Kinetics of oxidation of ascorbic acid by the [Mn3IV(μ-O)4(bipy)4(H2O)2]4+ ion (bipy=2,2'-bipyridine)

Mondal, Biswapriya ; Bhattacharya, Anup K. ; Banerjee, Rupendranath ; Bhrahma, G. S. ; Dash, A. C. (2000) Kinetics of oxidation of ascorbic acid by the [Mn3IV(μ-O)4(bipy)4(H2O)2]4+ ion (bipy=2,2'-bipyridine) Polyhedron, 19 (10). pp. 1213-1218. ISSN 0277-5387

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In the pH range 1.91-5.24, an aqueous solution of the complex [Mn3IV(μ -O)4(bipy)4(H2O)2]4+ (1) oxidises ascorbic acid quantitatively to dehydroascorbic acid and is itself reduced to MnII. In the presence of excess ascorbic acid, the reaction follows first-order kinetics. The first-order rate constant k0 measured in the presence of excess ascorbic acid increases linearly with increasing concentration of the reductant but decreases as more and more 2,2'-bipyridine is added. k0 also increases with [H+] but tends to saturate at higher [H+]. The proposed rate-determining step involves simultaneous transfer of one electron and one proton from the ascorbate ion to [Mn3IV(μ-O)4(bipy)3(H2O)4]4+, an aquated form of 1. Subsequent rapid reactions via a dinuclear {Mn2O2}3+ intermediate lead to the final products.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Kinetics; Manganese(IV); Ascorbic Acid; Electroprotic Reactions
ID Code:9031
Deposited On:29 Oct 2010 11:56
Last Modified:30 May 2011 06:08

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