Bis(2-carboxyanilinium) sulfate monohydrate

In the title hydrated molecular salt, 2C7H8NO2 +·SO4 2−·H2O, each cation in the asymmetric unit is stabilized by an intramolecular N—H⋯O hydrogen bond. The O atoms of the sulfate ion are disordered over two sets of sites with an occupancy ratio of 0.541 (13):0.459 (13), which possibly optimizes the acceptance of N—H⋯O hydrogen bonds from the cations. The crystal structure also features aromatic π–π stacking [centroid–centroid separation = 3.842 (2) Å] and a C—H⋯π interaction.

In the title hydrated molecular salt, 2C 7 H 8 NO 2 + ÁSO 4 2À ÁH 2 O, each cation in the asymmetric unit is stabilized by an intramolecular N-HÁ Á ÁO hydrogen bond. The O atoms of the sulfate ion are disordered over two sets of sites with an occupancy ratio of 0.541 (13):0.459 (13), which possibly optimizes the acceptance of N-HÁ Á ÁO hydrogen bonds from the cations. The crystal structure also features aromaticstacking [centroid-centroid separation = 3.842 (2) Å ] and a C-HÁ Á Á interaction.

Comment
The salts of aminobenzoic acids have been reported as medicines as well as precursor for in the field of pharmaceutics (Griss et al., 1984). These are also useful for autoxidation of the fats forming free radicals, hence, in comparison to sulfated metal oxides, these can be used for production of biodiesel (Pedanova et al., 1984;Refaat, 2010). The structure of title compound (I, Fig. 1) is being reported here. The molecules are stabilized due to intra as well as inter-molecular H-bondings and C-H···π interactions (Table 1, Fig. 2).
The π-π interaction between the centroids CgA and CgB of benzene rings A and B respectively, also play a role in the stabilization of molecules. The centroid to centroid distance is 3.842 (2) Å.

Experimental
Ethanolic solution of anthranilic acid (0.02 M) was refluxed in the presence of conc. H 2 SO 4 (0.01 M) for 30 min. The contents were kept at room temperature for 24 h. The crystalline material formed was washed with n-hexane, ethyl acetate and diethyl ether, respectively and dried. This material was dissolverd in ethanol and colorless prisms of (I) were obtainesd by slow evaporation at room temperature.

Refinement
Although all H-atoms were recognised from the difference fourier map but only coordinates of H-atoms of H 2 O were refined.