R. M. Naik, B. Kumar J. Rai, R. Rastogi, S. B. S. Yadav, "Kinetics and Mechanism of Oxidation of Hexamethylenediaminetetraacetatocobaltate(II) Complex by Periodate Ion in Aqueous Medium", Journal of Chemistry, vol. 7, Article ID 180576, 9 pages, 2010. https://doi.org/10.1155/2010/180576
Kinetics and Mechanism of Oxidation of Hexamethylenediaminetetraacetatocobaltate(II) Complex by Periodate Ion in Aqueous Medium
The kinetics and mechanism of oxidation of [CoII HDTA]4- (Where HDTA=Hexamethylenediamine tetraacetic acid} by periodate ion has been studied in aqueous acidic medium. The reactions has been investigated spectrophotometrically at λmax = 580 nm under pseudo- first -order condition by taking large excess of oxidant [IO4] at pH = 4.0±0.02, I = 0.1 M (CH3COONa + NaNO3).and temperature = 30± 0.1 °C The electron transfer reaction between [CoII HDTA] 4- and [IO4-] obeys inner sphere reaction pathway through the formation of long-lived intermediate complex which finally get converted into a corresponding [CoIIIHDTA] 3- complex as final reaction product. The experimental observations have shown that the reaction obey first- order dependence in [CoII HDTA] 4--. The variation of pseudo-first-order rate constants (kobs) with[IO4-], keeping other reaction variables fixed at constant value was found to obey the rate law: kobs=a[IO4-]2/b+c[IO4-], which is consistent with a three step mechanistic scheme. The values of kobs are almost constant with increasing pH, which can be attributed to the reaction of deprotonated form of [CoIII HDTA] 4- complex only, in the entire pH region. Eyring’s equation has been used to calculate the thermal or activation parameters and found to be, ΔH# = 28.69 kJ mole–1; ΔS# = – 481.13 J K-1 mole–1 respectively and support the proposed mechanistic scheme.
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