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The kinetics and mechanism of oxidation of triethylenetetraaminehexaacetatocobaltate(II) complex by periodate ion in aqueous medium

Naik, R.M. and Srivastava, A. and Verma, A.K. and Yadav, S.B.S. and Singh, R. and Prasad, Surendra (2007) The kinetics and mechanism of oxidation of triethylenetetraaminehexaacetatocobaltate(II) complex by periodate ion in aqueous medium. BioInorganic Reaction Mechanisms, 6 (3). pp. 185-192. ISSN 2191-2483

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Abstract

The kinetics and mechanism of oxidation of [Co(II)TTHA]4- (where TTHA = Triehylenetetraaminehexaaceticacid) by periodate ion has been studied in aqueous acidic medium. The reaction has been investigated spectrophotometrically at λmn = 550 nm under pseudo first- order condition by taking large excess of oxidant, [IO4-] at pH = 4.0 + 0.02, 1 = 0.1 M (CH3COONa + Na NO3) and at three different temperatures viz 150 C, 200 C and 250 C. The electron transfer reaction between [Co(II)TTHA]4- and , [IO4-] obeys inner- sphere reaction pathway through the formation of long lived intermediate complex which eventually get converted into a corresponding [Co(III)TTHA]3- complex as final reaction product. The experimental observations have shown that the reaction exhibit first- order dependence in [Co(II)TTHA]4- . The variation of pseudo- first- order rate constant (Kabc) with [IO4-] keeping other reaction variables fixed at constant value is found to obey the following empirical equation. Kabc = a[IO4-]2/b + c[IO4-] This rate law is consistent with a three step mechanistic scheme. The values of (Kabc) are almost invariant with increasing pH and attributed due to the reaction of deprotonated form of [Co(II)TTHA]4- complex and [IO4-] in the whole pH region. Eyring’s equations has been used to calculate the activation parameters and found to be ∆H* = 16.63 KJ mole-1 ; ∆S* = -214.00 JK-1 mole-1. These values are consistent with three step mechanistic scheme as proposed.

Item Type: Journal Article
Subjects: Q Science > QD Chemistry
Divisions: Faculty of Science, Technology and Environment (FSTE) > School of Biological and Chemical Sciences
Depositing User: Ms Mereoni Camailakeba
Date Deposited: 15 Nov 2007 09:52
Last Modified: 16 Jul 2012 14:29
URI: http://repository.usp.ac.fj/id/eprint/769
UNSPECIFIED

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