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/k1c)/(cm3/2 mol–1/2 s–1/2)=(5.93 ± 0.32)–(12500 ± 700)/θ, (logk12/k1/2c)/(cm3/2 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.