Kinetics and mechanism of the thermal gas-phase reaction between bis(trifluoromethyl)trioxide, CF3O3CF3, and 1,1-difluoroethylene, CF2CH2

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Abstract
The thermal addition of CF3O3CF3 to CF2CH2 has been investigated between 315.2 and 332.9 K. The initial pressure of CF3O3CF3(T) was varied between 15 and 100 Torr and that of CF2CH2(E) between 5 and 580 Torr. Several products of formula CF3O(E)nO2CF3 are formed, where n= 1–12. The sum of the products corresponds to the amount of T consumed and its distribution depends on the pressure of E. The reaction is homogeneous and its rate is not affected by the total pressure or the presence of inert gas. It is a free-radical telomerization represented by the basic steps: thermal formation of radicals CF3O and CF3 O2, chain initiation by addition of the CF3O radical to olefin, telomeric radical formation by successive additions to another molecule of alkene and termination of telomeric radicals. Their respective rate constants are designated by k1, ki, kg and kt. The olefin consumption rate is well represented by: –d[E]/dt=k1[T] [graphic omitted] where k′ i=(kti /k1/2 t)/(kgi /k1/2 t) attains its limiting value k′ ∞ at k′ 5. Within the experimental temperature and pressure range the mean chain length of telomerization text-decoration:overline n=(d[E]/dt)/k1[T] increases from 1.2 to 10. The estimated value of the rate constant for the addition of telomeric radicals to alkene is: kg= 6 ± 3 × 105 exp (–9.2 ± 2.5 kJ mol–1/RT) dm3 mol–1 s–1 and Eg= 9.2 ± 2.5 kJ mol–1. At 342.7 K the reaction turns into an explosion.

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