Browsing by Author "Tedder, John M."

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    Free Radical Addition to Olefins: Part 10.—Addition of Dibromofluoromethyl Radicals to Fluoroethylenes
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (6), 1973) Sloan, John P.; Tedder, John M.; Walton, John C.
    The gas phase photochemical addition of tribromofluoromethane to a series of fluoro-olefins has been studied over a range of temperatures. The products included those from addition of dibromofluoromethyl radicals to the olefins as well as cyclopropanes from addition of bromofluorocarbene. The mechanism of the reaction is discussed, and Arrhenius parameters for the addition of dibromofluoromethyl radicals are derived from competitive experiments with each olefin and ethylene. [graphic omitted] Activation energies, relative to ethylene, in kcal mol–1, A-factors in l. mol–1 s–1(1 cal = 4.184 J).
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    Free Radical Addition to Olefins: Part 11.—Telomerization of Tetrafluoroethylene with Dibromodifluoromethane and Trifluoroiodomethane
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Ashton, David S.; Tedder, John M.; Walton, John C.
    The telomerization of tetrafluoroethylene in the gas phase by CF2Br2 results in the formation of products of general formula Br[CF2]„Br n = 2-11. When CF3I was used the products were found to be CF3[CF2CF2]„I where n = 1 to 5. Transfer constants have been determined for radicals con taining various numbers of tetrafluoroethylene units, and Arrhenius parameters from temperature variation data. Trends in the transfer constants are compared with previous work in solution. The activation energies from the transfer constants are combined with known values of the activation energies of the addition steps to give estimates of the activation energies of the halogen abstraction steps.
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    Free Radical Addition to Olefins: Part 12.—Addition of Bromodifluoromethyl Radicals to Fluoroethylenes
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Tedder, John M.; Walton, John C.
    The kinetics of the photochemical addition of dibromodifluororncthanc to vinyl fluoride, 1,1- difluoroethylene and tetrafluoroethylene has been examined in gas phase experiments. The mech anism involves the addition of CF2Br- radicals to the alkene in a chain reaction. In the accessible range of alkene concentrations the chains are terminated not only by dimerization of the CF2Br- radicals but also by cross-terminations involving CF2Br- radicals and adduct radicals. Relative rate constants and Arrhenius parameters for the addition of CF2Br- radicals to specific sites in the alkenes have been measured from competitive experiments with ethylene. An estimate of the absolute Arrhenius parameters for the addition of CF2Br- radicals to ethylene is also given.
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    Photolysis of azocyclohexane alone and in an oxygen atmosphere
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (10), 1974) Currie, James L.; Sidebottom, Howard W.; Tedder, John M.
    The photolysis of azocyclohexane involves excited molecules which can be deactivated by collision or decompose into cyclohexyl radicals and nitrogen. Arrhenius parameters for reaction (11) have been estimated, cyclo-C6H11·+(cyclo-C6H11)N2 [graphic omitted] cyclo-C6 H12+ cyclo-C6H11N2-cyclo-C6H10˙k11= 105.6±0.1 exp(–6600 ± 1000 cal mol–1/RT) dm3 mol–1 s–1 and a disproportionation/combination rate constant ratio of 0.99 ± 0.10 for cyclohexyl radicals has been determined. The photolysis of azocyclohexane in an oxygen atmosphere and in the presence of cyclohexane yields cyclohexyl hydroperoxide and cyclohexanone as principal products. The results show that these are formed through a radical/radical reaction and no chain process is involved. Evidence is presented to show that the minor products, cyclohexene and water, are formed via a cyclohexyl-trioxyl radical cyclo-C6H11O3˙.