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Kinetics and Mechanistic Chemistry of Sodium N-Halobenzenesulfonamides Oxidative Decolorization of Azo Dye Acid Orange 10 in Acid Medium: Spectrophotometric Approach

Jayachamarajapura Pranesh Shubha, Yadati Madhusudhan , Puttaswamy

The kinetics of oxidative decolorization of acid orange 10 (AO10) by chloramine-B and bromamine-B in HClO4 medium has been investigated spectrophotometrically (λmax = 475 nm) at 298 K. Kinetic runs were performed under pseudo first-order conditions of [oxidant]o >> [AO10]o. Under identical experimental conditions, reactions with both the oxidants follow identical kinetics with a first-order dependence on each [oxidant]o and [AO10] and a fractional-order dependence on [HClO4]. Stoichiometry of the reaction was found to be 1:1 and the oxidation products were identified. The reaction was studied at different temperatures and various activation parameters have been computed. Effects of p-toluenesulfonamide, halide ions, ionic strength and dielectric constant of the medium have been investigated. Reaction mixture fails to induce polymerization of acrylonitrile. The rate of oxidation of AO10 is about two-fold faster with BAB as compared to CAB. This may be attributed to the difference in electrophilicities of Cl+ and Br+ ions and also the van der Waal’s radii of chlorine and bromine. Plausible mechanism and related rate law have been deliberated for the observed kinetics.