Ethyl 1-sec-butyl-2-p-tolyl-1H-benzimidazole-5-carboxylate

In the title compound, C21H24N2O2, the butyl group is disordered over two orientations with refined site occupancies of 0.883 (3) and 0.117 (3). The dihedral angle between the mean plane of benzimidazole ring system and the benzene ring is 39.32 (4)° and the dihedral angle between the mean plane of carboxylate group and the benzimidazole ring system is 6.87 (5)°. A weak intramolecular C—H⋯π interaction may have some influence on the conformation of the molecule. In the crystal structure, molecules are linked into infinite chains along the b axis by weak intermolecular C—H⋯O hydrogen bonds.

In the title compound, C 21 H 24 N 2 O 2 , the butyl group is disordered over two orientations with refined site occupancies of 0.883 (3) and 0.117 (3). The dihedral angle between the mean plane of benzimidazole ring system and the benzene ring is 39.32 (4) and the dihedral angle between the mean plane of carboxylate group and the benzimidazole ring system is 6.87 (5) . A weak intramolecular C-HÁ Á Á interaction may have some influence on the conformation of the molecule. In the crystal structure, molecules are linked into infinite chains along the b axis by weak intermolecular C-HÁ Á ÁO hydrogen bonds.
The geometric parameters of the title compound ( Fig. 1) are comparable to those closely related structures (Arumugam et al., 2010a,b,c). The butyl group is disordered over two positions with refined site-occupancies of 0.883 (3) and 0.117 (3). The dihedral angle between the mean plane of benzimidazole ring system (C7/N1/C8-C13/N2) and the benzene ring (C1-C6) is 39.32 (4)°. The mean plane of carboxylate group (O1/O2/C14-C16) is slightly twisted from the mean plane of benzimidazole ring system with a dihedral angle of 6.87 (5)°. In the crystal structure, the molecules are linked into infinite one-dimensional chains along b axis by intermolecular C12-H12A···O1 i hydrogen bonds (Fig. 2, Table 1). A weak intramolecular C20-H20C···Cg1 interaction may have some influence on the conformation of the molecule (Table 1).

Experimental
The title compound was synthesised using the previous procedures (Arumugam et al., 2010a,b,c) and recrystallized from EtOAc by slow evaporation technique.

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.98 Å and U iso (H) = 1.2 or 1.5 U eq (C). The rotating group model was applied for the methyl groups. The minor disorder component is refined isotropically. Fig. 1. The molecular structure of the title compound with atom labels and 50% probability displacement ellipsoids for non-H atoms. All disorder components are shown.

Figures
sup-2 Only the major disorder component is shown.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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 > 2sigma(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.