Kinetics of the reactions of FC(O)O2 radicals with F atoms and F2

Abstract The kinetics and the mechanism of the 248 nm laser flash photolysis of oxalyl fluoride, (FCO) 2 , in the presence of O 2 , F 2 and the bath gases He and SF 6 has been studied at 295 K. The kinetics was followed by monitoring the FC(O)O radical by absorption at 545 nm. Rate coefficient values of (3.4±0.7) × 10 −15 and (4.5±0.7) × 10 −12 cm 3  molecule −1  s −1 were determined for the reactions FC(O)O 2 +F 2 →FC(O)OOF+F and FC(O)O 2 +F→FC(O)O+OF, whereas the upper limits of 1×10 −17 and 9×10 −14 cm 3  molecule −1  s −1 were estimated for FC(O)O+F 2 →FC(O)OF+F and FC(O)O+FO 2 →FC(O)OF+O 2 . From isodesmic reaction schemes at the B3LYP/6-311++G(d,p) level of theory, the enthalpies of formation of FCO, FC(O)OF, FC(O)OOF and FC(O)OOO(O)CF were calculated to be −44.6±2, −102.9±2, −91.2±2 and −186.0±2 kcal mol −1 , respectively. Density functional theory and statistical adiabatic channel model calculations allow us to establish that the reaction between F atoms and FC(O)O 2 proceeds through the formation of an energized complex FC(O)OOF towards FC(O)O and OF in agreement with the experiments.