Kinetics and mechanism of the thermal gas‐phase oxidation of perfluorobutene‐2 in presence of trifluoromethyl hypofluorite

Abstract

AbstractThe oxidation of perfluorobutene‐2 (C4F8) initiated by trifluoromethyl hypofluorite (CF3OF) in presence of O2 has been studied at 323.1, 332.6, 342.5, and 352.0 K, using a conventional static system. The initial pressure of CF3OF was varied between 4.8 and 23.6 Torr, that of C4F8 between 48.7 and 302.4 Torr, and that of O2 between 51.5 and 270.4 Torr. Several runs were made in presence of 325.5–451.2 Torr of N2. The main products were COF2, CF3C(O)F, and CF3OC(O)F. Small amounts of compound containing CF(CF3)OC(O)CF3 group were also formed, as detected by 13C NMR spectroscopy. The oxidation is a homogeneous short‐chain reaction, attaining, at the pressure of O2 used, the pseudo‐zero‐order condition with respect to O2 as reactant. The reaction is independent of the total pressure. Its basic steps are as follows: the thermal generation of CF3O• radicals by the abstraction of fluorine atom of CF3OF by C4F8, the addition of CF3O• to the alkene, the formation of perfluoroalkoxy radicals RO• in presence of O2, and the decomposition of these radicals via the CC bond scission, giving products containing C(O)F end group and reforming RO• and CF3O• radicals. The mechanism consistent with experimental results is postulated. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 532–541, 2003