(E)-N'-(2,4,6-Trimethyl-benzyl-idene)isonicotinohydrazide.

The title isoniazid derivative, C(16)H(17)N(3)O, exists in an E configuration with respect to the Schiff base C=N bond. The pyridine ring is essentially planar [maximum deviation = 0.009 (3) Å]. The mean plane through the hydrazide unit forms dihedral angles of 38.38 (16) and 39.42 (16)°, respectively, with the pyridine and benzene rings. In the crystal structure, symmetry-related mol-ecules are linked via inter-molecular N-H⋯O hydrogen bonds into chains along [100]. The crystal structure is further stabilized by weak inter-molecular C-H⋯π inter-actions.

The title isoniazid derivative, C 16 H 17 N 3 O, exists in an E configuration with respect to the Schiff base C N bond. The pyridine ring is essentially planar [maximum deviation = 0.009 (3) Å ]. The mean plane through the hydrazide unit forms dihedral angles of 38.38 (16) and 39.42 (16) , respectively, with the pyridine and benzene rings. In the crystal structure, symmetry-related molecules are linked via intermolecular N-HÁ Á ÁO hydrogen bonds into chains along [100]. The crystal structure is further stabilized by weak intermolecular C-HÁ Á Á interactions.

Comment
In the search of new compounds, isoniazid derivatives have been found to possess potential tuberculostatic activity (Janin, 2007;Maccari et al., 2005;Slayden & Barry, 2000). Schiff bases have attracted much attention because of their biological activity (Kahwa et al., 1986). As part of our current work on the synthesis of (E)-N'-substituted isonicotinohydrazide derivatives, in this paper we report the crystal structure of the title isoniazid derivative. rings. The bond lengths and angles are consistent to those observed in closely related structures (Naveenkumar et al., 2009;2010a,b;Shi, 2005).
In the crystal structure ( Fig. 2), adjacent molecules are linked into one-dimensional chains along the [100] direction via intermolecular N2-H1N2···O1 i hydrogen bonds (Table 1). The crystal structure is further stabilized by weak intermolecular C16-H16B···Cg1 i interactions (Table 1) involving the centroid of the pyridine ring.

Experimental
The title isoniazid derivative was prepared following the procedure by Lourenco et al., (2008). The title derivative was prepared by the reaction between 2,4,6-trimethylbenzaldehyde (1.0 eq) with isoniazid (1.0 eq) in ethanol/water. After stirring for 1-3 h at room temperature, the resulting mixture was concentrated under reduced pressure. The residue was purified by washing with cold ethanol and ethyl ether to afford the pure derivative. Colourless single crystals suitable for X-ray analysis were obtained by slow evaporation with dimethyl sulfoxide.

Refinement
Atom H1N2 was located from difference Fourier map and allowed to refine freely. All other H atoms were placed in calculated positions, with C-H = 0.93 or 0.96 Å, U iso = 1.2 or 1.5 U eq (C). These H atoms were refined as riding on their parent atoms. A rotating group model was used for the methyl groups. Fig. 1. The molecular structure of the title derivative with atom labels and 50% probability ellipsoids for non-H atoms.  Glazer, 1986) operating at 100.0 (1)K.

Figures
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.