Ethyl (E)-1-(2-styryl-1H-benzimidazol-1-yl)acetate

In the title compound, C19H18NO2, the dihedral angle between the benzimidazole and phenyl ring planes is 18.18 (17)°. The atoms of the ethyl side chain are disordered over two sets of sites in a 0.50:0.50 ratio. In the crystal, intermolecular C—H⋯O hydrogen bonds and C—H⋯π contacts help to consolidate the packing.

The dihedral angle between the benzimidazole and styryl groups is 17.78 (1)°. The molecule is twisted with the N1-C4-C3-O1 torsion angle of 13.61 (4)° between the ethyl acetate and benzimidazole groups.
In the crystal, intermolecular C-H···O hydrogen bonds (Fig.2) link the molecules to chains along the b axis. In addition the C-H···π contacts (Table 1) further stabilize the crystal structure.

Refinement
Anomalous dispersion was negligible and Friedel pairs were merged before refimenent. The positional parameters of all the H atoms were calculated geometrically and refined as riding with U iso (H) = 1.2U eq (C,N) or 1.5U eq (methyl C). Fig. 1. The molecular structure of (I) with displacement ellipsoids drawn at the 30% probability level (all H atoms have been omitted for clarity).

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 > 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (