N-(3-Chloro-4-methylphenyl)succinamic acid

In the crystal structure of the title compound, C11H12ClNO3, the asymmetric unit contains two independent molecules. The N—H bond in the amide segment is anti to the meta-Cl atom in the benzene ring, in both molecules. The amide and carboxyl C=O bonds are also anti to each other and 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 angles between the benzene ring and the amide group are 40.6 (2) and 44.9 (3)° in the two independent molecules. In the crystal, molecules are packed into sheets parallel to the (11-3) plane through O—H⋯O and N—H⋯O hydrogen bonds.

In the crystal structure of the title compound, C 11 H 12 ClNO 3 , the asymmetric unit contains two independent molecules. The N-H bond in the amide segment is anti to the meta-Cl atom in the benzene ring, in both molecules. The amide and carboxyl C O bonds are also anti to each other and 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 angles between the benzene ring and the amide group are 40.6 (2) and 44.9 (3) in the two independent molecules. In the crystal, molecules are packed into sheets parallel to the (113) plane through O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds.
BTG thanks the University Grants Commission, Government of India, New Delhi, for a UGC-BSR one-time grant to faculty.

Experimental
The solution of succinic anhydride (0.01 mole) in toluene (25 ml) was treated dropwise with the solution of 3-chloro,4methylaniline (0.01 mole) also in toluene (20 ml) with constant stirring. The resulting mixture was stirred for about one hour and set aside for an additional hour at room temperature for completion of the reaction. The mixture was then treated with dilute hydrochloric acid to remove the unreacted 3-chloro-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. It was recrystallized to constant melting point from ethanol. The purity of the compound was checked and characterized by its infrared and NMR spectra.
Needle like colorless 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 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 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).

Special details
Experimental. CrysAlis RED (Oxford Diffraction, 2009) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.  (7) Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x+1, −y, −z; (iii) −x+1, −y+2, −z+1; (iv) −x+2, −y+3, −z+2.