Dehydration of Glucose to 5-(Hydroxymethyl)furfural and Anhydroglucose: Thermodynamic Insights

The G4 ab initio method was used in combination with the COSMO-SAC solvation model to predict the reaction free energies (ΔG) of glucose dehydration reactions in mixtures of water and dimethyl sulfoxide (DMSO). Experiments were also conducted to estimate the ΔG values for the dehydration of glucose to anhydroglucofuranose and levoglucosan. The predicted ΔG values were found to be in quantitative agreement with the experimental values. The calculations show that hexose dehydration to 5-(hydroxymethyl)­furfural (HMF) is an irreversible reaction, whereas glucose dehydration to anhydroglucose could be reversible depending upon the reaction conditions and choice of solvent. The calculations demonstrate the effect of a small amount of water in DMSO; this water can even be produced while dehydrating a highly concentrated solution of glucose and can affect glucose dehydration.