What absorbs at 1620 cm⁻¹ in an FTIR spectrum?
A band near 1620 cm⁻¹ can point to several functional groups. Below are the most likely assignments, ranked by how much published evidence supports each — every one traceable to literature (DOI) and cross-validated against our 130,000+ reference spectra and knowledge graph.
Backed by 8 cited sources
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Water (H2O) | 8 | 6 | 0.95 |
| Hydroxyl (O-H) | 7 | 6 | 0.9 |
| Amide | 7 | 5 | 1.0 |
| Carbonyl (C=O) | 6 | 6 | 0.9 |
| Carboxyl (COOH) | 4 | 4 | 0.9 |
| C=n | 3 | 3 | 0.9 |
| Aromatic ring | 3 | 2 | 0.9 |
| C c single bond | 2 | 2 | 0.95 |
| Alkyl C-H | 2 | 2 | 0.9 |
| Alkene (C=C) | 2 | 2 | 0.9 |
| Protein beta sheet | 2 | 1 | 0.9 |
| Fluorine (C-F) | 1 | 1 | 1.0 |
| Phenolic | 1 | 1 | 0.9 |
| N h | 1 | 1 | 0.9 |
| Carbohydrate | 1 | 1 | 0.9 |
| Ester | 1 | 1 | 0.8 |
| C-O single bond | 1 | 1 | 0.7 |
| Methyl | 1 | 1 | 0.7 |
| Lewis acid site | 1 | 0 | 0.9 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Literature behind these assignments
-
Amide confidence 1.0
“explicit assignment”
Kristoffersen 等 - 2020 - Fourier-transform infrared spectroscopy for monito DOI: 10.1038/s41598-020-64583-3 -
C c single bond confidence 0.95
“Explicit assignment: C-C vibration”
Zheng 等 - 2012 - Preparation and capacitance performance of Ag-grap DOI: 10.1016/j.jpowsour.2011.11.026 -
C c single bond confidence 0.9
“Peak due to C-C bond between PMMA and CNT.”
Bressanin 等 - 2018 - Electrically conductive nanocomposites of PMMA and DOI: 10.1007/s11696-018-0443-5 -
Water (H2O) confidence 0.9
“Explicit assignment: HOH bending mode at 1610-1620 cm-1.”
Futamata 等 - 2005 - ATR-SEIR study of anions and water adsorbed on pla DOI: 10.1016/j.susc.2005.06.020 -
Carbonyl (C=O) confidence 0.9
“Described as 'C=O stretching vibration'.”
Gopinath 等 - 2023 - Mechanical, structural and optical properties of p DOI: 10.15251/JOR.2023.191.23 -
Carbohydrate confidence 0.9
“Text: 'cellulose I spectra ... two distinct peaks at 1620 and 1720'”
Lapuz 等 - 2022 - Production of Nanocellulose Film from Abaca Fibers DOI: 10.3390/cryst12050601 -
Carbonyl (C=O) confidence 0.9
“Assigned to C=O.”
Ogunsile 等 - 2020 - Green synthesis of silver nanoparticles from leaf DOI: 10.1088/1757-899X/805/1/012032 -
Hydroxyl (O-H) confidence 0.9
“Bending vibrational mode of hydroxyl group.”
Singh 等 - 2012 - Detection of Defects in ZnO Nanoparticles by Spect DOI: 10.1063/1.4736887
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