Experimental and Theoretical Investigation of the Self-Reaction of Phenyl Radicals

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• 作者：Robert S. Tranter ; Stephen J. Klippenstein ; Lawrence B. Harding ; Binod R. Giri ; Xueliang Yang ; John H. Kiefer
• 刊名：Journal of Physical Chemistry A
• 出版年：2010
• 出版时间：August 19, 2010
• 年：2010
• 卷：114
• 期：32
• 页码：8240-8261
• 全文大小：686K
• 年卷期：v.114,no.32(August 19, 2010)
• ISSN：1520-5215

文摘

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.