Kinetic and mechanistic studies of indigocarmine oxidation by chloramine-T and chlorine in acidic buffer media

✍ Scribed by B. M. Venkatesha; S. Ananda; D. S. Mahadevappa; N. M. Made Gowda

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 580 KB
• Volume: 27
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550270706

✦ Synopsis

Oxidations of indigocarmine (IC) by chloramine-T (CAT) and aqueous chlorine (HOC1) in acidic buffer media, pH 2-6, have been kinetically studied at 30°C using spectrophotometry. The CAT reaction rate shows a first-order dependence on [IClo and an inverse fractional order on [p-toluenesulfonamidel. The effect of [CAT] on the rate is strongly pH dependent with a variable order of 1-2 on [CAT10 in the pH range 6-2. The chlorine reaction rate follows first-order in [ICIo and [HOClIo each in the pH range 6-2. Addition of halide ions and variation of ionic strength of the medium have no influence on the reaction rate. There is a negative effect of dielectric constant of the solvent. The kinetics of the IC oxidation with CAT at pH 6 and of that with HOCl at pHs 2-6 are similar suggesting similarity in their rate determining steps. A two-pathway mechanism for the CAT reaction and a one-pathway mechanism for the HOCl reaction, consistent with the kinetic data, have been proposed. Activation parameters have been calculated using the Arrhenius and Erying plots.