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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