Kinetic Studies on the Oxidation of Ninhydrin –Amino Acid Systems Using Alkaline Permanganate
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Date
2007-07
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Addis Ababa Universty
Abstract
The of kinetics of oxidation Ruheman’s Purple by aqueous alkaline permanganate in
alkaline medium at a constant ionic strength has been studied spectrophotometrically.
The oxidation process in alkaline medium under the conditions employed in the present
investigation proceeds initially through the formation of an RP-permanganate complex,
which again rearranges it self to form an other complex. The latter complex decomposes
into products up on reacting with alkali in fast stage of the reaction. The reaction
constants involved in the mechanism were derived. There is good agreement between the
experimental and calculated rate constants under different experimental condition. The
reaction between permanganate and Ruheman’s Purple in alkaline medium exhibits 1:2
stoichiometry (Ruheman’s Purple: KMnO4). The reaction shows first order dependence
on [permanganate] and apparent less than unit order dependence each on Ruhemann’s
Purple and alkali concentrations. Reaction rate increases with increase in ionic strength
and decrease in solvent polarity of the media. Initial addition of reaction products did not
affect the rate significantly. A mechanism of reaction involving the oxidant and substrate
has been proposed. The activation parameters were computed with respect to the slow
step of the mechanism and discussed.
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Keywords
kinetics of oxidation