The Studies On The Interactions Between Ionic Liquids And 5-Hydroxymethylfurfural And Its Derivatives By IR And NMR Spectroscopies

5-Hydroxymethylfurfural?5-HMF?derived from biomass has been considered as a green platform compound,which has a wide range of applications in manufacturing fine chemicals and biofuels.Ionic liquids?IL_s?have shown superior performance in the conversation of biomass to 5-HMF as reaction medium and/or catalyst.Nevertheless,the separation of 5-HMF from IL_s is very difficult and becomes a technical bottleneck for IL_s application in the preparation of 5-HMF.To resolve this problem,the understanding about the interactions between IL_s and 5-HMF is essential.Therefore,as a part of the project supported by the National Natural Science Foundation of China?No.21573060?,the effects of anionic structure snd ring type of the cation of the IL_s on the hydrogen bonding interactions between ionic liquids and 5-HMF or its derivatives have been investigated in the present work.The interaction modes and the interaction sites between IL_s and 5-HMF or its derivatives have been analyzed.The main contents are as follows.1.The hydrogen bonding interactions between IL_s and 5-HMF were determined as a function of mole fraction of 5-HMF in 5-HMF-ionic liquids binary mixtures?including [Bmim][CH₃COO],[Bmim][CF₃COO],[Bmim][C₂H₅COO],[Bmim][HSO₄],[Bmim][NO₃],[Bmim][CH₃OSO₃],[Bmim][OTf],[Bmim][N?CN?₂],[Bmim][BF₄]?by ATR-FTIR and ¹H NMR at 293 K.The influence of anion species of ionic liquids on the hydrogen bonding interactions between IL_s and 5-HMF has been investigated.It was found that the formation capability of hydrogen bonding of anion with 5-HMF was decreased in the sequence: [CH₃COO]-,[C₂H₅COO]->[HSO₄]->[CF₃COO]->[NO₃]->[N?CN?₂]->[CH₃OSO₃]->[OTf]->[BF₄]-.2.ATR-FTIR and ¹H NMR spectra have been used to investigate the hydrogen bonding interactions in the binary mixtures of [BuPy][NO₃]/5-HMF,[Py₁₄][NO₃]/5-HMF,[PP₁₄][NO₃]/5-HMF and [?Bu?₃NH][NO₃]/5-HMF at 293 K.The influence of cationic structures of the ionic liquids on the hydrogen bonding interactions between IL_s and 5-HMF has been analyzed.The results have shown that the formation capability of hydrogen bonding of cation with 5-HMF was increased in the sequence: [Py₁₄]+<[PP₁₄]+<[BuPy]+<[Bmim]+<[?Bu?₃NH]+.3.The hydrogen bonding interactions between IL_s and 5-HMF derivatives?2,5-DMF,2,5-DHMF and 5-MF?were determined as a function of mole fraction of 5-HMF derivatives in nine kinds of imidazolium-based ionic liquids above mentioned and in four kinds of IL_s with different cations through ATR-FTIR and ¹H NMR spectroscopies at 293 K.The influences of anion species and cationic structures of ionic liquids on the hydrogen bonding interactions between IL_s and 5-HMF derivatives have been investigated.It was found that no hydrogen bonding interaction was observed in the IL_s-2,5-DMF binary mixtures.However,for imidazolium-based IL_s/5-MF systems,the primary hydrogen bonding interaction is ascribed to H atom of C₂-H and C_4,5-H bonds in imidazole ring and O atom of C=O.In imidazolium-based IL_s /2,5-DHMF systems,the hydrogen bonding interaction between the anion of IL_s and H atom of O-H of 2,5-DHMF is major interaction,but this hydrogen bonding interaction is weaker than that formed by 2,5-DHMF itself.The formation capability of hydrogen bonding of cations with 5-MF was increased in the sequence: [Py₁₄]⁺<[PP₁₄]⁺<[Bu Py]⁺<[Bmim]⁺<[?Bu?₃NH]⁺.