Kinetics of the formation and hydrolysis of the Schiff's base of pyridoxal 5′-phosphate with hexylamine in water–dioxane

Abstract

The rate constants of the reaction between pyridoxal 5′-phosphate and hexylamine have been studied as a function of pH, in water–dioxane mixtures, at 25 °C, and at an ionic strength of 0.01. We have found that both the solvent effect and the intramolecular acid catalysis effect on the rates of formation, can be acceptably described on the basis of a log kⁱ₁versus(pK_Pi–pk_A1) correlation. kⁱ₁ rate constant for the reaction between free hexylamine and the ionic species of pyridoxal 5′-phosphate with i bound protons (P_i); pK_pi pK value of the P_i species; pK_A1 pK value of the hexylammonium ion.