What absorbs at 1573 cm⁻¹ in an FTIR spectrum?
A band near 1573 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 1573 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 | 7 | 7 | 1.0 |
| N h | 5 | 5 | 1.0 |
| Carboxyl (COOH) | 4 | 4 | 1.0 |
| Alkyl C-H | 4 | 3 | 1.0 |
| Secondary amine | 3 | 3 | 1.0 |
| Ring structure | 3 | 3 | 1.0 |
| Aromatic ring | 3 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Alkene (C=C) | 2 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| Oxygen heterocycle | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Nitrile | 1 | 1 | 1.0 |
| Protein alpha helix | 1 | 0 | 1.0 |
| Protein beta sheet | 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 | 1573, 1650, 1655 | Alkyl C-H, Amide, N h | 1 |
| polyurethanes | 1573, 1740, 1728 | N h, Amide, Alkyl C-H | 1 |
| CA | 1573, 1045, 1650 | Amide, Alkyl C-H, Carboxyl (COOH) | 1 |
| ionic liquids | 1573, 938, 1040 | Alkyl C-H | 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 1573 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
-
Carboxyl (COOH) confidence 1.0
“However, for esterification, the results were calibration showed better results carboxylate band, ν(COO-), at 1573 cm-1 relative to a single baseline at 1820 cm-1 for FTIR using only one peak.”
Monitoring Enzymatic Hydroesterification of Low-Cost Feedstocks by Fourier Transform InfraRed Spectroscopy DOI: 10.3390/catal9060535 -
confidence 1.0
“The amine band has also shifted from 1573 in cm-1 cm-1 in CA50AT.”
Characterizations of chitosan-ammonium triflate (NH4CF3SO3) complexes by FTIR and impedance spectroscopy DOI: 10.1002/pssa.200521016 -
Ring structure confidence 1.0
“is richer in ways especially in the spectral range of We 1573 and 1585 These bands are assigned to ring in-plane”
Moumene 等 - 2014 - Vibrational spectroscopic study of ionic liquids DOI: 10.1016/j.molstruc.2014.02.034 -
Nitrile confidence 1.0
“The sharp band at 2370 denoted the C≡N stretching of nitrile groups while weak the bands at 1573 and 1414 corresponded to C-H and C-N stretching vibrations respectively [36].”
Pai 等 - 2019 - Photocatalytic zinc oxide nanoparticles synthesis DOI: 10.1016/j.ijleo.2019.03.101 -
Nitrogen heterocycle confidence 1.0
“This transit Imidazole ring stretching 1573 Li+ site provides an alternative pathway for the mobility of ions Imidazole 1168 H-C-C and”
Plasticizing effect of 1-allyl-3-methylimidazolium chloride in cellulose acetate based polymer electrolytes DOI: 10.1016/j.carbpol.2011.11.037 -
Amide confidence 1.0
“Similarly, a new peak due to strongly hydrogen bonded urea cm(cid:2)1 moves the amide II peak centered at 1573 groups starts appearing as a shoulder at 1634 cm(cid:2)1 cm(cid:2)1 and increases in intenafter 30 min and develops into an extre”
Time-dependent morphology development in segmented polyetherurea copolymers based on aromatic diisocyanates DOI: 10.1002/polb.21652 -
Amide confidence 1.0
“Finally, as for cm-1 1646 and 1573 cm-1 correspond to amide I and II, respectively, while a new shoulder detected at 1719 the CS-g-PAA derivative, the bands observed at 1646 and 1573 correspond to amide I and II,”
Microencapsulation of Fluticasone Propionate and Salmeterol Xinafoate in Modified Chitosan Microparticles for Release Optimization DOI: 10.3390/molecules25173888 -
Aromatic ring confidence 1.0
“An 1477cm-1, 1573cm-1, 3316cm-1 bending vibrations between 3268 and aromatic C-H gives bands at and and be-”
Alkurdi 等 - 2022 - Development and Evaluation of a Novel Polymer Drug DOI: 10.1155/2022/7903310
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