Research Article: 2,3,4-Trihy­droxy­benzoic acid 0.25-hydrate

Date Published: March 01, 2012

Publisher: International Union of Crystallography

Author(s): Jin-Hang Li, Fu-Yue Dong, Fang Cai, Xiao-Feng Yuan, Ren-Wang Jiang.


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.

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For the natural distribution of 2,3,4-trihy­droxy­benzoic acid, see: Zhai et al. (2010 ▶); Xu & Chang (2010 ▶). For its anti­oxidant and anti­bacterial activities, see: Kodama et al. (2007 ▶); Friedman et al. (2003 ▶). For the inhibition of xanthine oxidase, see: Chang et al. (1995 ▶). For the crystal structure of the dihydrate pseudopolymorph, see: Prior & Sharp (2010 ▶). For π–π inter­actions in gallic acid pyridine monosolvate and in natural flavonoids, see: Dong et al. (2011 ▶); Jiang et al. (2009 ▶, 2002 ▶). For graph-set analysis, see: Etter et al. (1990 ▶); Bernstein et al. (1995 ▶).