Issue 45, 2014

Unimolecular reaction chemistry of a charge-tagged beta-hydroxyperoxyl radical

Abstract

β-Hydroxyperoxyl radicals are formed during atmospheric oxidation of unsaturated volatile organic compounds such as isoprene. They are intermediates in the combustion of alcohols. In these environments the unimolecular isomerization and decomposition of β-hydroxyperoxyl radicals may be of importance, either through chemical or thermal activation. We have used ion-trap mass spectrometry to generate the distonic charge-tagged β-hydroxyalkyl radical anion, ˙CH2C(OH)(CH3)CH2C(O)O, and investigated its subsequent reaction with O2 in the gas phase under conditions that are devoid of complicating radical–radical reactions. Quantum chemical calculations and master equation/RRKM theory modeling are used to rationalize the results and discern a reaction mechanism. Reaction is found to proceed via initial hydrogen abstraction from the γ-methylene group and from the β-hydroxyl group, with both reaction channels eventually forming isobaric product ions due to loss of either ˙OH + HCHO or ˙OH + CO2. Isotope labeling studies confirm that a 1,5-hydrogen shift from the β-hydroxyl functionality results in a hydroperoxyalkoxyl radical intermediate that can undergo further unimolecular dissociations. Furthermore, this study confirms that the facile decomposition of β-hydroxyperoxyl radicals can yield ˙OH in the gas phase.

Graphical abstract: Unimolecular reaction chemistry of a charge-tagged beta-hydroxyperoxyl radical

Supplementary files

Article information

Article type
Paper
Submitted
08 Jul 2014
Accepted
09 Oct 2014
First published
09 Oct 2014
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2014,16, 24954-24964

Author version available

Unimolecular reaction chemistry of a charge-tagged beta-hydroxyperoxyl radical

S. So, B. B. Kirk, A. J. Trevitt, U. Wille, S. J. Blanksby and G. da Silva, Phys. Chem. Chem. Phys., 2014, 16, 24954 DOI: 10.1039/C4CP02981J

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