An Intramolecular Hydrogen‐Shift in a Peroxy Radical at Cryogenic Temperatures: The Reaction of 2‐Hydroxyphenyl Radical with O2

Peroxy radical hydrogen‐shifts are pivotal elementary reaction steps in the oxidation of small hydrocarbons in autoignition and the lower atmosphere. Although these reactions are typically associated with a substantial barrier, we demonstrate that the [1,5]H‐shift in the peroxy species derived from...

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Bibliographic Details
Published in:Chemistry : a European journal 2020-09, Vol.26 (53), p.12119-12124
Main Author: Wagner, J. Philipp
Format: Article
Language:English
Subjects:
Argon
atmospheric chemistry
Benzoquinone
Chemistry
Cleavage
Cryogenic temperature
Electron transfer
Hydrogen
Infrared spectroscopy
Lower atmosphere
matrix isolation
Oxidation
Peroxy radicals
Reaction products
reactive intermediates
Spontaneous combustion
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Summary:Peroxy radical hydrogen‐shifts are pivotal elementary reaction steps in the oxidation of small hydrocarbons in autoignition and the lower atmosphere. Although these reactions are typically associated with a substantial barrier, we demonstrate that the [1,5]H‐shift in the peroxy species derived from the 2‐hydroxyphenyl radical 1 is so facile that it even proceeds rapidly in an argon matrix at 35 K through a proton‐coupled electron transfer mechanism. Hydrogen‐bound complexes of o‐benzoquinone are identified as the main reaction products by infrared spectroscopy although their formation through O−O bond scission is hampered by a barrier of 11.9 kcal mol−1 at the ROCCSD(T)/cc‐pVTZ/UB3LYP/6–311G(d,p) level of theory. Addition of O2 to the 2‐hydroxyphenyl radical at cryogenic temperatures does not stop at the peroxy radical, but leads to a facile hydrogen‐shift through a proton‐coupled electron transfer mechanism and O−O bond breaking instead.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.202000980