University of Illinois Urbana-Champaign

An Oh In Fluorine's Clothing – The Curious Rotational Spectroscopy Of Perfluorophenol

Welsh, Blair

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WF03_1.pptx
6490.pdf

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https://hdl.handle.net/2142/116914

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Title
An Oh In Fluorine's Clothing – The Curious Rotational Spectroscopy Of Perfluorophenol
Author(s)
Welsh, Blair
Contributor(s)
  • Zwier, Timothy S.
  • Hansen, Nils
  • Au, Kendrew
  • Zhang, Angie
  • Dewyer, Amanda
Issue Date
2022-06-22
Keyword(s)
Large amplitude motions, internal rotation
Abstract
\begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.35]{pfp_final.eps} \end{wrapfigure} Perfluorophenol (C$_{6}$F$_{5}$OH) is analogous to hexafluorobenzene (C$_{6}$F$_{6}$), with one fluorine atom replaced by a hydroxyl group. This substitution has a threefold effect: it provides a permanent dipole moment, the molecule remains very close to the oblate symmetric top limit, and intramolecular hydrogen bonds between the H and adjacent fluorine atoms are formed. Hydrogen can tunnel through the barrier to internal rotation of the OH group, lifting the degeneracy of the torsional states. These factors result in the unusual case of a polar, tunneling, near-symmetric top. To probe these effects, the 1 K rotational spectrum of perfluorophenol between 7.5 and 17.5 GHz has been measured using chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. The asymmetry parameter ($\kappa$) was experimentally determined to be 0.944, in agreement with the near-oblate geometries predicted by MP2/6-311++G(d,p) calculations. Tunneling splitting was observed for both \textit{a}-type and \textit{b}-type transitions due to the C-O bond axis lying between the \textit{a} and \textit{b} inertial axes; a consequence of the near-symmetry of perfluorophenol. The energy difference between the split 0$^{+}$ and 0$^{-}$ tunnelling levels was established to be 24.850 MHz. Preliminary wB97XD/6-311++G** calculations estimate a barrier to internal rotation ($V_{2}$) of approximately 1211 cm$^{-1}$. The observed energy splitting is much lower than might be expected of this barrier height when compared to other phenolic derivatives, the exact reason for which is still to be understood.
Publisher
International Symposium on Molecular Spectroscopy
Type of Resource
text
Genre of Resource
Conference Paper / Presentation
Language
eng
Handle URL
https://hdl.handle.net/2142/116914
DOI
https://doi.org/10.15278/isms.2022.WF03
Copyright and License Information
Copyright 2022 held by the authors

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Abstracts & Presentations - 2022 International Symposium on Molecular Spectroscopy PRIMARY