Molecular Structures of Isomeric Ortho, Meta, and Para Bromo-Substituted alpha-Methylsulfonyl-alpha-diethoxyphosphoryl Acetophenones by X-ray and DFT Molecular Orbital Calculations

The X-ray single crystal analysis of isomeric ortho, meta, and para bromo-substituted alpha-methylsulfonyl-alpha-diethoxyphosphoryl acetophenones showed that this class of compound adopts synclinal (gauche) conformations for both {[}-P(O)(OEt)(2)] and {[}-S(O)(2)Me] groups, with respect to the carbonyl functional group. The phosphonate, sulfonyl, and carbonyl functional groups are joined through an intramolecular network of attractive interactions, as detected by molecular orbital calculations at the M06-2X/6-31G(d,p) level. These interactions are responsible for the more stable conformations in the gas phase, which also persist in the solid-state structures. The main structural distinction in the title compounds relates to the torsion angle of the aryl group (with respect to the carbonyl group), which gives rise to different interactions in the crystal packing, due to the different positions of the Br atom. (AU)