Kinetics of the OH + Methyl Vinyl Ketone and OH + Methacrolein Reactions at Low Pressure

Abstract

The rate constants for the OH + methyl vinyl ketone and OH + methacrolein reactions have been measured in 2−5 Torr of He and over the temperature range 300−422 K using discharge-flow systems coupled with laser-induced fluorescence and resonance fluorescence detection of the OH radical. The rate constant for the OH + methyl vinyl ketone reaction was found to be (1.73 ± 0.21) × 10-11 cm3 molecule-1 s-1 at 5 Torr. No significant pressure dependence was observed between 2 and 5 Torr at 300 K, but a pressure dependence of the rate constant was measured at temperatures between 328 and 422 K. At 328 K, the termolecular rate constant (k0) was measured to be (6.71 ± 2.65) × 10-28 cm6 molecule-2 s-1. An Arrhenius expression of k0 = (9.9 ± 7.6) × 10-30 exp[(1440 ± 300)/T] cm6 molecule-2 s-1 over the temperature range 328−422 K was obtained from a weighted linear least-squares fit of the k0 data versus temperature. Unlike the OH + methyl vinyl ketone reaction, a significant pressure dependence of the rate constant fo...