3-(2-Chloro-6-fluorophenyl)-1-(2-thienyl)prop-2-en-1-one

The title chalcone derivative, C13H8ClFOS, crystallized as an inversion twin with two independent molecules in the asymmetric unit. The thiophene rings in both molecules are disordered over two sites: the ratios of occupancies for the major and minor components in the two molecules are 0.820 (2):0.180 (2) and 0.853 (2):0.147 (2). The dihedral angles between the major and minor components of the thiophene and benzene rings are 1.13 (18) and 2.2 (6)°, respectively, in one molecule, with corresponding values 6.09 (17) and 1.3 (6)° in the other. Weak intramolecular C—H⋯O and C—H⋯F interactions involving the prop-2-en-1-one group generate an S(5)S(5) ring motif, whereas a weak intramolecular C—H⋯Cl contact generates an S(6) ring motif. In the crystal structure, molecules of both the major and minor components are linked into infinite one-dimensional chains along the b axis. The crystal structure is stabilized by weak C—H⋯O, C—H⋯F, C—H⋯Cl and C—H⋯π interactions.

The title chalcone derivative, C 13 H 8 ClFOS, crystallized as an inversion twin with two independent molecules in the asymmetric unit. The thiophene rings in both molecules are disordered over two sites: the ratios of occupancies for the major and minor components in the two molecules are 0.820 (2):0.180 (2) and 0.853 (2):0.147 (2). The dihedral angles between the major and minor components of the thiophene and benzene rings are 1. 13 (18) and 2.2 (6) , respectively, in one molecule, with corresponding values 6.09 (17) and 1.3 (6) in the other. Weak intramolecular C-HÁ Á ÁO and C-HÁ Á ÁF interactions involving the prop-2-en-1-one group generate an S(5)S(5) ring motif, whereas a weak intramolecular C-HÁ Á ÁCl contact generates an S(6) ring motif. In the crystal structure, molecules of both the major and minor components are linked into infinite one-dimensional chains along the b axis. The crystal structure is stabilized by weak C-HÁ Á ÁO, C-HÁ Á ÁF, C-HÁ Á ÁCl and C-HÁ Á Á interactions.
Since the thiophene rings in both molecules are disordered over two sites, there will be four discrete modes of packing in the structure involving the major and minor components. In Fig. 2 only the molecules of the two major components are shown and they are linked into chains along the b axis. The crystal is stabilized by weak C-H···O, C-H···F and C-H···Cl interactions (Table 1) and further stabilized by C-H···π interactions (Table 1); Cg 1 , Cg 2 , Cg 3 , Cg 4 , Cg 5 and Cg 6 are the centroids of the S1A/C10A-C13A, S1B/C10B-C13B, S1X/C10A/C11X-C13X, S1Y/C10B/C11Y-C13Y, C1A-C6A and C1B-C6B rings, respectively.

Experimental
The title compound was synthesized by the condensation of 2-chloro-6-fluorobenzaldehyde (0.01 mol, 1.58 g) with 2-acetylthiophene (0.01 mol, 1.07 ml) in methanol (60 ml) in the presence of a catalytic amount of sodium hydroxide solution (5 ml, 30%). After stirring (6 h), the contents of the flask were poured into ice-cold water (500 ml) and left to stand for 5 h.
The resulting crude solid was filtered and dried. Colorless single crystals of the title compound suitable for x-ray structure determination were grown by slow evaporation of an acetone solution at room temperature.

Refinement
All H atoms were placed in calculated positions with d(C-H) = 0.93 Å, U iso =1.2U eq (C) for CH and aromatic. The highest residual electron density peak is located at 0.36 Å from F1B and the deepest hole is located at 0.56 Å from Cl1B. Similarity and rigid-bond restraints were applied to the disordered atoms in the thiophene rings. Even though the structure contains supplementary materials sup-2 heavy atoms, the absolute structure cannot be acertained from the Flack parameter because of the racemic twinning of the crystal with BASF = 0.43 (7). Fig. 1. The asymmetric unit of (I), showing 50% probability displacement ellipsoids and the atomic numbering. Weak intramolecular C-H···O, C-H···F and C-H···Cl interactions are drawn as dashed lines. The major disorder components are shown with the solid bonds whereas the minor disorder components are shown with open bonds.