(E)-N'-(4-Isopropyl-benzyl-idene)isonicotinohydrazide monohydrate.

In the title compound, C(16)H(17)N(3)O·H(2)O, the isonicotinohydrazide mol-ecule adopts an E conformation about the central C=N double bond. The dihedral angle between the pyridine and the benzene rings is 54.56 (15)°. In the crystal, mol-ecules are connected via N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds, forming a three-dimensional network.

In the title compound, C 16 H 17 N 3 OÁH 2 O, the isonicotinohydrazide molecule adopts an E conformation about the central C N double bond. The dihedral angle between the pyridine and the benzene rings is 54.56 (15) . In the crystal, molecules are connected via N-HÁ Á ÁO, O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds, forming a three-dimensional network. Experimental Crystal data C 16 H 17 N 3 OÁH 2 O M r = 285.34 Orthorhombic, P2 1 2 1 2 1 a = 7.7503 (2) Å b = 11.7894 (3) Å c = 17.2820 (4) Å V = 1579.08 (7) Table 1 Hydrogen-bond geometry (Å , ). In the last decade, tuberculosis (TB) has reemerged as one of the leading causes of death in the world, reaching nearly three million deaths annually (Bloom & Murray, 1992). Therefore, the search for new drugs for tuberculosis is of the utmost importance. Treatment regimens are based on a long-term and combined chemotherapy. The most used firstchoice drug is isoniazid, a bactericidal drug that acts both intracellularly in the macrophages and extracellularly in the necrotic tissue (Loenhout-Rooyackers & Veen, 1998). The derivatives of isoniazid have been found to possess potential tuberculostatic activity (Hearn et al., 2009;Tripathi et al., 2011). Herein, we present the crystal structure of the title compound, (I).

Experimental
The title compound was prepared by the reaction of 4-isopropyl benzaldehyde (0.15 g, 1 mmol) with isoniazid (0.14 g, 1 mmol) in EtOH (25 mL). After stirring for 3 h, at room temperature, the resulting mixture was concentrated. The precipitate was washed with EtOH to afford the title compound. Colourless blocks of the title compound suitable for Xray structure determination were recrystallized from EtOH by the slow evaporation of the solvent at room temperature.

Refinement
All hydrogen atoms were positioned geometrically [C-H = 0.93-0.98 Å; O-H = 0.84-0.85 Å] and were refined using a riding model, with U iso (H) = 1.2 or 1.5 U eq (C, O). A rotating group model was applied to the methyl groups Even though there is sufficient anomalous dispersion to find the absolute configuration as the compound crystallize out in a chiral space group and Cu radiation was used, this was unsuccessful as the crystal is a inversion twin [BASF ratio of 0.8 (4):0.2 (4)].  The asymmetric unit of the title compound, showing the atomic numbering and 30% probability displacement ellipsoids.

Computing details
Hydrogen bond is shown by dashed line.

Figure 2
A portion of the crystal packing showing hydrogen bonds as dashed lines. H atoms not involved in hydrogen bonding were omitted for clarity.

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1