Structure and barrier to methyl group internal rotation for (CF3)2CFCF2OCH3 and its isomer n-C4F9OCH3 (HFE-7100).
The hydrofluoroether C(4)F(9)OCH(3) (methoxynonafluorobutane, HFE-7100) has been studied by chirped pulse Fourier transform microwave spectroscopy as vapor from the liquid participates in a supersonic expansion of argon. Two isomers are present, (CF(3))(2)CFCF(2)OCH(3) and n-C(4)F(9)OCH(3), and in each case the rotational spectra of only one, dominating, conformer has been assigned. Rotational constants, centrifugal distortion constants, and barriers to methyl group internal rotation for the observed species have been experimentally determined for the first time. We note that Ray's asymmetry parameter for the (CF(3))(2)CFCF(2)OCH(3) isomer is 0.007 083(1), indicating almost "perfect" asymmetry. Also, electronic structure calculations show an extremely short C(frame)-O ether bond length of 1.337 Å.
Department of Chemistry, University of North Texas, Denton, Texas 6203-5017, USA.
G S
GS
Grubbs
S A
SA
Cooke