Kinetics and mechanism of oxidation of amido black by sodium N-halo-p-toluenesulfonamides in acidic medium: Spectrophotometric approach

Abstract

KEYWORDSThe kinetics of oxidative decolorization of amido black (AB, Naphthol blue black) by chloramine-T (CAT) and bromamine-T (BAT) in acidic medium has been investigated spectrophotometrically (λmax = 618 nm) at 298 K. Kinetic runs were performed under pseudo first-order conditions of [Oxidant] . Stoichiometry of the reaction was found to be 1:4 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 AB is about three-fold faster with BAT as compared to CAT. This may be attributed to the difference in electrophilicity of Cl + and Br + ions and also the Vander Waals radii of chlorine and bromine. Plausible mechanism and related rate law have been deliberated for the observed kinetics.

Kinetics of oxidation of chloroprocaine hydrochloride by N-halo-p-toluene sulfonamides in acid medium: A Mechanistic approach

“…A similar behaviour has been noted [5] in the oxidation of several other substrates using CAT and BAT. The facts furnished in the present research and the literature reports [33][34] led to conclude that BAT is a stronger oxidant compared to CAT.…”

“…Organic N-haloamines are sources of positive halogens and these reagents have been exploited as oxidant for a variety of substrates in both acidic and alkaline media [11][12][13]. Since organic N-haloamines have analogous chemical properties, it is predicted that identical equilibria exist in aqueous acidic and basic solutions of these compounds [18][19].…”

“…The important chlorine compound of this class is sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT), is a byproduct in the manufacture of saccharin. This reagent has been exploited as an oxidant for a variety of substrates in both acidic and alkaline media [1][2][3][4][5][6][7][8][9][10][11][12]. The bromine analogue of CAT, bromamine-T (BAT) is gaining importance as a mild oxidant and is found to be a better oxidizing agent than the chloro derivative [11][12].…”

Bromamine-T (TsNBrNa): A Biologically Significant, Versatile Bromo-Organic Reagent

“…Scheme 71 Oxidation of levocarnitine by bromamine-T Shubha et al demonstrated the oxidative decolourisation of amido black (AB, Naphthol blue black) using an economically feasible, simpler and eco-friendly protocol (Scheme 72). 99 The kinetics of the oxidation of AB by chloramine-T (CAT) and bromamine-T (BAT) was spectrophotometrically (λmax = 618 nm) investigated in an acid medium at 298 K and the rate law was deduced as…”

“…). 108 The reaction rate was found to exhibit a first-order dependence on both [oxidant]o, and [substrate]o, whereas a fractional-order dependence on the acid was recorded, leading to the rate law: rate = k[oxidant]o[BHCl][H + ] 0.52 . A rise in the reaction rate was encountered with a drop in the dielectric constant of the medium.…”