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Title: Kinetics and mechanism of the oxidation of cobalt (II) aminopolycarboxylate complex by periodate ion in aqueous medium
Authors: Sarkar, Joy
Chaturvedi, D D
Verma, Amit K
Singh, S K
Naik, R M
Issue Date: Jul-2003
Publisher: NISCAIR-CSIR, India
Abstract: The kinetics of reaction between [CoIIL2-n] [L =1,3, diamino-2-hydroxy propane tetraacetic acid (HPDTA) and propylenediamine tetraacetic acid (PDTA)] and period ate ion has been studied spectrophotometrically at λmax = 550 nm under pseudo-first order conditions by taking large excess of periodate in acidic medium at pH = 4.0 ± 0.02, I = 0.1 mol dm-3 (CH3COONa + NaNO3) and temp = 30 ± 0.1°C. Experimental observations revealed that a long lived intermediate is formed during the course of reaction which is converted to the Corresponding [CoIIIL3-n] complex. The above reactions are found to obey the general rate law, rate = (k2 [IO4¯] + k3 [IO42-]) [CoIIL2-n]. A four step mechanistic scheme involving electron transfer through inner sphere complex formation has been proposed. Activation parameters have been evaluated from Arrhenius and Eyring's equations. The values of activation parameters for [CoII PDTA]2- and IO4- are ΔH# = 47.65 kJ mol-1, ΔS# = -259.41 JK-1 mol-1 and for [CoII HPDTA]2- and IO4- they are ΔH# = 13.46 kJ mol-1, ΔS# = -252.56 JK-1 mol-1.
Page(s): 1639-1643
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections:IJC-A Vol.42A(07) [July 2003]

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