Kinetics Study of the Reactions of 4‑Methyl-2-Pentanone and m‑Ethyl Toluene with Hydroxyl Radicals between 240 and 340 K and 1–8 Torr Using the Relative Rate/Discharge Flow/Mass Spectrometry Technique

The kinetics of reactions of 4-methyl-2-pentanone (MIBK) and m-ethyl toluene (MET) with hydroxyl radicals has been studied at a total pressure of 1–8 Torr and 240–340 K using the RR/DF/MS technique. The rate constant for the reaction of MIBK with the hydroxyl radical was found to be essentially pressure-independent in the range of 1–3 Torr. The rate constant for MET reaction with the hydroxyl radical increased with pressure at 1–5 Torr, and a high pressure limit was reached at 5 Torr. At 298 K, rate constants (in cm³ molecule^–1 s^–1) of k_MIBK+OH(298 K) = (1.25 ± 0.21) × 10^–11 and k_MET+OH(298 K) = (2.05 ± 0.23) × 10^–11 were determined with n-nonane as the reference compound, while k_MIBK+OH(298 K) = (1.25 ± 0.11) × 10^–11 and k_MET+OH(298 K) = (1.88 ± 0.17) × 10^–11 were obtained with 1,4-dioxane as the reference compound, where k_MIBK+OH was measured at 1 Torr and k_MET+OH was measured at 5 Torr. The rate constant of MIBK reaction with the hydroxyl radical was found to be negatively dependent on temperature at 240–340 K, with an Arrhenius expression of k_MIBK+OH(T) = (2.00 ± 0.07) × 10^–12 exp[(535 ± 11)/T] cm³ molecule^–1 s^–1. The rate constant of MET reaction with the hydroxyl radicals was also found to negatively depend on temperature at 240–340 K but with nonlinear behavior in the Arrhenius plot.