N′-[4-(Dimethylamino)benzylidene]acetohydrazide

The title compound, C11H15N3O, crystallizes with two independent molecules per asymmetric unit which differ slightly in their side-chain orientations: the C=N—N—C torsion angle is −176.2 (3)° in one of the molecules and −179.83 (3)° in the other. Each independent molecule adopts a trans configuration with respect to the C=N bond. The two independent molecules are related by a pseudo-inversion center and they exist as a N—H⋯O hydrogen-bonded dimer. The dimers are linked into zigzag chains along [100] by C—H⋯O hydrogen bonds.

The title compound, C 11 H 15 N 3 O, crystallizes with two independent molecules per asymmetric unit which differ slightly in their side-chain orientations: the C N-N-C torsion angle is À176.2 (3) in one of the molecules and À179.83 (3) in the other. Each independent molecule adopts a trans configuration with respect to the C N bond. The two independent molecules are related by a pseudo-inversion center and they exist as a N-HÁ Á ÁO hydrogen-bonded dimer. The dimers are linked into zigzag chains along [100] by C-HÁ Á ÁO hydrogen bonds.   Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x; Ày þ 1 2 ; z À 1 2 ; (ii) x; Ày þ 1 2 ; z þ 1 2 ; (iii) x À 1 2 ; Ày þ 1 2 ; Àz.
The two independent molecules are related by a pseudo inversion center, and in the crystal they exist as N-H···O hydrogen-bonded dimers. The dimers are linked into a zigzag chain along the 'a' axis by C-H···O hydrogen bonds. (Table 1).
Experimental 4-Dimethylaminobenzaldehyde (1.49 g, 0.01 mol) and acetohydrazide (0.74 g, 0.01 mol) were dissolved in stirred methanol (20 ml) and left for 3.5 h at room temperature. The resulting solid was filtered off and recrystallized from ethanol to give the title compound in 87% yield. Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution at room temperature (m.p. 490-493 K).

Refinement
H atoms were positioned geometrically (N-H = 0.86 Å and C-H = 0.93 or 0.96 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C,N) and 1.5U eq (C methyl ).

Refinement
Refinement on F 2 Hydrogen site location: inferred from neighbouring sites Least-squares matrix: full H-atom parameters constrained

Special details
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.