A potentiometric study into the stability of the Schiff's base formed between pyridoxal 5′-phosphate and hexylamine in water–dioxane mixtures

Abstract

We have developed a fast and accurate potentiometric method to characterize the pH-dependent, Schiff's base formation equilibria in water–organic cosolvent mixtures. This method has been applied to the reaction between pyridoxal 5′-phosphate and hexylamine in water–dioxane. We have found that, at neutral and basic pH, the Schiff's base is more stable in the lower polarity media. It is suggested that this is a secondary effect, due to the fact that Schiff's base formation is accompanied by charge neutralization.