Thermochemistry and kinetics of the Acetonyl radicals + NO2: A theoretical study

Document Type

Conference Proceeding

Publication Date

12-1-2010

Abstract

Thermochemical properties for reactants, intermediates and transition state structures in the acetonyl radicals with NO2 reaction systems are analyzed to evaluate reaction paths and kinetics. The initial association reactions form either of two products: nitro alkanes (RNO2) or alkylnitrites (RONO) adducts. Enthalpies of formation (ΔH f°298) are determined using isodesmic reaction analysis at the CBS QB3 composite and density functional levels. Entropies (S°298) and heat capacities [Cp°(T)] are determined using geometric parameters and vibration frequencies obtained at the B3LYP/6-311G(2d,d,p) level of theory. Internal rotor contributions are included in S and Cp(T) values in place of torsion frequencies. Detailed potential energy surfaces for the reactions are presented, with intramolecular isomerization high pressure rate parameters calculated from transition state theory. The chemically activated R• + NO2 systems are modeled using quantum Rice-Ramsperger-Kassel (QRRK) theory, with Master Equation analysis for falloff. At atmospheric pressure and temperature both association paths of the R• + NO2 → reactions proceed almost primarily to stabilization with a fraction of reaction to lower energy products. At combustion temperatures, the R• + NO2 → R-ONO* adduct primarily dissociates to RCO• + NO via chemical activation reaction and the HNO molecular elimination reaction. Rate constants for abstraction of H from the above carbonyl species by NO to form acetylformaldehyde plus HNO also studied.

Identifier

78751547014 (Scopus)

ISBN

[9780816910656]

Publication Title

Aiche Annual Meeting Conference Proceedings

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