Issue 10, 2000

General acid–base catalysis in the reversible disproportionation reaction of N-chlorotaurine

Abstract

Third-order rate constants for the general base-catalysed reaction between N-chlorotaurine and its protonated form, kBT (M−2 s−1), and for general acid catalysis of the reverse process, kBH+T (M−2 s−1), have been determined in aqueous solution at 25 °C and I = 0.5 M (NaClO4). The slopes for the Brønsted correlations for the forward and the reverse reactions give β = 0.55 and α = 0.48, respectively. These results suggest that a proton transfer is involved in the rate determining step of the reaction. The high acidity of protonated N,N-dichlorotaurine in aqueous solution rules out the possibility of a stepwise mechanism involving this species as an intermediate. We propose that disproportionation of N-chlorotaurine takes place by a concerted process, where proton and chlorine transfer occur simultaneously in the transition state. This mechanism differs from that found for the transfer of chlorine from a chloramine to an amine.

Article information

Article type
Paper
Submitted
16 May 2000
Accepted
01 Aug 2000
First published
06 Sep 2000

J. Chem. Soc., Perkin Trans. 2, 2000, 2109-2114

General acid–base catalysis in the reversible disproportionation reaction of N-chlorotaurine

J. M. Antelo, F. Arce, P. Calvo, J. Crugeiras and A. Ríos, J. Chem. Soc., Perkin Trans. 2, 2000, 2109 DOI: 10.1039/B003929M

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