N-(4-Chloro-3-nitrophenyl)maleamic acid

In the molecule of the title compound, C10H7ClN2O5, the acyclic C=C double bond is cis configured. The C=O and O—H bonds of the acid group are in a relatively rare anti position to each other, due to the donation of intramolecular hydrogen bond to the amide by the carboxyl group. The nitro group is significantly twisted [dihedral angle = 66.9 (3)°] out of the plane of the remaining atoms, which are almost coplanar (r.m.s. deviation for non-H atoms except the nitro group = 0.202 Å). In the crystal, N—H⋯O hydrogen bonds link the molecules into zigzag chains running along the b axis.

In the molecule of the title compound, C 10 H 7 ClN 2 O 5 , the acyclic C C double bond is cis configured. The C O and O-H bonds of the acid group are in a relatively rare anti position to each other, due to the donation of intramolecular hydrogen bond to the amide by the carboxyl group. The nitro group is significantly twisted [dihedral angle = 66.9 (3) ] out of the plane of the remaining atoms, which are almost coplanar (r.m.s. deviation for non-H atoms except the nitro group = 0.202 Å ). In the crystal, N-HÁ Á ÁO hydrogen bonds link the molecules into zigzag chains running along the b axis.
BTG thanks the University Grants Commission, Government of India, New Delhi, for a special grant under a UGC-BSR one-time grant to faculty.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5827). As part of our studies on the substituent effects on the structures and other aspects of N-(aryl)-amides (Gowda et al., 2000(Gowda et al., , 2003Chaithanya 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-(4-Chloro-3-nitrophenyl)maleamic acid has been determined ( Fig. 1). The conformations of the N-H and the C═O bonds in the amide segment are anti to each other. The N-H bond is also anti to the meta-nitro group. Further, the conformation of the amide C═O is anti to the H atom on the adjacent -CH group, while the carboxyl C═O of the acid segment is syn to the adjacent -CH group. Furthermore, the C═O and O-H bond of the acid group are in relatively rare anti position to each other, due to the donation of hydrogen bond to the amide by the carboxyl group, similar to that observed in N-(3-Chloro-4-methylphenyl)maleamic acid (I) (Chaithanya et al., 2012).
The dihedral angle between the phenyl ring and the amide group in the title compound is 11.52 (27)°, compared to the value of 6.55 (99)° in (I).
In the structure, the pairs of O-H···O and N-H···O intermolecular hydrogen bonds pack the molecules into zigzag chains (Table 1, Fig.2).

Experimental
Maleic anhydride (0.025 mol) in toluene (25 ml) was treated dropwise with 4-chloro-3-nitroaniline (0.025 mol) also in toluene (20 ml) with constant stirring. The resulting mixture was stirred for about 30 min and set aside for an additional 30 min at room temperature for the completion of reaction. The mixture was then treated with dilute hydrochloric acid to remove the unreacted 4-chloro-3-nitroaniline. The resultant solid N-(4-Chloro-3-nitrophenyl)maleamic acid was filtered under suction and washed thoroughly with water to remove the unreacted maleic anhydride and maleic acid. It was recrystallized to constant melting point from ethanol. The purity of the compound was checked and characterized by its infrared spectra.
Rod like colorless single crystals of the title compound used in X-ray diffraction studies were grown in an ethanol solution by slow evaporation of the solvent (0.5 g in about 30 ml of ethanol) 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-  (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.