4-Hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide monohydrate

In the title compound, C15H14N2O4·H2O, the dihedral angle between the two aromatic rings is 33.3 (5)°. The methoxy group is twisted slightly away from the attached benzene ring [C—O—C—C = 13.8 (9)°]. An intramolecular O—H⋯N hydrogen bond is observed. In the crystal structure, the molecules are linked into a two-dimensional network parallel to the (010) plane by intermolecular N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds

In the crystal structure, the molecules are linked into a two-dimensional network parallel to the (010) by intermolecular N-H···O, O-H···O and C-H···O hydrogen bonds (Table 1).

Experimental
The title compound was prepared by the Schiff base condensation of 2-hydroxy-3-methoxybenzaldehyde (0.1 mol) and 4hydroxybenzohydrazide (0.1 mmol) in 95% ethanol (50 ml). The excess ethanol was removed by distillation. The colourless solid obtained was filtered and washed with ethanol. Single crystals suitable for X-ray diffraction were obatined by slow evaporation of a 95% ethanol solution at room temperature.

Refinement
The imino and water H atoms were located in a difference map and refined with N-H, O-H and H···H distances restrained to 0.90 (1), 0.85 (1), and 1.37 (2) Å, respectively. The other H atoms were positioned geometrically (C-H = 0.93-0.96 Å and O-H = 0.82 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C) and 1.5U eq (C methyl and O). A rotating group model was used for methyl and hydroxyl groups. In the absence of significant anomalous scattering effects, Friedel pairs were averaged.

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.  (6) 156 (6)