KINETICS AND MECHANISM OF OXIDATION OF ASCORBIC-ACID BY COBALT(III) COMPLEXES IN MICELLAR MEDIA

The kinetics of oxidation of L-ascorbic acid (H(2)A) by Co(bipy)(3)(3), Co(edta)(-) and Co(atda) (tmd) complexes have been studied spectrop hotometrically in the presence of cationic, cetyl trimethylammonium br omide (CTAB) and anionic, sodium dodecylsulphate (SDS) surfactants in weakly acidic and basic media. The rate of ascorbic acid oxidation is influenced by the ionic nature of the micelle, hydrophobicity of the c oordinated ligands and the overall charge of the complex used. Ascorbi c acid oxidation by Co(bipy)(3)(3+) is slowed down in the presence of SDS while rate acceleration is observed in CTAB micellar medium. CTAB micelles also lead to rate enhancement in ascorbic acid oxidation by C o(edta)(-) complex. However, micellar effect is not very pronounced in the case of neutral Co(atda) (tmd) complex as oxidant. Based on kinet ic results it can be inferred that the hydrophobic interactions are do minant in the case of Co(bipy)(3)(3+) and electrostatic interactions p lay an important role for Co(edta)(-) complex.