Reactions of the iso-butyl radical during 1,1′-azoisobutane pyrolysis |
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Authors: | G McKay J M C Turner |
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Abstract: | Quantitative analysis of the products formed in 1,1′-azoisobutane pyrolyses in the temperature range of 553°–602°K has shown that the major reactions of the iso-butyl radical are Analysis of initial rate data gave log10k4/(kc)1/2(cm?3/2.mol 1/2.sec?1/2) = 7.54±0.44 ? (136.5 + 4.8) kJ/mol/2.303RT, the Arrhenius parameters obtained being in good agreement with thermodynamic data for reaction (4). Measured values of ka/(kc)1/2 where ka is the rate constant of the reaction iC4H9 + AIB → iC4H10 +. AIB were consistent with published parameters determined by photolysis of 1,1′-azoisobutane. Combination of photolysis and pyrolysis data gave log10 ka/(kc)1/2(cm3/2.mol?1/22.sec?1/2) = 3.68 ± 0.15 ? (27.2 ± 1.2) kJ/mol/2.303RT. The crosscombination ratio for methyl and iso-butyl radicals has been found to be 0.25, indicating that the geometric mean rule does not hold for methyl and iso-butyl radicals. |
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