What absorbs at 3490 cm⁻¹ in an FTIR spectrum?
A band near 3490 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 3490 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 |
|---|---|---|---|
| Hydroxyl (O-H) | 8 | 8 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| N h | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| chitosan | 3490, 1650, 1655 | Methacrylate, Hydroxyl (O-H), Methoxy (OCH3) | 1 |
| gelatin | 3490, 1652, 3300 | Methacrylate, Hydroxyl (O-H) | 1 |
| Fe3O4 | 3490, 2358, 1673 | Hydroxyl (O-H), Methacrylate | 1 |
| polyester | 3490, 1700, 1250 | Methacrylate, Methoxy (OCH3) | 1 |
| TiO2 | 3490, 1700, 1093 | Hydroxyl (O-H), Methacrylate, Methoxy (OCH3) | 1 |
| bio-based | 3490, 1720, 1740 | Methacrylate, Hydroxyl (O-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 3490 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
-
Hydroxyl (O-H) confidence 1.0
“prevalence of gypsum, of the calcium sulfate dihydrate crystalline variety, was confirmed by the IR absorption bands ascribed to the stretching vibration of OH groups at 3490 and 3395 cm-1, bands at 1680 and 1621 cm-1 associated with deform”
New Insights into the Medieval Hispano-Muslim Panel Painting: The Alfarje Found in a Balearic Casal (Spain) DOI: 10.3390/molecules28031235 -
Hydrogen bond confidence 1.0
“The author analyzed the FTIR ter/intramolecular hydrogen bonds and confirmed the cellulose I transition (3290 cm-1 and bands of inter/intramolecular hydrogen bonds and confirmed the cellulose I transition 3333 cm-1) to cellulose II (3440 cm”
Impact of NaOH Concentration on Deweaving of Cotton Fabric in Aqueous Solutions DOI: 10.3390/su13042015 -
Chitosan confidence 1.0
“1 Infrared Spectroscopy cm-1 Investigation of IR spectral data of chitosan films showed a broad band around 3490 due to presence of -OH and -NH groups.”
Development and Evaluation of Cefadroxil Drug Loaded Biopolymeric Films Based on Chitosan-Furfural Schiff Base DOI: 10.3797/scipharm.0912-20 -
Hydroxyl (O-H) confidence 1.0
“The broader absorption centered at 3490 is due to OH groups experiencing stronger”
Mino 等 - 2016 - A surface science approach to TiO2 P25 photocataly DOI: 10.1016/j.apcatb.2016.05.029 -
Hydroxyl (O-H) confidence 1.0
“The cm-1, both uncured and cured UPR samples showed a band at about 3490 originating from cm-1, origspectra of both uncured and cured UPR samples showed a band at about 3490 OH stretching vibration.”
The Effect of Glycol Derivatives on the Properties of Bio-Based Unsaturated Polyesters DOI: 10.3390/polym14152970 -
Hydroxyl (O-H) confidence 1.0
“analyzed in the mid-IR due to broad O-H stretching vibra3490cm(cid:3)1 tions at approximately (Tamm and Tatulian, 1997), which may be an indication of fluid inclusions, water of hydration, or water held in a crystal structure (Anderson et a”
Preston 和 Genge - 2010 - The Rhynie Chert, Scotland, and the Search for Lif DOI: 10.1089/ast.2008.0321 -
Hydroxyl (O-H) confidence 1.0
“Indeed, the stretching vibrations of the cm-1, C-H C-N and are appeared at 2877 and 1382 Furthermore, the absorption bands centered at 3490 and cm-1 1639 are attributed to the acidic OH and carbonyl groups, respectively, which all confirm t”
Ultrasound-Promoted preparation and application of novel bifunctional core/shell Fe3O4@SiO2@PTS-APG as a robust catalyst in the expeditious synthesis of Hantzsch esters DOI: 10.1038/s41598-023-33990-7 -
Hydroxyl (O-H) confidence 1.0
“It is obvious that the peak at 1738/cm is caused by stretching vibration of the functional group of Discussions C-O and the peak at 3490/cm is attributed to the stretching Fourier-transform infrared spectroscopy analysis vibration of functi”
Shirazaki 等 - 2017 - Electrospun Gelatinpoly(Glycerol Sebacate) Membra DOI: 10.4103/abr.abr_197_16
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