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 x 10(-15) T (1.51)exp(1,190.91/T) cm(3) molecule(-1) s(-1), k (2) = 5.95 x 10(-18) T (1.98)exp(-4,622.45/T) cm(3) molecule(-1) s(-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.