4-Methylbenzoic acid–N′-[(E)-4-methylbenzylidene]pyridine-4-carbohydrazide–water (1/1/1)

In the title hydrated 1:1 adduct, C8H8O2·C14H13N3O·H2O, the Schiff base molecule exists in an E conformation with respect to the N=C bond [1.2843 (13) Å] and the dihedral angle between the pyridine ring and the benzene ring is 1.04 (5)°. In the crystal, molecules are linked by N—H⋯O, C—H⋯O, O—H⋯O and O—H⋯N hydrogen bonds into sheets lying parallel to the ab plane. The crystal structure also features π–π interactions with centroid–centroid distances of 3.6224 (6) and 3.7121 (6) Å.

In the title hydrated 1:1 adduct, C 8 H 8 O 2 ÁC 14 H 13 N 3 OÁH 2 O, the Schiff base molecule exists in an E conformation with respect to the N C bond [1.2843 (13) Å ] and the dihedral angle between the pyridine ring and the benzene ring is 1.04 (5) . In the crystal, molecules are linked by N-HÁ Á ÁO, C-HÁ Á ÁO, O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds into sheets lying parallel to the ab plane. The crystal structure also featuresinteractions with centroid-centroid distances of 3.6224 (6) and 3.7121 (6) Å .
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009  The structures of isoniazid and its various derivatives have been described previously (Wang et al., 2007;Jing et al., 2005). Here, the synthesis and crystal structure of its Schiff base derivative (I) is reported. The Schiff base, N′-[(E)-(4methylphenyl)methylidene]pyridine-4-carbohydrazide was synthesized by the condensation of isoniazid with 4-methylbenzaldehyde in absolute alcohol in presence of hydrochloric acid. During the crystallization, the synthesized Schiff base crystallized with 4-methyl benzoic acid (which is a side product obtained by the auto-oxidation of unreacted 4-methyl benzaldehyde) and one molecule of water to form title compound (I) (Fig. 1).

Experimental
A mixture of isoniazid (1.4 g, 0.01 mol) and 4-methylbenzaldehyde (1.2 g, 0.01 mol) in 15 ml of absolute alcohol containing two drops of hydrochloric acid was refluxed for about 3 h. On cooling, a solid was separated out. The solid was filtered out and recrystallized from DMF. Colourless blocks of (I) were grown from DMF by slow evaporation method. During the crystallization, the synthesized Schiff base was crystallized with 4-methyl benzoic acid (which was a side product obtained by the auto-oxidation of unreacted 4-methyl benzaldehyde) and one molecule of water to form the title compound (I). (M.p: 428 K).

Refinement
The O-and N-bound H atoms were located in a difference

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids.

Figure 2
The crystal packing of the title compound, viewed along the a axis. H atoms not involved in the intermolecular interactions (dashed lines) have been omitted for clarity. 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.