“…This interaction leads to a strong preference of the trans orientation of the C−D bond relative to the lone pair. The influence of the anomeric effect on the conformational properties has been studied extensively by theoretical methods for the model compound dihydroxymethane (methanediol), CH 2 (OH) 2 . − Depending on the orientation of the O−X bonds, the following four conformations have to be considered for CY 2 (OX) 2 compounds: 1 …”
The geometric structure and conformational properties
of bis(fluorooxy)difluoromethane,
CF2(OF)2, were
determined by gas electron diffraction and theoretical methods (ab
initio and density functional calculations). The
electron diffraction intensities are reproduced best by a mixture of
70(10)% (+sc,+sc) and 30(10)% (sc,ap)
conformers,
corresponding to ΔH° =
H°(sc,ap) − H°(+sc,+sc)
= 0.9(3) kcal mol-1. This
experimental result is reproduced
very well by HF/6-31G* and MP2/6-31G* calculations (ΔE =
0.7 kcal mol-1), but not by the HF/3-21G and
the
density functional (SVWN/6-311G*, BLYP/6-311G*, B3LYP/6-311+G*)
approximations. In addition, the conformational properties of CF2(OH)2 and
CH2(OF)2 were investigated theoretically.
The experimental and theoretical
results are discussed in terms of anomeric effects.
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