Effect of Acidity of Ionic Liquids on Hydrogen Bonding Interaction between Ionic Liquids and Lignin Monomers

Abstract

In this text, a fundamental analysis for the interaction of lignin derived aromatic monomers in the presence of ionic liquids (ILs) at room temperature has been carried out by using NMR in deuterated DMSO solvent. The study was performed to examine the effect of both Brønsted acidic and non-acidic protons of ILs on lignin derived aromatic monomers. The aromatic monomers (i. e. vanillin and 4-hydroxy, 3-methoxyacetophenone) have assorted functionalities such as -CHO, -C(O)C, -OCH3 and OH. Additionally, this study was also accomplished with aromatic monomer (i. e. cumene) that does not contain any functionality, as above mentioned monomers. Alteration of the ILs (neutral and Brønsted acidic ILs) and aromatic monomers have shown a significant effect on interaction (inter and intra; weak and strong) of acidic proton under neutral and acidic medium. These were also confirmed by the reliable NMR techniques. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim