Ethyl 1-sec-butyl-2-(2-hydroxyphenyl)-1H-benzimidazole-5-carboxylate 0.25-hydrate

In the title compound, C20H22N2O3·0.25H2O, the water molecule (occupancy 0.25) is disordered across a crystallographic inversion center. The dihedral angle between the hydroxyphenyl ring and the benzimidazole ring system is 59.31 (9)°. In the crystal structure, molecules are connected by intermolecular O—H⋯N and C—H⋯O hydrogen bonds. The crystal structure is further stabilized by a weak C—H⋯π interaction involving the imidazole ring.

In the title compound, C 20 H 22 N 2 O 3 Á0.25H 2 O, the water molecule (occupancy 0.25) is disordered across a crystallographic inversion center. The dihedral angle between the hydroxyphenyl ring and the benzimidazole ring system is 59.31 (9) . In the crystal structure, molecules are connected by intermolecular O-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds. The crystal structure is further stabilized by a weak C-HÁ Á Á interaction involving the imidazole ring.

Comment
Benzimidazoles belong to one of the well known and most extensively studied class of compounds due to their biological activity such as antitumour (Garuti et al., 2004), antiviral (Bonfanti et al., 2008), antibacterial (Ozden et al., 2008) and analgesic properties (Shao et al., 2005). These derivatives are anti-inflammatory (Blythin et al., 1986) and can be carcinogenic (Snow et al., 2007). As the benzimidazole derivative is of much importance, we have undertaken the X-ray crystal structure determination of the title compound.

Experimental
The title compound was synthesised according to the previous procedure described by us (Arumugam et al., 2010a,b,c).
The product was recrystallized from EtOAc to yield the title compound as colourless crystals.

Refinement
All hydrogen atoms were positioned geometrically [C-H = 0.93 or 0.97Å] and were refined using a riding model, with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was applied to the methyl groups. In the final refinement cycles the occupancy of the water molecule, O1W, which is disordered over a crystallographic inversion centre, was fixed at 25%.

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 s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 > 2σ(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.

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