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Table 2 List of the main infrared bands (cm−1) of collagen tannins [25,26,27]

From: Model study of the leather degradation by oxidation and hydrolysis

Absorption maximum (cm−1) Assignment
Collagen
~ 3310 Amide A: vN–H
~ 3080 Amide B: vN–H
~ 2960 vC–H
~ 1630 Amide I: vC=O
~ 1545 Amide II: vC–N, δN–H
~ 1450 δCH2 of proline
~ 1400 δC–O–H, δNH2
~ 1340 vCH2 δC–H
~ 1240 Amide III: vC–N, δN–H
~ 1080 and 1030 vC–O, vC–O–C
Common for all tannins
~ 1610 vC=C aromatic ring
~ 1512 vC=C aromatic ring
~ 1450 vC=C aromatic ring
~ 1210 vC–O, δC–OH
~ 1035 βC–H deformation, vC–O
Hydrolysable tannins
~ 1705–1730 vC=O
~ 1320 vC–O and O–H deformation
~ 1085 vC–O–C
~ 871 γOH, γC–H
~ 760 γ aromatic δC–H
Condensed tannins
~ 1285 vC–O pyran ring
~ 1160 vC–O–C
~ 1113 vC–O–C
~ 843 C–H deformation
  1. v, stretching; δ, bending; β, in plane; γ, out-of plane