2,4-Dihydroxy-N′-(4-methoxybenzylidene)benzohydrazide

The molecule of the title compound, C15H14N2O4, displays a trans configuration with respect to the hydrazide C=N bond. The dihedral angle between the two benzene rings is 15.0 (2)°. In the crystal structure, molecules are linked through intermolecular O—H⋯N and O—H⋯O hydrogen bonds, forming layers parallel to the ab plane; an intramolecular N—H⋯O hydrogen bond is also present.

The molecule of the title compound, C 15 H 14 N 2 O 4 , displays a trans configuration with respect to the hydrazide C N bond. The dihedral angle between the two benzene rings is 15.0 (2) . In the crystal structure, molecules are linked through intermolecular O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds, forming layers parallel to the ab plane; an intramolecular N-HÁ Á ÁO hydrogen bond is also present.
The molecule of the title compound displays a trans configuration with respect to the C=N bond (Fig. 1). The dihedral angle between the two benzene rings is 15.0 (2)°. The molecular conformation is stabilized by an intramolecular N-H···O hydrogen interaction (Table 1). In the crystal, molecules are linked through intermolecular O-H···N and O-H···O hydrogen bonds (Table 1), forming layers parallel to the ab plane ( Fig. 2).
Experimental 4-Methoxybenzaldehyde (0.1 mmol, 13.6 mg) and 2,4-dihydroxybenzoic acid hydrazide (0.1 mmol, 16.8 mg) were dissolved in a 95% ethanol solution (10 ml). The mixture was stirred at room temperature to give a clear colourless solution. Crystals of the title compound were formed by gradual evaporation of the solvent over a period of three days at room temperature.

Refinement
Atom H2A was located in a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å. All other H atoms were placed in idealized positions and constrained to ride on their parent atoms, with O-H = 0.82 Å, C-H = 0.93-0.96 Å, and with U iso (H) = 1.2U eq (C) or 1.5U eq (C, O) for methyl and hydroxy H atoms. In the absence of significant anomalous scattering effects, Friedel opposites were merged in the final refinement.

Special details
Geometry. All e.s. 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.