A study of mercury(II)-catalysed substitution of cyanide in hexacyanoferrate(II) by 2-methylpyrazine: effects of inhibitor on the catalysed reaction |
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Authors: | Neetu Bansal |
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Institution: | (1) School of Biological and Chemical Sciences, The University of the South Pacific, Laucala Campus, Suva, Fiji Islands |
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Abstract: | The kinetics and mechanism of the mercury(II)-catalysed ligand substitution reaction between potassium hexacyanoferrate(II)
and 2-methylpyrazine (2-Mepz), in potassium hydrogen phthalate buffer of pH 3.50 ± 0.02 at 25.0 ± 0.1 °C and constant ionic
strength of 0.1 M, were studied spectrophotometrically by measuring the absorbance of the yellow-coloured product at 447 nm
(λmax). The reaction was studied under pseudo-first-order conditions using excess of 2-Mepz. The reaction was found to obey first-order
dependence in concentration of both Fe(CN)6]4− and 2-Mepz. At higher concentrations of 2-Mepz, the effect of 2-Mepz] levels off. A complex behaviour is observed on varying
Hg2+]. The effect of pH on the reaction rate was also analysed. The effects of dielectric constant and water content of the reaction
medium have been interpreted in terms of the formation of a polar activated complex and suggest an Id mechanism. The inhibitory effect of 2,3-dimercaptopropanol on the reaction was also studied and explained in terms of binding
of this species to the catalyst. |
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