What absorbs at 490 cm⁻¹ in an FTIR spectrum?
A band near 490 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 490 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 |
|---|---|---|---|
| Metal oxygen | 5 | 4 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 1 | 1.0 |
| Silicon nitrogen | 2 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 1.0 |
| N n bond | 1 | 1 | 1.0 |
| Metalloid oxygen | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 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 |
|---|---|---|---|
| gelatin | 490, 1652, 3300 | Alkyl C-H | 1 |
| PVDF | 490, 1160, 840 | 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 490 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 main absorption bands of ZI 0.7 photozyme were present in the FTIR-ATR spectra of the coated 0.6 nm) cm-1) surfaces, precisely asymmetric (1125 and 1180 and 0.5 cm-1) (490 symmetric (1036 stretching of O=S=O groups and S-O-C cm-1).”
Chiono 等 - 2012 - Layer-by-layer coating of photoactive polymers for DOI: 10.1021/bm800141v -
confidence 1.0
“1,575-1,490 cm-1, N-H bending and C-N stretching vibration), (3) suitable for the examination of ground plant-based food”
Molecular basis of structural makeup of hulless barley in relation to rumen degradation kinetics and intestinal availability in dairy cattle: A novel approach DOI: 10.3168/jds.2011-4564 -
confidence 1.0
“Assigned to α-crystalline phase.”
Spectroscopic and thermal investigations of poly(vinylidene fluoride) films composites with LaNi3Co2 DOI: 10.1002/crat.200610789 -
Metalloid oxygen confidence 1.0
“VibrationsofZn-Otetrahedralbond 490 488 488 488 (ZnO4) 200 400 600 800 Te-O 615 622 624 625 bending stretching vibrations units in TeO4 (cm-1) Raman shift Te-O 660 667 667 688 bending vibrations in TeO3”
Gold nanoparticles assisted surface enhanced Raman scattering and luminescence of Er3+ doped zinc–sodium tellurite glass DOI: 10.1016/j.jlumin.2014.11.032 -
Silicon nitrogen confidence 1.0
“(cm(cid:2)2) K Reference Bond Mode Wavenumber (cm(cid:2)1) symmetric stretching 490 - [15] Si-N N-Si3 Si-H Si-H wag-rocking”
Effect of PECVD silicon oxynitride film composition on the surface passivation of silicon wafers DOI: 10.1016/j.solmat.2011.09.052 -
confidence 1.0
“Mn2+ 490 is due to the Mn-O stretch The possible reason is that some of the O2cm-1 combining with to form MnO in the thermal solution.”
Hu 等 - 2018 - Photoluminescence of ZnS Mn quantum dot by hydrot DOI: 10.1063/1.5010833 -
Ring structure confidence 1.0
“The bands identified at 860, 850, 620, 520 1.217 0.951 C9 490cm-1 and have been assigned to ring in-plane bending modes 1.217 0.951 C10”
FTIR and FT Raman, molecular geometry, vibrational assignments, ab initio and density functional theory calculations for 1,5-methylnaphthalene DOI: 10.1016/j.saa.2010.09.002 -
Aromatic ring confidence 1.0
“explicit assignment”
Antistatic and Dielectric properties of one-dimensional Al2+:Nd2O3 nanowire doped polyaniline nanocomposites for electronic application DOI: 10.1016/j.sna.2018.07.018
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