Microwave spectrum of a superacid and its monohydrate: Tunneling and large amplitude motion in CF3SO2OH and CF3SO2OH-H2O

Huff, Anna

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https://hdl.handle.net/2142/104294 Copy

Description

Title

Microwave spectrum of a superacid and its monohydrate: Tunneling and large amplitude motion in CF3SO2OH and CF3SO2OH-H2O

Author(s)

Huff, Anna

Contributor(s)

• Leopold, Kenneth R.
• Smith, C.J.
• Love, Nathan

Issue Date

2019-06-19

Keyword(s)

Non-covalent interactions

Abstract

The triflic acid monomer (CF$_{3}$SO$_{2}$OH) and its 1:1 complex with water (CF$_{3}$SO$_{2}$OH-H$_{2}$O) have been observed by chirped-pulse and cavity Fourier transform microwave spectroscopy. A pair of tunneling states was identified in the rotational spectra for both species. For CF$_{3}$SO$_{2}$OH, the assignment of \textit{b}-type spectra led to the direct measurement and experimental determination of the tunneling energy ($\Delta$E = 52.96704(90) MHz). M06-2X/6-311++G(3df,3pd) calculations predict a 2.8 kcal/mol barrier for the tunneling motion of the hydroxyl proton rotating around the S-O bond through a transition state in which the O-H is oriented \textit{anti} with respect to the CF$_{3}$ group. A complete $360^{\circ}$ scan of the hydroxyl proton around the S-O bond shows an additional transition state in the \textit{syn} orientation resulting in a 6.2 kcal/mol barrier. In the CF$_{3}$SO$_{2}$OH-H$_{2}$O complex, spectral doublets were observed with an approximate 3:1 intensity ratio indicative of an equivalent exchange of the protons in H$_{2}$O resulting from rotation about its C$_{2}$ axis. The proposed water motion is further supported by the quenching of the spectral pairs for the asymmetrically deuterated CF$_{3}$SO$_{2}$OH-DOH complex. Despite the strong acidity of triflic acid, no evidence of protonation of the water was observed.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/104294

DOI

https://doi.org/10.15278/isms.2019.WB07

Copyright and License Information

Copyright 2019 Anna Huff

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