Table 2.
Main bands in the ATR-FTIR spectra of Hibiscus syriacus flowers and leaves and their assignments. Peak positions are expressed in cm−1.
| Part of the Plant | Assignment | |
|---|---|---|
| Flower | Leaves | |
| 3289 | 3335 | Bonded O-H stretching (cellulose) |
| 2919 | 2917 | –CH2 asymmetric stretching of alkyls (cutine, wax, pectin, fatty acids, and fatty alcohols) |
| 2850 | 2849 | –CH2 symmetric stretching (cutine and wax, fatty acids, and fatty alcohols) CH2–(C6)—bending (cellulose) |
| 1734 | 1734 | C=O stretching of alkyl ester; and C=O lactone |
| 1634 | C=C in coumarin derivatives; amide I/C=O stretch (hemicellulose, bonded ketones, quinones…). | |
| 1607 | Aromatic C–C and C=C skeletal stretching; COO—antisymmetric stretching (polygalacturonic and pectin ester); and C=N | |
| 1544 | Amide II/Aromatic skeletal. Typical of carotenoids. | |
| 1441 | 1443 1417 |
C=C stretching, aromatics H2O vapor; O–CH3 stretching; and C–H bending of CH2 or CH3 |
| 1373 1317 |
1369 1316 |
|
| C–H (cellulose) | ||
| 1242 | 1240 | Amide III/C–C–O asymmetric stretching acetylated glucomannan; C–O stretching of aryl ether; and C–O and OH of COOH groups |
| 1147 | 1147 | C–O–C in bridge asymmetric (cellulose); C–C in plane (β-carotene) |
| 1100 | 1103 | C–O–C stretching in the pyranose ring skeletal (cellulose) |
| 1033 | 1050 | C–H bending vibrations in of planes. |
| 1019 | C–H bending (typical of carotenes); polygalacturonic acid (a variety of pectin in plant cuticles), and pectins. Typical of cyclopropenoid grouping | |
| 719 | 720 | CH2 rocking |