Table 3.

Assignment of Fourier transform infrared spectroscopy (FT-IR)spectra of the initial sample, solid residue, and DES-Lignin.

Wavenumbers (cm−1)	Assignment (Bond)	DES-Lignin	Solid Residue	Initial Sample
3410	O–H stretching vibration	3410	3410	3410
2924	C–H stretching vibration in methyl, methylene	2924	2924	2924
1710	C=O stretching vibration	1710	1710	1710
1600, 1510	Aromatic ring skeleton vibration	1600, 1510	-	1600, 1510
1460	C–H deformation vibration in –CH2–	1460	1460	1460
1426	C–H bending vibration in –CH2– of cellulose	-	1426	1426
1373	C–H bending vibration of aliphatic compounds	-	1373	1373
1325, 1220	C–O stretching vibration of syringyl units	1325, 1220	1325	1325, 1220
1270	C–O stretching vibration of guaiacyl units	1270	-	1270
1164	C–O–C symmetrical stretching vibration in carbohydrate	-	1164	1164
1120/835	C–H stretching vibration of syringyl units	1120/835	-	1120/835
1056	C=O stretching vibration in carbohydrate	-	1056	1056
1035	C–H bending vibration of guaiacyl units	1035	1035	1035