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Table 5 Main assignments of lignin, polysaccharide and protein Fourier transform infrared bands.a

From: Advanced biorefinery in lower termite-effect of combined pretreatment during the chewing process

 

Wavenumbers (cm-1)

Assignments

Lignin

 

1

1714 to 1725

Stretching of C = O unconjugated to aromatic rings (oxidized side-chains)

3

1655

Stretching of C = O conjugated to aromatic rings

4

1594 to 1609

Aromatic ring vibrations and C = O stretching

6

1504 to 1515

Aromatic ring vibrations

7

1462 to 1464

Asymmetric C-H bending (in CH3 and -CH2-)

8

1421 to 1424

Aromatic ring vibrations

10

1365

Symmetric deformation of C-H in methyl groups

11

1360

Phenolic hydroxyl vibrations

12

1270 (shoulder)

Vibrations of guaiacyl rings and stretching vibrations of C-O bonds

13

1216 to 1225

C-C, C-O and C = O stretching (G condensed > G etherified)

14

1160

Deformation vibrations of C-H bonds on benzene rings

16

1090 to 1075

Deformation vibrations of C-O bonds in secondary alcohols and aliphatic ethers

17

1030 to 1033

Deformation vibrations of C-H bonds in aromatic rings

Polysaccharide

 

9

1370

Symmetric bending of aliphatic C-H

15

1030 to 1170

C-O stretching in alcohols

18

890

β-Glycosidic linkages in pyranose units

Protein

 

2

1655 to 1658

C = O stretching in amides (I)

5

1516

C = O stretching in amides (II)

  1. aReferred to references 32 to 34.