What absorbs at 3369 cm⁻¹ in an FTIR spectrum?
A band near 3369 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 3369 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) | 7 | 7 | 1.0 |
| N h | 4 | 3 | 1.0 |
| Methacrylate | 3 | 2 | 1.0 |
| Acetate | 3 | 2 | 1.0 |
| Carbonyl (C=O) | 3 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Water (H2O) | 2 | 1 | 1.0 |
| Ketone | 2 | 1 | 1.0 |
| Ester | 2 | 1 | 1.0 |
| Carboxyl (COOH) | 2 | 1 | 1.0 |
| Amide | 2 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 0.9 |
| Urethane | 1 | 1 | 0.9 |
| Secondary amine | 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 |
|---|---|---|---|
| polyurethane | 3369, 2270, 1700 | Methacrylate, Acetate, N h | 1 |
| polypropylene | 3369, 1030, 1600 | Methacrylate, Acetate, 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 3369 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
-
Carbonyl (C=O) confidence 1.0
“The peak of carbonyl (C=O) was observed at 3369 cm-1 [23].”
Mudri 等 - 2020 - Comparative Study of Aromatic and Cycloaliphatic I DOI: 10.3390/polym12071494 -
Hydroxyl (O-H) confidence 1.0
“The peak at 3368.78 indicates the O-H stretching of alcohol.”
Agrawal 等 - 2023 - Biotreatment of azo dye containing textile industr DOI: 10.21203/rs.3.rs-1876766/v2 -
Hydroxyl (O-H) confidence 1.0
“The strong broadband observed in MRSG at around wavenumbers 3487 and 3369 cm-1 signify that OH was assigned to the stretching mode of hydroxyl functional group”
The Physico-Chemical and Mineralogical Characterization of Mg-Rich Synthetic Gypsum Produced in a Rare Earth Refining Plant DOI: 10.3390/su13094840 -
C-O single bond confidence 1.0
“are recognized at 2686 and 961 After the reactive extruding, the FTIR spectrum of MP/PER/PP cm-1 cm-1 exhibits that the peaks of C-OH at 3369 and 1016 of PER and (P=O)-OH at 2686 and 961”
He 等 - 2019 - Novel Intumescent Flame Retardant Masterbatch Prep DOI: 10.3390/polym11010050 -
confidence 1.0
“of MET with compritol by the closed melt method, as Diffuse reflectance infrared fourier transform spectroscopy depicted in Figure 2, it is clear that the physical mixture cm-1 cm-1, Two typical bands at 3369 and 3294 relative shows approxi”
Jagdale 等 - 2011 - Preparation and Characterization of Metformin Hydr DOI: 10.4103/0975-1483.83758 -
Hydroxyl (O-H) confidence 1.0
“Figure 4(a) shows 3479cm-1 3369cm-1 and positive bands only originate fromthe O-H stretch of Tyr174 or not, whereasthe the negative in the presence of pHtrII.”
Kandori 等 - 2010 - Protein-Protein Interaction Changes in an Archaeal DOI: 10.1155/2010/424760 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Characterization of Sea Surface Microlayer and Marine Aerosol Organic Composition Using STXM-NEXAFS Microscopy and FTIR Spectroscopy DOI: 10.1021/acsearthspacechem.2c00119 -
Acetate confidence 1.0
“Conflict of Interests As shown in Figure 8, the stretching resonance of NH (3368.55cm-1 ) and C=O stretching vibration of amide I The authors declare that there is no conflict of interests (1645.49cm-1 band”
Liao 等 - 2016 - Probing into the Interaction of Nicotine and Bovin DOI: 10.1155/2016/9580136
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a literature-backed analysis — in seconds.