What absorbs at 1490 cm⁻¹ in an FTIR spectrum?
A band near 1490 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 1490 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 | 9 | 8 | 1.0 |
| Carboxyl (COOH) | 7 | 7 | 1.0 |
| Amide | 6 | 6 | 1.0 |
| Alkene (C=C) | 5 | 5 | 1.0 |
| Alkyl C-H | 5 | 5 | 1.0 |
| N h | 5 | 5 | 1.0 |
| Ring structure | 5 | 5 | 1.0 |
| Nitrogen heterocycle | 5 | 4 | 1.0 |
| Bromine | 4 | 2 | 1.0 |
| C c single bond | 3 | 3 | 1.0 |
| Secondary amine | 3 | 3 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| C=n | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Lewis acid site | 2 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| N eq o | 1 | 1 | 1.0 |
| N n bond | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 0.9 |
| Quaternary ammonium | 1 | 1 | 0.9 |
| Sulfur heterocycle | 1 | 1 | 0.8 |
| Bronsted acid site | 1 | 0 | 0.9 |
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 |
|---|---|---|---|
| TiO2 | 1490, 1700, 1093 | Carboxyl (COOH) | 1 |
| polyaniline | 1490, 1565, 1570 | Aromatic ring, Amide | 1 |
| asphalt binder | 1490, 1700, 1242 | Aromatic ring, Alkene (C=C) | 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 1490 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
-
Alkyl C-H confidence 1.0
“As shown in the graph, the SBS-modified binder did not show bands at 1490 cm-1 and 1540 wavenumbers representing deformation and stretching vibrations of the cm-1 C-H bond, but the wavenumbers of 700 and 966 representing polybutadiene and M”
Analysis of the Properties of Modified Asphalt Binder by FTIR Method DOI: 10.3390/ma15165743 -
Amide confidence 1.0
“Other bands were seen at 1490 and 1560 [FU pte indicating of amid II, C-N stretching and N-H bending [38].”
Rafe 和 Razavi - 2015 - Effect of Thermal Treatment on Chemical Structure DOI: 10.1080/10942912.2014.999864 -
Amide confidence 1.0
“cm-1 cm-1 plan, 802 corresponds to para di-substituted ring, 1119 is due to delocalization of 7 cm-1 cm-1 electrons in aromatic ring, 1298 corresponds to C - N stretching vibration, 1490 due cm-1”
Antistatic and Dielectric properties of one-dimensional Al2+:Nd2O3 nanowire doped polyaniline nanocomposites for electronic application DOI: 10.1016/j.sna.2018.07.018 -
confidence 1.0
“The absorption band at 1000 cm-1 and 1490 cm-1 shows the characteristics of tertiary amine and diethyl”
Room temperature self-healing natural rubber based on ionic supramolecular network DOI: 10.1063/5.0016183 -
Amide confidence 1.0
“LLM confirmed rule peak-group candidate”
Simple quantitative analysis of Escherichia coli K-12 internalized in baby spinach using Fourier Transform Infrared spectroscopy DOI: 10.1016/j.ijfoodmicro.2010.09.013 -
Lignin confidence 1.0
“The cm-1 cm-1 peak at 1490 and 1298 are typical of lignin (Biagini et al., 2006, Chan and Wang, 2016a, Liu et al., 2015, Matias et al., 2000, Zancada et al., 2003, Liu et al., 2020, Wang et al., 2020).”
Optimization of primary sewage sludge and coal lignite by microwave assisted pyrolysis for the production of bio oil DOI: 10.1080/09593330.2020.1797903 -
C=n confidence 1.0
“Associated with C=N and C=C stretching vibrations of quinone and benzene rings.”
Synthesis of Uniform Polyaniline Nanofibers through Interfacial Polymerization DOI: 10.3390/ma5081487 -
Lewis acid site confidence 1.0
“The spectra also show a band at 1490 150 common to a vibration mode of pyridine coordinated to the catalysts' Lewis acid sites and”
TiO2 Catalyzed Dihydroxyacetone (DHA) Conversion in Water: Evidence That This Model Reaction Probes Basicity in Addition to Acidity DOI: 10.3390/molecules27238172
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