Reactions of trifluoromethyl radicals. V. Hydrogen abstraction from methyl acetate and methyl (²H₃)Acetate

Abstract

Hydrogen abstraction by CF₃ radicals from CH₃COOCH₃ and CD₃COOCH₃ has been studied in the temperature range 78-242°, and data have been obtained for the reactions:

CF₃ + CH₃COOCH₃ → CF₃H+[C₃H₅O₂]              (3)

CF₃ + CH₃COOCH₃ → CF₃H+CH₂COOCH₃             (4)

CF₃ + CD₃COOCH₃ → CF₃D+CD₂COOCH₃             (6) CF₃ + CD₃COOCH₃ → CF₃H+CD₃COOCH₂             (7) The corresponding rate constants, based on the value of 10^13.36 cm³ mol^-1 S^-1 for the recombination of CF₃ radicals, are given by (k in cm³ mol^-1 s^-1 and E in J mol^-1):

logk₃ = (11.52±0.05)-(35430±380)/19.145T      (3)

logk₄ = (11.19±0.07)-(34680±550)/19.145T      (4)

logk₆ = (11.34±0.06)-(46490±490)/19.145T      (6)

logk₇ = (11.26±0.05)-(36440±400)/19.145T      (7)

At 400 K, 59% of abstraction occurs from the acetyl group, and 41 % from the methoxy group. The kinetic isotope effect at 400 K for attack on the acetyl group is 25, due mainly to a difference in activation energies.