Reaction and complex formation between OH radical and acetone

Kinetics and mechanism of the reaction of OH with CH3C(O)CH3 have been studied by discharge-flow experiments and CCSD(T) quantum chemical computations. In the experiments, the rate coefficient for the overall reaction, OH + CH3C(O)CH3 → products (1), and the branching ratio for the specific reaction channel OH + CH3C(O)CH3 → CH2C(O)CH3 + H2O (1a) have been determined to be k1 = (1.04 ± 0.03) × 1011 cm3 mol−1 s−1 and Γ1a = k1a/k1 = 0.50 ± 0.04, respectively (T = 298 K). Two different reaction pathways have been characterized by ab initio calculations. Both H atom abstraction and OH addition to the CO group have been found to occur through hydrogen bonded OH···CH3C(O)CH3 complexes. Most of our results support recent findings (M. Wollenhaupt, S. A. Carl, A. Horowitz and J. N. Crowley, J. Phys. Chem. A, 2000, 104, 2695; M. Wollenhaupt and J. N. Crowley, J. Phys. Chem. A, 2000, 104, 6429) but contradictions remain concerning the mechanism of this atmospherically important reaction.