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

The kinetics and the mechanism of the 248 nm laser flash photolysis of oxalyl fluoride, (FCO)2, in the presence of O2, F2 and the bath gases He and SF6 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 cm3 molecule−1 s−1 were determined for the reactions FC(O)O2+F2→FC(O)OOF+F and FC(O)O2+F→FC(O)O+OF, whereas the upper limits of 1×10−17 and 9×10−14 cm3 molecule−1 s−1 were estimated for FC(O)O+F2→FC(O)OF+F and FC(O)O+FO2→FC(O)OF+O2. 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)O2 proceeds through the formation of an energized complex FC(O)OOF towards FC(O)O and OF in agreement with the experiments.