Electrochemical study of the reaction between progressively alkylated thiazine leucodyes and Fe(III) on a glassy carbon electrode

An electrochemical investigation on five progressively alkylated thiazine dyes in the presence of Fe(III) ions is reported. The theory of the catalytic regeneration mechanism involving an electrode reaction followed by a coupled chemical reaction is applied to derive kinetic parameters of homogeneous reaction. The second-order rate constant for the reaction of thiazine leucodyes with Fe(III) ions was found to increase from 0.25 x 10(4) to 1.6 x 10(4) dm(3) mol(-1) s(-1) upon monomethylation and to vary from 0.7 x 10(4) for the dimethyl derivative to 1.4 x 10(4) dm(3) mol(-1) s(-1) for the tetramethyl one. The electron-donating nature as well as the hydrophobic characteristics of the methyl group influence the kinetics of the homogeneous reaction.