N′-[(E)-1-(2-Hydroxyphenyl)ethylidene]pyrazine-2-carbohydrazide

The title compound, C13H12N4O2, crystallized with two independent molecules (A and B) in the asymmetric unit. Molecule B is planar to within 0.044 (3) Å for all non-H atoms, while molecule A is slightly twisted, with a dihedral angle of 6.29 (4)° between the mean planes of the pyrazine-2-carbohydrazide and 1-(2-hydroxyphenyl)ethanone moieties (r.m.s. deviations = 0.0348 and 0.0428 Å, respectively). S(5) and S(6) ring motifs are formed in both molecules due to the presence of intramolecular O—H⋯N and N—H⋯N hydrogen bonds. In the crystal, molecules A and B are linked by a C—H⋯O hydrogen bond. They stack along the a-axis direction, forming columns with π–π interactions involving inversion-related pyrazine and benzene rings [centroid–centroid distances = 3.5489 (13)–3.8513 (16) Å].

The title compound, C 13 H 12 N 4 O 2 , crystallized with two independent molecules (A and B) in the asymmetric unit. Molecule B is planar to within 0.044 (3) Å for all non-H atoms, while molecule A is slightly twisted, with a dihedral angle of 6.29 (4) between the mean planes of the pyrazine-2carbohydrazide and 1-(2-hydroxyphenyl)ethanone moieties (r.m.s. deviations = 0.0348 and 0.0428 Å , respectively). S(5) and S(6) ring motifs are formed in both molecules due to the presence of intramolecular O-HÁ Á ÁN and N-HÁ Á ÁN hydrogen bonds. In the crystal, molecules A and B are linked by a C-HÁ Á ÁO hydrogen bond. They stack along the a-axis direction, forming columns withinteractions involving inversion-related pyrazine and benzene rings [centroidcentroid distances = 3.5489 (13)-3.8513 (16) Å ].

D-HÁ
In the crystal, molecules A and B are linked by a C-H···O hydrogen bond (Table 1 and Fig. 2). They stack along the a axis direction forming columns with π-π interactions involving inversion related pyrazine and benzene rings.

Experimental
The title compound was prepared by the condensation of an equimolar ratio of pyrazine-2-carbohydrazide (0.50 g, 3.6 mmol) and 1-(2-hydroxyphenyl)ethanone (0.45 ml, 3.6 mmol) in methanol by stirring well and then refluxing of 5 h. The resulting reaction mixture was allowed to cool over night. The precipitated solid was filtered, washed with petroleum ether and recrystallized from chloroform in petroleum ether and then dried under reduced pressure over CaCl 2 to give colourless prisms.

Refinement
The H-atom of the amide and one of the methyl groups were refined with U iso (H) = 1.2U eq (N) and = 1.5U eq (C-methyl).  View of the molecular structure of the two independent molecules (A and B) of the title compound, with atom labelling.
Displacement ellipsoids are drawn at the 50% probability level. The intramolecular hydrogen bonds are shown as dashed lines (see Table 1 for details).

Figure 2
The crystal packing diagram of the title compound, viewed along the a axis. The various hydrogen bonds are shown as dashed lines (see Table 1 for details).

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 esds 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 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.