(E)-4-Chloro-N′-[1-(4-hydroxyphenyl)ethylidene]benzohydrazide

The molecule of the title compound, C15H13ClN2O2, displays a trans configuration with respect to the C=N double bond. The dihedral angle between the two benzene rings is 15.1 (3)°. A strong intramolecular O—H⋯N hydrogen bond is observed. In the crystal structure, molecules are linked through intermolecular N—H⋯O hydrogen bonds, forming chains running along [101].

The molecule of the title compound, C 15 H 13 ClN 2 O 2 , displays a trans configuration with respect to the C N double bond. The dihedral angle between the two benzene rings is 15.1 (3) . A strong intramolecular O-HÁ Á ÁN hydrogen bond is observed. In the crystal structure, molecules are linked through intermolecular N-HÁ Á ÁO hydrogen bonds, forming chains running along [101].

Related literature
For bond-length data, see: Allen et al. (1987). For related structures, see: Yang (2007Yang ( , 2008a. For general background, see: Bernardo et al. (1996) Table 1 Hydrogen-bond geometry (Å , ).   et al., 2001;Bernardo et al., 1996;Paul et al., 2002). Recently, we have reported a few Schiff base compounds (Yang, 2007(Yang, , 2008a. As a further investigation of this work, the crystal structure of the title compound is reported here. The molecule of the title compound displays a trans configuration with respect to the C?N double bond (Fig. 1). The dihedral angle between the two benzene rings is 15.1 (3)°. All the bond lengths are within normal ranges (Allen et al., 1987).
The C8═N2 bond length of 1.287 (3) Å conforms to the value for a double bond. The N1-C7 bond length of 1.355 (3) Å is intermediate between a C-N single bond and a C?N double bond, because of conjugation effects in the molecule. There is a strong intramolecular hydrogen bond between the hydroxyl hydrogen and N2.
In the crystal structure, molecules are linked through intermolecular N-H···O hydrogen bonds (Table 1) Experimental 1-(2-Hydroxyphenyl)ethanone (0.1 mmol, 13.6 mg) and 4-chlorobenzohydrazide (0.1 mmol, 17.0 mg) were dissolved in MeOH (10 ml). The mixture was stirred at room temperature to give a clear colourless solution. Single crystals of the title compound were obtained by gradual evaporation of the solvent over a period of 12 d at room temperature.

Refinement
Atom H1 was located in a difference Fourier map and refined isotropically, with N-H distance restrained to 0.90 (1) Å and with a U iso value of 0.08 Å 2 . Other H atoms were placed in idealized positions and constrained to ride on their parent atoms, with a O-H distance of 0.82 Å, C-H distances of 0.93-0.96 Å, and with U iso (H) = 1.2U eq (C) and 1.5U eq (O2 and C15).

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 Rfactors(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.