Recombination of 1,1-dimethylpropyl peroxy radicals in polar solvents |
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Authors: | T. G. Denisova V. F. Shuvalov |
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Abstract: | The kinetics of 1,1-dimethylpropyl peroxy radicals recombination in polar solvents—water, methanol, and their mixtures—was studied by EPR spectroscopy in combination with the stopped-flow method, and the rate constants of this reaction were determined. Peroxyl radicals were generated by mixing solutions of Ce4+ sulfate and 1,1-dimethylpropyl hydroperoxide. The observed EPR signal of the peroxyl radical is a singlet with a g-factor of 2.015 ± 0.001, and a line width of ΔH = (1.36 ± 0.02) × 10?3 T for methanol and ΔH = (9.7 ± 0.2) × 10?4 T for water. The measured rate constants of (CH3)2C(O2·)CH2CH3 radical recombination at 298 K are 2kt = (3.9 ± 0.4) × 104 L mol?1 s?1 for water and 2kt = (5.2 ± 0.5) × 103 L mol?1 s?1 for methanol. A linear relationship between ln(2kt) and the Kirkwood function (ε?1)/(2ε + 1), where e is the dielectric constant of the medium, has been established, indicating an important role of nonspecific solvation in the recombination of tertiary peroxyl radicals. |
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