Mechanism of the OH-propene-O2 reaction: Anabinitio study

The reaction of OH radicals with olefins is known to be important in atmospheric chemistry. From experimental data a global mechanism has been proposed, but the regioselectivity of the products is uncertain. In this work, the OH–propene–O2 reaction has been studied with ab initio molecular orbital techniques. Reactants, transition structures, intermediate species and products are optimized at the UMP2/6-31G** level for the two possible addition paths. In the first step, OH adducts are obtained with the OH radical linked to either the terminal or the central C atoms. Consideration of the second step, the addition of O2, is required to explain the observed experimental data. The selectivity of the total reaction is found to be temperature and pressure dependent, but independent of the preferred site for the OH attack.