Current location: JICS Archive > Vol. 5 > No. 1 > Articles : 1
The Kinetics and Mechanism of Oxidation of Hexacyanoferrate(II) by Periodate Ion in Highly Alkaline Aqueous Medium
R.M. Naik*, A. Srivastava and A. Asthana
Department of Chemistry, University of Lucknow, Lucknow-226 007 (U.P) India
The oxidation of hexacyanoferrate(II) by periodate ion has been studied spectrophotometrically by registering an increase in absorbance at 420 nm (λmax of yellow colored [Fe(CN)63-] complex under pseudo first-order conditions by taking excess of [IO4-] over [Fe(CN)64-]. The reaction conditions were: pH = 9.5 ± 0.02, I = 0.1 M (NaCl) and Temp. = 25 ± 0.1 °C. The reaction exhibited first-order dependence on each [IO4-] and [Fe(CN)64-]. The effects of variations of pH, ionic strength and temperature were also studied. The experimental observations revealed that the periodate ion exists in its protonated forms viz. [H2IO6]3- and [H3IO6]2- while [Fe(CN)6]4- is present in its deprotonated form throughout the pH region selected for the present study. It has also been observed that deprotonated form of [Fe(CN)64-] and protonated forms of periodate ion are the most reactive species towards oxidation of [Fe(CN)64-]. The repetitive spectral scan is provided as an evidence to prove the conversion of [Fe(CN)64-] to [Fe(CN)63-] in the present reaction. The activation parameters have also been computed using the Eyring's plot and found to be, ΔH‡ = 51.53 ± 0.06 kJ mol-1, ΔS‡= -97.12 ± 1.57 J K-1 mol-1 and provided in support of a most plausible mechanistic scheme for the reaction under study.
Keywords: Kinetics and mechanism, Hexacyanoferrate(II) oxidation, Periodate oxidation, Hexacyanoferrate(II), Periodate
