KINETIC AND MECHANISM OF OXIDATION OF ETHYLENEDIAMINETETRAACETIC ACIDBY ALKALINE HEXACYANOFERRATE(III)

The kinetics of oxidation of ethylenediaminetetraacetic acid (EDTA) by hexacyanoferrate(III) have been studied spectrophotometrically (lambd a = 420 nm) at pH = 11.0, I = 0.5 mol dm(-3) (NaClO4) and temperature 45 degrees. The examination of rater data shows that the rate law is d [Fe(CN)(6)(3-)]/dt = k(f)[Fe(CN)(6)(3-)] [EDTA(4-)] with a second orde r rate constant k(f) = 4.5 x 10(-2) dm(3) mol(-1) s(-1). The rate of r eaction has been followed as a function of pH in the range 7.5-12.0. T he rate is found to increase. The reactive species of EDTA are H(2)L(2 -), HL(3-) and L(4-). The resolved rate constants due to tile reaction of [Fe(CN)(6)](3-) with EDTA(4-), HEDTA(3-) and H(2)EDTA(2-) are calc ulated. The effect of ionic strength is found to be positive. The acti vation parameters are also calculated from Arrbenius plots. An electro n transfer mechanism is suggested for the reaction.