N-(4-Chlorophenyl)-N′-(4-methylphenyl)succinamide

The asymmetric unit of the title compound, C17H17ClN2O2, contains one half-molecule with a center of symmetry at the mid-point of the central C—C bond. The dihedral angle between the benzene ring and the adjacent NH—C(O)—CH2 group is 39.9 (1)°. The methyl and Cl groups are disordered with respect to the para-positions of the benzene ring, with site-occupation factors of 0.5 each. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into chains parallel to the baxis.

The asymmetric unit of the title compound, C 17 H 17 ClN 2 O 2 , contains one half-molecule with a center of symmetry at the mid-point of the central C-C bond. The dihedral angle between the benzene ring and the adjacent NH-C(O)-CH 2 group is 39.9 (1) . The methyl and Cl groups are disordered with respect to the para-positions of the benzene ring, with site-occupation factors of 0.5 each. In the crystal, intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into chains parallel to the baxis.
BSS thanks the University Grants Commission, Government of India, New Delhi, for the award of a research fellowship under its faculty improvement program.

Comment
The amide and sulfonamide moieties are important constituents of many biologically significant compounds. As part of our studies on the substituent effects on the structures and other aspects of N-(aryl)-amides (Arjunan et al., 2004;Bhat & Gowda, 2000;Saraswathi et al., 2011), N-(aryl)-methanesulfonamides (Gowda et al., 2007) and arylsulfonamides (Gowda et al., 2003), in the present work, the structure of N-(4-Chlorophenyl),N-(4-methylphenyl)-succinamide (I) has been determined (Fig.1). The asymmetric unit of (I) contains half a molecule with a center of symmetry at the mid-point of the central C-C bond, similar to that obseved in bis(2-chlorophenylaminocarbonylmethyl)disulfide (II) (Pierrot et al., 1984), (Saraswathi et al., 2011) The conformations of the amide O atoms are anti to the H atoms attached to the adjacent C atoms.
The dihedral angle between the benzene ring and the NH-C(O)-CH 2 segment in the two halves of the molecule is 39.9 (1)°, compared to the value of 43.5 (1)° in (III).
The packing of molecules in the crystal linked by of N-H···O hydrogen bonds (Table 1) is shown in Fig. 2.

Experimental
Succinic anhydride (0.01 mol) in toluene (25 ml) was treated drop wise with 4-chloroaniline (0.01 mol) also in toluene (20 ml) with constant stirring. The resulting mixture was stirred for 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 unreacted 4-chloroaniline. The resultant solid N-(4-chlorophenyl)-succinamic acid was filtered under suction and washed thoroughly with water to remove the unreacted succinic anhydride and succinic acid. The compound was recrystallized to constant melting point from ethanol. The purity of the compound was checked by elemental analysis and characterized by its infrared and NMR spectra.
The N-(4-chlorophenyl)succinamic acid obtained was then treated with phosphorous oxychloride and excess of 4-methylaniline at room temperature with constant stirring. The resultant mixture was stirred for 4 h, kept aside for additional 6 h for completion of the reaction and poured slowly into crushed ice with constant stirring. It was kept aside for a day. The resultant solid, N-(4-chlorophenyl), N-(4-methylphenyl)-succinamide was filtered under suction, washed thoroughly with 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.
Rod 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).
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 bond lenghts C4-C9 were restrained to 1.54 (1) Å and C4-CL1 to 1.74 (1) Å, respectivily. The U ij components of these atoms were restrained to approximate isotropic behavoir (Nardelli, 1999). Fig. 1. Molecular structure of the title compound, showing the atom labelling scheme and displacement ellipsoids are drawn at the 50% probability level. symmetry code: (i) -x + 1, -y, -z + 1.   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.