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Kinetic and mechanistic studies of indigocarmine oxidation by chloramine‐T and chlorine in acidic buffer media
Author(s) -
Venkatesha B. M.,
Ananda S.,
Mahadevappa D. S.,
Gowda N. M. Made
Publication year - 1995
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550270706
Subject(s) - chemistry , ionic strength , chlorine , reaction rate constant , arrhenius equation , kinetics , inorganic chemistry , reaction rate , aqueous solution , activation energy , catalysis , organic chemistry , physics , quantum mechanics
Oxidations of indigocarmine (IC) by chloramine‐T (CAT) and aqueous chlorine (HOCl) 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 [IC] 0 and an inverse fractional order on [ p ‐toluenesulfonamide]. The effect of [CAT] on the rate is strongly pH dependent with a variable order of 1–2 on [CAT] 0 in the pH range 6–2. The chlorine reaction rate follows first‐order in [IC] 0 and [HOCl] 0 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. © 1995 John Wiley & Sons, Inc.