POLAROGRAPHIC KINETIC STUDY OF OXIDATION OF METAL COMPLEXES BY CHLORITE ION .I. OXIDATION OF FERROUS CITRATE TARTRATE AND ETHYLENEDIAMINETETRAACETATE AND CUPROUS AMMINE COMPLEXES

The kinetics of the oxidation of ferrous citrate, ferrous tartrate, ferrous EDTA, and cuprous ammine by chlorite ion, ClO2-, have been studied in 1 F NH3-1 F NH4Cl by the catalytic current technique of dc polarography. The reaction orders appear to be first order in both complex and chlorite. The oxidation rates of the citrate and tartrate complexes are not reproducible and are probably complicated by the presence of polymeric species in slow equilibrium with monomeric forms. The rate constants for the oxidation of the ferrous complexes are between 103 and 104 l./(mole sec). This value for FeEDTA2- is 3.0 X 104 ± 0.3 X 104 l./(mole sec) as compared with 44 ± 3.7 l./(mole sec) for cuprous ammine. The difference in rate constants is attributed to the slowing effect of ligand rearrangement in the oxidation of Cu(NH3)2+ to Cu(NH3)42+. Several types of mechanisms which are possible f r the redox reactions considered are discussed. © 1969, American Chemical Society. All rights reserved.