Kinetics and thermochemistry of the reaction of 3-methylpropargyl radical with molecular oxygen

Timo T. Pekkanen, Raimo S. Timonen, György Lendvay, Matti P. Rissanen, Arkke J. Eskola

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4 Citations (Scopus)
8 Downloads (Pure)

Abstract

We have measured the kinetics and thermochemistry of the reaction of 3-methylpropargyl radical (but-2-yn-1-yl) with molecular oxygen over temperature (223-681 K) and bath gas density ( 1.2-15.0×1016 cm-3 ) ranges employing photoionization mass-spectrometry. At low temperatures (223-304 K), the reaction proceeds overwhelmingly by a simple addition reaction to the -CH2 end of the radical, and the measured CH3CCCH2•+O2 reaction rate coefficient shows negative temperature dependence and depends on bath gas density. At intermediate temperatures (340-395 K), the addition reaction equilibrates and the equilibrium constant was determined at different temperatures. At high temperatures (465-681 K), the kinetics is governed by O2 addition to the third carbon atom of the radical, and rate coefficient measurements were again possible. The high temperature CH3CCCH2•+O2 rate coefficient is much smaller than at low T, shows positive temperature dependence, and is independent of bath gas density. In the intermediate and high temperature ranges, we observe a formation signal for ketene (ethenone). The reaction was further investigated by combining the experimental results with quantum chemical calculations and master equation modeling. By making small adjustments ( 2-3kJmol-1 ) to the energies of two key transition states, the model reproduces the experimental results within uncertainties. The experimentally constrained master equation model was used to simulate the CH3CCCH2•+O2 reaction system at temperatures and pressures relevant to combustion.

Original languageEnglish
Pages (from-to)299-306
Number of pages8
JournalPROCEEDINGS OF THE COMBUSTION INSTITUTE
Volume37
Issue number1
DOIs
Publication statusPublished - 1 Jan 2019
Externally publishedYes
Publication typeA1 Journal article-refereed

Keywords

  • Ab initio quantum chemistry
  • Combustion chemistry
  • Experimental gas kinetics
  • Master equation modeling
  • Propargyl radical

ASJC Scopus subject areas

  • General Chemical Engineering
  • Mechanical Engineering
  • Physical and Theoretical Chemistry

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