Review Article
Structural Characterization of Lignin and Its Degradation Products with Spectroscopic Methods
Table 4
Assignments of signals in
13C NMR spectrum to functional groups in lignin [
31,
38,
49,
71].
| Chemical shift/ppm | Assignments |
| 167–178 | Unconjugated -COOH | 162–168 | Conjugated -COOH | 140–155 | C3, C4 aromatic ether or hydroxyl | 127–140 | C1, aromatic C-C | 123–127 | C5, aromatic C-C | 117–123 | C6, aromatic C-H | 114–117 | C5, aromatic C-H | 106–114 | C2, aromatic C-H | 78–90 | Aliphatic Cβ-O | 67–78 | Aliphatic Cα-O | 54–57.5 | Methoxyl |
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