4-tert-Butylamino-3-nitrobenzoic acid

In the title compound, C11H14N2O4, all non-H atoms lie in a mirror plane except for one of the methyl groups which deviates from the mirror plane by 0.919 (3) Å and is twisted by a torsion angle of 62.9 (2)°. An intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal packing, the molecules are linked together by O—H⋯O hydrogen bonds, forming dimers with graph-set motif R 2 2(8) which propagate along the a-axis direction. C—H⋯O contacts link adjacent dimers with a graph-set motif C 2 2(7), forming chains along b, and further consolidate the structure into a three-dimensional network. The crystal packing is further strengthened by short intermolecular O⋯O=C [2.655 (4) Å] contacts.

In the title compound, C 11 H 14 N 2 O 4 , all non-H atoms lie in a mirror plane except for one of the methyl groups which deviates from the mirror plane by 0.919 (3) Å and is twisted by a torsion angle of 62.9 (2) . An intramolecular N-HÁ Á ÁO hydrogen bond generates an S(6) ring motif. In the crystal packing, the molecules are linked together by O-HÁ Á ÁO hydrogen bonds, forming dimers with graph-set motif R 2 2 (8) which propagate along the a-axis direction. C-HÁ Á ÁO contacts link adjacent dimers with a graph-set motif C 2 2 (7), forming chains along b, and further consolidate the structure into a three-dimensional network. The crystal packing is further strengthened by short intermolecular OÁ Á ÁO C [2.655 (4) Å ] contacts.
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 (Brouillette et al., 1999;Williams et al., 1995). As a part of our ongoing study on such compounds, in this paper, we present the crystal structure of the title compound (I) which was synthesized as an intermediate.

4-tert-Butylamino
In the asymmetric unit of (I), all non-hydrogen atoms lie in a mirror plane except the methyl-C9A moiety, which is deviated from the mean plane by 0.919 (3) Å and twisted by a torsion angle C6-N2-C7-C9 of 62.9 (2) Å.
An intramolecular N-H···O hydrogen bond generates a ring of motif S(6) (Bernstein et al., 1995) (Fig. 1). In the crystal packing, the molecules are linked together by O-H···O hydrogen bonds to form dimers with the graph set motif R 2 2 (8) which propagate along the a-direction (Table 1). C-H···O contacts link adjacent dimers with a graph set motif C 2 2 (7) (Fig. 2) to form chains along the b-direction and further consolidate the structure into a 3D network. The crystal packing is further strengthened by short intermolecular O···O i-ii = 2.655 (4)Å contacts; symmetry code: (i) 1-x, y, 1-z; (ii) 1-x, 1-y, 1-z.

Experimental
Compound (I) was prepared by refluxing ethyl 4-(tert-butylamino)-3-nitrobenzoate (0.7 g, 0.0026 mol) (Mohd Maidin et al., 2008) and KOH (0.14 g, 0.0026 mol) in aqueous ethanol (10 ml) for 3 h. Ethanol was then removed in vacuo and the reaction mixture was diluted with water (15 ml). The aqueous layer was washed with dichloromethane (10 ml × 2) and acidified with concentrated hydrochloric acid to bring about the precipitation of the desired benzoic acid. Recrystallization of the precipitate with hot ethyl acetate afforded yellow crystals of the title compound (I).

Refinement
H atoms were positioned geometrically [C-H = 0.93-0.96 Å] and refined using a riding model with U iso (H) = 1.2U eq (C) and 1.5U eq (methyl C). A rotating-group model was used for the methyl groups. The O-and N-bound hydrogen atoms were located from the Fourier map and allowed to refine freely. Fig. 1. The molecular structure of (I), showing 50% probability displacement ellipsoids and the atom numbering scheme. Intramolecular hydrogen bonding is shown as a dashed line.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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 > 2sigma(F 2 ) is used only for calculating R-factors(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.