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Table 1 Most important absorption bands of the mid-infrared spectra of winter wheat straw

From: Rapid estimation of sugar release from winter wheat straw during bioethanol production using FTIR-photoacoustic spectroscopy

Peak no. in Fig. 1 Wavenumber (cm−1) Vibration Assignment
1 3380 O-H stretching of bonded and non-bonded hydroxyl groups Included water i; lignin e
2 2920 Asymmetric C-H stretching Aliphatic methylene b, e, g, k
3 2850 Symmetric C-H stretching
4 1735 Un-conjugated C = O stretching Xylan (hemicellulose) a–c, e, f, i, j
5 1650 O-H bending Absorbed water a, i
Conjugated C-O stretching Carboxylates a, i
6 1600 Aromatic ring vibration Lignin a, c, g, j
C = C skeletal vibration
C = O stretching
7 1510 Aromatic ring vibration Lignin a, c, d, g, j
8 1460 C-H deformation Lignin a, c; xylan j
9 1429 C-H deformation Lignin a, g, I, j
CH2 scissoring Crystalline cellulose b
10 1370 Symmetric C-H deformation Crystalline cellulose k; hemicellulose a, i
11 1320 C-H vibration Cellulose, hemicellulose, lignin a
CH2 wagging Cellulose, hemicellulose c
12 1240 C-O stretching Xylan (hemicellulose) a, i
13 1160 C-O-C asymmetric stretching Crystalline cellulose b, j, k; hemicellulose a, h
14 1111 In-plane ring stretching Crystalline cellulose b, h, j
15 1053 C-O stretching Crystalline cellulose; hemicellulose a, b, h, k
16 898 C-O-C stretching Amorphous cellulose k
  1. aPandey and Pitman [28]
  2. bGwon et al. [36]
  3. cSills, Gossett [16]
  4. dGollapalli et al. [22]
  5. eXu et al. [15]
  6. fKristensen et al. [18]
  7. gMerk et al. [42]
  8. hCorgie et al. [19]
  9. iCui et al. [43]
  10. jChen et al. [44]
  11. kCiolacu et al. [27]