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Issue 38, 2016
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Observation of a new channel, the production of CH3, in the abstraction reaction of OH radicals with acetaldehyde

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Abstract

Using laser flash photolysis coupled to photo-ionization time-of-flight mass spectrometry (PIMS), methyl radicals (CH3) have been detected as primary products from the reaction of OH radicals with acetaldehyde (ethanal, CH3CHO) with a yield of ∼15% at 1–2 Torr of helium bath gas. Supporting measurements based on laser induced fluorescence studies of OH recycling in the OH/CH3CHO/O2 system are consistent with the PIMS study. Master equation calculations suggest that the origin of the methyl radicals is from prompt dissociation of chemically activated acetyl products and hence is consistent with previous studies which have shown that abstraction, rather than addition/elimination, is the sole route for the OH + acetaldehyde reaction. However, the observation of a significant methyl product yield suggests that energy partitioning in the reaction is different from the typical early barrier mechanism where reaction exothermicity is channeled preferentially into the newly formed bond. The master equation calculations predict atmospheric yields of methyl radicals of ∼9%. The implications of the observations in atmospheric and combustion chemistry are briefly discussed.

Graphical abstract: Observation of a new channel, the production of CH3, in the abstraction reaction of OH radicals with acetaldehyde

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Publication details

The article was received on 07 Jun 2016, accepted on 26 Aug 2016 and first published on 30 Aug 2016


Article type: Paper
DOI: 10.1039/C6CP03970G
Author version available: Download Author version (PDF)
Citation: Phys. Chem. Chem. Phys., 2016,18, 26423-26433
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    Observation of a new channel, the production of CH3, in the abstraction reaction of OH radicals with acetaldehyde

    N. U. M. Howes, J. P. A. Lockhart, M. A. Blitz, S. A. Carr, M. T. Baeza-Romero, D. E. Heard, R. J. Shannon, P. W. Seakins and T. Varga, Phys. Chem. Chem. Phys., 2016, 18, 26423
    DOI: 10.1039/C6CP03970G

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