(E)-N′-(4-Chlorobenzylidene)-1-benzofuran-2-carbohydrazide monohydrate

The title compound, C16H11ClN2O2·H2O, exists in an E conformation with respect to the N=C bond. The benzofuran ring system forms a dihedral angle of 1.26 (4)° with the benzene ring. In the crystal, molecules are linked via (N,C)—H⋯O bifurcated acceptor hydrogen bonds and (O,O,C)—H⋯O trifurcated acceptor hydrogen bonds, forming layers parallel to the bc plane.

Hydrazones of aliphatic and aromatic methyl ketones yield pyrazole-4-carboxaldehyde on formylation by treatment with Vilsmeier reagent. Hydrazones derived from anisaldehyde and 4-nitro-5-ethoxycarbonyl phenylhydrazine showed excellent NLO property (Vijayakumar et al., 2011). Prompted by these observations, the title compound was synthesized and its crystal structure is reported.

Experimental
The title compound was obtained by refluxing a mixture of 1-benzofuran-2-carbohydrazide (0.01 mol), 4-chlorobenzaldehyde (0.01 mol) in ethanol (30 ml) and 3 drops of concentrated sulfuric acid for 1 h. Excess ethanol was removed from the reaction mixture under reduced pressure. The solid product obtained was filtered, washed with ethanol and dried. Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol-N,N-dimethylformamide (DMF) (3:1) solution.

Figure 2
The crystal structure of the title compound, viewed along the b axis. H atoms not involved in hydrogen bonds (dashed lines) have been omitted for clarity.

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.

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