Theoretical dynamic studies on the reaction of CH₃C(O)CH _3-nF_n with the hydroxyl radical and the chlorine atom

The mechanisms of the reactions: CH₃C(O)CH₂F + OH/Cl→products (R1/R2) and CH₃C(O)CF₃ + OH/Cl→products (R3/R4) are studied over a wide temperature range (200-2000 K) by means of the dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MP2/cc-pVDZ and B3LYP/6-311G(d,p) levels. The energy profiles of the reactions are then refined with the interpolated single-point-energy method (ISPE) at the BMC-CCSD level. The canonical variational transition-state theory (CVT) with the small-curvature-tunneling (SCT) correction method is used to calculate the rate constants. Using group-balanced isodesmic reactions as working chemical reactions, the standard enthalpies of formation for CH₃C(O)CH ₂F, CH₃C(O)CF₃, CH₃C(O)CHF, CH ₂C(O)CH₂F, and CH₂C(O)CF₃ are evaluated at the CCSD(T)/6-311 + G(2d,p)//MP2/ cc-pVDZ level of theory. The results indicate that the hydrogen abstraction is dominated by removal from the fluoromethyl position rather than from the methyl position.