Experimental and theoretical investigation of the self-reaction of phenyl radicals

Robert S. Tranter, Stephen J. Klippenstein, Lawrence B. Harding, Binod R. Giri, Xueliang Yang, John H. Kiefer

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64 Scopus citations


A combination of experiment and theory is applied to the self-reaction kinetics of phenyl radicals. The dissociation of phenyl iodide is observed with both time-of-flight mass spectrometry, TOF-MS, and laser schlieren, LS, diagnostics coupled to a diaphragmless shock tube for temperatures ranging from 1276 to 1853 K. The LS experiments were performed at pressures of 22 ± 2, 54 ± 7, and 122 ± 6 Torr, and the TOF-MS experiments were performed at pressures in the range 500-700 Torr. These observations are sensitive to both the dissociation of phenyl iodide and to the subsequent self-reaction of the phenyl radicals. The experimental observations indicate that both these reactions are more complicated than previously assumed. The phenyl iodide dissociation yields ∼6% C6H4 + HI in addition to the major and commonly assumed C6H5 + I channel. The self-reaction of phenyl radicals does not proceed solely by recombination, but also through disproportionation to benzene + o-/m-/p-benzynes, with comparable rate coefficients for both. The various channels in the self-reaction of phenyl radicals are studied with ab initio transition state theory based master equation calculations. These calculations elucidate the complex nature of the C6H5 self-reaction and are consistent with the experimental observations. The theoretical predictions are used as a guide in the development of a model for the phenyl iodide pyrolysis that accurately reproduces the observed laser schlieren profiles over the full range of the observations.

Original languageEnglish (US)
Pages (from-to)8240-8261
Number of pages22
JournalJournal of Physical Chemistry A
Issue number32
StatePublished - Aug 19 2010
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


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