Mechanism of the OH - Propene-O-2 reaction: An ab initio study

The reaction of OH radicals with olefins is known to be important in atmosp heric chemistry. From experimental data a global mechanism has been propose d, but the regioselectivity of the products is uncertain. In this work, the OH-propene-O-2 reaction has been studied with ab initio molecular orbital techniques. Reactants, transition structures, intermediate species and prod ucts 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 linke d to either the terminal or the central C atoms. Consideration of the secon d step, the addition of O-2, is required to explain the observed experiment al data. The selectivity of the total reaction is found to be temperature a nd pressure dependent, but independent of the preferred site for the OH att ack. (C) 1999 John Wiley & Sons, Inc.