The Pure Rotational Spectra of the Two Lowest Energy Conformers of the Asymmetric Ether C 4H 9OC 2H 5
An experimental study has been performed shedding light on the conformational energies of the asymmetric ether n-butyl ethyl ether. Rotational spectroscopy between 7.8 GHz and 16.2 GHz has identified two conformers of n-butyl ethyl ether, C 4H 9OC 2H 5. in these experiments spectra were observed as the target compound participated in an argon expansion from high to low pressure causing molecular rotational temperatures to be below 4 K. For one conformer, 95 pure rotational transitions have been recorded, for the second conformer, 20 pure rotational transitions were recorded. Rotational constants and centrifugal distortion constants are presented for both butyl ethyl ether conformers. the structures of both conformers have been identified by exploring the multi-dimensional molecular potential energy surface using ab initio calculations. From the numerous low energy conformers identified using ab initio methods, the three lowest conformers were pursued at increasingly higher levels of theory, i.e. complete basis set extrapolations, coupled cluster methods, and also taking into consideration zero point vibrational energies. the two conformers observed experimentally are only revealed to be the two lowest energy conformers when high levels of quantum chemical methodologies are employed.
B. E. Long et al., "The Pure Rotational Spectra of the Two Lowest Energy Conformers of the Asymmetric Ether C 4H 9OC 2H 5," Journal of Molecular Spectroscopy, vol. 269, no. 1, pp. 113-118, Elsevier, Jan 2011.
The definitive version is available at http://dx.doi.org/10.1016/j.jms.2011.05.008
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