2-[4-(2-Methylpropyl)phenyl]-N′-[(E)-1-phenylethylidene]propanehydrazide

In the title compound, C21H26N2O, the dihedral angle between the two aromatic rings is 85.90 (19)°. The propenone–hydrazide unit forms dihedral angles of 21.62 (8) and 72.83 (9)°, respectively, with the terminal and central aromatic rings. The 2-methylpropyl group is disordered over two sites, with occupancies of 0.533 (13) and 0.467 (13). In crystal structure, molecules are linked into centrosymmetric dimers by paired N—H⋯O and C—H⋯O hydrogen bonds. In addition, C—H⋯π interactions are observed.


Comment
Ibuprofen belongs to the class of Non-Steroidal anti-Inflammatory Drugs (NSAIDs) with antipyretic, anti-inflammatory and analgesic properties (Palaska et al., 2002). Hydrazones containing an azometine -NHN═CH-moiety are synthesized by heating the appropriate substituted hydrazines/hydrazides with aldehydes and ketones in solvents like ethanol, methanol, tetrahydrofuran, butanol, glacial acetic acid, ethanol-glacial acetic acid. Another synthetic route for the synthesis of hydrazones is the coupling of aryldiazonium salts with active hydrogen compounds (Rollas & Kuckguzel, 2007). Hydrazide-hydrazones compounds are not only intermediates but they are also very effective organic compounds of their own. Hydrazones have been demonstrated to possess antimicrobial, anticonvulsant, analgesic, anti-inflammatory, antiplatelet, antitubercular, anticancer and antitumoral activities (Bedia et al., 2006;Rollas et al., 2002;Terzioglu & Gursoy, 2003). Prompted by these and in continuation of our work, (Fun et al., 2008) we are interested in the synthesis and crystal structure determination of ibuprofen derivatives. We report here the crystal structure of the title compound (I).

Experimental
The title compound was obtained by refluxing 2-[4-(2-methylpropyl)phenyl]propanehydrazide (0.01 mol) and acetophenone (0.01 mol) in ethanol (30 ml) with 3 drops of concentrated sulfuric acid for 1 h. The excess ethanol was removed from the reaction mixture under reduced pressure. The solid product obtained was filtered, washed with ethanol and dried. Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution (yield 87%; m.p.380-381 K).
H atoms were positioned geometrically (N-H=0.86Å and C-H=0.93-0.98Å) and refined using a riding model with, U iso (H)=1.2U equ (C,N) and 1.5U equ (C methyl ). A rotating group model was used for the methyl groups.

Special details
Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.
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.