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Issue 17, 2019
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The mechanism and rate constants for oxidation of indenyl radical C9H7 with molecular oxygen O2: a theoretical study

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Abstract

Ab initio G3(MP2,CC)//B3LYP/6-311G(d,p) calculations have been carried out to map out the C9H7O2 potential energy surface in relation to the reaction of the 1-indenyl radical with molecular oxygen. The resulting energetics and molecular parameters of the species involved in the reaction have been then utilized in Rice–Ramsperger–Kassel–Marcus master equation calculations of temperature- and pressure-dependent reaction rate constants and product branching ratios. The results demonstrate that, while the reaction is insignificant at low temperatures, at higher temperatures, above 800 K or higher depending on the pressure, the prevailing reaction channel leads to the formation of the 1-H-inden-1-one + OH products via a 1,3-H shift from C to O in the initial association complex W1 accompanied by OH elimination through a high barrier of 25.6 kcal mol−1. The branching ratio of 1-H-inden-1-one + OH increases from ∼61% to ∼80% with temperature, whereas c-C6H4-CH2CHO + CO (32–12%) and coumarin + H (7–6%) are significant minor products. The total rate constant of the indenyl + O2 reaction leading to the bimolecular products is independent of pressure and exceeds 1.0 × 10−15 cm3 molecule−1 s−1 only at temperatures above 2000 K, reaching 6.7 × 10−15 cm3 molecule−1 s−1 at 2500 K. The indenyl + O2 reaction is concluded to be too slow to play a substantial role in oxidation of the five-member ring in indenyl and the present results corroborate the assertion that molecular oxygen is not an efficient oxidizer of five-member-ring radicals.

Graphical abstract: The mechanism and rate constants for oxidation of indenyl radical C9H7 with molecular oxygen O2: a theoretical study

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Publication details

The article was received on 26 Feb 2019, accepted on 03 Apr 2019 and first published on 03 Apr 2019


Article type: Paper
DOI: 10.1039/C9CP01122F
Phys. Chem. Chem. Phys., 2019,21, 8915-8924

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    The mechanism and rate constants for oxidation of indenyl radical C9H7 with molecular oxygen O2: a theoretical study

    A. R. Ghildina, D. P. Porfiriev, V. N. Azyazov and A. M. Mebel, Phys. Chem. Chem. Phys., 2019, 21, 8915
    DOI: 10.1039/C9CP01122F

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