N′-(2,6-Difluorobenzylidene)pyridine-4-carbohydrazide

In the title compound, C13H9F2N3O, the pyridine ring forms a dihedral angle of 16.92 (7)° with the benzene ring. In the crystal, molecules are linked via N—H⋯O, C—H⋯O and C—H⋯F, with the same O atom accepting two bonds.

In the title compound, C 13 H 9 F 2 N 3 O, the pyridine ring forms a dihedral angle of 16.92 (7) with the benzene ring. In the crystal, molecules are linked via N-HÁ Á ÁO, C-HÁ Á ÁO and C-HÁ Á ÁF, with the same O atom accepting two bonds.

Comment
In view of the importance of isoniazid and its various Schiff base derivatives (Chen, 2006;Nie et al., 2006), the synthesis and crystal structure of the title Schiff base is reported.

Experimental
A mixture of isoniazid (1.4 g, 0.01 mol) and 2,6-difluorobenzaldehyde (1.4 ml, 0.01 mol) in 15 ml of absolute alcohol containing 2 drops of hydrochloric acid was refluxed for about 3 h. On cooling, the solid was separated, which was then filtered and recrystallized from DMF. The single crystal was grown from DMF by the slow evaporation method. (m.p. > 523 K).

Refinement
Atom H1N2 was located in a difference Fourier map and refined freely with N2-H1N2 = 0.884 (18) Å. The remaining H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 Å and U iso (H) = 1.2 U eq (C).

Figure 2
The crystal structure of the title compound, viewed along the a axis. H atoms not involved in hydrogen bonds (dashed lines) have been omitted for clarity.  (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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.