Oxidation of toluidine blue by chlorite in acid and mechanisms of the uncatalyzed and Ru(III)-catalyzed reactions: a kinetic approach

Sreekanth B Jonnalagadda; Brijesh K Pare

doi:10.1021/jp1062644

Oxidation of toluidine blue by chlorite in acid and mechanisms of the uncatalyzed and Ru(III)-catalyzed reactions: a kinetic approach

J Phys Chem A. 2010 Nov 25;114(46):12162-7. doi: 10.1021/jp1062644. Epub 2010 Nov 3.

Authors

Sreekanth B Jonnalagadda¹, Brijesh K Pare

Affiliation

¹ School of Chemistry, University of KwaZulu-Natal, Westville Campus, Chiltern Hills, P Bag X54001, Durban 4000, South Africa. jonnalgaddas@ukzn.ac.za

PMID: 21043529
DOI: 10.1021/jp1062644

Abstract

The complex mechanism of the uncatalyzed and Ru(III)-catalyzed oxidation of toluidine blue [(7-amino-8-methylphenothiazin-3-ylidene)dimethyl ammonium chloride, TB(+)Cl(-)] (λ(max) = 626 nm) by acidic chlorite is elucidated by a kinetic approach. Both the uncatalyzed and catalyzed reactions had a first-order dependence on the initial ClO(2)(-) and H(+) concentrations ([ClO(2)(-)](0) and [H(+)](0), respectively). The catalyzed reaction had a first-order dependence on the initial Ru(III) concentration ([Ru(III)](0)). The overall reaction of toluidine blue and chlorite ion was as follows: TB(+) + 5ClO(2)(-) + H(+) = P + 2ClO(2) + 2HCOOH + 3Cl(-) + H(2)O, where P is (7-amino-8-methyl-5-sulfoxophenothiazin-3-ylidene)amine. Consistent with the experimental results, the pertinent reaction mechanisms are proposed.