engleski

Peroxyl Radicals as Multielectron Oxidants

The reaction rate constants of halogenated alkylperoxyl radicals as a function of pH, the solvent polarity, and the substituent electronegativity, as well as the primary yields of the reaction products, I3- and I2.-, were determined by using the pulse radiolysis method. The yields of I3- as the final product were determined by using the -radiolysis method. The results are in accordance with the reaction mechanism which proposed the addition of an iodide ion into a peroxyl group and the formation of the ROOI.- radical as a primary intermediate. Further reaction with another iodide ion liberates the iodine molecule and the alkoxyl radical. The latter oxidizes another iodide ion into an iodine molecule which in the end gives the oxidation of three iodide ions per one peroxyl radical. The obtained high yields of I3- in the reaction of some nonhalogenated peroxyl radicals (with the participation of H+ ions in the reaction) suggested the occurrence of a multi-electron transfer mechanism in these systems as well. The reaction rate constants of the CCl3O2. radical with another electron or H-atom donors (halogenides, organic sulfur compounds, and 2-propanol) were determined from the changes of the conductivity signal by using the pulse radiolysis method. It has been shown that the rate constants decrease with increasing the reduction potential of the X2.-/2X- couple. It was also proved that halogenated peroxyl radicals react with organic sulfides and disulfides via a multi-electron transfer mechanism. The products of these reactions, the organic sulfoxide and thiolsulfinate, were undoubtedly proved, and their yields were quantitatively determined. It has been shown that the reaction rate constants strictly depend on the reduction potentials of the reactant.

alkylperoxyl radicals ; multielectron transfer ; reaction rate constants ; sulfides ; disulfides

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