Glucose transformation to 5-hydroxymethylfurfural in acidic ionic liquid: A quantum mechanical study

Area of Science:

• Computational Chemistry
• Chemical Reaction Engineering
• Green Chemistry

Background:

• Biomass conversion is crucial for sustainable chemical production.
• Understanding reaction mechanisms in different solvents is key to optimizing processes.
• 5-hydroxymethylfurfural (HMF) is a vital platform chemical derived from biomass.

Purpose of the Study:

• To investigate the isomerization of glucose to fructose and the subsequent transformation to HMF.
• To compare reaction mechanisms and energy barriers in ionic liquids (ILs) and water.
• To elucidate the role of solvent effects on these chemical transformations.

Main Methods:

• Utilized the Reference Interaction Site Model Self-Consistent Field Spatial Electron Density Distribution (RISM-SCF-SEDD) method.
• Coupled RISM-SCF-SEDD with ab initio electronic structure theory, specifically Coupled Cluster Single, Double, and Perturbative Triple excitation (CCSD(T)).
• Analyzed reaction pathways, activation free energies, and solvent effects through free energy decomposition and radial distribution functions.

Main Results:

• Glucose isomerization to fructose favors a cyclic mechanism in water (23.8 kcal mol⁻¹) and an open-chain mechanism in ILs (32.4 kcal mol⁻¹).
• Fructose transformation to HMF proceeds via a cyclic mechanism with activation barriers of 16.0 kcal mol⁻¹ in water and 21.5 kcal mol⁻¹ in ILs.
• RISM-SCF-SEDD effectively explained solvent effects in ILs on reaction energetics.

Conclusions:

• Solvent choice significantly influences the glucose-to-fructose isomerization pathway.
• The transformation of fructose to HMF is feasible in both aqueous and IL solutions.
• Computational insights provide a foundation for designing efficient HMF production processes.