(E)-2-(2,3-Dimethylanilino)-N′-[2-methyl-5-(prop-1-en-2-yl)cyclohex-2-enylidene]benzohydrazide

The asymmetric unit of the title compound, C25H29N3O, comprises two crystallographically independent molecules. The dihedral angles between the benzene rings in the two molecules are 59.7 (2) and 61.27 (18)°. The cyclohexene rings adopt sofa and half-chair conformations. In the crystal, molecules are connected via N—H⋯O and weak C—H⋯O hydrogen bonds, forming chains along the a axis. In each molecule, there is an intramolecular N—H⋯O hydrogen bond.

The asymmetric unit of the title compound consists of two crystallographically independent (E)-2-(2,3-dimethylphenyl- In the crystal structure (Fig. 2), molecules are connected via intermolecular N-H···O and C-H···O hydrogen bonds, forming one-dimensional chains along the a-axis. In each molecule the is an intramolecular N-H···O hydrogen bond.

Experimental
The title compound was prepared by the reaction of carvone, 2-methyl-5-(prop-1-en-2-yl)cyclohex-2-enone (0.15 g, 1 mmol) and 2-(2,3-dimethylphenylamino)benzohydrazide (0.26 g, 1 mmol) in ETOH (25 mL). After stirring for 3 h, at room temperature, the resulting mixture was concentrated. The precipitate washed with ETOH to afford the title compound. Colorless blocks of the title compound suitable for X-ray structure determination were recrystallized from ETOH by the slow evaporation of the solvent at room temperature. The crystals are very brittle and shatter easily upon cutting so data were collected using a crystal which was a long needle.

Refinement
All H atoms were positioned geometrically [C-H = 0.93-0.98 Å and N-H = 0.86 Å] and were refined using a riding model, with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was applied to the methyl groups. The standard uncertainty of the refined Flack parameter indicates the result is inconclusive. The structure contains psuedosymmetry but examination of the systematic absences and the inability to refine the structure in the higher symmetry space group confirm the current choice of space group.

Figure 1
The asymmetric unit of the title compound, showing 10% probability displacement ellipsoids. Hydrogen atoms omitted for clarity.  The crystal packing of the title compound (I).

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s 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 > 2σ(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.