Formation of bromodifluoroacetyl fluoride, CF2BrC(O)F, in the thermal gas-phase oxidation of bromotrifluoroethene, CF2CFBr, initiated by trifluoromethylhypofluorite, CF3OF

The oxidation of CF2CFBr by molecular O2, initiated by CF3OF, has been studied at 273, 253.5, 239 and 218 K. The initial pressure of CF3OF was varied between 0.9 and 2.4 Torr, that of CF2CFBr between 11.5 and 30.7 Torr and that of O2 between 42.5 and 100.7 Torr. The main product was CF2BrC(O)F (yields 81–95% based on the CF2CFBr consumed). Minor amounts of C(O)F2 and C(O)FBr and traces of bromotrifluoroethene epoxide were also formed. The reaction is a chain reaction with bromine atoms as chain carriers. Its basic steps are: the thermal generation of CF3O radical by abstraction of fluorine atom from CF3OF, chain initiation by addition of CF3O to the double bond of alkene, leading, in presence of O2, to the formation of bromine atom and chain propagation by the reaction of bromine atom with CF2CFBr, originating CF2BrCFBrO radical. The predominant fate of the latter is the bromine atom extrusion with CC bond scission playing the minor role. The full mechanism is postulated.