4-Methylanilinium 3,5-dinitrobenzoate

The crystal structure of the title compound, C7H10N+·C7H3N2O6 −, displays N—H⋯O hydrogen bonding between the ammonium groups and the O atoms of the 3,5-dinitrobenzoate anions. Intermolecular C—H⋯O interactions further stabilize the packing. An O atom of each of the nitro groups is disordered over two sites with site occupancy factors of 0.59 (5) and 0.41 (6).

The crystal structure of the title compound, C 7 H 10 N + Á-C 7 H 3 N 2 O 6 À , displays N-HÁ Á ÁO hydrogen bonding between the ammonium groups and the O atoms of the 3,5-dinitrobenzoate anions. Intermolecular C-HÁ Á ÁO interactions further stabilize the packing. An O atom of each of the nitro groups is disordered over two sites with site occupancy factors of 0.59 (5) and 0.41 (6).   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Probing the dielectric-ferroelectric properties of organic ligands (Li et al., 2008), the title compound has been prepared in our laboratory. In this article, the preparation and crystal structure of the title compound have been presented. A related structure, that of 4-tethylanilinium dichloroacetate, has been reported previously (Basaran et al., 1991).

Experimental
The title compound was obtained by the addition of 3,5-dinitrobenzoic acid (4.66 g, 0.022 mol) to a solution of 4-methylaniline (2.14 g, 0.02 mol) in ethanol, in the stoichiometric ratio 1.1:1. After two weeks, good quality single crystals were obtained by slow evaporation.

Refinement
O3 and O6 atoms of the nitro groups were disordered over two sites with site occupancy factors 0.59 (5) and 0.41 (6).
Positional parameters of all the H atoms were calculated geometrically and the H atoms were set to ride on the C and N atoms to which they are bonded with N-H = 0.89 Å and C-H = 0.93 and 0.96 Å for aryl and methyl H-atoms, respectively, with U iso (H) = 1.2U eq (C or N). Fig. 1

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. 0.0338 (9) 0.0401 (10) 0.0327 (9) 0.0041 (7) −0.0020 (7) 0.0007 (8)  O1 0.0631 (9) 0.0534 (9) 0.0552 (9) 0.0088 (7) 0.0223 (7) 0.0144 (7) (7) 173.