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Table 2 Main absorption peaks (FTIR spectra) of extracted ambers from plant fossils from the Crato Formation

From: Revealing the diversity of amber source plants from the Early Cretaceous Crato Formation, Brazil

Functional group Band, wavelength [μm] Band, wavenumber [cm−1] Intensity Assignment
O-H 2.95 3390 medium Stretching of O-H bonds
-CH2 -CH3 3.40 2940 strong Stretching of C-H bonds
-CH2 -CH3 6.90 1450 medium Scissoring and bending of C-H bonds
-CH2 -CH3 7.25 1380 medium Bending of C-H bonds
-CH2 -CH3 11.39 878 weak C=CH2: out-of-plane bending of H in terminal methylene group
-C=O 5.80 1724 medium Stretching of C=O double bonds
-C-O- 8.15, 8.60 1227, 1163 medium/weak Absorption of C-O single bonds
-C-O- 9.60, 9.85 1042, 1015 weak Absorption of C-O single bonds (alcohol)
C=C 6.05 1654 weak C=C stretching
-C-H aromatic 12.10, 14.10 826, 709 weak Out-of-plane bending of aromatic C-H