Theoretical studies and rate constants calculation for the reactions of acetone with fluorine and bromine atoms

Theoretical investigations are carried out on the multichannel reactions CH₃COCH₃ + F (R1) and CH₃COCH₃ + Br (R2) by means of direct dynamics methods. The minimum energy path (MEP) is obtained at the MP2/6-31 + G(d,p) level, and energetic information is further refined at the MC-QCISD (single-point) level. The rate constants are calculated by the improved canonical variational transition-state theory (ICVT) with the small-curvature tunneling (SCT) contributions in a wide temperature range 200-1,500 K for the title reactions, H-abstraction channel is favored for the two reactions. The theoretical overall rate constants are in good agreement with the available experimental data and are found to be k_1a = 3.22 × 10^-15 T^{1. 51}exp(1,190.91/T) cm³ molecule ^-1s^-1, k₂ = 5.95 × 10^-18 T^1.98exp(-4,622.45/T) cm³molecule ^-1s^-1. Furthermore, the rate constants of reaction Cl + CH₃COCH₃ (R3) calculated in the other paper are added to discuss the reactivity trend of different halogen reaction with acetone on the rate constants of this class of hydrogen abstraction reactions.