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

Journal Article


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Abstract


  • Gas-phase product detection studies of o-hydroxyphenyl radical and O2 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 (C6H4O2, m/z 108) and cyclopentadienone (C5H4O, 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 O2 are also reported and concur with the assignment of o-benzoquinone as the dominant product. 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 + O2 and its charge-tagged counterpart. The prevailing reaction mechanism, after O2 addition, involves a facile 1,5-H shift in the peroxyl 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 + O2 and decarbonylation of o-benzoquinone serve as plausible OH and CO sources in combustion.

Authors


  •   Prendergast, Matthew (external author)
  •   Kirk, Benjamin B. (external author)
  •   Savee, John D. (external author)
  •   Osborn, David L. (external author)
  •   Taatjes, Craig A. (external author)
  •   Masters, Kye Simeon (external author)
  •   Blanksby, Stephen J. (external author)
  •   da Silva, Gabriel (external author)
  •   Trevitt, Adam J.

Publication Date


  • 2016

Citation


  • Prendergast, M. B., Kirk, B. B., Savee, J. D., Osborn, D. L., Taatjes, C. A., Masters, K., Blanksby, S. J., da Silva, G. & Trevitt, A. J. (2016). Formation and stability of gas-phase o-benzoquinone from oxidation of ortho-hydroxyphenyl: a combined neutral and distonic radical study. Physical Chemistry Chemical Physics, 18 (6), 4320-4332.

Scopus Eid


  • 2-s2.0-84957563512

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=4625&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/3602

Has Global Citation Frequency


Number Of Pages


  • 12

Start Page


  • 4320

End Page


  • 4332

Volume


  • 18

Issue


  • 6

Place Of Publication


  • United Kingdom

Abstract


  • Gas-phase product detection studies of o-hydroxyphenyl radical and O2 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 (C6H4O2, m/z 108) and cyclopentadienone (C5H4O, 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 O2 are also reported and concur with the assignment of o-benzoquinone as the dominant product. 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 + O2 and its charge-tagged counterpart. The prevailing reaction mechanism, after O2 addition, involves a facile 1,5-H shift in the peroxyl 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 + O2 and decarbonylation of o-benzoquinone serve as plausible OH and CO sources in combustion.

Authors


  •   Prendergast, Matthew (external author)
  •   Kirk, Benjamin B. (external author)
  •   Savee, John D. (external author)
  •   Osborn, David L. (external author)
  •   Taatjes, Craig A. (external author)
  •   Masters, Kye Simeon (external author)
  •   Blanksby, Stephen J. (external author)
  •   da Silva, Gabriel (external author)
  •   Trevitt, Adam J.

Publication Date


  • 2016

Citation


  • Prendergast, M. B., Kirk, B. B., Savee, J. D., Osborn, D. L., Taatjes, C. A., Masters, K., Blanksby, S. J., da Silva, G. & Trevitt, A. J. (2016). Formation and stability of gas-phase o-benzoquinone from oxidation of ortho-hydroxyphenyl: a combined neutral and distonic radical study. Physical Chemistry Chemical Physics, 18 (6), 4320-4332.

Scopus Eid


  • 2-s2.0-84957563512

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=4625&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/3602

Has Global Citation Frequency


Number Of Pages


  • 12

Start Page


  • 4320

End Page


  • 4332

Volume


  • 18

Issue


  • 6

Place Of Publication


  • United Kingdom