Formation of bromodifluoroacetyl fluoride, CF 2BrC(O)F, in the thermal gas-phase oxidation of bromotrifluoroethene, CF 2CFBr, initiated by trifluoromethylhypofluorite, CF 3OF

Abstract

The oxidation of CF 2CFBr by molecular O 2, initiated by CF 3OF, has been studied at 273, 253.5, 239 and 218 K. The initial pressure of CF 3OF was varied between 0.9 and 2.4 Torr, that of CF 2CFBr between 11.5 and 30.7 Torr and that of O 2 between 42.5 and 100.7 Torr. The main product was CF 2BrC(O)F (yields 81–95% based on the CF 2CFBr consumed). Minor amounts of C(O)F 2 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 CF 3O radical by abstraction of fluorine atom from CF 3OF, chain initiation by addition of CF 3O to the double bond of alkene, leading, in presence of O 2, to the formation of bromine atom and chain propagation by the reaction of bromine atom with CF 2CFBr, originating CF 2BrCFBrO radical. The predominant fate of the latter is the bromine atom extrusion with C C bond scission playing the minor role. The full mechanism is postulated.