N′-(2-Hydroxy-4-methoxybenzylidene)-4-methylbenzohydrazide

The asymmetric unit of the title compound, C16H16N2O3, contains four independent molecules with different conformations; the dihedral angles between the two benzene rings in the molecules are 39.7 (3), 45.4 (3), 50.6 (3) and 51.6 (3)°. Intramolecular O—H⋯N hydrogen bonds are observed in the molecule. In the crystal, N—H⋯O hydrogen bonds link the molecules into two crystallographically independent chains propagating in [010], and each chain is formed by two alternating independent molecules. Weak C—H⋯O interactions also occur.

The asymmetric unit of the title compound, C 16 H 16 N 2 O 3 , contains four independent molecules with different conformations; the dihedral angles between the two benzene rings in the molecules are 39.7 (3), 45.4 (3), 50.6 (3) and 51.6 (3) . Intramolecular O-HÁ Á ÁN hydrogen bonds are observed in the molecule. In the crystal, N-HÁ Á ÁO hydrogen bonds link the molecules into two crystallographically independent chains propagating in [010], and each chain is formed by two alternating independent molecules. Weak C-HÁ Á ÁO interactions also occur.
The asymmetric unit of the title compound contains four independent molecules with different conformations -the dihedral angles between the two benzene rings in the molecules A, B, C, and D are 39.7 (3), 45.4 (3), 50.6 (3) and 51.6 (3)°, respectively. The bond distances and angles are within normal ranges (Allen et al., 1987), and agree well with the corresponding bond distances and angles reported for closely related compounds (Suleiman Gwaram et al., 2010;Liu et al., 2011;Zhou et al., 2011).
Intermolecular N-H···O hydrogen bonds (Table 1) link the molecules into two crystallographically independent chains propagating in [010], and each chain is formed by two alternating independent molecules. Weak intermolecular C-H···O interactions (Table 1) consolidate further the crystal packing (Fig. 2).

Experimental
To a methanol solution (20 ml) of 2-hydroxy-4-methoxybenzaldehyde (0.1 mmol, 15.6 mg) and 4-methylbenzohydrazide (0.1 mmol, 15.0 mg), a few drops of acetic acid were added. The mixture was refluxed for 1 h and then cooled to room temperature. The white crystalline solid was collected by filtration, washed with cold methanol and dried in air. Single crystals, suitable for X-ray diffraction, were obtained by slow evaporation of a methanol solution of the product in air.

Refinement
N-bound H atoms were located in a difference Fourier map and were refined with a distance restraint, N-H = 0.90 (1) Å.

N′-(2-Hydroxy-4-methoxybenzylidene)-4-methylbenzohydrazide
Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.