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

The
X-ray single crystal analysis of isomeric ortho, meta, and
para bromo-substituted α-methylsulfonyl-α-diethoxyphosphoryl
acetophenones showed that this class of compound adopts synclinal
(gauche) conformations for both [-P­(O)­(OEt)2] and
[-S­(O)2Me] 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.