(E)-3-Phenyl-3-(3-phenyl-1H-1-pyrazolyl)-2-propenal

In the title compound C18H14N2O, the pendant rings make dihedral angles of 66.1 (1)° and 13.9 (1) with the central ring. In the crystal, two molecules form a cyclic centrosymmetric R 2 2(22) dimer through pairs of C—H⋯O bonds. These dimers are further connected into zigzag chains extending along the b axis through C—H⋯π and C—H⋯O interactions.

In the title compound C 18 H 14 N 2 O, the pendant rings make dihedral angles of 66.1 (1) and 13.9 (1) with the central ring.
In the crystal, two molecules form a cyclic centrosymmetric R 2 2 (22) dimer through pairs of C-HÁ Á ÁO bonds. These dimers are further connected into zigzag chains extending along the b axis through C-HÁ Á Á and C-HÁ Á ÁO interactions.

Comment
Pyrazole refers both to the class of simple aromatic ring organic compounds and of the heterocyclic series characterized by a 5-membered ring structure composed of three carbon atoms and two nitrogen atoms in adjacent positions and to the unsubstituted parent compound. Being so composed and having pharmacological effects on humans, they are classified as alkaloids although they are rare in nature. Pyrazole and its derivatives are successfully tested for their antifungal (Chen & Li, 1998), antihistaminic (Mishra et al.,1998), anti-inflammatory (Smith et al., 2001), antiarrhythmic and sedative (Bruno et al., 1990), hypoglycemic (Cottineau et al., 2002), antiviral (Baraldi et al., 1998) and pesticidal (Londershausen, 1996) activities.
An ORTEP plot of the molecule is shown in Fig. 1. The pyrazole ring adopts planar conformation. The phenyl rings and the plane of the pyrazole ring are making the dihedral angles of 66.1 (1)° (with C12/C17 ring) and 13.9 (1)° (with C31/C36 ring). The two phenyl rings are oriented with the dihedral angle of 79.9 (1)°. Further, pyrazole ring is making an angle of 15.8 (2)° with the propenal plane (C11,C1A,C2A,O1). The sum of the angles at N1 of the pyrazole ring (359.8 (1)°) is in accordance with sp 2 hybridization (Beddoes et al., 1986). The C-N bond lengths in the pyrazole ring are 1.326 (2) and 1.355 (2) Å, which are shorter than a C-N single bond length of 1.443 Å, but longer than a double bond length of 1.269 Å, (Jin et al.,2004), indicating electron delocalization.
The crystal packing is stabilized through moderate C-H···O, C-H···N and C-H···π interactions (Table 1). Two symmetry-related molecules form a cyclic centrosymmetric R 2 2 (22) dimer through C35-H35···O1 i bond around the inversion centers of the unit cell (Fig 2). These dimers are connected into two zigzag chains extending along the b axis through C-H···π and another C-H···O interaction (Bernstein et al., 1995).

Experimental
To a mixture of 1-phenyl-1-ethanone N-[(E)-1-phenylethylidene]hydrazone (0.003 mole) and 3 ml of dimethyl formamide kept in ice bath at 0 °C, phosphorous oxycholride (0.024 mole) was added dropwise for 5 to 10 minutes. The reaction mixture was then irradiated under microwaves for 30 sec. The process of the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was poured into crushed ice and extracted with dichloromethane. The organic layer was dried over anhydrous sodium sulfate. The different compound was separated by column chromatography using petroleum ether and ethyl acetate mixture as eluent. This isolated compound was recrystallized to obtain the title compound.