What absorbs at 1525 cm⁻¹ in an FTIR spectrum?
A band near 1525 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 1525 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 |
|---|---|---|---|
| N h | 9 | 9 | 1.0 |
| Amide | 7 | 6 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Alkene (C=C) | 3 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Fluorine (C-F) | 1 | 1 | 1.0 |
| Nitro (NO2) | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| Protein alpha helix | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 0.9 |
| Lignin | 1 | 1 | 0.7 |
| Silicon (Si) | 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 |
|---|---|---|---|
| PVA | 1525, 1660, 2930 | Alkyl C-H, Amide | 1 |
| Nanotube | 1525, 1540, 1080 | Amide, N h, Alkyl C-H | 1 |
| PVC | 1525, 834, 1195 | Alkyl C-H | 1 |
| soil | 1525, 575, 1240 | 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 1525 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
“COO-/C=C C-H vibrations 3rd peak showing the three main vibrational modes of CO (in order 2 (1620cm-1), 1525cm-1 (C=C).”
Demyan 等 - 2013 - Combining a coupled FTIR-EGA system and in situ DR DOI: 10.5194/bg-10-2897-2013 -
Amide confidence 1.0
“Transmittance peak at 1525 cm-1 corresponding to band II of amide.”
Ryu 等 - 2010 - Carbon Nanotube Mat as Mediator-Less Glucose Senso DOI: 10.1166/jnn.2010.1892 -
Protein alpha helix confidence 1.0
“Nevertheless, the peaks at 1540, 1545, and 1551 cm-1 are usually assigned to α-helical structure, while the peaks at 1520 to 1525 cm-1 are assigned to cm-1 cm-1 are are usually usually assigned assigned to to α-helical α-helical structure,”
Sadat 和 Joye - 2020 - Peak Fitting Applied to Fourier Transform Infrared DOI: 10.3390/app10175918 -
N-O bond confidence 1.0
“The sharp cm(cid:1)1 C-NO peak at 1525 is attributed to asymmetric vibrations 2 cm(cid:1)1 1164-960 (NPOE), and the vibration bonds around corre-”
Evidence on the 2-nitrophenyl octyl ether (NPOE) facilitating Copper(II) transport through polymer inclusion membranes DOI: 10.1016/j.memsci.2015.12.013 -
confidence 1.0
“Budhian also found that increasing cm-1 N-H Vibrations group 1525”
Influence of Polyvinyl Alcohol (PVA) on PVA-Poly-N-hydroxyethyl-aspartamide (PVA-PHEA) Microcrystalline Solid Dispersion Films DOI: 10.1208/s12249-020-01811-z -
confidence 1.0
“Fourier Transform Infrared Spectroscopy (FTIR) characteristic peak of N-H at 3318 cm-1 and the N-H band at 1525 cm-1;”
Structural Conformation Comparison of Different Clear Aligner Systems: An In Vitro Study DOI: 10.3390/dj10050073 -
confidence 1.0
“ostreatus mushrooms were positively correlated with regions at 1650 cm-1 (N-H bending of primary amines and C=O stretching in the amide I region) [42,44,47], 1525 cm-1 (amide II region) and 1020 cm-1 (pyranose compounds in carbohydrates).”
Pleurotus Mushrooms Content in Glucans and Ergosterol Assessed by ATR-FTIR Spectroscopy and Multivariate Analysis DOI: 10.3390/foods9040535 -
Nitro (NO2) confidence 1.0
“1525, 1633 The former two bands can be assigned to symmetric and asymmetric stretching bands of the nitro group of NS, respectively, and the last one is assignable to the C=C stretching band of the vinyl group.”
Selective hydrogenation of nitrostyrene to aminostyrene over Pt/TiO2 catalysts : Effects of pressurized carbon dioxide and catalyst preparation conditions DOI: 10.1016/j.supflu.2011.02.016
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