2-Methylamino-5-nitrobenzoic acid

The title compound, C8H8N2O4, is almost planar (r.m.s. deviation = 0.037 Å) and an intramolecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, inversion dimers linked by pairs of O—H⋯O hydrogen bonds generate R 2 2(8) loops. Intermolecular N—H⋯O hydrogen bonds (involving the same H atom that forms the intramolecular hydrogen bond) link the dimers into infinite sheets lying parallel to (102).

The title compound, C 8 H 8 N 2 O 4 , is almost planar (r.m.s. deviation = 0.037 Å ) and an intramolecular N-HÁ Á ÁO hydrogen bond generates an S(6) ring. In the crystal, inversion dimers linked by pairs of O-HÁ Á ÁO hydrogen bonds generate R 2 2 (8) loops. Intermolecular N-HÁ Á ÁO hydrogen bonds (involving the same H atom that forms the intramolecular hydrogen bond) link the dimers into infinite sheets lying parallel to (102).
The authors acknowledge the provision of funds for the purchase of diffractometer and encouragement by Dr Muhammad Akram Chaudhary, Vice Chancellor, University of Sargodha. ARR also acknowledges the Higher Education Commission, Government of Pakistan, for generous support of a research project (20-819).

Comment
The benzodiazepines constitute a very diverse class of heterocyclic compounds with plethora of biological activities such as anti-caner (Kamal et al., 2010) and anti-HIV (Blank et al., 2009) agent. The title compound (I, Fig. 1) was synthesized as a precursor for the synthesis of benzodiazepine derivative and it will also be utilized for the metal complexation.
The crystal structures of N-methylanthranilic acid (II) (Dhaneshwar & Pant, 1972) has been published. The title compound differs from (II) due to substitution of nitro group at at position five.
The asymmetric unit of title compound is essentially planar with r. m. s. deviation of 0.0366 Å from the least square plane of (C1-C8/N1/N2/O1/O2/O3). There exist a S(6) ring motif (Bernstein et al., 1995) due to N-H···O type of intramolecular H-bondings. The molecules are dimerised due to inversion related O-H···O type of H-bondings with R 2 2 (8) ring motifs. The dimers are interlinked in the form of infinite two dimensional polymeric sheets due to H-bonding of N-H···O type (Fig. 2).

Experimental
To HNO 3 (1.83 g, 0.03 mol) taken in an ice chilled round bottom flask the H 2 SO 4 (2.6 g, 0.026 mol) was added as drops with constant stirring. A solution of N-methylanthranilic acid (2 g, 0.01 mol) in EtOAc (25 ml) was added as drops to the nitrating mixture in ice chilled water bath and stirred for half an hour followed by 3 hours reflux. The reaction mixture was neutralized and extracted with EtOAc (3 × 30 ml). The organic layer was dried over anhydrous Na 2 SO 4 and concentrated under reduce pressure that afforded purple needles of (I) upon standing.

Refinement
Although H atoms were appeared in difference Fourier map but were positioned geometrically with (C-H = 0.93-0.96 and O-H = 0.82 Å) and refined as riding with U iso (H) = xU eq (C), where x = 1.5 for methyl and hydroxy H-atoms and x = 1.2 for other H atoms.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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.