N-(2,4-Dimethylphenyl)-4-methylbenzamide

In the molecule of the title compound, C16H17NO, the N—H and C=O bonds are anti to each other and the two benzene rings form a dihedral angle of 75.8 (1)°. The amide group is twisted by 28.1 (3) and 76.3 (2)° out of the planes of the 4-methylphenyl and 2,4-dimethylphenyl rings, respectively. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into chains running along the c axis. The crystal studied was hemihedrally twinned with a twin law resulting from a twofold rotation about the a axis.

In the molecule of the title compound, C 16 H 17 NO, the N-H and C O bonds are anti to each other and the two benzene rings form a dihedral angle of 75.8 (1) . The amide group is twisted by 28.1 (3) and 76.3 (2) out of the planes of the 4methylphenyl and 2,4-dimethylphenyl rings, respectively. In the crystal, intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into chains running along the c axis. The crystal studied was hemihedrally twinned with a twin law resulting from a twofold rotation about the a axis.

Comment
As part of a study of the substituent effects on the crystal structures of benzanilides (Gowda et al., 2003(Gowda et al., , 2009a(Gowda et al., ,b, 2010, in the present work, the structure of N-(2,4-dimethylphenyl)4-methylbenzamide has been determined. In the structure, the The amide group is twisted by 28.1 (3) and 76.3 (2) ° out of the planes of the 4-methylphenyl and 2,4-dimethylphenyl rings, respectively. Intermolecular N-H···O hydrogen bonds (Table 1) link the molecules into chains running along the c axis of the crystal (Fig. 2).

Experimental
The title compound was prepared according to the literature method (Gowda et al., 2003). Plate-like colourless crystals were obtained from a slow evaporation of its ethanolic solution at room temperature.

Refinement
Twinning was discovered, with two twin domains in a 1:1 ratio. and taken into account from the early stages of data collection. The twin law was determined as the matrix (-0.9998 0.0015 -0.8619/ -0.0001 -1.0000 -0.0003/ 0.0000 -0.0005 1.0001), which corresponds to a twofold rotation about the a axis. The non-diagonal matrix element of -0.8619 has a near-rational value of -6/7. Inspection of diffraction patterns and HKL files confirmed that reflections are overlapped mainly in the zones with l = 0 and l = 7. The twin scale factor was refined to a final value of 0.484 (2). All hydrogen atoms were positioned with idealized geometry using a riding model with C-H = 0.93 Å or 0.96 Å, and N-H = 0.86 Å, and with U iso (H) = 1.2U eq (Caromatic, N) and 1.5U eq (C-methyl). Fig. 1. Molecular structure of (I) showing the atom labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are represented as small spheres of arbitrary radii.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 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.