Table 1 FTIR absorption bands and assignments for kraft and soda lignins

3450–3400

O–H stretching (phenolic OH and aliphatic OH)`

2960–2925

C–H stretching (CH3 and CH₂ groups)

2855–2840

C–H stretching (OCH₃)

1715–1705

C=O stretching (unconjugated ketone, carbonyl and ester groups)

~ 1600

C–C stretching (aromatic skeleton)

1513

C–C stretching (aromatic skeleton)

1460

C–H deformation (asymmetric in –CH₃ and –CH₂)

1425

C–C stretching (aromatic skeleton) with C-H in-plane deformation

1270

C–O stretching vibration of secondary alcohol

~ 1220

C–O(H) + C–O (Ar) (phenolic OH and ether in syringyl and guaiacyl)

1115

Ar–CH in plane deformation (syringyl)

~ 1030

C–O(H) + C–O(C) (first order aliphatic Oh and ether

815–795

C–H out of plane (aromatic ring)