Oxidation of picolinic acid hydrazide by hexacyanoferrate (iii) in sodium hydroxide medium under pseudo first order condition

The objective of the present study is to examine the kinetics and mechanism of Single electron transfer redox reaction of Picolinic acid hydrazide (Pi-AH) by hexacyanoferrate(III) called HCF(III) in Sodium hydroxide medium which involves Fe(CN)63-.The Spectrophotometric monitoring of oxidation of Pi-AH by HCF(III)) was carried out. The kinetic determination of its mechanism in sodium hydroxide medium under pseudo first order condition was done. The formation of complex takes place during the course of the reaction between the reactants, which on decomposition in the subsequent step gives the products. The reaction proceeds by direct Single electron transfer with intervention of free radical and the order of reaction was found to be one with respect to the concentration of hydrazide (Pi-AH) and hexacyanoferrate HCF (III).The specific rate of the reaction increases with an increase in the concentration of hydrazide and hexacyanoferrate HCF (III). The salt effect that is ionic strength effect is positive ie addition of KCl increases the rate of reaction; hence the reaction must be between species of the same charges. Increase in the concentration of NaOH increases the rate of reaction and decreases with decrease in dielectric constant of the medium of the Reaction. The effect of temperature was studied between 25oC to 45oC. The activation parameters were determined and the values support the proposed mechanism as evidenced by considerable decrease in entropy of activation.(-ΔS # = 22.09 J K-1 mol-1) The progress of the reaction was followed by measuring the absorbance (A) of the HCF(III) at 420 nm.