(E)-N′-(2-Hydroxybenzylidene)-2-(4-isobutylphenyl)propanohydrazide

The title hydrazide compound, C20H24N2O2, exists in a trans configuration with respect to the acyclic C=N bond and an intramolecular O—H⋯N hydrogen bond generates an S(6) ring motif. The mean plane through the formohydrazide unit is essentially planar [maximum deviation = 0.025 (2) Å], and forms dihedral angles of 24.45 (16) and 87.14 (16)° with the two benzene rings. In the crystal structure, intermolecular N—H⋯O and C—H⋯O hydrogen bonds link neighbouring molecules into extended chains along the c axis, which incorporate R 2 2(16) ring motifs. An intermolecular C—H⋯π interaction is also observed.

The title hydrazide compound, C 20 H 24 N 2 O 2 , exists in a trans configuration with respect to the acyclic C N bond and an intramolecular O-HÁ Á ÁN hydrogen bond generates an S(6) ring motif. The mean plane through the formohydrazide unit is essentially planar [maximum deviation = 0.025 (2) Å ], and forms dihedral angles of 24.45 (16) and 87.14 (16) with the two benzene rings. In the crystal structure, intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds link neighbouring molecules into extended chains along the c axis, which incorporate R 2 2 (16) ring motifs. An intermolecular C-HÁ Á Á interaction is also observed.

Experimental
The title compound was obtained by refluxing for 1 h salicylaldehyde (0.01 mol), 2-(4-isobutylphenyl)propanehydrazide (0.01 mol) and ethanol (30 ml) with the addition of three drops of concentrated sulphuric acid. The solid product obtained was filtered, washed with ethanol and dried. Colourless blocks of (I) were obtained by slow evaporation from ethanol. Yield was 74 %. M.p. 426 K.

Refinement
The H atoms bound to atoms O1 and N2 were located from the difference Fourier map and allowed to refine freely. All the other H atoms were placed in calculated positions, with C-H = 0.93 -0.97 Å, and as riding, with U iso = 1.2 or 1.5 U eq (C). A rotating group model was used for the methyl groups. The reflection (020) was omitted from the refinement as   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.