(2E)-1-(3-Chlorophenyl)-3-phenylprop-2-en-1-one

In the title compound, C15H11ClO, the dihedral angle between the mean planes of the benzene ring and the chloro-substituted benzene ring is 48.8 (3)°. The dihedral angles between the mean plane of the prop-2-ene-1-one group and the mean planes of the 3-chlorophenyl and benzene rings are 27.0 (4) and 27.9 (3)°, respectively. In the crystal, weak intermolecular C—H⋯π-ring interactions occur.

In the title compound, C 15 H 11 ClO, the dihedral angle between the mean planes of the benzene ring and the chlorosubstituted benzene ring is 48.8 (3) . The dihedral angles between the mean plane of the prop-2-ene-1-one group and the mean planes of the 3-chlorophenyl and benzene rings are 27.0 (4) and 27.9 (3) , respectively. In the crystal, weak intermolecular C-HÁ Á Á-ring interactions occur.
KV thanks the UGC for the sanction of a Junior Research Fellowship and for a SAP Chemical grant. RJB acknowledges the NSF MRI program (grant No. CHE-0619278) for funds to purchase an X-ray diffractometer.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: TK2596).

Comment
Chalcones are known as the precursors of all flavonoid type natural products in biosynthesis (Marais et al., 2005). Chalcones exhibit various biological activities like insecticidal, antimicrobial, antichinoviral, antipicorniviral and bacteriostatic properties. Azachalcones, the derivatives of chalcones with an annular nitrogen atom in the phenyl ring, were reported to have a wide range of biological activities, such as antibacterial, antituberculostatic and anti-inflammatory. An important feature of chalcones are their ability to act as activated unsaturated systems in conjugated addition of carbanions in presence of suitable basic catalysts. Many chalcones have been described for their high antimalarial activity, probably as a result of Michael addition of nucleophilic species to the double bond of the enone (Troeberg et al., 2000;Ram et al., 2000). Licochalcone A, isolated from Chinese liquorice roots, has been reported as being highly effective in chloroquine resistant Plasmodium falciparum strains in a [3H] hypoxanthine uptake assay (Chen et al., 1994). Chalcones are also finding applications as organic non-linear optical materials (NLO) due to their good SHG conversion efficiencies . Recently, non-linear optical studies on a few chalcones and their derivatives were reported (Poornesh et al., 2009;Shettigar et al., 2006;2008). In continuation with our studies of chalcones (Jasinski et al., 2007) and their derivatives and owing to the importance of these flavanoid analogs, the title chalcone, (I), was synthesized and its crystal structure reported herein.
The title compound, (I), is a chalcone with 3-chlorophenyl and benzene rings bonded at the opposite ends of a propenone group, the biologically active region (Fig.1). The dihedral angle between mean planes of the benzene and chloro substituted benzene rings is 48.8 (3)° as compared to 14.3 (7)° in the 4-chloro benzene analogue compound (Li & Su, 1994). The angles between the mean plane of the prop-2-ene-1-one group and the mean planes of the 3-chlorophenyl and benzene rings are 27.0 (4)° and 27.9 (3)°, respectively, as compared to 19.4 (2)° and 11.9 (9)° in the aforementioned 4-chloro benzene compound. While no classical hydrogen bonds are present, weak intermolecular C-H···π-ring interactions are observed which contribute to the stability of crystal packing (Table 1).
Experimental 50% KOH was added to a mixture of 3-chloro acetophenone (0.01 mol) and benzaldehyde (0.01 mol) in 25 ml of ethanol (Scheme 2). The mixture was stirred for an hour at room temperature and the precipitate was collected by filtration and purified by recrystallization from ethanol. The single-crystal was grown from ethyl acetate by slow evaporation method and yield of the compound was 72% (m.p.: 354-356 K). Analytical data for C 15 H 11 ClO: Found (Calculated): C%: 74.19 (74.23); H%: 4.55 (4.57).

Hydrogen-bond geometry (Å, °)
Cg1 is the centroid of the C1-C6 ring and Cg2 is the centroid of the C10-C15 ring.