2,3,4-Trihydroxybenzoic acid 0.25-hydrate

Abstract

The asymmetric unit of the title compound, C7H6O5·0.25H2O, 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 R33(12)] involving O—H...O hydrogen bonds. The two acid molecules are further linked through a cyclic R22(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.