(2E)-1-(2,6-Dichloro-3-fluorophenyl)-3-(4-fluorophenyl)prop-2-en-1-one

In the title compound, C15H8Cl2F2O, the C=C double bond is in the E configuration. In the cyrstal, C—H⋯O hydrogen bonds connect the molecules into chains along the c axis. A π–π interaction of 3.628 (1) Å is also observed between two polyhalogenated benzene rings. The dichlorosubstituted ring exhibits partial disorder over two sets of sites, with site-occupancy factors of 0.573 (3) and 0.427 (3).

In the title compound, C 15 H 8 Cl 2 F 2 O, the C C double bond is in the E configuration. In the cyrstal, C-HÁ Á ÁO hydrogen bonds connect the molecules into chains along the c axis. Ainteraction of 3.628 (1) Å is also observed between two polyhalogenated benzene rings. The dichlorosubstituted ring exhibits partial disorder over two sets of sites, with siteoccupancy factors of 0.573 (3) and 0.427 (3).
The C═C double bond of the Michael system is in the E configuration. The fluorine atom on the polyhalogenated phenyl ring, together with its attached carbon atom is disordered over two sites, as are the ring CH meta to it. The site occupancy factors refined to 0.573 (3) and 0.427 (3). The least-squares planes defined by the carbon atoms of the two rings make a dihedral angle of 82.37 (8)° (Fig. 1).
In the crystal structure, intermolecular C-H···O hydrogen bonds are observed (Table 1 and Fig. 2), forming a 6membered chelate ring. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for this pattern is C 1 1 (5)C 1 1 (7) on the unitary level. Molecules are connected into chains along the crystallographic c axis. A π-π interaction of 3.628 (1) Å is also observed between two polyhalogenated phenyl rings. The packing of the title compound in the crystal structure is shown in Fig. 3.

Experimental
To a stirred solution of 1-(2,6-dichloro-3-fluorophenyl)ethanone (1 g, 4.8 mmol) and 4-fluorobenzaldehyde (0.59 g, 4.8 mmol) in ethanol (10 ml), powdered KOH (0.4 g 7.2 mmol) was added at 273 K. The reaction mixture was stirred at room temperature for 1 h. After completion of the reaction, the reaction mixture was poured into ice cold water and acidified with 1.5 N HCl (pH ~3). The resulting precipitate was filtered and dried to afford 1.3 g of the title compound as a pale yellow solid in 86% yield. Single crystals suitable for the diffraction study were grown from a mixture of toluene:acetone (v:v = 1:1) by slow evaporation at room temperature (m.p.: 421-424 K).

Refinement
H atoms were placed in calculated positions (C-H = 0.95 Å) and were included in the refinement in the riding model approximation, with U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures   Fig. 1. The molecular structure of the title compound, with anisotropic displacement ellipsoids drawn at the 50% probability level. For clarity, only the major component of the disorder model is depicted.