Review Article
Structural Characterization of Lignin and Its Degradation Products with Spectroscopic Methods
Table 2
Assignments of signals in FTIR spectrum to functional groups in lignin [
25,
29,
38].
| | Wavenumbers/cm−1 | Assignments | Functional groups and structures in lignin |
| | 3400–3600 | v (O-H) | Free -OH | | 3100–3400 | v (O-H) | Associated -OH | | 2820–2960 | v (C-H) | -CH2, -CH3 | | 2920 | v (C-H) | Carboxylic -OH | | 2650–2890 | v (C-H) | Methyl group in methoxyl | | 1771 | v (C = O) | Aromatic | | 1700–1750 | v (C = O) | Unconjugated ketones, carbonyls, and ester groups | | 1722 | v (C = O) | Aliphatic | | 1650–1680 | v (C = O) | Conjugated p-substituent carbonyl and carboxyl | | 1500–1600, 1420–1430 | v (aromatic skeletal) | Benzene ring | | 1450–1470, 1360–1370 | v (C-H) | -CH2, -CH3 | | 1325–1330, 1230–1235 | v (C-O) | Syringyl ring | | 1270–1275 | v (C-O) | Guaiacyl ring | | 1215 | v (C-O) | Ether | | 1140–1145 | v (C-H) | Guaiacyl | | 1130 | v (C-H) | Syringyl | | 1085–1090 | v (C-O) | Secondary alcohol and aliphatic ether | | 1025–1035 | v (C-O, C-H) | Aromatic ring and primary alcohol | | 750–860 | v (C-H) | Aromatic ring |
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