(E)-3-[4-(Hexyloxy)phenyl]-1-(2-hydroxyphenyl)prop-2-en-1-one

In the title compound, C21H24O3, the conformation of the enone group is s–cis. The benzene rings are inclined at an angle of 7.9 (1)°. The alkoxy tail is planar, with a maximum deviation from the least-squares plane of 0.009 (2) Å, and adopts a trans conformation throughout. An intramolecular O—H⋯O interaction between the keto and hydroxy groups forms S(6) ring motifs. In the crystal, molecules are arranged in a head-to-tail manner down the a axis and are subsequently stacked along the b axis, forming molecular sheets parallel to the ab plane. The crystal structure is further stabilized by weak C—H⋯π interactions and short C⋯O [3.376 (2) Å] contacts.

In the title compound, C 21 H 24 O 3 , the conformation of the enone group is s-cis. The benzene rings are inclined at an angle of 7.9 (1) . The alkoxy tail is planar, with a maximum deviation from the least-squares plane of 0.009 (2) Å , and adopts a trans conformation throughout. An intramolecular O-HÁ Á ÁO interaction between the keto and hydroxy groups forms S(6) ring motifs. In the crystal, molecules are arranged in a head-to-tail manner down the a axis and are subsequently stacked along the b axis, forming molecular sheets parallel to the ab plane. The crystal structure is further stabilized by weak C-HÁ Á Á interactions and short CÁ Á ÁO [3.376 (2) Å ] contacts.

Comment
The biological properties of chalcones derivatives, such as their anticancer (Bhat et al., 2005), antimalarial (Xue et al., 2004), antiangiogenic and antitumour (Lee et al., 2006) and antiplatelet (Zhao et al., 2005) activities, have been extensively reported. Synthetic and naturally occurring chalcones are of interest and have been widely studied and developed as one of the pharmaceutically important molecules. As part of our studies, we have synthesized the title chalcone derivative, (I). Its antibacterial activity was tested against E. coli ATCC 8739 and the compound demonstrated antimicrobial activity. In this paper, we report the crystal structure of the title compound.
The zigzag alkoxyl tail adopts an all-trans conformation with the largest deviation from the ideal value being -179.3 (2)°f or C17-C18-C19-C20 torsion angle. The alkoxyl chain is planar with the maximum deviation from the least-squares plane of 0.009 (2)Å at C18. The zigzag plane makes a dihedral angle of 2.2 (1)° with the attached benzene ring.
The keto and hydroxy groups in the molecule form an intramolecular O1-H1O1···O2 interaction (Table 1) generating a ring of graph-set motif S(6) (Bernstein et al., 1995). In the crystal structure, the molecules are arranged into a head-to-tail manner down the a axis (Fig. 2). Molecules are subsequently stacked along the b axis, forming molecular sheets parallel to the ab plane. In the absence of conventional hydrogen bonds, the crystal packing is strengthened by the presence of weak C-H···π interactions between atom C20 of the alkoxyl tail and the C1-C6 benzene ring (Table 1). There is also a short C···O (x, 1.5-y, 0.5+z ) [3.376 (2)Å] contact.

Experimental
A mixture of 2-hydroxyacetophenone (2.72 ml, 20 mmol) and 4-hexyloxybenzaldehyde (4.12 ml, 20 mmol) and KOH (4.04 g, 72 mmol) in 60 ml of methanol was heated at reflux for 24 h. The reaction was cooled to room temperature and acidified with cold diluted HCl (2 M). The resulting precipitate was filtered, washed and dried. After redissolving in hexane, followed by few days of slow evaporation, crystals were collected.

sup-2 Refinement
The O-bound H atom was located in a difference Fourier map and refined freely. All the C-bound H atoms were positioned geometrically and refined using a riding model with C-H = 0.93-0.97 Å. The U iso values were constrained to be -1.5U equ (methyl H atoms) and -1.2U equ (other H atoms). The rotating model group was applied for the methyl group.
Figures Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom numbering scheme. The intramolecular interaction is shown as dashed line.   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 > σ(F 2 ) is used only for calculating Rfactors(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.