Reaction of Cl with CF 3CH 2OCHO: A mechanistic and kinetic study

Abstract

The mechanism and kinetics of the reaction CF 3CH 2OCHO + Cl are investigated theoretically by using a dual-level direct dynamics method. The geometries and frequencies are calculated at the B3LYP/6-311G(d,p), B3LYP/6-311+G(d,p), and MP2/6-31G(d,p) levels, and high-level single-point energy calculations are performed at the BMC-CCSD level. It is shown that the reaction proceeds exclusively via two hydrogen abstraction channels, while the Cl addition–elimination channel is unfavorable. Furthermore, the rate constants of the two H-abstraction channels are evaluated by means of canonical variational transition-state theory (CVT) with the small-curvature tunneling (SCT) correction over a temperature range of 200–1000 K. The overall rate constant at room temperature is in good agreement with the experimental value. This study show that the formyl-H-abstraction channel is the major reaction pathway at low temperatures, while as the temperature increases, methylene-H-abstraction channel becomes more important and competes with the former. The three parameter rate-temperature expression is fitted to be k = 0.17 × 10 −20 T 3.13exp(−23.9/ T) cm 3 molecule −1 s −1 (200–1000 K). The present study may assist in further laboratory work.