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Title: Formation and stability of gas-phase o-benzoquinone from oxidation of ortho-hydroxyphenyl: A combined neutral and distonic radical study

Gas-phase product detection studies of o-hydroxyphenyl radical and O 2 are reported at 373, 500, and 600 K, at 4 Torr (533.3 Pa), using VUV time-resolved synchrotron photoionisation mass spectrometry. The dominant products are assigned as o-benzoquinone (C 6H 4O 2, m/z 108) and cyclopentadienone (C 5H 4O, m/z 80). It is concluded that cyclopentadienone forms as a secondary product from prompt decomposition of o-benzoquinone (and dissociative ionization of o-benzoquinone may contribute to the m/z 80 signal at photon energies ≳9.8 eV). Ion-trap reactions of the distonic o-hydroxyphenyl analogue, the 5-ammonium-2-hydroxyphenyl radical cation, with O 2 are also reported and concur with the assignment of o-benzoquinone as the dominant product. In addition, the ion-trap study also provides support for a mechanism where cyclopentadienone is produced by decarbonylation of o-benzoquinone. Kinetic studies compare oxidation of the ammonium-tagged o-hydroxyphenyl and o-methylphenyl radical cations along with trimethylammonium-tagged analogues. Reaction efficiencies are found to be ca. 5% for both charge-tagged o-hydroxyphenyl and o-methylphenyl radicals irrespective of the charged substituent. G3X-K quantum chemical calculations are deployed to rationalise experimental results for o-hydroxyphenyl + O 2 and its charge-tagged counterpart. The prevailing reaction mechanism, after O 2 addition, involves a facile 1,5-H shift in the peroxylmore » radical and subsequent elimination of OH to yield o-benzoquinone that is reminiscent of the Waddington mechanism for β-hydroxyperoxyl radicals. These results suggest o-hydroxyphenyl + O 2 and decarbonylation of o-benzoquinone serve as plausible OH and CO sources in combustion.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4] ;  [4] ;  [5] ;  [1]
  1. Univ. of Wollongong, Wollongong (Australia)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  4. Queensland Univ. of Technology, Brisbane (Australia)
  5. The Univ. of Melbourne, Melbourne (Australia)
Publication Date:
Report Number(s):
SAND-2016-10073J
Journal ID: ISSN 1463-9076; PPCPFQ; 648109
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 18; Journal Issue: 6; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Research Org:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1329619