Probing Elusive Cations: Infrared Spectroscopy of Protonated Acetic Acid.

08:00 EDT 11th April 2019 | BioPortfolio

Summary of "Probing Elusive Cations: Infrared Spectroscopy of Protonated Acetic Acid."

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.


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This article was published in the following journal.

Name: The journal of physical chemistry letters
ISSN: 1948-7185


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