Kinetics and mechanism of the thermal gas-phase oxidation of 1,1-dichlorodifluoroethene, CF2CCl2, by molecular oxygen in the presence of trifluoromethylhypofluorite, CF3OF

Abstract

The oxidation of CF₂CCl₂, initiated thermally by the addition of CF₃OF to the alkene, has been investigated between 245.1 and 262.3 K. The initial pressures of gases were in the following ranges: CF₃OF 0.7–9.2 Torr;† CF₂CCl₂, 2.9–40.8 Torr; O₂, 5.3–661.9 Torr. Numerous runs were made in the presence of N₂ at pressures varying from 44.6 to 700.5 Torr. In two runs 355.7 and 403.7 Torr of CF₄ were added. The main product was CF₂CIC(O)Cl. [graphic omitted], COF₂ and COCl₂ were formed in minor amounts. The oxidation is a homogeneous chain reaction, whose rate increases with total pressure. The following mechanism, where E = CF₂CCl₂, R = CF₃CCl₂, CF₃OCF₂CCl₂ or CF₂ClCCl₂, R′= CF₃, CF₃OCF₂ or CF₂Cl and M = effective pressure, explains the experimental results: CF₃OF + E = R + CF₃O (1) CF₃O + E = R (2), R + O₂+ M = RO₂+ M (3, 7) 2RO₂= 2RO + O₂(4,8), RO = R′C(O)Cl + Cl (5,9) Cl + E = R (6), 2R = recombination products (10) R + CF₃OF = RF + CF₃O (11), RO₂+ E = RO₂(E)(12) RO₂(E)= RO + [graphic omitted] (13), RO₂(E)+ O₂+ M = RO₂(E)O₂+ M (14), 2RO₂(E)O₂= 2RO₂(E)O + O₂(15), RO₂(E)O = RO + COF₂+ COCl₂(16), k₉=(7 ± 3)× 10¹³ exp (–39.3 ± 6 kJ mol^–1/RT) s^–1, k₁₂=(1.9 ± 1)× 10⁸ exp (–19.9 ± 6 kJ mol^–1/RT) dm³ mol^–1 s^–1.