Electron transfer reaction in the chromium(VI)-manganese(II) system in the presence of ethylenediaminetetraacetic acid (EDTA)

Author: Babu Prabijna  

Publisher: Springer Publishing Company

ISSN: 0340-4285

Source: Transition Metal Chemistry, Vol.29, Iss.8, 2004-11, pp. : 885-892

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Abstract

Upon addition of Cr VI to a solution of ethylenediaminetetraacetic acid (EDTA) and Mn II, a transient species appears which has an absorption maximum at 500 nm. Kinetic studies of the outer-sphere oxidation of the Mn II-EDTA complex with the Cr VI-EDTA complex have been investigated by visible spectrophotometry at 25 °C. The formation of a transient species has been characterized spectrophotometrically and the encounter complex formation constants have been determined (KOS = 1.75 × 102 and 1.66 × 103 mol-2 dm6 for [EDTA] and [MnII] variations, respectively). The effect of total [EDTA], [MnII], [Cr VI] and [HClO4] on the rate of the reaction was determined. On addition of HClO4, there is a decrease in the rate constants. The reaction product is the CrIII-EDTA complex with max = 400 and 550 nm. On the basis of the various observations and product characterization a most plausible outer-sphere mechanism has been envisaged.

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