N′-[(E)-4-Bromobenzylidene]-1-benzofuran-2-carbohydrazide monohydrate

The title compound, C16H11BrN2O2·H2O, exists in a trans conformation with respect to the N=C bond [1.2815 (14) Å] and the benzofuran ring system forms a dihedral angle of 2.96 (5)° with the benzene ring. In the crystal, the ketone O atom accepts two O—H⋯O and one C—H⋯O hydrogen bond, and the water O atom accepts an N—H⋯O interaction. Together, these lead to infinite layers lying parallel to (100).

The title compound, C 16 H 11 BrN 2 O 2 ÁH 2 O, exists in a trans conformation with respect to the N C bond [1.2815 (14) Å ] and the benzofuran ring system forms a dihedral angle of 2.96 (5) with the benzene ring. In the crystal, the ketone O atom accepts two O-HÁ Á ÁO and one C-HÁ Á ÁO hydrogen bond, and the water O atom accepts an N-HÁ Á ÁO interaction. Together, these lead to infinite layers lying parallel to (100).

Comment
As part of our ongoing synthetic and structural studies of hydrazones with possible biological activities (Fun et al., 2012a,b), the title compound, (I), was synthesized and its crystal structure is now reported.

Experimental
The title compound was obtained by refluxing a mixture of 1-benzofuran-2-carbohydrazide (0.01 mol), 4-bromobenzaldehyde (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. Colourless blocks were obtained by slow evaporation of an ethanol-N,N-dimethylformamide (DMF) (3:1) solution.

Refinement
Atom H1N1 was located in a difference Fourier map and refined freely [N1-H1N1 = 0.890 (17) Å]. O-bound H atoms were located in a difference Fourier map and refined using a riding model with O-H = 0.8182 or 0.8477 Å. The rest of hydrogen atoms were positioned geometrically and refined using a riding model with C-H = 0.93 Å and U iso (H) = 1.2 U eq (C).

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.