Modeling interactions between a β‐O‐4 type lignin model compound and 1‐allyl‐3‐methylimidazolium chloride ionic liquid

Abstract

Aiming at understanding the molecular mechanism of the lignin dissolution in imidazolium-based ionic liquids (ILs), this work presents a combined quantum chemistry (QC) calculation and molecular dynamics (MD) simulation study on the interaction of the lignin model compound, veratrylglycerol-β-guaiacyl ether (VG) with 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The monomer of VG is shown to feature a strong intramolecular hydrogen bond, and its dimer is indicated to present important π-π stacking and intermolecular hydrogen bonding interactions. The interactions of both the cation and anion of [Amim]Cl with VG are shown to be stronger than that between the two monomers, indicating that [Amim]Cl is capable of dissolving lignin. While Cl anion forms a hydrogen-bonded complex with VG, the imidazolium cation interacts with VG via both the π-π stacking and intermolecular hydrogen bonding. The calculated interaction energies between VG and the IL or its components (the cation, anion, and ion pair) indicate the anion plays a more important role than the cation for the dissolution of lignin in the IL. Theoretical results provide help for understanding the molecular mechanism of lignin dissolution in imidazolium-based IL. The theoretical calculations on the interaction between the lignin model compound and [Amim]Cl ionic liquid indicate that the anion of [Amim]Cl plays a more important role for lignin dissolution although the cation also makes a substantial contribution.

Combining Cost‐Efficient Cellulose and Short‐Chain Carboxylic Acid Production: The Polyoxometalate (POM)‐Ionosolv Concept

“…Two approaches for ionic liquid deconstruction have been investigated. Initially, there was a focus on cellulose dissolving ionic liquids, most prominently 1‐ethyl‐3‐methylimidazolium acetate, [EMIM][OAc] . More recently, a subclass of ionic liquids was discovered that has a high activity for separating cellulose and lignin but do not dissolve cellulose .…”

Mechanism and Improved Dissolution of Glycyrrhetinic Acid Solid Dispersion by Alkalizers

“…Moreover, the wettability of the drug increased from the H-bond between the alkalizers and Kollidon ® VA64. These results show that the intermolecular interaction in SD systems is important for improving the solubility and dissolution of GA [68]. The in vitro dissolution test was performed for API (pure), BSD, LA-TSD, and MG-TSD in HCl (pH 1.2), pH 4.5, pH 6.8, and pH 7.4 buffers.…”

“…This stronger intermolecular interaction destroys the stable crystal structure of GA, which is the inherent reason for the increased solubility of GA. Similarly, the binding energy of the GA-MG ion pair is lower than that of the GA-LA ion pair, and the hydrogen bond of the MG-VA extrudate is stronger than that of LA extrudate [68]. This explains why the dissolution of MG-TSD is higher than that of LA-TSD.…”

“…In most cases, shortening the bond length can strengthen the bond [67]. The intermolecular H-bond is thought to be responsible for the poor solubility of drugs [68]. According to the results of molecular docking, shorter bond distance and smaller binding energy mean that there is a strong hydrogen bond between GA molecules, which may be a potential factor to limit the dissolution of GA. From an energy point of view, the binding energy of GA-alkalizer ion complexes is much less than that of GA molecules, which indicates the interaction between alkalizers and GA is stronger than that between GA molecules.…”

Towards understanding of delignification of grassy and woody biomass in cholinium-based ionic liquids

“…(2017) 7 and Ji et al (2012) 28 performed QC calculations on ILlignin systems and deduced that stronger H-bonding interactions between lignin and imidazolium-based IL mixtures drive lignin dissolution. Further, Zhu et al (2017) studied the dissolution behavior of lignin (veratrylglycerol-β-guaiacyl ether) in 1-allyl-3-methylimidazolium chloride ([Amim]Cl) by both QC and molecular dynamics (MD) simulations 29 and showed that chloride anions form strong hydrogen bonds with lignin, while the cation [Amim] + interacts with lignin via weaker π-π stacking and van der Waals interactions. In the literature, imidazolium-based cations are the most studied ILs for lignin dissolution by both computational and experimental.…”