Kinetics and mechanisms for the reactions of phenyl radical with ketene and its deuterated isotopomer: An experimental and theoretical study

YongMan Choi, Ming-Chang Lin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Kinetics and mechanism for the reaction of phenyl radical (C 6H5) with ketene (H2Cβ=Cα=O) were studied by the cavity ring-down spectrometric (CRDS) technique and hybrid DFT and ab initio molecular orbital calculations. The C6H5 transition at 504.8 nm was used to detect the consumption of the phenyl radical in the reaction. The absolute overall rate constants measured, including those for the reaction with CD2CO, can be expressed by the Arrhenius equation k = (5.9 ± 1.8) × 1011 exp[-(1160 ± 100)/ T] cm3mol-1s-1 over a temperature range of 301-474K. The absence of a kinetic isotope effect suggests that direct hydrogen abstraction forming benzene and ketenyl radical is kinetically less favorable, in good agreement with the results of quantum chemical calculations at the G2MS//B3LYP6-31G(d) level of theory for all accessible product channels, including the above abstraction and additions to the Cα, C β, and O sites. For application to combustion, the rate constants were extrapolated over the temperature range of 298-2500 K under atmospheric pressure by using the predicted transition-state parameters and the adjusted entrance reaction barriers Eα = Eβ = 1.2 kcalmol -1; they can be represented by the following expression in units of cm3mol-1s-1: kα = 6.2 × 1019T-2.3 exp[-7590/1] and kβ = 3.2 × 104T2.4 exp[-246/T].

Original languageEnglish
Pages (from-to)225-232
Number of pages8
JournalChemPhysChem
Volume5
Issue number2
DOIs
StatePublished - 20 Feb 2004

Keywords

  • Calculations
  • Density functional
  • Kinetics
  • Quantum chemistry
  • Radical reactions
  • Reaction mechanisms

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