(2E)-3-[4-(Benzyloxy)phenyl]-1-(2,6-dichloro-3-fluorophenyl)prop-2-en-1-one

In the title compound, C22H15Cl2FO2, a chalcone derivative featuring a threefold-halogenated aromatic substituent, the conformation about the C=C bond is E. In the crystal C—H⋯F and C—H⋯Cl contacts connect the molecules into undulating sheets parallel to (101). In addition, C—H⋯π interactions are also present.

In the title compound, C 22 H 15 Cl 2 FO 2 , a chalcone derivative featuring a threefold-halogenated aromatic substituent, the conformation about the C C bond is E. In the crystal C-HÁ Á ÁF and C-HÁ Á ÁCl contacts connect the molecules into undulating sheets parallel to (101). In addition, C-HÁ Á Á interactions are also present.
The C=C bond in the Michael system is (E)-configured. The least-squares planes defined by the respective carbon atoms of the two terminal aromatic moieties intersect at an angle of 48.50 (10) ° and enclose angles of 62.82 (11) ° and 74.58 (8) ° with the least-squares plane defined by the carbon atoms of the central phenyl group. The larger of the latter two angles is created by the halogenated phenyl moiety (Fig 1).
In the crystal, intermolecular C-H···F and C-H···Cl contacts whose range invariably falls by more than 0.1 Å below the sum of van-der-Waals radii of the corresponding atoms are observed. These contacts are exclusively supported by hydrogen atoms on the central as well as the terminal non-halogenated phenyl group and connect the molecules to undulated sheets parallel to [1 0 1]. In addition, C-H···π interactions are present. Details about metrical parameters of these contacts as well as information about their symmetry can be found in Table 1. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the C-H···F as well as the C-H···Cl contacts necessitate a C 1 1 (11)C 1 1 (17) descriptor on the unary level. The shortest intercentroid distance between two aromatic systems was found at 4.5552 (12) Å and is apparent between the central as well as the halogenated phenyl moiety in neighbouring molecules.

Experimental
To a stirred solution of 1-(2,6-dichloro-3-fluorophenyl)ethanone (1 g, 4.8 mmol) and 4-(benzyloxy)benzaldehyde (1.01 g, 4.8 mmol) in ethanol (10 ml), powdered KOH (0.40 g, 7.2 mmol) was added at 273 K. The reaction mixture was stirred at room temperature for 2 h. After completion of the reaction, the mixture was poured into ice cold water, acidified with HCl (1.5 N) until the pH value was approximately 3. The solid that precipitated was filtered and dried to afford the title compound as off-white solid, yield: 1.8 g (95%). Single crystals suitable for the X-ray diffraction study were grown from a mixture of toluene and acetone (v:v = 1:1) by slow evaporation at room temperature.

Refinement
Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å for aromatic and vinylic carbon atoms, C-H 0.99 Å for methylene groups) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C).