N′-[(E)-4-Hydroxy-3-methoxybenzylidene]pyridine-4-carbohydrazide

In the title compound, C14H13N3O3, the two six-membered rings are oriented at a dihedral angle of 15.17 (11)° and an intramolecular O—H⋯O hydrogen bond occurs. In the crystal, molecules interact by way of N—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds, thereby generating S(5) chain and R 2 1(7) ring motifs.

In the title compound, C 14 H 13 N 3 O 3 , the two six-membered rings are oriented at a dihedral angle of 15.17 (11) and an intramolecular O-HÁ Á ÁO hydrogen bond occurs. In the crystal, molecules interact by way of N-HÁ Á ÁO, O-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds, thereby generating S(5) chain and R 2 1 (7) ring motifs.
In the title compound the pyridine ring A (C1-C3/N1/C4/C5) and the benzene ring of vanilline B (C8-C13) are planar with a maximum r. m. s. deviations of 0.0061 and 0.0122 Å respectively, from their mean square planes. The dihedral angle between A/B is 15.17 (11)°. The intramolecular H-bonding of O-H···O type completes S(5) ring motif (Bernstein et al., 1995). There also exist R 2 1 (7) ring motif due to intermolecular H-bondings of C-H···O and N-H···O type (Table 1, Fig. 2). The molecules are stabilized in the form of two dimensional polymeric sheets owing to intermolecular H-bondings of O-H···N type (Fig. 2).

Experimental
To a hot stirred solution of isoniazid (1.37 g, 0.01 mol) in ethanol (15 ml) was added vanillin (1.52 g, 0.01 mol). The resultant mixture was then heated under reflux. After an hour precipitates were formed. The reaction mixture was further heated about 30 min for the completion of the reaction which was monitored through TLC. The reaction mixture was cooled to room temperature, filtered and washed with hot ethanol. Yellow needles of (I) were obtained by recrystallization of the crude product in 1,4-dioxan:ethanol (1:1) after two days.

Refinement
In the absence of significant anomalous dispersion effects, Friedel pairs were averaged before refinement.
The H-atoms were positioned geometrically (O-H = 0.82 Å, N-H = 0.86 Å, C-H = 0.93-0.96 Å) and refined as riding with U iso (H) = 1.2U eq (carrier) or 1.5U eq (methyl C). Fig. 1. View of (I) with displacement ellipsoids drawn at the 50% probability level. H-atoms are shown by spheres of arbitrary radius. The dotted line represent the intramolecular H-bondings. Fig. 2. The partial packing of (I), which shows that molecules form two dimensional polymeric chains.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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 Rfactors(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.