N,N′-(Methylenedi-p-phenylene)dibenzamide

The title compound, C27H22N2O2, consists of two chemically equivalent halves. However, it displays no crystallographic symmetry, only an approximate local twofold symmetry (r.m.s. deviation = 0.15 Å between the two halves of the molecule) is observed. In the crystal, molecules are connected by two antiparallel classical N—H⋯O hydrogen bonds, forming broad chains parallel to (10). A series of weak C—H⋯N/O hydrogen bonds is also present.

The title compound, C 27 H 22 N 2 O 2 , consists of two chemically equivalent halves. However, it displays no crystallographic symmetry, only an approximate local twofold symmetry (r.m.s. deviation = 0.15 Å between the two halves of the molecule) is observed. In the crystal, molecules are connected by two antiparallel classical N-HÁ Á ÁO hydrogen bonds, forming broad chains parallel to (101). A series of weak C-HÁ Á ÁN/ O hydrogen bonds is also present.

Related literature
For general background to the chemistry of polymers and polyamides, see Ataei et al. (2005); Yang et al. (2002). For related structures, see: Im & Jung (2000).
The molecule of the title compound is shown in Fig. 1. Molecular dimensions may be regarded as normal, as may the trans geometry at the amide groups. The molecule possesses no crystallographic symmetry, but displays approximate twofold symmetry with a r.m.s. deviation of 0.15 Å between the two halves of the molecule. There are however significant differences between torsion angles of chemically equivalent amide groups, e.g. C1-N1-C24-C25 -  (Table 1).

S2. Experimental
All reagents and organic solvents were of analytical grade and commercially available. The title compound was accidentally generated during the reaction of 4,4′-diaminodiphenylmethane with 2-thiophene-carbonyl chloride; it was isolated from the reaction mixture by column chromatography in 30% yield and then purified by recrystallization from ethanol. Colourless single crystals suitable for X-ray analysis were obtained after one week by slow evaporation from an ethanolic solution. Crystals formed as thin plates or somewhat thicker laths; both proved to have the same cell constants.

S3. Refinement
NH H atoms were refined freely. Other H atoms were placed in calculated positions and refined using a riding model with C-H arom 0.95 Å, C-H methylene 0.99 Å; these hydrogen U values were fixed at 1.2 × U(eq) of the parent atom. Data are 99.6% complete to 2θ 145°.  Thermal ellipsoid plot (50% probability level) of the title compound.

Figure 2
Packing diagram viewed parpendicular to (101). Classical H bonds are indicated by thick dashed lines. H atoms not involved in these H bonds are omitted for clarity.

N,N′-(Methylenedi-p-phenylene)dibenzamide
Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 R-factors(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. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)