Strathprints logo
Strathprints Home | Open Access | Browse | Search | User area | Copyright | Help | Library Home | SUPrimo

Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media

Impert, Olga and Katafias, A. and Kita, Przemyslaw and Mills, Andrew and Pietkiewiez-Graczyk, Aleksandra and Wrzeszcz, Grzegorz (2003) Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media. Dalton Transactions, 2003 (3). pp. 348-353. ISSN 1472-7773

Full text not available in this repository. (Request a copy from the Strathclyde author)

Abstract

The kinetics of a fast leuco-Methylene Blue (LMB) re-oxidation to Methylene Blue (MB) by copper(II)-halide (Cl-, Br-) complexes in acidic aqueous media has been studied spectrophotometrically using a stopped-flow technique. The reaction follows a simple first order rate expression under an excess of the copper(II) species (and H+(aq)), and the pseudo-first order rate constant (k'(obs)) is largely independent of the atmosphere used (air, oxygen, argon). The rate law, at constant Cl- (Br-) anion concentration, is given by the expression: (d[MB+])/dt = ((k(a)K[H+] + k(b))/(1 + K[H+])).[Cu-II][LMB] = k'(obs)[LMB], where K is the protonation constant, and k(a) and k(b) are the pseudo-second order rate constants for protonated and deprotonated forms of LMB, respectively The rate law was determined based on the observed k'(obs) vs. [Cu-II] and [H+] dependences. The rate dramatically increases with [Cl-] over the range: 0.1-1.5 M, reflecting the following reactivity order: Cu2+(aq) << CuCl+(aq) <...< CuCl42-. The slow re-oxidation of LMB by oxygen has also been briefly examined at different [H+]. ESR results provide clear evidence for the formation of an intermediate radical. The mechanistic consequences of all these results are discussed.

Item type: Article
ID code: 430
Keywords: LEUCOMETHYLENE BLUE, ASCORBIC-ACID, EQUILIBRIUM, SYSTEM, Chemistry
Subjects: Science > Chemistry
Department: Faculty of Science > Pure and Applied Chemistry
Related URLs:
    Depositing user: Mr Derek Boyle
    Date Deposited: 10 Mar 2006
    Last modified: 12 Mar 2012 10:35
    URI: http://strathprints.strath.ac.uk/id/eprint/430

    Actions (login required)

    View Item