The molecular structure of phenetole studied by microwave spectroscopy and quantum chemical calculations

ABSTRACT

A pulsed molecular beam Fourier transform microwave spectrometer operating in the frequency range 2–26.5 GHz was used to measure the spectrum of phenetole (ethyl phenyl ether or ethoxybenzene, C₆H₅OC₂H₅). The conformational landscape is completely determined by the orientations of the phenyl ring and the ethyl group. A two-dimensional potential energy surface was calculated at the MP2/6-311++G(d,p) level of theory. Two conformers were found: the trans conformer has a C_s symmetry, and the gauche conformer has the ethyl group tilted out of the phenyl plane by about 70°. Totally, 186 rotational transitions were assigned to the more stable planar trans conformer, and fitted using a semi-rigid rotor model to measure accuracy. Highly accurate rotational and centrifugal distortion constants were determined. Several method and basis set combinations were applied to check for convergence and to compare with the experimentally deduced molecular parameters.

KEYWORDS:

• Structure determination
• rotational spectroscopy
• phenyl ring

Acknowledgments

We thank the IT Center of the RWTH Aachen University for free computer time.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Land Nordrhein-Westfalen and the Université Paris-Est Créteil. L.F. thanks the Université Paris Est-Créteil for travel funding, which enabled her to work at Paris for two months.