Measurements and Modeling of HO2Formation in the Reactions ofn-C3H7andi-C3H7Radicals with O2

Estupinan, E. G.; Klippenstein, Stephen J.; Taatjes, Craig A.

doi:10.1021/jp046514s

Cited by 38 publications

(85 citation statements)

References 103 publications

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“…Good agreement between kinetic modeling and experimentally observed time-dependent OH and HO 2 profiles was achieved with modest adjustments of the calculated barrier heights. 46,47 With the exception of the isomerization reaction of the δ-hydroperoxy butyl radical, the CBS-QB3 barriers are slightly lower (by an average of 1.1 kcal mol −1 ) than those obtained of DeSain et al However, the overall agreement between the two sets of data is reasonable and the differences are comparable to the combined errors in the ab initio methods.…”

Section: ■ Methodsmentioning

confidence: 62%

High-Pressure Rate Rules for Alkyl + O₂ Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals

et al. 2012

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The unimolecular reactions of hydroperoxy alkyl radicals (QOOH) play a central role in the low-temperature oxidation of hydrocarbons as they compete with the addition of a second O(2) molecule, which is known to provide chain-branching. In this work we present high-pressure rate estimation rules for the most important unimolecular reactions of the β-, γ-, and δ-QOOH radicals: isomerization to RO(2), cyclic ether formation, and selected β-scission reactions. These rate rules are derived from high-pressure rate constants for a series of reactions of a given reaction class. The individual rate expressions are determined from CBS-QB3 electronic structure calculations combined with canonical transition state theory calculations. Next we use the rate rules, along with previously published rate estimation rules for the reactions of alkyl peroxy radicals (RO(2)), to investigate the potential impact of falloff effects in combustion/ignition kinetic modeling. Pressure effects are examined for the reaction of n-butyl radical with O(2) by comparison of concentration versus time profiles that were obtained using two mechanisms at 10 atm: one that contains pressure-dependent rate constants that are obtained from a QRRK/MSC analysis and another that only contains high-pressure rate expressions. These simulations reveal that under most conditions relevant to combustion/ignition problems, the high-pressure rate rules can be used directly to describe the reactions of RO(2) and QOOH. For the same conditions, we also address whether the various isomers equilibrate during reaction. These results indicate that equilibrium is established between the alkyl, RO(2), and γ- and δ-QOOH radicals.

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Section: ■ Methodsmentioning

confidence: 62%

High-Pressure Rate Rules for Alkyl + O₂ Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals

et al. 2012

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“…Above the stabilization limit the CH 2 CH 2 CH 2 OOH species is incorporated into the CH 3 CH 2 CH 2 OO well, and the master-equation methodology calculates unimolecular reactions from the CH 2 CH 2 CH 2 OOH configuration, for example, formation of oxirane + OH products, effectively as formally direct reactions from CH 3 CH 2 CH 2 OO. The present model leaves unchanged the stationary points responsible for the HO 2 -forming channels in the propyl + O 2 reaction, so the agreement with experiment for those channels [30,31] is retained. As a result, the present model represents a widely-validated set of stationary points that can be used to predict rate coefficients at many different conditions.…”

Section: Resultsmentioning

confidence: 82%

New experiments and validated master-equation modeling for OH production in propyl+O2 reactions

Huang

Merthe

Zádor

et al. 2011

Proceedings of the Combustion Institute

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“…These reaction pathways continue to be the focus of intense scrutiny and theoretical attention; for example, recent studies have shown [34][35][36] The MCH radical isomers are denoted by a number for a radical site on the ring or "X" for a radical site on the CH 3 group. Fig.…”

Section: Discussionmentioning

confidence: 99%

Modeling and experimental investigation of methylcyclohexane ignition in a rapid compression machine

Pitz¹,

Naik²,

Mhaoldúin³

et al. 2007

Proceedings of the Combustion Institute

175

234

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A new chemical kinetic reaction mechanism has been developed for the oxidation of methylcyclohexane (MCH), combining a new low-temperature mechanism with a recently developed high temperature mechanism. Predictions from this kinetic model are compared with experimentally measured ignition delay times from a rapid compression machine. Computed results were found to be particularly sensitive to isomerization rates of methylcyclohexylperoxy radicals. Three different methods were used to estimate rate constants for these isomerization reactions. Rate constants based on comparable alkylperoxy radical isomerizations corrected for the differences in the structure of MCH and the respective alkane, predicted ignition delay times in very poor agreement with the experimental results. The most significant drawback was the complete absence of a region of negative temperature coefficient (NTC) in the model results using this method, although a prominent NTC region was observed experimentally. Alternative estimates of the isomerization reaction rate constants, based on the results from previous experimental studies of low temperature cyclohexane oxidation, provided much better agreement with the present experiments, including the pronounced NTC behavior. The most important feature of the resulting methylcyclohexylperoxy radical isomerization reaction analysis was found to be the relative rates of isomerizations that proceed through 5-, 6-, 7-and 8--3-membered transition state ring structures and their different impacts on the chainbranching behavior of the overall mechanism. Theoretical implications of these results are discussed, with particular attention on how intramolecular H atom transfer reactions are influenced by the differences between linear alkane and cycloalkane structures.

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Measurements and Modeling of HO₂Formation in the Reactions ofn-C₃H₇andi-C₃H₇Radicals with O₂

Cited by 38 publications

References 103 publications

High-Pressure Rate Rules for Alkyl + O₂ Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals

High-Pressure Rate Rules for Alkyl + O₂ Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals

New experiments and validated master-equation modeling for OH production in propyl+O2 reactions

Modeling and experimental investigation of methylcyclohexane ignition in a rapid compression machine

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Measurements and Modeling of HO2Formation in the Reactions ofn-C3H7andi-C3H7Radicals with O2

Cited by 38 publications

References 103 publications

High-Pressure Rate Rules for Alkyl + O2 Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals

High-Pressure Rate Rules for Alkyl + O2 Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals

New experiments and validated master-equation modeling for OH production in propyl+O2 reactions

Modeling and experimental investigation of methylcyclohexane ignition in a rapid compression machine

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Measurements and Modeling of HO₂Formation in the Reactions ofn-C₃H₇andi-C₃H₇Radicals with O₂

High-Pressure Rate Rules for Alkyl + O₂ Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals

High-Pressure Rate Rules for Alkyl + O₂ Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals