Origin of 5‐Hydroxymethylfurfural Stability in Water/Dimethyl Sulfoxide Mixtures

Abstract

In the present work, we combined vibrational spectroscopy with electronic structure calculations to understand the solvation of HMF in DMSO, water, and DMSO/water mixtures and to provide insights into the observed hindrance of HMF rehydration and aldol condensation reactions if it is dissolved in DMSO/water mixtures. To achieve this goal, the attenuated total reflection FTIR spectra of a wide composition range of binary and ternary mixtures were measured, analyzed, and compared to the findings of ab initio DFT calculations. The effect of solvent on the HMF C-O and O-H vibrational modes reveals significant differences that are ascribed to different intermolecular interactions between HMF and DMSO or water. We also found that DMSO binds to HMF more strongly than water, and interactions with the HMF hydroxyl group are stronger than those with the HMF carbonyl group. We also showed the preferential solvation of HMF C-O groups by DMSO if HMF is dissolved in DMSO/water mixed solvent. Frontier molecular orbital theory was used to examine the influence of the solvent on side reactions. The results show that HMF solvation by DMSO increases its LUMO energy, which reduces its susceptibility to nucleophilic attack and minimizes undesirable hydration and humin-formation reactions. This result, together with the preferential solvation of HMF by DMSO, provide an explanation for the enhanced HMF stability in DMSO/water mixtures observed experimentally.

New Frontiers in the Catalytic Synthesis of Levulinic Acid: From Sugars to Raw and Waste Biomass as Starting Feedstock

“…Solvents also affect the selectivity of the reaction. DMSO is particularly selective towards 5-HMF because it suppresses the hydrolysis of 5-HMF to LA and formic acid and the humins formation [2,62], due to the strong interaction between the C=O group in 5-HMF and DMSO, which limits hydration and intermolecular condensation reactions [90]. However, there are other issues that must be considered during the choice of the solvent, such as the feasibility of its separation and recycling, its cost and its environmental effects.…”

Novel Ordered Mesoporous Carbon Based Sulfonic Acid as an Efficient Catalyst in the Selective Dehydration of Fructose into 5-HMF: the Role of Solvent and Surface Chemistry

“…13 In the current research, it is known to a great extent 3 that the distribution of products and in particular the selectivity toward HMF formation is highly dependent on the type (physicochemical properties) of the catalyst, reaction solvent, and temperature and development of new selective and effective protocols for this process has attracted broad research activity. [14][15][16][17] The first important issue in developing an economically and environmentally benign process for HMF formation is a green solvent in terms of easy separation, purity of the final product and low E factor [E-factor=total waste (kg)/product (kg)]. 2,18 Although from the standpoint of advance green and sustainable chemistry using water as a reaction solvent is a long-standing goal and thus often preferable, the difficulty in separating and purifying highly water soluble HMF, the higher possibility of rehydrating HMF in water, and the deactivation of the acid catalysts are important issues that need to be respected.…”

Solvation dynamics and energetics of intramolecular hydride transfer reactions in biomass conversion

“…Though water is the most preferred solvent, experimental studies have shown that the addition of a co-solvent to water or replacing water with an alternate solvent can significantly alter conversions and selectivities in these reactions. [16][17][18][19] (ii) On the other hand, solvent can also directly participate in the reaction. (i) A solvent can either preferentially solvate an ''active'' functional group of a biomass molecule or its derivative and protect it from taking part in the reaction, thus precluding a particular reaction pathway.…”