Solid-State ¹³C CP/MAS NMR for Alkyl-O-Aryl Bond Determination in Lignin Preparations

Abstract

Several lignin preparations (Freudenberg lignin, Björkman lignin and Pepper lignin), technical lignins (soda, soda-AQ, Kraft, Kraft-AQ and hydrolysis), dimeric lignin model compounds and different polysaccharides (galactoglucomannan, arabinogalactan, xylan and arabinan) were analysed by solid-state 13 C CP/MAS NMR. Signals' assignment in solid-state NMR lignin spectra was performed on the basis ofthe conducted studies and literature data.It wasestablished that there exists strong linear correlation (r = 0.985) between Alkyl-O-Aryl inter-unit bonds' content in lignin and integral signals intensity in NMR spectra in the range of chemical shifts of 96-68 ppm. The integral signals intensity was measured in respect to the reference integral signals in the range of chemicalshifts of 162-102 ppm, which is typical for aromatic carbon atoms.To eliminate the effect from the carbohydrates contained in lignin, the correction factor for calculation was determined, i.e. 0.67% of the area of integration for each percent of carbohydrates. It was shown that the solid-state 13 C CP/MAS NMR method allowed to determine Alkyl-O-Aryl bonds' content in both soluble and insoluble lignin preparations, and also to quantify methoxyl groups' content in soluble preparations.

Synthesis and Characterization of Polyrotaxanes Comprising γ‐CDs and Distal Azide‐Terminated PHEMA Using Propargylamine Monosubstituted β‐CDs as End Stoppers

“…[ 9,13,15 ] Interestingly, a ratio of the integration area of quaternary carbon atoms of the main chain shielded by γ‐CDs to the unshielded ones was estimated around 0.30 in PR‐46‐23γ‐CD‐4. [ 24 ] This value is well in accordance with the coverage ratio of γ‐CDs determined by 1 H NMR analysis as mentioned above.…”

Lignin Metabolism by Selected Fungi and Microbial Consortia for Plant Stimulation: Implications for Biologically Active Humus Genesis

“…Major peaks shown in the control are very similar to those of starch, which could be ascribed to components of the potato broth ( 29 ). However, the small peaks near 174 and 147 ppm that may correspond to carboxylic and phenol groups, respectively ( 30 ), suggest that some lignin-derived components are present in the supernatant of the control, which is consistent with the result of the SEC and mass spectrometry results ( Fig. 2 and 3 ).…”

The Synergistic Action of Electro-Fenton and White-Rot Fungi in the Degradation of Lignin

“…Moreover, decreasing signal intensities for -OCH 3 were observed at 56.5 ppm, implying that the degradation of lignin by the three studied white-rot fungi could cause demethoxylation and demethylation. The bands of β-5, β-β, and β-O-4 (62-75 ppm) (Evstigneyev et al, 2018) became weak and narrow in Figures 4B,C, implying that L. edodes had a more significant influence on lignin during the degradation than the other two fungi (Sun et al, 2016).…”