(3 <i>E</i> )-1,1,1-Trichloro-4-methoxy-4-phenylbut-3-en-2-one

The title compound, C 11 H 9 Cl 3 O 2 , (common name: β-aryl-β-methoxyvinyl trichloromethylketone) was crystallized from a chloroform solution at room temperature. The asymmetric unit comprises one molecule with all atoms in general positions and the E isomerism about the central vinyl entity could be undoubtedly determined. Weak intramolecular interactions between the ketone and the phenyl groups can be suggested, as two O...C distances [2.9154 (17) and 2.9780 (15) Å] are shorter than the van der Waals radii sum for the respective atoms (3.35 Å). As a result of the sp 3 C atoms and the C—C single bond between the phenyl ring and the central alkene fragment, the molecule is not planar. In the crystal, the molecules are linked by Cl...O weak interactions along the a -axis direction (2.962 Å intermolecular distances, compared to the 3.34 Å for the vdW radius sum) and these contacts were observed over the Hirshfeld surfaces set as d norm , shape-index and curvedness modes. The Hirshfeld surface analysis mapped over the d norm property indicates that four major contributions for the crystal cohesion are the H...Cl/Cl...H (34.2%), H...H (22.2%), H...C/C...H (13.5%) and H...O/O...H (10.6%) contacts. In addition, quantum-mechanical properties were calculated using the B3LYP/6–31 G( d , p ) monomer wavefunctions model. The calculations were performed from a single molecular entity within a radial cluster of symmetry-generated molecules, with the radius set to 3.8 Å, and the total intermolecular energies between the molecular pairs range from −3.5 kJ/mol to −22.4 kJ mol −1 . An expanded structure section, set to 3 × 3 × 3 unit cells, was used for the visualization of the energy-framework (only the total energy property was selected and the energy cut-off was set to 10.0 kJ/mol). The synthesis and 1 H/ 13 C NMR data of the title compound are already published in the literature [Siqueira et al. (1994). Quim. Nova , 17 , 24–26].