What absorbs at 3280 cm⁻¹ in an FTIR spectrum?
A band near 3280 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 3280 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) | 23 | 22 | 1.0 |
| N h | 20 | 16 | 1.0 |
| Secondary amine | 8 | 6 | 1.0 |
| Amide | 6 | 6 | 1.0 |
| Hydrogen bond | 3 | 3 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Water (H2O) | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Amine primary | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Ring structure | 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 |
|---|---|---|---|
| PVA | 3280, 1660, 2930 | Hydroxyl (O-H), Amide | 1 |
| polysaccharide | 3280, 1637, 1320 | Hydroxyl (O-H), N h, Amide | 1 |
| silver nanoparticles | 3280, 1636, 1631 | Hydroxyl (O-H), Amide, N h | 1 |
| polysaccharides | 3280, 1053, 1143 | 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 3280 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
“Strong absorption was observed at 3279.62, 3272.35 glucose and galactose and xylose with different concentracm-1 corresponding to the hydroxyl vibration and 3331.21 tion which is dependent on many factors.”
Evaluation of the effect of soluble polysaccharides of palm kernel cake as a potential prebiotic on the growth of probiotics DOI: 10.1007/s13205-018-1362-4 -
Alkyl C-H confidence 1.0
“Regarding the above, API exhibit a strong band at1636cm-1,characteristicofβ-sheetstructures(Aceitunoappropriate to the C-H stretching vibration, and an N-H cm-1 et al., bond strain vibration band at 3280 belonging to the Medina 2013).”
Garcia-de la Rosa 等 - 2023 - Rheological and structural properties of complex c DOI: 10.24275/rmiq/Alim3003 -
Hydroxyl (O-H) confidence 1.0
“(b) AV film and (c) and PAV films had more or less similar peaks cm-1 in which the first broad peak at 3280.32 (AV) and cm-1 3292.86 (PAV) indicated the presence of carboxylic cm-1 acid O-H stretch;”
Synthesis and characterization of eco-friendly bioplastic from low-cost plant resources DOI: 10.1007/s42452-019-1460-x -
Amine primary confidence 1.0
“LLM confirmed rule peak-group candidate”
Kustiyah 等 - 2022 - Effect of Calcium Carbonate Content on the Mechani DOI: 10.22146/ijc.72135 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Ogunsile 等 - 2020 - Green synthesis of silver nanoparticles from leaf DOI: 10.1088/1757-899X/805/1/012032 -
confidence 1.0
“Characteristic peaks cm-1 appear at wavelengths: 3280 due to N-H stretching of amide A band in proteins, 2920 cm-1 cm-1 cm-1 due to C-H stretching of fatty acids, 1635 and 1540 due to amide I and II”
Quantification of live Lactobacillus acidophilus in mixed populations of live and killed by application of Attenuated Reflection Fourier Transform Infrared Spectroscopy combined with Chemometrics DOI: 10.1016/j.jpba.2018.03.009 -
N-O bond confidence 1.0
“The FTIR results showed that there was cm-1 no stretching vibration absorption peak of N-H group on 3280 and vibration compound peak cm-1 of C-N group and N-H group in amide group on 1540 in highly purified NR compared to 1 natural rubber (”
Study on molecular structure and property of highly purified natural rubber DOI: 10.1016/j.jaap.2018.05.018 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Abead 等 - 2023 - Study physical characteristics of Polyvinyl Alcoho DOI: 10.15764/pche.2014.02001.
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