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 (Δ G ) of glucose dehydration reactions in mixtures of water and dimethyl sulfoxide (DMSO). Experiments were also conducted to estimate the Δ G values for the dehydration of glucose to anhydroglucofuranose and levoglucosan. The predicted Δ G 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.