Theoretical kinetic investigation of the multichannel mechanism of O(3P) atmospheric oxidation reaction of but-3-enal

Several levels of theory such as Møller-Plesset MP2, G3, and CBS-QB3, have been used in order to investigate the complex and multichannel potential energy surface of the reaction of but-3-enal with the triplet oxygen atom. The results show that the O-addition channel is dominant. The different possible pathways of oxygen atom attack are thoroughly studied to better understand and explain the reaction mechanism. Regarding the oxidation of but-3-enal by triplet oxygen O(3P), it is shown that the major thermodynamic product is H3CC(O)CH2C(O)H (P3) being the most stable for the whole reaction. However, the most favored product kinetically is H2CC(OH)CH2C(O)H (P2). For the H-abstraction second possible pathway, the most favored product both kinetically and thermodynamically is found to be P8. The activation energy and calculated rate constants are consistent with the proposed addition mechanism.