Reaction of Ferricyanideand Methyl Viologen with Free Radicals Produced by Ultrasound in AqueousSolutions.

The redox reactions of organic radicals, with Fe(CN)63–and methylviologen, generated from the sonochemical decomposition of aliphaticalcohols in aqueous solutions, have been studied. The number of radicalsproduced was found to relate to the amount of adsorbed alcohol molecules(Gibbs surface excess) at the gas–aqueous solution interfacefor any bulk solution concentration of the alcohol. The majority ofthe radicals produced stem from the thermal degradation of the alcoholmolecules that have entered imploding cavitation bubbles. The maximumrate of reduction at 355 kHz, of Fe(CN)63–, was 2.6 ± 0.3 μMmin–1, whereas for methyl viologen, it was 1.2 ±0.3 μM min–1under the conditions used. Thedifference in the rates is attributed to the reaction of various pyrolyticallyproduced organic radicals with the methyl viologen radical cation.The possible reactions occurring in the sonolysis of alcohol/watersystems are discussed in detail. [ABSTRACT FROM AUTHOR]