Kinetics and mechanism of the thermal gas-phase reaction between trifluoromethylhypofluorite CF3OF, and tetrachloroethene

The thermal gas-phase reaction of CF3OF with CCl2CCl2 has been studied between 313.8 and 343.8 K. The initial pressure of CF3OF was varied between 10.8 and 77.5 torr and that of CCl2CCl2 between 3.7 and 26.8 torr. CF3OF was always present in excess, varying the initial ratio of CF3OF to that of CCl2CCl2 from 1.3 to 10. Three products were formed: CF3OCCl2CCl2F, CCl2FCCl2F, and CF3O(CCl2CCl2)(2)OCF3. The yields of CF3OCCl2CCl2F were 98-99.5%, based on the sum of the products, The reaction was a homogeneous chain reaction not affected by the total pressure. In presence of O-2 the oxidation of CCl2CCl2 to CCl3C(O)Cl and COCl2 occurred. The proposed basic reaction steps are: generation of the radicals CF3O. and CCl2FCCl2. (k(1)) in a biomolecular process between CF3OF and CCl2CCl2, formation of the radical CF3OCCl2CCl2. by addition of CF3O. to CCl2CCl2, chain generation of CF3O. by abstraction of fluorine atom from CF3OF by CF3OCCl2CCl2. (k(4)), and chain termination by recombination of the radicals CF3OCCl2CCl2.. The expressions obtained for the constants k(1) and k(4) are: k(1) = 3.16 +/- 0.6 x 10(7) exp(-15.2 +/- 1.7 Kcal mol(-1)/RT) dm(3) mol(-1) s(-1); k(4) = 3.7 +/- 0.5 x 10(9) exp(-6.0 +/- 1.1 Kcal mol(-1)/RT) dm(3) mol(-1) s(-1). (C) 1996 John Wiley & Sons, Inc.