Kinetics And Mechanism Of Oxidation Of Organic Compound By Cu(Ⅲ) Ion Spectrophotometrically

Based on the studies of oxidation of some simple organic compounds by Cu(III) complex, Indian researcher proposed the electron transfer mechanism, which applied inprotonated complexes [Cu(OH)2(H3IO6)]- as the active species to undergo electron transfer reaction.The main existing form of transition metals complex in highest oxidation state has been reviewed. The kinetics and mechanism of oxidations of (1) dihydric alcohols with a meta active group and a series of hydroxy-acid salts with a ortho active group by ditelluratocuprate(III), and (2) dihydric alcohols with a meta active group and ethylene glycol monobutyl ether by diperiodatocuprate(III) in alkaline medium by the method of spectrophotometry were investigated. We also studied the influence of OH-on the constant of rate. If the deprotonated complexes [Cu(OH)2(HIO6)]3- was presumed as the active species, the plot of 1/kobs vs f([OH-])/[OH-] should be linear, which was in accordance with our experimental results. However, if the inprotonated complexes [Cu(OH)2(H3IO6)]- was presumed as the active species, the plot of 1/kobs vs Φ([OH-])/[OH-] was a curve, which was not consistent with our experimental results. Based on calculated and experimental results, we proposed that the mechanism should be that the deprotonated complex was the active species, forming the intermediate adduct with the reductant and completing the reaction through electron transfer. Furthermore, in terms of mechanism, we found that there existed difference between the ortho-compound and the meta-compound. Based on the studies, we know that the reaction rate of the determining-step changed with the changing of the position of the oxidized group. The reaction rate of the ortho-complex is bigger than that of the meta-complex, we proposed that it might because the penta-cyclic compound formed by ortho-compound is more stable than the hexa-cyclic compound formed by meta-compound, and the spatial hindrance of the former is less than that of the latter. In addition, the reaction rate of the determining-step changed with the changing of the ortho group of the oxidized group. The rate constants of the determining-step have such a sequence: sodium glycollate < 2-hydroxy butyric acid salt < amygdalic acid salt. It might because the ethyl is electron donor, it might result from the conjugated π bond within benzene ring, so the electron density of the coordinated oxygen increases in turns, which leads to the increasing ability to formation of the intermediate adduct, thereby the reaction rate increases in turns. The supposed mechanism could favorably explain the reaction results. Meanwhile, the rate constants (k) and activation parameters were obtained at different temperatures.The hypothesis that the complex was existed as the deprotonated form was supported by our experimental results. Our studies on this kind of system will provide us with more dynamical parameters, and provide theoretical foundation for the route design of the organic synthesis and quantitative analysis of analytical chemistry.