋯O hydrogen-bonding inter­actions involving the phenol groups and the water mol­ecule, and weak π–π inter­actions [minimum ring centroid separation = 3.731 (3) Å], give a three-dimensional network.