N-(3,4-Dimethylphenyl)-4-methylbenzamide

The title compound, C16H17NO, crystallizes with two molecules in the asymmetric unit. The conformation of the N—H bond is anti to the meta-methyl substituent in the aniline ring in the first molecule and syn in the second molecule. The dihedral angles between the two benzene rings are 52.6 (1) and 10.5 (1)° in the first and second molecules, respectively. Intermolecular N—H⋯O hydrogen bonds link the molecules into chains running along the b axis of the crystal.

The title compound, C 16 H 17 NO, crystallizes with two molecules in the asymmetric unit. The conformation of the N-H bond is anti to the meta-methyl substituent in the aniline ring in the first molecule and syn in the second molecule. The dihedral angles between the two benzene rings are 52.6 (1) and 10.5 (1) in the first and second molecules, respectively. Intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into chains running along the b axis of the crystal.
The asymmetric unit of the cell in (I) contains two independent molecules. In the first molecule, the conformation of the N-H bond is anti to the meta-methyl-substituent in the disubstituted phenyl ring, while in the second molecule this conformation is syn. The dihedral angles between the two benzene rings are 52.6 (1)° and 10.5 (1)° in the first and second molecules, respectively. The central amido group -NH-C(=O)-forms dihedral angles of 22.2 (2)° and 31.2 (1)° with the benzoyl ring, and 30.6 (1)° and 25.5 (1)° with the disubstituted phenyl ring, in the two independent molecules.
The packing diagram of molecules in (I) showing the intermolecular N-H···O hydrogen bonds (Table 1) involved in the formation of molecular chains running along the b-axis is shown in Fig. 2.

Experimental
The title compound was prepared according to the literature method (Gowda et al., 2003). The purity of the compound was checked by determining its melting point. It was characterized by recording its infrared and NMR spectra. Single crystals of the title compound used in X-ray diffraction studies were obtained from a slow evaporation of its ethanolic solution at room temperature.

Refinement
H atoms were placed in calculated positions with N-H distances of 0.86 Å and C-H distances in the range 0.93-0.96 Å.
All hydrogen atoms were constrained to ride on their parent atoms. The U iso (H) values were set at 1.2U eq (C aromatic, N) and 1.5 U eq (C methyl ). The U values of the atom pairs C23-C34 and C7-O1 were subject to a rigid bond restraint (DELU instruction), i.e. the components of the displacement parameters in the direction of the bond were restrained to be equal within an effective standard deviation 0.004. The C16 and C36 methyl group exhibit orientational disorder in the hydrogen atom positions. The two sets of methyl hydrogen atoms were refined with equal occupancy.

Special details
Geometry. All e.s. 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. Atomic displacement parameters (Å 2 )