Browsing by Author "Chamberlain, G. A."

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    Photochemistry of Anhydrides: Part 2.—Photolysis of Perfluoropropionic Anhydride : A New Source of C2F5 Radicals
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (1), 1972) Chamberlain, G. A.; Whittle, E.
    The photolysis of the vapour of (C2F5CO)2O in the temperature range 20–213°C is described quantitatively by the overall reaction (C2F5CO)2O +hν→ CO + CO2+ n-C4F10, with the effective primary process being (C2F5CO)2O +hν→ CO + CO2+ 2C2F5. The anhydride was photolyzed in the presence of both CH4 and cyclohexane and the following reactions occur: C2F5+ CH4→ C2F5H + CH3(7), C2F5+ c-C6H12→ C2F5H + c-C6H11(8), C2F5+ C2F5→ C4F10. (4) For these reactions, log(k7/k½c)/(cm[fraction three-over-two] mol–½ s–½)=(5.01 ± 0.28)–(11490 ± 560)/θ, log(k8/k½c)/(cm[fraction three-over-two] mol–½ s–½)=(5.68 ± 0.25)–(6440 ± 380)/θ, where θ= 2.303 RT/cal mol–1 and kc is the rate constant for reaction (4). It is concluded that Arrhenius parameters for abstraction of H from a given RH by CF3, C2F5 and n-C3F7 radicals are almost identical. When (C2F5CO)2O is photolyzed with cyclohexene both H-abstraction (kH) and addition to the double bond (kadd) occur with log(kH/kadd)=(0.67 ± 0.07)–(2530 ± 120)/θ.
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    Photochemistry of Anhydrides: Part 1.—Photolysis of Perfluoroacetic Anhydride Vapour: A New Source of CF3 Radicals
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (1), 1972) Chamberlain, G. A.; Whittle, E.
    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.