Table 2.

FTIR spectral peak assignments for various functional groups and linkages.

Bond assignments	Bond (cm−1)	% Transmittance
		RS	A	D
Out of plane C–H vibration in lignin	786	96.10	88.09	97.17
Deformation of C–H linkage in cellulose	896	96.54	89.29	96.89
Stretching of C–O in cellulose and hemicellulose	1049	92.16	76.48	93.66
C–O–C vibrations in cellulose and hemicellulose	1165	96.18	87.57	97.39
C–O stretching of the aryl group in lignin	1239	97.56	92.22	97.96
C–O stretching in guaiacyl aromatic methoxyl groups	1265	98.03	93.86	97.87
Typical of pure cellulose	1319	97.60	92.68	97.53
C–H vibration in cellulose	1325	97.89	93.05	97.47
Typical of pure cellulose	1372	97.90	92.62	97.11
Deformation of C–H linkage in cellulose and hemicellulose	1375	97.60	92.38	96.76
A symmetric CH2 bending vibration attributed to crystalline cellulose	1435–1421	98.29–97.37	92.52–91.50	97.71–96.13
C=O stretching of carbonyl related to hemicelluloses and lignin	1513	97.73	93.34	97.29
Aromatic skeletal vibrations	1601	97.62	92.78	98.43
H–O–H bending of adsorption	1648	97.29	92.85	98.37
Unconjugated C=O stretching in xylans	1741	98.97	97.76	98.82
Asymmetric stretching of CH2 group33	2916	98.44	94.49	96.92
O–H stretching of lignin	3301	98.10	93.83	95.71
Hydrogen-bonded O–H groups34	3318	98.23	93.92	95.85