NMR studies of lignin and lignin-derived products: recent advances and perspectives

Present review focuses on the most recent results (the interim of 2019-2023) in a liquid-phase NMR of lignin and the lignin-derived products and related chemicals. Collected and discussed are the recent applications of 1H, 13C, and 31P NMR spectroscopy together with NMR of less popular nuclei to the structural studies and practical recommendations in this field. Owing to the complexity of lignin and the products of its transformation, their NMR spectra consist of a number of overlapping signals belonging to different structural types. In this regard, comprehensive studies of lignin by means of NMR over the past several decades revealed characteristic functional groups of lignin and lignin-related products together with spectral regions in which they resonate. Quantitative NMR spectra of 1H and 13C together with less popular nuclei like 31P are used to characterize different structural units of lignin (such as guacil, syringil, and p-hydroxyphenyl) providing aromatic and saturated carbons spread over many structural moieties.

The bibliography includes 54 references.