Kinetic Study of the Gas-Phase Reactions of Cl Radicals with 3-Pentanone and 3-Hexanone

The discharge flow mass spectrometric technique has been used to determine the absolute rate coefficients of the gas-phase reactions of Cl atoms with 3-pentanone (1) and 3-hexanone (2) in the temperature range 260−333 K and at a total pressure of 1 Torr. The rate constant data ( k (1) and k (2) at different temperatures) were used to derive the Arrhenius expressions, k (1) = (1.5 ± 0.7) × 10 -10 exp[(−281 ± 138)/ T ] cm 3 molecule -1 s -1 and k (2) = (1.6 ± 0.4) × 10 -9 exp[(−884 ± 69)/ T ] cm 3 molecule -1 s -1 . At 298 K and 1 Torr, the products of both reactions have been studied. Reactions 1 and 2 have been found to proceed through an abstraction mechanism, leading to HCl + C 5 H 9 (O) and HCl + C 6 H 11 (O), respectively. The branching ratio for the abstraction channel was determined at 298 K and 1 Torr, as 0.97 ± 0.10 for reaction 1 and 0.98 ± 0.08 for reaction 2. The results obtained are related to previous studies, and the mechanism and atmospheric implications for both reactions are discussed.