What absorbs at 1502 cm⁻¹ in an FTIR spectrum?
A band near 1502 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 1502 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 |
|---|---|---|---|
| Aromatic ring | 4 | 4 | 1.0 |
| Ring structure | 3 | 3 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Quaternary ammonium | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Nitrate | 1 | 0 | 0.7 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| cellulose | 1502, 1735, 1650 | Amide | 1 |
| hemicelluloses | 1502, 1735, 1270 | Aromatic ring | 1 |
| polymers | 1502, 1726, 1743 | Amide | 1 |
| lignin | 1502, 1035, 1510 | Aromatic ring | 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 1502 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
-
confidence 1.0
“The absorption bands at 668 1502 cm-1 cm-1 and 1440 indicate the metallic stretching vibrations in Fe - O.”
Effect of Gd and Nb on Dielectric and Magnetic Transition temperature of BaTiO3- Li0.5Fe2.5O4 Composites DOI: 10.1016/j.physb.2019.02.035 -
Ring structure confidence 1.0
“Ring stretching 1556 1556 1558 Ring stretching 1502 1498 1498 - Coordinate bond 1461 1461 +CH bending”
Intercalation and in situ formation of coordination compounds with ligand 8-hydroxyquinoline-5-sulfonic acid in the interlayer space of layered silicate magadiite by solid-solid reactions DOI: 10.1016/j.micromeso.2018.02.038 -
Alkyl C-H confidence 1.0
“The peaks at 1502, 1508 and 1249 vibration.27 cm-1 CH stretching are related to C=C bonds in the aromatic”
Allouch 等 - 2019 - CHARACTERIZATION OF COMPONENTS ISOLATED FROM ALGER DOI: 10.1016/j.pecs.2012.02.002 -
Alkene (C=C) confidence 1.0
“266 cm-1 The spectra also exhibited a low-intensity band at 1502 associated with C=C 267 cm-1, vibrations of aromatic rings, bands at 1486 and 1469 associated with CH and CH”
Franca 等 - 2020 - Monitoring diclofenac adsorption by organophilic a DOI: 10.1016/j.envpol.2013.04.012 -
Acetate confidence 1.0
“absorbance from bands at 1730 1502 1370 1234 and 834 (Figure S2B), absorbance from bands at 1730 cm-1, 1502 cm-1, 1370 cm-1, 1234 cm-1, and 834 cm-1 (Figure S2B), which C=O which are mainly ascribed to the stretch in the glucuronic acid of”
Even Visually Intact Cell Walls in Waterlogged Archaeological Wood Are Chemically Deteriorated and Mechanically Fragile: A Case of a 170 Year-Old Shipwreck DOI: 10.3390/molecules25051113 -
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 -
Ring structure confidence 1.0
“The presence of a band at 1502 cm-1 indicates the tetrazole (CN 4) ring.”
Mahapatra 等 - 2011 - Dissolution Enhancement and Physicochemical Charac DOI: 10.14227/DT180111P39 -
Alkyl C-H confidence 1.0
“The peaks cm-1 at 2923 and 2835 can be assigned to the C-H stretching and the peaks at 1502 and cm-1 1589 were assigned to the C=C stretching bond in the aromatic ring (dashed line cm-1, pointed in Figure 3).”
Development of an Electrospun Patch Platform Technology for the Delivery of Carvedilol in the Oral Mucosa DOI: 10.3390/nano12030438
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