Mimic models of peroxidase--kinetic studies of the catalytic oxidation of hydroquinone by H2O2.

The reactions of hydroquinone with hydrogen peroxide catalyzed by transition metal ions Cu2+, Fe2+, Fe3+, Co2+ and Mn2+ were investigated in aqueous solution at 25 degrees C. Two copper (II) complexes (bis(dimethylglyoxime) copper(II) and 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-dienatocopper(II)iodide) were prepared. Their catalytic activities on this oxidation were kinetically investigated in aqueous solution and in cetyltrimethylammonium bromide (CTAB) micellar solution at 25 degrees C. The kinetic equations for micellar catalysis and metallomicellar catalysis were established, respectively. CTAB micelle enhances the reaction rate due to its concentrated and electrostatic effects on substrates and/or intermediate. Metallomicelle exhibits remarkable catalytic activity on this oxidation reaction, which is attributed to the active center and the microenvironment effects. Metallomicelle enhances the rate of reaction by activating hydroquinone anion. The presence of co-ligand of imidazole (or pyridine) remarkably increases the catalytic activity of metal complex in micelle system in contrast to it lowers the activity of the complex in aqueous solution. Metallomicelles could be treated as the mimic models of peroxidase.