N,N′-Diphenylsuberamide

In the title compound (systematic name: N,N′-diphenyloctanediamide), C20H24N2O2, the two phenyl rings make an interplanar angle of 76.5 (2)°. The crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds, which link the molecules into chains running along the b axis. The crystal studied was non-merohedrally twinned, the fractional contribution of the minor twin component being 0.203 (2).

In the title compound (systematic name: N,N 0 -diphenyloctanediamide), C 20 H 24 N 2 O 2 , the two phenyl rings make an interplanar angle of 76.5 (2) . The crystal structure is stabilized by intermolecular N-HÁ Á ÁO hydrogen bonds, which link the molecules into chains running along the b axis. The crystal studied was non-merohedrally twinned, the fractional contribution of the minor twin component being 0.203 (2).

Comment
The amide moiety is an important constituent of many biologically significant compounds. As a part of studying the effect of ring and side chain substitutions on the structures of this class of compounds (Gowda et al., 2007;2009a,b), the crystal structure of N,N-bis(phenyl)-suberamide has been determined (I) (Fig. 1).

Experimental
Suberic acid (0.3 mol) was heated with thionyl chloride (1.2 mol) at 120°C for 4 hours. The acid chloride obtained was treated with aniline (0.6 mol). The product obtained was added to crushed ice to obtain the white precipitate. It was thoroughly washed with water and then with saturated sodium bicarbonate solution and washed again with water. It was then given a wash with 2 N HCl. It was again washed with water, filtered, dried and recrystallised to constant point (186-188°C) from ethanol-Tetrahydrofuran mixture in the ratio 1:4.
Plate like colourless single crystals of the title compound used in X-ray diffraction studies were obtained by a slow evaporation of its solution at room temperature.

Refinement
The crystal used for data collection was a non-merohedral twin. The twin law was found to be a twofold axis about the [1 0 4] direct lattice direction. The final refinement was made using the HKLF4 format of the HKL file, and using the INS file having the twin matrix (-1 0 0 / 0 -1 0 / 0.5 0 1) in the TWIN instruction. The fractional contribution of the minor twin component refined to 0.203 (2). The C-bounded hydrogen atoms were positioned with idealized geometry using a riding model with C-H = 0.93 Å or 0.97 Å. Amide H atoms were refined with N-H distance restrained to 0.85 (3) Å. The U iso (H) values were set at 1.2U eq (C, N).

Figures
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.