N′-(3-Chlorobenzylidene)-4-hydroxybenzohydrazide

The molecule of the title compound, C14H11ClN2O2 adopts an E conformation of the azomethine double bond and the dihedral angle between the benzene rings is 38.96 (13)°. In the crystal, molecules are linked by N—H⋯O and O—H⋯O (with the ketone O atom as acceptor) and C—H⋯O (with the hydroxy O atom as acceptor) hydrogen bonds, forming a three-dimensional network.

The molecule of the title compound, C 14 H 11 ClN 2 O 2 adopts an E conformation of the azomethine double bond and the dihedral angle between the benzene rings is 38.96 (13) . In the crystal, molecules are linked by N-HÁ Á ÁO and O-HÁ Á ÁO (with the ketone O atom as acceptor) and C-HÁ Á ÁO (with the hydroxy O atom as acceptor) hydrogen bonds, forming a three-dimensional network.

Related literature
For a related structure and background to the chemistry of the N-acylhydrazone unit, see: Taha et al. (2012). For a related structure, see: Hao (2009 Table 1 Hydrogen-bond geometry (Å , ).

Experimental
The title compound was synthesized by refluxing a mixture of 3-chlorobenzaldehyde (2 mmol, 0.23 ml), methanol (20 ml) and 3 drops of acetic acid. 4-hydroxybenzohydrazide (2 mmol, 0.304 g) was added into above mentioned mixture at ambient temperature and refluxed for 3 h with vigorous stirring. Progress of the reaction mixture was monitored by thin layer chromatography. After the completion of the reaction (TLC Analysis), the solvent of the reaction mixture was slowly evaporated at room temperature by keeping it in an open atmosphere in order to obtained colourless blocks (0.44 g, 80.3% yield).

Refinement
H atoms on phenyl ring and methine carbon were positioned 0.93 Å (CH) and constrained to ride on their parent atoms with U iso (H)= 1.2U eq (CH). The H atoms on the nitrogen (N-H= 0.79 (3) Å) and oxygen (O-H= 0.89 (2) Å) atoms were located in difference fourier maps and refined isotropically.

Figure 2
The crystal packing of the title compound I. Only hydrogen atoms involved in hydrogen bonding are shown. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.21 e Å −3 Δρ min = −0.20 e Å −3 Absolute structure: Flack (1983), 1060 Friedel pairs Flack parameter: 0.12 (9) 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.