Authors : S. V. Pore
Page Nos : 120-124
Description :
Abstract: The kinetics and mechanism of oxidation of reactions between hexacyanoferrate (III) and Nicotinic acid hydrazide (NAH) were studied spectrophotometrically in sodium hydroxide medium under pseudo first order condition. The mechanism involves the formation of complex between the reactants, which decomposes in the subsequent step to give products. The reaction proceeds by direct one electron transfer with intervention of free radical and the order of reaction was found to be one with respect to hydrazide and hexacyanoferrate (III).The specific rate increases with an increase in the concentration of hydrazide and hexacyanoferrate (III). The salt that is ionic strength effect is positive ie addition of potassium chloride increases the rate of reaction, hence the reaction must be between species of the same charges. Increase in sodium hydroxide concentration increases the reaction rate and decreases with decrease in dielectric constant. The effect of temperature was studied between 25 to 45 oC. The activation parameters were determined and the values support the proposed mechanism as evidenced by considerable decrease in entropy of activation.(-ΔS # = 26.45 J K-1 mol-1)The progress of the reaction was followed by measuring the absorbance(A) of the hexacyanoferrate (III) at 420 nm.
Keywords: HCF(III) , NAH, hydrazides, kinetics, oxidation, redox reaction.
