Catalysis of limonene oxidation by cationic surfactants in combination with transition metal acetylacetonates

The joint action of cationic surfactants and transition metal acetylacetonates on the oxidation of limonene (1-methyl-4-isopropenyl-1-cyclohexene) was studied. All mixed compositions exhibited a synergistic effect, i.e., the oxygen absorption rate in the presence of both components was several times the sum of the rates of oxidation catalyzed by the surfactant alone and the transition metal compound alone. The strongest synergistic effect was observed for the CTABr-Co(II) and CTACl-Cu(II) combinations. A detailed study of the limonene oxidation kinetics in the presence of CTABr and Co(acac)(2) has shown that the synergy mechanism consists in that Co(acac)(2) and the primary oxidation product hydroperoxide form mixed micelles in which hydroperoxides are activated and Co(acac)(2) is concentrated.