Hoyermann, Karlheinz

[["dc.bibliographiccitation.firstpage","8954"],["dc.bibliographiccitation.issue","31"],["dc.bibliographiccitation.journal","Physical Chemistry Chemical Physics"],["dc.bibliographiccitation.lastpage","8968"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Hoyermann, Karlheinz"],["dc.contributor.author","Maarfeld, Sven"],["dc.contributor.author","Nacke, Frank"],["dc.contributor.author","Nothdurft, Joerg"],["dc.contributor.author","Olzmann, Matthias"],["dc.contributor.author","Wehmeyer, Jens"],["dc.contributor.author","Welz, Oliver"],["dc.contributor.author","Zeuch, Thomas"],["dc.date.accessioned","2018-11-07T08:48:26Z"],["dc.date.available","2018-11-07T08:48:26Z"],["dc.date.issued","2010"],["dc.description.abstract","The kinetics of cycloalkyl + O reactions were studied with respect to their rate coefficients and the product branching ratios from the decomposition of the chemically activated cycloalkoxy radicals. Rate coefficients for the reactions of cyclohexyl (c-C6H11), cycloheptyl (c-C7H13) and cyclooctyl (c-C8H15) radicals with oxygen atoms were determined with an experimental setup consisting of a discharge flow reactor with molecular beam sampling and REMPI/TOF-MS detection. The following rate coefficients were obtained (units: cm(3)/mol(-1) s(-1)): k(c-C6H11 + O) = (1.33 +/- 0.24) x 10(14)(T/298 K)(0.11) (T = 250-600 K), k(c-C7H13 + O) = (1.85 +/- 0.25) x 10(14) (T = 298 K), k(c-C8H15 + O) = (1.56 +/- 0.20) x 10(14)(T/298 K)(0.66+/-0.15) (T = 268-363 K). Stable products were determined by quantitative FTIR spectroscopy. The decomposition of the cycloalkoxy radicals leads besides beta-C-H bond fission (yields: 24% for c-C6H11O, 20-25% for c-C8H15O) mainly to alkyl radicals by ring-opening via beta-C-C bond cleavage. These open-chain alkyl radicals further decompose mainly by beta-C-C bond scission. An increase of the total pressure from 4 mbar to 1 bar had no effect on the product distribution for the reaction c-C6H11 + O, whereas for the reaction c-C8H15 + O further decomposition of the ring-opening product is significantly suppressed at 1 bar. The experimental results on the channel branching and its pressure dependence were rationalized with the statistical rate theory. A comparison of the experimental and modeling results indicates a significant influence of hindered internal rotations (HIRs) on the reactions of the ring-opening products. The harmonic approximation to describe these modes was shown to be inadequate, while a treatment as one-dimensional HIRs led to a significantly improved agreement between experimental and modeling results. Implications of our findings for the formation of secondary organic aerosol and high-temperature combustion are discussed."],["dc.identifier.doi","10.1039/b925920a"],["dc.identifier.isi","000280514800032"],["dc.identifier.pmid","20520884"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/21207"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Royal Soc Chemistry"],["dc.relation.issn","1463-9076"],["dc.title","Rate coefficients for cycloalkyl plus O reactions and product branching in the decomposition of chemically activated cycloalkoxy radicals: an experimental and theoretical study"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","157"],["dc.bibliographiccitation.journal","Proceedings of the Combustion Institute"],["dc.bibliographiccitation.lastpage","164"],["dc.bibliographiccitation.volume","32"],["dc.contributor.author","Hoyermann, Karlheinz"],["dc.contributor.author","Nacke, Frank"],["dc.contributor.author","Nothdurft, Joerg"],["dc.contributor.author","Olzmann, Matthias"],["dc.contributor.author","Wehmeyer, Jens"],["dc.contributor.author","Zeuch, Thomas"],["dc.date.accessioned","2018-11-07T08:35:25Z"],["dc.date.available","2018-11-07T08:35:25Z"],["dc.date.issued","2009"],["dc.description.abstract","The primary product formation of the C(3)H(5) + O reaction in the gas phase has been studied at room temperature. Allyl radicals (C(3)H(5)) and O atoms were generated by laser flash photolysis at lambda = 193 nm of the precursors C(3)H(5)Cl, C(3)H(5)Br, C(6)H(10) (1,5-hexadiene), and SO(2), respectively. The educts and the products were detected by using quantitative FTIR spectroscopy. The combined product analysis of the experiments with the different precursors leads to the following relative branching fractions: C(3)H(5) + O -> C(3)H(4)O + H (47%), C(2)H(4) + H + CO (41'%), H(2)CO + C(2)H(2) + H (7%), CH(3)CCH + OH and CH(2)CCH(2) + OH (<5%). The rate of reaction has been studied relative to CH(3)OCH(2) + O and C(2)H(5) + O in the temperature range from 300 to 623 K. Here, the radicals were produced via the fast reactions of propene, dimethyl ether, and ethane, respectively, with atomic fluorine. Laser-induced multiphoton ionization combined with TOF mass spectrometry and molecular beam sampling from a flow reactor was used for the specific and sensitive detection of the C(3)H(5), C(2)H(5), and CH(3)COCH(2) radicals. The rate coefficient of the reaction C(3)H(5) + O was derived with reference to the reaction C(2)H(5) + O leading to k(C(3)H(5) + O) = (1.11 +/- 0.2) x 10(14) cm(3)/(mol s) in the temperature range 300-623 K. The C(3)H(5) + O rate and channel branching, when incorporated in a suitable detailed reaction mechanism, have a large influence on benzene and allyl concentration profiles in fuel-rich propene flames, on the propene flame speed, and on propene ignition delay times. (C) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved."],["dc.identifier.doi","10.1016/j.proci.2008.06.220"],["dc.identifier.isi","000264756800013"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/18064"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Inc"],["dc.relation.issn","1540-7489"],["dc.title","The reaction of allyl radicals with oxygen atoms-rate coefficient and product branching"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","13608"],["dc.bibliographiccitation.issue","11"],["dc.bibliographiccitation.journal","Molecules"],["dc.bibliographiccitation.lastpage","13622"],["dc.bibliographiccitation.volume","18"],["dc.contributor.author","Seidel, Lars"],["dc.contributor.author","Hoyermann, Karlheinz"],["dc.contributor.author","Mauss, Fabian"],["dc.contributor.author","Nothdurft, Joerg"],["dc.contributor.author","Zeuch, Thomas"],["dc.date.accessioned","2018-11-07T09:17:45Z"],["dc.date.available","2018-11-07T09:17:45Z"],["dc.date.issued","2013"],["dc.description.abstract","Photochemically driven reactions involving unsaturated radicals produce a thick global layer of organic haze on Titan, Saturn's largest moon. The allyl radical self-reaction is an example for this type of chemistry and was examined at room temperature from an experimental and kinetic modelling perspective. The experiments were performed in a static reactor with a volume of 5 L under wall free conditions. The allyl radicals were produced from laser flash photolysis of three different precursors allyl bromide (C3H5Br), allyl chloride (C3H5Cl), and 1,5-hexadiene (CH2CH(CH2)(2)CHCH2) at 193 nm. Stable products were identified by their characteristic vibrational modes and quantified using FTIR spectroscopy. In addition to the (re-) combination pathway C3H5+C3H5 -> C6H10 we found at low pressures around 1 mbar the highest final product yields for allene and propene for the precursor C3H5Br. A kinetic analysis indicates that the end product formation is influenced by specific reaction kinetics of photochemically activated allyl radicals. Above 10 mbar the (re-) combination pathway becomes dominant. These findings exemplify the specificities of reaction kinetics involving chemically activated species, which for certain conditions cannot be simply deduced from combustion kinetics or atmospheric chemistry on Earth."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2013"],["dc.identifier.doi","10.3390/molecules181113608"],["dc.identifier.fs","600601"],["dc.identifier.isi","000330311500033"],["dc.identifier.pmid","24192913"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9485"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/28241"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Mdpi Ag"],["dc.relation.issn","1420-3049"],["dc.rights.access","openAccess"],["dc.title","Pressure Dependent Product Formation in the Photochemically Initiated Allyl plus Allyl Reaction"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]