N-(4-Methyl-2-nitrophenyl)succinamic acid

In the title compound, C11H12N2O5, the conformation of the N—H bond in the amide segment is syn to the ortho-nitro group in the benzene ring. The amide C=O and the carboxyl C=O of the acid segment are syn to each other and both are anti to the H atoms on the adjacent –CH2 groups. Furthermore, the C=O and O—H bonds of the acid group are in syn positions with respect to each other. The dihedral angle between the benzene ring and the amide group is 36.1 (1)°. The amide H atom shows bifurcated intramolecular hydrogen bonding with an O atom of the ortho-nitro group and an intermolecular hydrogen bond with the carbonyl O atom of another molecule. In the crystal, the N—H⋯O(C) hydrogen bonds generate a chain running along the [100] direction. Inversion dimers are formed via a pair of O—H⋯O(C) interactions, that form an eight-membered hydrogen-bonded ring involving the carboxyl group.

In the title compound, C 11 H 12 N 2 O 5 , the conformation of the N-H bond in the amide segment is syn to the ortho-nitro group in the benzene ring. The amide C O and the carboxyl C O of the acid segment are syn to each other and both are anti to the H atoms on the adjacent -CH 2 groups. Furthermore, the C O and O-H bonds of the acid group are in syn positions with respect to each other. The dihedral angle between the benzene ring and the amide group is 36.1 (1) . The amide H atom shows bifurcated intramolecular hydrogen bonding with an O atom of the ortho-nitro group and an intermolecular hydrogen bond with the carbonyl O atom of another molecule. In the crystal, the N-HÁ Á ÁO(C) hydrogen bonds generate a chain running along the [100] direction. Inversion dimers are formed via a pair of O-HÁ Á ÁO(C) interactions, that form an eight-membered hydrogen-bonded ring involving the carboxyl group.
BTG thanks the University Grants Commission, Government of India, New Delhi, for a UGC-BSR one-time grant to faculty.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: KP2388). As part of our studies on the substituent effects on the structures and other aspects of N-(aryl)-amides (Gowda et al., 1999Chaithanya et al., 2012), N-(aryl)-methanesulfonamides (Gowda et al., 2007), N-chloroarylsulfonamides (Jyothi & Gowda, 2004) and N-bromoarylsulfonamides (Usha & Gowda, 2006), in the present work, the crystal structure of N-(2-nitro-4-methylphenyl)succinamic acid has been determined ( Fig. 1). The conformation of the N-H bond in the amide segment is syn to the ortho-nitro group in the benzene ring, similar to that observed between the N-H bond and the ortho-chloro atom in N-(2-chloro-4-methylphenyl)-succinamic acid (I) (Chaithanya et al., 2012).

Experimental
The solution of succinic anhydride (0.01 mol) in toluene (25 mL) was treated dropwise with the solution of 2-nitro,4methylaniline (0.01 mol) also in toluene (20 mL) with constant stirring. The resulting mixture was stirred for about one h and set aside for an additional h at room temperature for completion of the reaction. The mixture was then treated with dilute hydrochloric acid to remove the unreacted 2-nitro-4-methyl-aniline. The resultant title compound was filtered under suction and washed thoroughly with water to remove the unreacted succinic anhydride and succinic acid. Repeated recrystallisations from ethanol were applied until the constant melting point. The purity of the compound was checked and characterised by its infrared and NMR spectra.
Needle like yellow single crystals used in X-ray diffraction studies were grown in ethanolic solution by slow evaporation of the solvent at room temperature.

Refinement
The H atoms of the NH group and the OH group were located in a difference map and later restrained to the distance N-H = 0.86 (2) Å and O-H = 0.82 (2) Å, respectively. The other H atoms were positioned with idealized geometry using a riding model with the aromatic C-H = 0.93 Å and methylene C-H = 0.97 Å. All H atoms were refined with isotropic displacement parameters set at 1.2 U eq (C-aromatic, N) and 1.5 U eq (C-methyl).  (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).  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 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.  (17)