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

Abstract

The title compound, C₁₁H₉Cl₃O₂, (common name: <em>β</em>-aryl-<em>β</em>-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 <em>E</em> 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&sdot;&sdot;&sdot;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 <em>sp</em>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&sdot;&sdot;&sdot;O weak interactions along the <em>a</em>-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 <em>d</em>_norm, shape-index and curvedness modes. The Hirshfeld surface analysis mapped over the <em>d</em>_norm property indicates that four major contributions for the crystal cohesion are the H&sdot;&sdot;&sdot;Cl/Cl&sdot;&sdot;&sdot;H (34.2%), H&sdot;&sdot;&sdot;H (22.2%), H&sdot;&sdot;&sdot;C/C&sdot;&sdot;&sdot;H (13.5%) and H&sdot;&sdot;&sdot;O/O&sdot;&sdot;&sdot;H (10.6%) contacts. In addition, quantum-mechanical properties were calculated using the B3LYP/6–31 G(<em>d</em>,<em>p</em>) monomer wavefunctions model. The calculations were performed from a single molecular entity within a radial cluster of symmetry-generated molecules, with the <em>radius</em> 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 ¹H/¹³C NMR data of the title compound are already published in the literature [Siqueira <em>et al</em>. (1994). <em>Quim</em>. <em>Nova</em>, 17, 24–26].