A comprehensive reaction-path search for the oligomerization of 5-(hydroxymethyl)furfural (HMF) based on quantum chemical calculations was conducted to clarify the mechanism of humin formation in the oxidation of HMF to furan-2,5-dicarboxylic acid (FDCA), in which humin is a typical macromolecular byproduct. The present procedure repeatedly utilizes the multi-component artificial-force-induced reaction (MC-AFIR) method to investigate multistep oligomerization reactions. Although humin formation has been reported even in reagent-grade HMFs with 97-99% purity during their storage at low temperatures, no direct addition path of two HMFs with <185 kJ mol−1 barrier has been found, suggesting humin formation is caused by a reaction with impurities. Based on the reaction conditions, we considered the reactions of HMF + H2O, HMF + OH−, and HMF + O2 and identified three reaction paths with <65 kJ mol−1 barrier for the reaction of HMF + OH−. Further, the suppression of humin formation by the acetal protection of HMF is computationally confirmed.
CITATION STYLE
Tashiro, K., Kobayashi, M., Nakajima, K., & Taketsugu, T. (2023). Computational survey of humin formation from 5-(hydroxymethyl)furfural under basic conditions. RSC Advances, 13(24), 16293–16299. https://doi.org/10.1039/d3ra02870d
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