Kinetics and mechanism of oxidation of <em>n</em>-butyric and <em>iso</em>-butyric acid hydrazides by hexacyanoferrate(lll) in acidic medium

Abstract

The title reaction, studied spectrophotometrically, exhibits first order rate dependence each on [hexacyanoferrate (III)]_o and [hydrazide]_o. The effect of [HClO₄] on oxidation rate is a curious one. On increasing [HClO₄], initially the rate decreases but tends to attain limiting value at higher concentration of HCIO₄. The reaction rate is slightly enhanced by an increase in ionic strength. However, at constant ionic strength, rate is insensitive to the added salts like NaNO₃, NaCIO₄, NaCl, KCI, LiCI and K₄ Fe(CN)₆. The entropy of activation is negative whereas dielectric effect of the binary solvent (water + methanol) is positive. Carboxylic acid and N₂ are identified as oxidation products. A suitable mechanism and a rate law consistent with the experimental results are proposed.