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

Abstract

The rate constants of alkaline fading of a number of triphenylmethane (TPM) dyes including methyl green (ME2+), brilliant green (BG+), fuchsin acid (FA2−), and bromophenol blue (BPB2−) 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 ME2+ increased and those of FA2− and BPB2− 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.

Organic additives stabilize RNA aptamer binding of malachite green

“…This discovery provides a simple way to stabilize aptamer binding, which is beneficial for applications that rely on MGA for accurate detection of MG. This inhibition strategy may also be applied to other triphenylmethane compounds that are susceptible to hydrolysis, for instance, to stabilize aptasensors of crystal violet [43][44][45][46]. To date, more than 10 5 triphenylmethane compounds ((Ph)3-C) and 9,000 substructures of MG have been reported to date (SciFinder).…”

“…Triphenylmethane compounds have been commercially and analytically used as bacteriological stains, pH indicators, therapeutic agent and food dyes [45]. However, the use of some triphenylmethane compounds has been banned for farming due to their potential toxicity, thus the detection and monitoring of triphenylmethane compounds is of consumer importance [17].…”

Nitrophenol Violet as a New Tool for Studying of Kinetics of Reactions in Solutions

“…Alkaline fading reactions of triphenylmethine dyes have long been used to study the kinetics of organic reactions and factors affecting the rate constant. − A number of dyes, mainly cationic, R z+ , such as crystal violet, have been proposed for the use of this reaction in the educational process. − However, it is also of interest to include the anionic dyes, R z– , in the study. A higher level of education can be achieved by conducting a parallel comparative experiment with reactions of cationic and anionic dyes in two student groups, since the increasing polarity of the medium or ionic strength decelerates the reactions between R z+ and HO – and accelerates that of R z– with HO – . − The most commonly used anionic dyes, bromophenol blue and phenolphthalein, interact with the hydroxide ion more slowly than cationic ones, and their use in experiments takes a long time. , …”