Reactivity of Phenoxy Acetic Acid and Oxidation Kinetics Using Pyrazinium Chlorochromate

Abstract

The oxidation of phenoxy acetic acid by pyrazinium chlorochromate has been studied in aqueous acetic acid medium
(60 %). The reaction showed fractional order for substrate and HClO4, first order for the oxidant and the low
dielectric constant favors the reaction. Using the Eyring least square method the activation and thermodynamic
parameters were evaluated. The enthalpy of change in activation (ΔH# = 6.56 KJ/mol), entropy of change in
activation (ΔS# = -208.43 KJ/mol) and the activation energy, Ea = 9.08 KJ/mol were calculated from the temperature
effects. The linear graph obtained proved good regression and slope values. The phenoxy acetic acid is oxidized into
quinone through the formation of activated complex. The absence of free radical mechanism has been ruled out and
the involvement of two electrons transferred by manganous ions facilitated the reaction and the plausible mechanism
has been proposed.