What absorbs at 3302 cm⁻¹ in an FTIR spectrum?
A band near 3302 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 3302 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 | 2 | 1.0 |
| Amide | 3 | 3 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 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 |
|---|---|---|---|
| Polyamide | 3302, 1663, 1541 | Amide, Alkyl C-H, N h | 1 |
| nanocellulose | 3302, 1540, 1646 | Alkyl C-H, Amide, Hydroxyl (O-H) | 1 |
| HCl | 3302, 1708, 1032 | Hydroxyl (O-H), N h | 1 |
| starch | 3302, 1650, 1540 | Hydroxyl (O-H), Alkyl C-H, Amide | 1 |
| glycerol | 3302, 1585, 1630 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| chitosan | 3302, 1650, 1655 | Alkyl C-H, Amide, 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 3302 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
-
Amide confidence 1.0
“Amongst the gelatin the amide A group was recorded at 3304, 3291, 3292, and 3302 cm-1 for PG-FG 100-0, PGfilms, FG showed the lowest peak amide B wave number, indicating the single bond NH3 FG 50-50, PG-FG 0-100, and BG, respectively, which”
Application of Poultry Gelatin to Enhance the Physicochemical, Mechanical, and Rheological Properties of Fish Gelatin as Alternative Mammalian Gelatin Films for Food Packaging DOI: 10.3390/foods12030670 -
Hydroxyl (O-H) confidence 1.0
“FTIRspectraforstarch/MMTsamplesareshowninFig.2(b),and Increasing the glycerol content further highlights the typical 3627cm-1, the shift of band from the free OH group of pristine anti-plasticization to plasticization threshold, which have”
Glycerol/starch/Na+-montmorillonite nanocomposites: A XRD, FTIR, DSC and 1H NMR study DOI: 10.1016/j.carbpol.2010.10.018 -
Amide confidence 1.0
“Amide peaks at 3302 corresponding to -NH to reduce interfacial tension, have been considered.”
Salehi-Mobarakeh 等 - 2013 - Polyamide grafting onto ethylene-vinyl alcohol cop DOI: 10.1515/polyeng-2013-0104 -
Alkyl C-H confidence 1.0
“Another broad and 300°C-400°C 3302.03cm-1 endothermic peak at was attributed to the thermal describing CH stretching, conjugated C=O, CH”
Abdullah 等 - 2023 - Formulation of pH-responsive highly swellable hydr DOI: 10.3389/fbioe.2023.1190322 -
Aromatic ring confidence 1.0
“cm-1 cm-1 The broadband at 3302 indicates the aromatic OH group of resorcinol, whereas that at 1607 cm-1 refers to the aromatic ring stretches.”
Awadallah-F 和 Al-Muhtaseb - 2019 - Influence of Chitosan Addition on Resorcinol-Forma DOI: 10.3390/app9214582 -
Carbohydrate confidence 1.0
“The spectrum showed a broad band centered at 3302 cm-1, which corresponds to the sugar residue ν-OH groups stretching vibration (-H bonded).”
Optimization and Characterization of a Novel Exopolysaccharide from Bacillus haynesii CamB6 for Food Applications DOI: 10.3390/biom12060834 -
Metal oxygen confidence 1.0
“(2013), which showed an adsorption peak at 3302 cm-1 and identified as O-H stretch, which in this case indicated the presence of a bound hydroxide compound in crude palm empty fruit bunches (PEFB) [28].”
Physicochemical Properties of Membrane Adsorber from Palm Empty Fruit Bunch (PEFB) by Acid Activation DOI: 10.3390/membranes11120917 -
Amide confidence 1.0
“LLM confirmed rule peak-group candidate”
Physicochemical Characterization of Bilayer Hybrid Nanocellulose-Collagen as a Potential Wound Dressing DOI: 10.3390/ma13194352
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