Photochemistry of anhydrides. Part 1.—Photolysis of perfluoroacetic anhydride vapour: a new source of CF3 radicals

Abstract

The photolysis of perfluoroacetic anhydride was studied in the temperature range 19–177°C using wavelengths in the range 254–265 nm. The photolysis is exceptionally simple and is quantitatively described by the reactions (CF₃CO)₂O +hν→ 2CF₃+ CO + CO₂, CF₃+ CF₃ [graphic omitted] C₂F₆, The anhydride was tested as a source of CF₃ radicals by photolyzing it in the presence of CH₄ and of cyclohexane. For the reactions CF₃+ CH₄→ CF₃H + CH₃(7), CF₃+ c-C₆H₁₂→ CF₃H + c-C₆H₁₁, (12), we obtain log(k₇/k¹_c)/(cm^3/2 mol^–1/2 s^–1/2)=(5.93 ± 0.32)–(12500 ± 700)/θ, (logk₁₂/k^1/2_c)/(cm^3/2 mol^–1/2 s^–1/2)=(5.18 ± 0.15)–(5560 ± 220)/θ, where θ= 2.303 RT/cal mol^–1. These results agree with previous ones obtained using conventional sources of CF₃ radicals. We conclude that perfluoroacetic anhydride is a convenient new source of CF₃ radicals.