Rate rules for the reactions of oxygen atoms with terminal alkenes

The reaction of ground state atomic oxygen with terminal alkenes plays an important role in both atmospheric and combustion chemistry. Because of its complicated nature, which involves intersystem crossing from the triplet to the singlet potential energy surface, its channel specific reactivity has been explored only for a few species in restricted temperature and pressure ranges. Here, we report results of crossed molecular beam experiments and theoretical computations for the O(3P) + 1-butene reaction. It is found that traditional rate rules methods where the reactivity of larger size molecules is extrapolated from simpler homologues is not valid for this reaction class. A viable alternative is proposed that allows to predict the reactivity of the whole O(3P) + terminal alkenes reaction class across wide temperature and pressure ranges, encompassing atmospheric and combustion conditions. The present results suggest that all O(3P) reactions with unsaturated hydrocarbons implemented with extrapolated rate constants in kinetic mechanisms should be revised.