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Kinetics and mechanism of exchange of cyanide in hexacyanoferrate(II) by N-methylpyrazinium ion in the presence of mercury(II) as a catalyst

Prasad, Surendra (2003) Kinetics and mechanism of exchange of cyanide in hexacyanoferrate(II) by N-methylpyrazinium ion in the presence of mercury(II) as a catalyst. Transition Metal Chemistry, 28 (1). pp. 1-8. ISSN 0340-4285

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Abstract

The kinetics of the mercury(II) catalysed ligand exchange of the hexacyanoferrate(II) complex with the N-methylpyrazinium ion (Mpz+) in a potassium hydrogen phthalate buffer medium has been investigated at 25.0′ 0.1 °C, pH 5.0 ′0.02 and ionic strength, I= 0.1 M (KNO3). The reaction was followed spectrophotometrically in the aqueous medium by measuring the increase in absorbance of the intense blue complex [Fe(CN)5Mpz]2-at its λmax 655 nm. The effect of pH, and the concentrations of [Fe(CN)(4Th and Mpz+on the reaction rate have been studied and analysed. The varying catalytic activity of mercury(II) as a function of concentration has also been explained. The kinetic data suggest that substitution follows an interchange dissociative (Id) mechanism and occurs via formation of a solvent-bound intermediate. The effects of the dielectric constant of the medium on the reaction rates have been used to visualize the formation of a polar activated complex and an interchange dissociative mechanism for the reaction. A mechanism has been proposed in order to interpret the kinetic data. Kinetic evidence is reported for the displacement of CN by Mpz+ in [Fe(CNl64J Activation parameters for the catalysed and uncatalysed reaction have been evaluated, and lend further support to the proposed mechanism.

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: 23 Apr 2003 21:29
Last Modified: 17 Jul 2003 17:06
URI: http://repository.usp.ac.fj/id/eprint/2805
UNSPECIFIED

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