Insight into Chemical Reactions from First-Principles Simulations:  The Mechanism of the Gas-Phase Reaction of OH Radicals with Ketones

The gas-phase reaction of OH radicals with ketones is investigated using Car-Parrinello molecular dynamics. With a set of dynamical simulations we show that two different reaction mechanisms are important in this system. At higher energies the normal abstraction of hydrogen atoms dominates. In contrast, at low energies the formation of a seven-membered ring is observed that causes an enhancement of the abstraction of the hydrogen atoms at the β carbon atoms.