Study of malachite green fading in water-ethanol-ethylene glycol ternary mixtures

Article abstract of DOI:10.1007/s10953-012-9916-2

The rate constant of malachite green (MG⁺) alkaline fading was measured in water-ethanol-ethylene glycol ternary mixtures. This reaction was studied under pseudo-first-order conditions at 283-303 K. In each series of experiments, the concentration of ethanol was kept constant and the concentration of ethylene glycol was changed. It was shown that due to hydrogen bonding and hydrophobic interaction between MG⁺ and alcohol molecules the observed reaction rate constant, k_obs, increased in the water-ethanol-ethylene glycol ternary mixtures. The fundamental rate constants of MG⁺ fading in these solutions (k₁, k_{- 1} and k₂) were obtained by the SESMORTAC model. Analysis of k₁ and k₂ values in solutions containing constant ethanol concentrations show that in low concentrations of ethylene glycol, hydrogen bonding formed between ethanol and ethylene glycol molecules and in high concentrations of ethylene glycol, ethanol as a solvent for ethylene glycol affected the reaction rate.