Bis-trifluoromethyl Effect: Doubled Transitions in the Rotational Spectra of Hexafluoroisobutene, (CF 3) 2C=CH 2
Rotational spectra for hexafluoroisobutene, and its 13C isotopologues, have been recorded between 8 and 16 GHz using a chirped pulse, Fourier transform microwave spectrometer. Notably, all spectra observed are doubled with separations between the doublets being between 1 and 60 MHz. We propose that the bis-trifluoromethyl groups of the target molecule are staggered in the equilibrium configuration, and that a novel, out-of-phase rotation through a F-CCC-F planar configuration with low barrier (<100 cm -1), leads to the observed doubled rotational spectra.
G. S. Grubbs et al., "Bis-trifluoromethyl Effect: Doubled Transitions in the Rotational Spectra of Hexafluoroisobutene, (CF 3) 2C=CH 2," Journal of Physical Chemistry A, vol. 116, no. 31, pp. 8169-8175, American Chemical Society (ACS), Jan 2012.
The definitive version is available at https://doi.org/10.1021/jp305812z
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