Solution-state NMR Analysis of Lignocellulosics in Nonderivatizing Solvents

This chapter gives a brief overview of various new methods employed in solution-state 1D and 2D NMR spectroscopy of lignocellulose. It focuses on three substrates in particular: whole lignocellulosic biomass, unmodified high molecular weight celluloses, and modified cellulose nanocrystals (CNCs). Early approaches for the characterization of whole lignocelluosic biomass by 2D solution state NMR were to first derivatize the lignocellulosic substrates for easier dissolution into chloroform and other common NMR solvents. Ionic liquid-based electrolytes are also promising solvents for the solution state analysis of nanocelluloses in both a pure and chemically modified form. One approach to the solution-state NMR analysis of lignocellulose materials is that mainly developed by Argyropoulos, based on P NMR. The general idea involves converting the hydroxyl groups of lignin and cellulose to phosphite esters (phosphitylation), which are well resolved in the solution state P NMR spectral range.