N-(2-Chlorophenyl)-N′-(2-methylphenyl)succinamide

In the title compound, C17H17ClN2O2, the asymmetric unit contains half a molecule with a centre of symmetry at the mid-point of the central C—C bond. The conformations of the amide O atoms are anti to the methylene atoms. Further, the N—H bonds in the amide fragments are anti to the ortho-chloro/methyl groups in the adjacent benzene rings. The dihedral angle between the benzene ring and the NH—C(O)—CH2 segment in the two halves of the molecule is 62.0 (2)°. In the crystal, a series of N—H⋯O intermolecular hydrogen bonds link the molecules into column-like infinite chains along the a axis. The methyl and Cl groups are disordered with respect to the ortho positions of the benzene ring, with site-occupation factors of 0.5 each.

In the title compound, C 17 H 17 ClN 2 O 2 , the asymmetric unit contains half a molecule with a centre of symmetry at the midpoint of the central C-C bond. The conformations of the amide O atoms are anti to the methylene atoms. Further, the N-H bonds in the amide fragments are anti to the orthochloro/methyl groups in the adjacent benzene rings. The dihedral angle between the benzene ring and the NH-C(O)-CH 2 segment in the two halves of the molecule is 62.0 (2) . In the crystal, a series of N-HÁ Á ÁO intermolecular hydrogen bonds link the molecules into column-like infinite chains along the a axis. The methyl and Cl groups are disordered with respect to the ortho positions of the benzene ring, with site-occupation factors of 0.5 each.
BSS thanks the University Grants Commission, Government of India, New Delhi for the award of a research fellowship under its faculty improvement programme.
The conformations of the amide O atoms are anti to the H atoms attached to the adjacent C atoms. Further, the conformations of the N-H bonds in the amide fragments are anti to the ortho-chloro/methyl groups in the adjacent benzene rings, similar to that observed with respect to the meta-chloro/methyl groups in (III), and the anti conformations observed with respect to the ortho-methyl groups in (V), but contrary to the syn conformations observed between the N-H bonds in the amide fragments and the ortho-chloro groups in the adjacent benzene rings of (IV). The packing of molecules in the crystal linked by of N-H···O hydrogen bonds (Table 1)  water, dilute sodium hydroxide solution and finally with water. It was recrystallized to constant melting point from a mixture of acetone and toluene (3:1 v/v). The compound was characterized by its infrared and NMR spectra.
Needle like colorless single crystals used in X-ray diffraction studies were grown in a mixture of acetone and toluene (3:1 v/v) at room temperature.

Refinement
The H atom of the NH group was located in a difference map and later restrained to the distance N-H = 0.86 (2) Å. The other H atoms were positioned with idealized geometry using a riding model with the aromatic C-H = 0.93 Å, methyl C-H = 0.97 Å, and the methylene C-H = 0.97 Å.
All H atoms were refined with isotropic displacement parameters. The U iso (H) values were set at 1.2U eq (C-aromatic, N) and 1.5U eq (C-methyl).
The residual electron-density features are located in the region of Cl1 and C2. The highest peak is 0.66 Å from Cl1 and the deepest hole is 0.23 Å from C2.
C9 and Cl1 are disordered and were refined using a split model. The corresponding site-occupation factors were fixed to 0.50:0.50. The U ij components of C9 were restrained to approximate isotropic behavoir (Nardelli, 1999). The bond lengths C2-C9 and C2-Cl1 were restrained to 1.54 (1) and 1.74 (1) Å, respectively. Fig. 1. Molecular structure of the title compound, showing the atom labelling scheme and displacement ellipsoids are drawn at the 50% probability level. Symmetry operation to generate second half: -x + 1, -y, -z.