Methyl Vinyl Ketone+OH and Methacrolein+OH Oxidation Reactions: A Master Equation Analysis of the Pressure- and Temperature-Dependent Rate Constants

• Published in: Chemistry : a European journal Vol. 13; no. 4; pp. 1180 - 1190
• Main Authors: Ochando-Pardo, Montserrat, Nebot-Gil, Ignacio, González-Lafont, Àngels, Lluch, José M.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 22.01.2007; WILEY‐VCH Verlag
• Subjects: gas-phase reactions; kinetics; master equation; methacrolein; methyl vinyl ketone; oxidation
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200600529

High‐level electronic structure calculations and master equation analyses were carried out to obtain the pressure‐ and temperature‐dependent rate constants of the methyl vinyl ketone+OH and methacrolein+OH reactions. The balance between the OH addition reactions at the high‐pressure limit, the OH addition reactions in the fall‐off region, and the pressure‐independent hydrogen ions involved in these multiwell and multichannel systems, has been shown to be crucial to understand the pressure and temperature dependence of each global reaction. In particular, the fall‐off region of the OH addition reactions contributes to the inverse temperature dependence of the rate constants in the Arrhenius plots, leading to pressure‐dependent negative activation energies. The pressure dependence of the methyl vinyl ketone+OH reaction is clearly more important than in the case of the methacrolein+OH reaction owing to the weight of the hydrogen ion process in this second system. Comparison of the theoretical rate constants and the experimental measurements shows quite good agreement. High‐level electronic structure calculations, combined with RRKM theory and the MultiWell computer program suite for solving the master equation, allow the pressure and temperature dependence of the rate constants of the methyl vinyl ketone+OH and methacrolein+OH oxidation reactions to be explained (see figure).