Kinetics and mechanism of thermal gas-phase oxidation of hexafluoropropenein the presence of trifluoromethylhypofluorite, CF3OF

The oxidation of hexafluoropropene with molecular oxygen in the presence of CF3OF has been studied at 303.0, 313.0 and 323.4 K, using a conventional s tatic system. The initial pressure of CF3OF was varied between 1.7 and 16.6 Torr, that of C3F6 between 10.0 and 120.2 Torr and that of O-2 between 82. 0 and 599.8 Torr. Several runs were made in the presence of 325.3-499.2 Tor r of N-2. Major products were COF2, CF3C(O)F, CF3OC(O)F and a new compound, CF3OCF2OCF2C(O)F. The latter was characterised by the determination of its relative molecular mass and its IR spectrum, which is consistent with the calculated one using theoretical approximations. Small amounts of CF3OCF2C( O)F were also formed. The oxidation is an homogeneous chain reaction, attai ning, at the pressure of O-2 used, the pseudo-zero-order condition with res pect to O-2 as a reactant. It is independent of the total pressure. The bas ic steps are: the thermal generation of CF3O. radicals by abstraction of th e fluorine atom from CF3OF by C3F6, chain initiation by the addition of CF3 O. to olefin leading, in the presence of O-2, to the formation of haloalkox y radicals, which decompose via the C-C scission to give products containin g C(O)F group and CF3. radicals, reforming CF3O.. The full mechanism is pos tulated.