The kinetics and mechanism of oxidation of hexacyanoferrate(II) by periodate ion in highly alkaline aqueous medium

Abstract

The oxidation of hexacyanoferrate(II) by periodate ion has been studied spectrophotometrically by registering an increase in absorbance at 420 nm ( max of yellow colored [Fe(CN) 6 3-] complex under pseudo first-order conditions by taking excess of [IO 4 -] over [Fe(CN) 6 4-]. The reaction conditions were: pH = 9.5 ± 0.02, I = 0.1 M (NaCl) and Temp. = 25 ± 0.1 ºC. The reaction exhibited first-order dependence on each [IO 4 -] and [Fe(CN) 6 4-]. 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. [H 2 IO 6 ] 3-and [H 3 IO 6 ] 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) 6 4-] and protonated forms of periodate ion are the most reactive species towards oxidation of [Fe(CN) 6 4-]. The repetitive spectral scan is provided as an evidence to prove the conversion of [Fe(CN) 6 4-] to[Fe(CN) 6 3-] in the present reaction. The activation parameters have also been computed using the Eyring's plot and found to be, H ‡ = 51.53 ± 0.06 kJ mol -1 , S ‡ = -97.12 ± 1.57 J K -1 mol -1 and provided in support of a most plausible mechanistic scheme for the reaction under study.

The kinetics of the reduction of tetraoxoiodate(VII) by n-(2-hydroxylethyl)ethylenediaminetriacetatocobaltate(II) ion in aqueous perchloric acid

“…The stoichiometry of 2:1 obtained in this reaction is similar to the ones obtained for the reaction of the IO 4 -with oneelectron transfer reductants [4,7,9,14,16] but differs from 1:3.5 [10] and 2:3 [6,17,19] for the reaction of the IO 4 -with two-electron transfer reductants. The stoichiometry obtained in this reaction is consistent with the IO 3 -product.…”

“…They are also important oxidants for metal ions and organic compounds [3]. Its reduction reaction has generated interest as evidenced by available literature [4][5][6][7][8][9][10][11][12][13][14][15][16]. In these studies different acid dependences with respect to [Oxidant] and [Reductant] and mechanisms of reaction were reported.…”

“…While most of the studies reported inner-sphere mechanism [4][5][6][7][11][12][13][14][15], which is typical of IO 4 -reactions, others [8,9] reported outer-sphere mechanistic pathway and yet [10] established both parallel outer-/inner-sphere mechanism. The redox reaction of IO 4 -occurring by the inner-sphere mechanism is favored when it involves reductants that can offer bridging ligands [4,[16][17][18].…”

Flow‐injection chemiluminescence determination of haemoglobin in the blood

“…In Potassium ferrocyanide the iron has the oxidation state II and can undergo oxidation by strong oxidizing agents, such as H 2 O 2 . During the process of this oxidation by H 2 O 2 , the OH* excimer formed is able to release or transmit its energy to fluorescent chemical species.…”

Spectrophotometric Determination of Ruthenium Utilizing its Catalytic Activity on Oxidation of Hexacyanoferrate(II) by Periodate Ion in Water Samples

“…Except the Ru(III) concentration, the concentration of the reactants, pH and ionic strength were judiciously chosen from the kinetic examination of the catalytic electron transfer reaction [39]. The reaction conditions under which the catalytic activity of Ru(III) was optimum were selected for quantitative analysis.…”