Isotopic Dependence of the Hydrogen-Transfer-Triggered Methyl-Group Rotation in Deuterated 5-Methyltropolone

Published

September 19, 2017

Author(s)

Francis J. Lovas, Vadim V. Ilyushin, Alyssa M. Johnson, Jenna Hohl, Emily A. Cloessner, Richard Lavrich

Abstract

We present here the first experimental study of the microwave spectrum of deuterated 5-methyltropolone, a molecule which exhibits two large-amplitude motions: an intramolecular hydrogen transfer (deuterium transfer in the current case of deuterated 5-methyltropolone) and a methyl torsion. The main goal of this study was to get information on the isotopic dependence of the main tunneling parameters of 5-methyltropolone in the framework of two dimensional tunneling formalism, which previously has shown some counterintuitive results for isotopic dependence of tunneling parameters in 2- methylmalonaldehyde. Measurements were carried out by Fourier-transform microwave spectroscopy in the 9 to 26 GHz frequency range. Theoretical analysis was carried out using a tunneling-rotational Hamiltonian based on a G12m extended-group-theory formalism. Our global fit of 384 transitions to 17 molecular parameters gave a weighted root-mean-square deviation of 0.8. The current study on the isotopic dependence of the main tunneling parameters in 5-methyltropolone supports the assumption of possible “leakage” between tunneling parameters in the two-dimensional tunneling formalism in use.

Citation

Journal of Molecular Spectroscopy

Volume

343

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.jms.2017.09.004

Keywords

hydrogen transfer, internal rotation, large-amplitude motion, microwave spectrum, tunneling Hamiltonian, tunneling splittings

Citation

Lovas, F. , Ilyushin, V. , Johnson, A. , Hohl, J. , Cloessner, E. and Lavrich, R. (2017), Isotopic Dependence of the Hydrogen-Transfer-Triggered Methyl-Group Rotation in Deuterated 5-Methyltropolone, Journal of Molecular Spectroscopy, [online], https://doi.org/10.1016/j.jms.2017.09.004 (Accessed October 17, 2025)