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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

170.9

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.