Chemical composition of lignocellulosic biomass in the wood of Abies religiosa across an altitudinal gradient

Table 2 Assignment of functional groups and polymers to FTIR bands

Band number	Wavenumber (cm⁻¹)	Assigned band	References	Assigned polymer
1	3340	O–H stretching	[38, 39, 43–45]	C, H, L
2	2891	C–H stretching	[39, 43, 44]	C, H, L
3	1735	C=O stretching in non-conjugated ketones and free aldehydes	[39, 43, 44, 48]	H, L
4	1660	C=O stretchings conjugated in p-substituent aromatic ketones and unconjugated carbonyls	[39, 44, 47, 48]	L
5	1600	Aromatic ring vibration	[39, 43, 44, 48]	L
6	1508	C=C Stretching in aromatic structures	[39, 43, 44, 47, 48]	L
7	1451	C–H deformation, asymmetric bending vibration of –CH₃ and –CH₂ groups	[39, 43, 44, 46–48]	L
8	1422	CH₂ stretching, C–O–H in plane bending vibration	[39, 49]	C
9	1368	C–H bending	[39]	C, H
10	1316	C–H deformation vibration, C–O–H in plane bending vibration	[39, 44, 49]	C, H, L
11	1264	Aromatic rings vibration of Guaiacyl units	[43, 44]	L
12	1231	C–O stretching of Guaiacyl units	[39]	L
13	1156	C–O–C asymmetric stretching	[39, 44]	C, H
14	896	Glucose ring stretching, C1–H deformation, C–H Stretching out of plane of aromatic ring	[39, 47]	C
15	808	C–H out-of-plane bending	[36]	L

Represented polymers correspond to: Cellulose (C), Hemicellulose (H) and Lignin (L)