The isomerization of d-glucose into d-fructose in aqueous alkaline solutions

Abstract

To relate kinetic data of previous publications about the isomerization of d-glucose into d-fructose in aqueous, alkaline media in the temperature range 22–71°, a simple kinetic model has been developed, which allows transformation of the rate constants published. The kinetic model has been based on the generally accepted enolate-ion isomerization mechanism, and comprises rate constants that are independent of the hydroxyl-ion concentration. The relationship between the hydroxyl ion-dependent and -independent rate constants is given. Given the reliability boundaries, it appears from the transformed literature data that the hydroxyl ion-independent rate constants of the forward and reverse reaction are about the same. The validity of the model at higher temperatures (67–104°) has been confirmed. From an Arrhenius plot, it has been deduced that the apparent activation-energy, related to the hydroxyl ion-independent rate constants, of the forward and reverse reaction is ≈, 121 kJ. mol −1.