ABSTRACT
The detailed reaction mechanism and kinetics of Criegee intermediate CH2OO with acrolein were investigated. CH2OO may add to the CâO or CâC double bond of acrolein to form a five-membered ring adducts, and it may also insert the terminal oxygen atom or insert itself into the C-H bond of acrolein. The addition reactions are more favorable in energy than the insertion reactions. The master equation calculation show that the most competitive reaction channel is the 1,3-cycloaddition of CH2OO across the CâO double bond forming the secondary ozonide (SOZ). The lowest energy pathway for SOZ decomposition involves the formation of the singlet biradical intermediate by ring fission, the H-shift isomerization and the dissociation to products. The calculated overall rate constant decreases as the temperature increases from 200 to 500 K, and at 298 K, it is 4.31 × 10-12 cm3 molecule-1 s-1. The branching ratio of collisionally stabilized SOZ increases with the increase of pressure. At low pressure, some of SOZ decompose to HCOOH + acrolein or HCHO + acrylic acid. The pressure dependence of this reaction is in agreement with the previous theoretical and experimental observations for the reaction of CH2OO with acetaldehyde.
