N-(2-Chloro-5-methylphenyl)succinamic acid

In the title compound, C11H12ClNO3, the conformation of the N—H bond in the amide segment is syn with respect to the ortho-Cl atom. The amide and carboxyl C=O groups are syn to each other. Furthermore, the C=O and O—H bonds of the carboxyl group are in syn positions with respect to each other. The dihedral angle between the benzene ring and the amide group is 47.8 (2)°. In the crystal, molecules are connected by pairs of O—H⋯O hydrogen bonds, forming inversion dimers. The dimers are further linked by N—H⋯O hydrogen bonds into double chains along the b-axis direction.

In the title compound, C 11 H 12 ClNO 3 , the conformation of the N-H bond in the amide segment is syn with respect to the ortho-Cl atom. The amide and carboxyl C O groups are syn to each other. Furthermore, the C O and O-H bonds of the carboxyl group are in syn positions with respect to each other. The dihedral angle between the benzene ring and the amide group is 47.8 (2) . In the crystal, molecules are connected by pairs of O-HÁ Á ÁO hydrogen bonds, forming inversion dimers. The dimers are further linked by N-HÁ Á ÁO hydrogen bonds into double chains along the b-axis direction.

Comment
The amide and sulfonamide moieties are important constituents of many biologically important compounds. As a part of our studies of the substituent effects on the structures and other aspects of N-(aryl)-amides (Gowda et al., 2001;Saraswathi et al., 2011), N-(aryl)-methanesulfonamides (Jayalakshmi & Gowda, 2004), N-(aryl)-arylsulfonamides (Gowda et al., 2005) and N-chloro-arylsulfonamides (Gowda et al., 1996), in the present work, the crystal structure of N-(2-chloro-5methylphenyl)succinamic acid (I) has been determined ( Fig. 1). The conformation of the N-H bond in the amide segment is syn to the ortho-chloro group and anti to the meta-methyl group in the benzene ring, similar to the syn conformation observed between the amide hydrogen and the ortho-Cl and anti conformation between the amide hydrogen and the meta-Cl in the benzene ring of N-(2,5-dichlorophenyl)-succinamic acid (II) (Saraswathi et al., 2011).
Further, the conformations of the amide oxygen and the carboxyl oxygen of the acid segment are syn to each other.
The C═O and O-H bonds of the acid group are in syn position to each other, similar to that observed in (II).
The dihedral angle between the phenyl ring and the amide group is 47.8 (2)°.
The intermolecular O-H···O and N-H···O hydrogen bonds pack the molecules into infinite chains along the b-axis direction (Table 1, Fig.2).
The modes of interlinking carboxylic acids by hydrogen bonds is described elsewhere (Leiserowitz, 1976). The packing of molecules involving dimeric hydrogen-bonded association of each carboxyl group with a centrosymmetrically related neighbor has also been observed (Jagannathan et al., 1994).

Experimental
The solution of succinic anhydride (0.01 mole) in toluene (25 ml) was treated with the solution of 2-chloro,5-methylaniline (0.01 mole) also in toluene (20 ml), added dropwise with permanent 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 diluted hydrochloric acid to remove the unreacted 2-chloro-5-methyl-aniline. The resultant title compound was filtered under suction and washed thoroughly with water to remove the unreacted succinic anhydride and succinic acid. The product was recrystallized to constant melting point from ethanol. The purity of the compound was checked and characterized by its infrared and NMR spectra.
Rod like colorless single crystals used in X-ray diffraction studies were grown from ethanolic solution by slow evaporation at room temperature.

Refinement
The H atoms of the NH and OH groups were located in a difference map and later restrained to the distances N-H = 0.86 (2) Å and O-H = 0.82 (2) Å, respectively. The other H atoms were positioned with idealized geometry and refined 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 to 1.2 times of the U eq of the parent atom). Fig. 1. Molecular structure of the title compound, showing the atom labelling scheme and with displacement ellipsoids drawn at the 50% probability level. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq