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Table 3 Assignment of signals in 13 C-NMR spectra of lignin

From: Differences in the adsorption of enzymes onto lignins from diverse types of lignocellulosic biomass and the underlying mechanism

ppm Assignments
172.6 C = O
166.3 -COO- in FA and CA esters
161.6 C-4 in FA and CA esters
159.9 C-4 in H
152.1 C-3/C-5 in S etherified, C-3/C′-3 in 5-5′ etherified
147.2 C-3/C-5 in S, C-4/C-3 in G
145.2 C-α in FA and CA esters, C-4 in G not etherified
130.0 C-2/C-6 in FA and CA ethers
124.7 C-α in coniferyl alcohol
115.8 C-3/C-5 in FA and CA esters, C-3/C-5 in H, C-5 in G
113.7 C-2 in G
103.6 C-2/C-6 in S
83.0 C-β in β-O-4, C-α in β-5 and β-β
72.3 C-α in β-O-4
66.2 C-γ in β-5
62.8 C-5 in xyl internal unit
60.1 C-γ in β-O-4
55.7 -OCH3
28.9 -CH2-(C5-CH2-C5)
21.0 -CH3 in acetyl group
15.2 γ-methyl in n-propyl side chain
  1. CA, p-coumaric acid; FA, ferulic acid; G, guaiacyl; H, hydroxyphenyl; NMR, nuclear magnetic resonance; S, syringyl.