Kinetics of Fading of Some Triphenylmethane Dyes: Effects of Electric Charge, Substituent, and Aqueous Binary Mixtures of Dimethyl Sulfoxide and 2-Propanol

摘要

The rate constants of alkaline fading of a number of triphenylmethane (TPM) dyes including methyl green (ME~(2+)), brilliant green (BG~+), fuchsin acid (FA~(2-)), and bromophenol blue (BPB~(2-)) were obtained in aqueous binary mixtures of ~(2-)propanol (protic solvent) and dimethyl sulfoxide (DMSO) (aprotic solvent) at different temperatures. It was observed that the reaction rate constants of BG~+ and ME~(2+) increased and those of FA~(2-) and BPB~(2-) decreased with an increase in weight percentages of aqueous ~(2-)propanol and DMSO binary mixtures. ~(2-)Propanol and DMSO interact with the used TPM molecules through hydrogen bonding and ion-dipole interaction, respectively, in addition to their hydrophobic interaction with TPM dyes. The fundamental rate constants of a fading reaction in these solutions were obtained by the SESMORTAC model. Also, the effect of electric charge and substituent groups of a number of TPM dyes on their alkaline fading rate was studied.