Julia A. Davies
Probing elusive cations: infrared spectroscopy of protonated acetic acid
Davies, Julia A.; Besley, Nicholas A.; Yang, Shengfu; Ellis, Andrew M.
Nicholas A. Besley
Andrew M. Ellis
Protonated carboxylic acids, (RCOOH)H+, are the initial intermediates in acid-catalyzed (Fischer) esterification reactions. However the identity of the isomeric form is under debate. Surprisingly, no optical spectra have been reported for any isomer of the protonated carboxylic acid monomer, despite it being a fundamental organic cation. Here, we address these issues by using a new approach to prepare cold He-tagged cations of protonated acetic acid (AA), which entails electron ionization of helium nanodroplets containing metastable dimers of AA. The protonated species is subsequently probed using infrared photodissociation spectroscopy and, following a comparison with calculations, we identify the two isomers whose roles are debated in Fischer esterification. These are the carbonyl-protonated E,Z isomer and the metastable hydroxyl-protonated isomer. Our technique provides a novel approach that can be applied to other elusive ionic species.
|Journal Article Type||Article|
|Publication Date||Apr 11, 2019|
|Journal||The Journal of Physical Chemistry Letters|
|Publisher||American Chemical Society|
|Peer Reviewed||Peer Reviewed|
|APA6 Citation||Davies, J. A., Besley, N. A., Yang, S., & Ellis, A. M. (2019). Probing elusive cations: infrared spectroscopy of protonated acetic acid. Journal of Physical Chemistry Letters, 10, 2108-2112. doi:10.1021/acs.jpclett.9b00767|
|Keywords||General Materials Science|
|Additional Information||This document is the unedited Author’s version of a submitted Work that was subsequently accepted for publication in Journal of Physical Chemistry Letters, copyright © American Chemical Society after peer review. To access the final edited and published work see https://pubs.acs.org/do...021/acs.jpclett.9b00767|
This file is under embargo until Apr 12, 2020 due to copyright restrictions.