What absorbs at 1559 cm⁻¹ in an FTIR spectrum?
A band near 1559 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
Quick answer
A band near 1559 cm⁻¹ is usually interpreted by checking which functional groups repeatedly co-occur there in the literature, then confirming at least one or two additional peaks in the same sample. This page ranks those assignments by accumulated evidence rather than by a single fixed textbook rule.
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Amide | 5 | 5 | 1.0 |
| Alkene (C=C) | 4 | 4 | 1.0 |
| C c single bond | 3 | 3 | 1.0 |
| Aromatic ring | 3 | 2 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 0.8 |
| Alkyl C-H | 1 | 0 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| chitosan | 1559, 1650, 1655 | Amide | 2 |
| saliva | 1559, 1648, 1664 | Amide | 1 |
| blood | 1559, 2965, 1117 | Amide | 1 |
| CMC | 1559, 1423, 1196 | Amide | 1 |
Materials are shown only when the same literature pool supports this band and at least one additional characteristic peak.
Spectrum logic
This band becomes meaningful only when read with its neighboring peaks. In practice, analysts first look at the assignments above, then check whether the same sample also shows other peaks expected for the same structural motif. A lone band near 1559 cm⁻¹ is usually not enough for material identification by itself.
Real-world usage
This type of query is common in polymer identification, unknown plastic screening, QC troubleshooting, recycled-material verification, and literature-backed peak assignment review.
Common mistakes
- Treating one isolated band as proof of a material without checking at least one or two supporting peaks.
- Ignoring overlap: multiple functional groups can contribute near the same wavenumber.
- Skipping validation when additives, blends, oxidation, or contamination may distort the spectrum.
Verification advice
When ambiguity remains, validate the hypothesis with DSC, GC-MS, or TGA, especially for blends, degraded samples, and filled polymers.
Literature behind these assignments
-
Amide confidence 1.0
“cm)1 cm)1) cm)1 cm)1 (CH scissors), 1395.3 (symmetric region bands (1558.8, 1540.3, and 1507 and stretch), 1457.1 sharp 1500 2 cm)1 cm)1 cm)1 3), 1244.9 (amide III), 1162.9 (C-O, lipid ester), and peak differentiate Catalina dressing (G) (a”
Elkins - 2011 - Rapid Presumptive Fingerprinting of Body Fluids DOI: 10.1111/j.1556-4029.2011.01870.x -
Amide confidence 1.0
“intensity of ethylenic bond frequency at 1562 cm-1 The result from this study indicated that the amide II band at 1559 that may contribute to the amine-NH group was specific for CLCG.”
Synthesis, Characterization, and Antibacterial Activity of Cross-Linked Chitosan-Glutaraldehyde DOI: 10.3390/md11051534 -
C c single bond confidence 1.0
“The electrochemical (Figure 1B) show the peak at wavenumber 1559 corC=C impedance spectroscopy (EIS) was also carried out to find responding to C-C and skeletal (ring) vibrations.”
Thakur 和 Lokhande - 2017 - Effect of dip time on the electrochemical behavior DOI: 10.1515/epoly-2016-0160 -
Nitrogen heterocycle confidence 1.0
“The characteristic peak at 1559 in for supercapacitors because of its good electrical conductivthe FTIR spectrum is due to pyrrole ring vibrations confirms ity, water soluble monomer, easy production, low oxidation the formation of PPy.”
C10H8N2-PPy hybrid flexible electrodes: SILAR synthesis and electrochemical study DOI: 10.1007/s10854-017-8074-0 -
Chitosan confidence 1.0
“The characteristic cm-1 chitosan band from 1559 shifts in the spectrum of the P2 sample and several peaks of lower intensities are observed, which may indicate some intermolecular interactions of cm-1 amine groups [55].”
Hydrogel Films Based on Chitosan and Oxidized Carboxymethylcellulose Optimized for the Controlled Release of Curcumin with Applications in Treating Dermatological Conditions DOI: 10.3390/molecules26082185 -
Aromatic ring confidence 1.0
“matched the C=C stretching in aromatic molecules of phesize and polydispersity index (PDI) were determined using cm-1 nyl and amide compounds, with a weak peak at 1559 dynamic light scattering (DLS) on a Zetasizer Nano ZS from owing to arom”
Enhancement of cytotoxic and antioxidant activities of Digenea simplex chloroform extract using the nanosuspension technique DOI: 10.1007/s00449-022-02833-6 -
Amide confidence 1.0
“The peak at 1559 can be attributed to amide I vibrations of cm-1 proteins and was shifted to 1559 in the ZnO NPs due to linking of the proteins with the surface of the NPs [39].”
Improved Photocatalytic and Antioxidant Activity of Olive Fruit Extract-Mediated ZnO Nanoparticles DOI: 10.3390/antiox12061201 -
C c single bond confidence 1.0
“The sharp peaks for nitro compounds (N-O symmetric stretch) N-O asymmetric stretch Nitro compounds 1504.7608 1507.6201 1505.7042 1501.9015 - C-C stretch (in-ring) Aromatics 1559.0875”
Hydrolysis, Microstructural Profiling and Utilization of Cyamopsis tetragonoloba in Yoghurt DOI: 10.3390/fermentation9010045
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