The reactions of the branched alkyl radicals iso-butyl and neo-pentyl with oxygen atoms - An experimental and theoretical study

W. Hack, K. Hoyermann, M. Olzmann, B. Viskolcz, J. Wehmeyer, T. Zeuch

Research output: Contribution to journalArticle

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Abstract

The reactions of the branched primary alkyl radicals iso-butyl and neo-pentyl radicals with atomic oxygen at room temperature and low pressure have been studied with respect to the mechanism of the multiple reaction channels and the rate coefficients. The primary products and the yield of the reaction channels have been determined by quantitative FTIR spectroscopy using laser flash photolysis for the production of the radicals and atoms (iso-C4H10 + Cl, neo-C5H12 + Cl; Cl from the photolysis of CFCl3, O from SO2). In an independent experimental arrangement of a conventional discharge flow reactor with molecular beam sampling, the hydrocarbon radicals were detected mass spectrometrically after specific laser induced multiphoton ionization, thus allowing the measurement of the rate coefficients with reference to the reaction C2H5 + O(κ = 1.04 ×1014 cm3/mol s). Both reactions show multichannel behaviour via the formation of a highly excited alkoxy radical followed by C-C and C-H bond cleavage and, in the case of iso-C4H9 with a hydrogen atom in the 2-position, a direct abstraction to OH radicals: iso-C4H9 + O → iso-C4H9O∗ iso-C4H9+O → HCHO + 2-C3H7 (47±3)% → (CH3)2CHCHO + H (28±2)% iso-C4H9 + O → (CH3)2CCH2 + OH (25±3)% k(iso-C4H9 + O) = (8:9 ± 1:6) × 1013 cm3=mols neo-C5H11 + O → neo-C5H11+O neo-C5H11+O → HCHO + t-C4H9 (65 ±4)% → t-C4H9CHO + H (34±4)% k2(neo-C5H11 + O) = (9:7 ± 2:1) × 1013 cm3=mols The experimental results for the branching ratio for the C-C and C-H cleavage in the alkoxy intermediate are discussed in terms of statistical rate theory.

Original languageEnglish
Pages (from-to)1005-1013
Number of pages9
JournalProceedings of the Combustion Institute
Volume30
Issue number1
DOIs
Publication statusPublished - 2005

Fingerprint

Photolysis
oxygen atoms
Oxygen
Atoms
Laser spectroscopy
Molecular beams
Hydrocarbons
Ionization
Hydrogen
Sampling
photolysis
Lasers
cleavage
coefficients
laser spectroscopy
Temperature
molecular beams
flash
alkoxyl radical
hydrogen atoms

Keywords

  • Hydrocarbon oxidation
  • Mechanism and rate constant
  • Radical reaction
  • Reaction kinetics

ASJC Scopus subject areas

  • Mechanical Engineering
  • Chemical Engineering(all)
  • Physical and Theoretical Chemistry

Cite this

The reactions of the branched alkyl radicals iso-butyl and neo-pentyl with oxygen atoms - An experimental and theoretical study. / Hack, W.; Hoyermann, K.; Olzmann, M.; Viskolcz, B.; Wehmeyer, J.; Zeuch, T.

In: Proceedings of the Combustion Institute, Vol. 30, No. 1, 2005, p. 1005-1013.

Research output: Contribution to journalArticle

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abstract = "The reactions of the branched primary alkyl radicals iso-butyl and neo-pentyl radicals with atomic oxygen at room temperature and low pressure have been studied with respect to the mechanism of the multiple reaction channels and the rate coefficients. The primary products and the yield of the reaction channels have been determined by quantitative FTIR spectroscopy using laser flash photolysis for the production of the radicals and atoms (iso-C4H10 + Cl, neo-C5H12 + Cl; Cl from the photolysis of CFCl3, O from SO2). In an independent experimental arrangement of a conventional discharge flow reactor with molecular beam sampling, the hydrocarbon radicals were detected mass spectrometrically after specific laser induced multiphoton ionization, thus allowing the measurement of the rate coefficients with reference to the reaction C2H5 + O(κ = 1.04 ×1014 cm3/mol s). Both reactions show multichannel behaviour via the formation of a highly excited alkoxy radical followed by C-C and C-H bond cleavage and, in the case of iso-C4H9 with a hydrogen atom in the 2-position, a direct abstraction to OH radicals: iso-C4H9 + O → iso-C4H9O∗ iso-C4H9+O → HCHO + 2-C3H7 (47±3){\%} → (CH3)2CHCHO + H (28±2){\%} iso-C4H9 + O → (CH3)2CCH2 + OH (25±3){\%} k∞(iso-C4H9 + O) = (8:9 ± 1:6) × 1013 cm3=mols neo-C5H11 + O → neo-C5H11+O neo-C5H11+O → HCHO + t-C4H9 (65 ±4){\%} → t-C4H9CHO + H (34±4){\%} k2(neo-C5H11 + O) = (9:7 ± 2:1) × 1013 cm3=mols The experimental results for the branching ratio for the C-C and C-H cleavage in the alkoxy intermediate are discussed in terms of statistical rate theory.",
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T1 - The reactions of the branched alkyl radicals iso-butyl and neo-pentyl with oxygen atoms - An experimental and theoretical study

AU - Hack, W.

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AU - Olzmann, M.

AU - Viskolcz, B.

AU - Wehmeyer, J.

AU - Zeuch, T.

PY - 2005

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N2 - The reactions of the branched primary alkyl radicals iso-butyl and neo-pentyl radicals with atomic oxygen at room temperature and low pressure have been studied with respect to the mechanism of the multiple reaction channels and the rate coefficients. The primary products and the yield of the reaction channels have been determined by quantitative FTIR spectroscopy using laser flash photolysis for the production of the radicals and atoms (iso-C4H10 + Cl, neo-C5H12 + Cl; Cl from the photolysis of CFCl3, O from SO2). In an independent experimental arrangement of a conventional discharge flow reactor with molecular beam sampling, the hydrocarbon radicals were detected mass spectrometrically after specific laser induced multiphoton ionization, thus allowing the measurement of the rate coefficients with reference to the reaction C2H5 + O(κ = 1.04 ×1014 cm3/mol s). Both reactions show multichannel behaviour via the formation of a highly excited alkoxy radical followed by C-C and C-H bond cleavage and, in the case of iso-C4H9 with a hydrogen atom in the 2-position, a direct abstraction to OH radicals: iso-C4H9 + O → iso-C4H9O∗ iso-C4H9+O → HCHO + 2-C3H7 (47±3)% → (CH3)2CHCHO + H (28±2)% iso-C4H9 + O → (CH3)2CCH2 + OH (25±3)% k∞(iso-C4H9 + O) = (8:9 ± 1:6) × 1013 cm3=mols neo-C5H11 + O → neo-C5H11+O neo-C5H11+O → HCHO + t-C4H9 (65 ±4)% → t-C4H9CHO + H (34±4)% k2(neo-C5H11 + O) = (9:7 ± 2:1) × 1013 cm3=mols The experimental results for the branching ratio for the C-C and C-H cleavage in the alkoxy intermediate are discussed in terms of statistical rate theory.

AB - The reactions of the branched primary alkyl radicals iso-butyl and neo-pentyl radicals with atomic oxygen at room temperature and low pressure have been studied with respect to the mechanism of the multiple reaction channels and the rate coefficients. The primary products and the yield of the reaction channels have been determined by quantitative FTIR spectroscopy using laser flash photolysis for the production of the radicals and atoms (iso-C4H10 + Cl, neo-C5H12 + Cl; Cl from the photolysis of CFCl3, O from SO2). In an independent experimental arrangement of a conventional discharge flow reactor with molecular beam sampling, the hydrocarbon radicals were detected mass spectrometrically after specific laser induced multiphoton ionization, thus allowing the measurement of the rate coefficients with reference to the reaction C2H5 + O(κ = 1.04 ×1014 cm3/mol s). Both reactions show multichannel behaviour via the formation of a highly excited alkoxy radical followed by C-C and C-H bond cleavage and, in the case of iso-C4H9 with a hydrogen atom in the 2-position, a direct abstraction to OH radicals: iso-C4H9 + O → iso-C4H9O∗ iso-C4H9+O → HCHO + 2-C3H7 (47±3)% → (CH3)2CHCHO + H (28±2)% iso-C4H9 + O → (CH3)2CCH2 + OH (25±3)% k∞(iso-C4H9 + O) = (8:9 ± 1:6) × 1013 cm3=mols neo-C5H11 + O → neo-C5H11+O neo-C5H11+O → HCHO + t-C4H9 (65 ±4)% → t-C4H9CHO + H (34±4)% k2(neo-C5H11 + O) = (9:7 ± 2:1) × 1013 cm3=mols The experimental results for the branching ratio for the C-C and C-H cleavage in the alkoxy intermediate are discussed in terms of statistical rate theory.

KW - Hydrocarbon oxidation

KW - Mechanism and rate constant

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KW - Reaction kinetics

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