Osmium(VIII) catalyzed kinetics and mechanism of indoles oxidation with aryl-N-haloamines in alkaline medium

Rangappa, K. S. and Ramachandra, H. and Mahadevappa, D. S. and Made Gowda, N. M. (1996) Osmium(VIII) catalyzed kinetics and mechanism of indoles oxidation with aryl-N-haloamines in alkaline medium. International Journal of Chemical Kinetics, 28 (4). pp. 265-274.

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Abstract

The kinetics of oxidation of the title substrates by sodium N-haloarylsulfonamides (or aryl-N-haloamines), chloramine-T (CAT), bromamine-T (BAT), chloramine-B (CAB), and bromamine-B (BAB), catalyzed by osmium(VIII) in alkaline medium has been studied ae 30 degrees C. The corresponding oxindoles and arylsulfonamides have been characterized as reaction products The reaction rate shows a first-order dependence each on indole](0) and oxidant](0), a fractional-order on Os(VIII)], and an inverse first-order on OH-]. Addition of arylsulfonamide, chloride and bromide, and variation of ionic strength of the medium have no effect on the reaction rate. There is a negative effect of dielectric constant of the solvent. Activation parameters have been calculated from the Arrhenius and Eyring plots. Hammett correlation of substituent effects indicates an LFE relationship with rho = -1.0, showing the formation of an electron deficient transition state. From enthalpy-entropy relationships and Exner correlations, the isokinetic temperatures (333 K and 326 K) have been determined for the reactions of CAT and BAT, respectively. Proton inventory studies in H2O-D2O mixtures have shown the involvement of a single exchangeable proton of OH- ion in the transition state. A mechanism consistent with the observed kinetics has been proposed. (C) 1996 John Wiley & Sons, Inc.

Item Type:	Article
Subjects:	C Chemical Science > Chemistry
Divisions:	Department of > Chemistry
Depositing User:	Users 23 not found.
Date Deposited:	22 May 2021 06:46
Last Modified:	07 Jul 2022 08:01
URI:	http://eprints.uni-mysore.ac.in/id/eprint/16568

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