Interaction between hydrogen peroxide and cobalt(II) acetylacetonate in the system of reverse micelles of triton X-100 nonionic surfactant in cyclohexane

Abstract

The yield of free radicals upon the decomposition of hydrogen peroxide catalyzed by cobalt acetylacetonate (Co(acac)2) in the systems of reverse micelles of TX-100/n-hexanol and AOT in cyclohexane at 37°C was studied with the inhibitor method using a stable nitroxyl radical as a spin trap. It is shown that, in micellar AOT solutions in cyclohexane as well as in n-decane, H2O2 and Co(acac)2 in practice do not react, because H2O2 is localized in a micelle water pool and Co(acac)2, in the organic phase. Therefore, the generation of radicals is not observed in AOT solutions in cyclohexane, whereas, in aqueous solution, Co(acac)2 catalyzes the radical decomposition of H2O2. In the system of mixed reverse micelles of TX-100 and n-hexanol in cyclohexane, at equal overall concentrations of H2O2 and Co(acac)2, the rate of radical formation is much higher than in aqueous solution; i.e., the micellar catalysis of the radical decomposition of H2O2 takes place. It follows from measurements of UV and ESR spectra and the kinetics of changes in the content of peroxides in the reaction mixture that TX-100 and n-hexanol react with free radicals formed upon H2O2 decomposition and with atmospheric oxygen.