Science and Technology Production
Article
Authorship
ULIC, SONIA ELIZABETH
;
Oberhammer, H.
Date
2004
Publishing House and Editing Place
American Chemical Society
Magazine
JOURNAL OF PHYSICAL CHEMISTRY A,
vol. 108
(pp. 1844-1850)
American Chemical Society
Summary
Information provided by the agent in
SIGEVA
Abstract The geometric structures and conformational properties of bis(fluoromethyl) ether, CH2FOCH2F, bis(difluoromethyl) ether, CHF2OCHF2, and of pentafluoromethyl ether, CF3OCHF2, have been studied with gas electron diffraction and quantum chemical methods(B3LYP/6-31G* and MP2 with 6-31G*, cc-pVTZ or 6-311G(2df) basis sets). IR(matrix) spectra have been recorded for CF3OCHF2. The most stable [sc,sc] conformer of CH2FOCH2F possesses C2 symmetry with the C-F bond of both CH2F groups in synclin...
Abstract The geometric structures and conformational properties of bis(fluoromethyl) ether, CH2FOCH2F, bis(difluoromethyl) ether, CHF2OCHF2, and of pentafluoromethyl ether, CF3OCHF2, have been studied with gas electron diffraction and quantum chemical methods(B3LYP/6-31G* and MP2 with 6-31G*, cc-pVTZ or 6-311G(2df) basis sets). IR(matrix) spectra have been recorded for CF3OCHF2. The most stable [sc,sc] conformer of CH2FOCH2F possesses C2 symmetry with the C-F bond of both CH2F groups in synclinal orientation (f (C-O-C-F) = 70(2)°). A small contribution (£ 14%) of the [sc,-sc] form with CS symmetry can not be excluded. CHF2OCHF2 exists in the gas phase as a mixture of two forms. In the main [ap,sp] conformer (82(8)%) one C-H bond is oriented antiperiplanar, the other one synperiplanar. This latter C-H bond nearly eclipses the opposite O-C bond with f (C-O-C-H) = 18(2)°. Nearly eclipsed orientation of the C-H bond is also favored in CF3OCHF2 with f (C-O-C-H) = 19(3)°. According to IR(matrix) spectra a small (8(3)%) contribution of the [ap] conformer with the C-H bond antiperiplanar relative to the opposite O-C bond is present at room temperture. The conformational properties of these fluorinated dimethyl ethers can be rationalized by orbital interaction energies derived from a natural bond orbital (NBO) analysis.
Show more
Show less