What absorbs at 3281 cm⁻¹ in an FTIR spectrum?
A band near 3281 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 3281 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 | 7 | 1.0 |
| N h | 5 | 5 | 1.0 |
| Amide | 2 | 2 | 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 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Secondary amine | 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 |
|---|---|---|---|
| honey | 3281, 2005, 1199 | Hydroxyl (O-H), Amide | 1 |
| silver nanoparticles | 3281, 1636, 1631 | Hydroxyl (O-H), Amide, N 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 3281 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
“The addition of 200 µl SK, a - ± The FTIR spectrum showed characteristic absorption positive control to the clots at 37 °C, showed 76.7% clot cm-1 frequencies of the O-H stretching group at 3281 lysis.”
Biosynthesis of silver nanoparticles using Haloferax sp. NRS1: image analysis, characterization, in vitro thrombolysis and cytotoxicity DOI: 10.1186/s13568-021-01235-3 -
Hydroxyl (O-H) confidence 1.0
“into a macroscopic cm-1 Previous FTIR studies show that the wave number at 3281 was the stretching vibrations of O-H and N-H of polysaccharides, sugar alcohols, glycosides, amino acids and proteins;”
Xu 等 - 2019 - Biological Effects of High-Voltage Electric Field DOI: 10.3390/app9183829 -
Hydroxyl (O-H) confidence 1.0
“Mannitol presented a cm-1 cm-1 sented a characteristic peak at ~3281 (-OH stretching vibration), ~2947 (C-H characteristic peak at ~3281cm-1 (-OH stretching vibration), ~2947 cm-1 (C-H stretching cm-1”
Almotairi 等 - 2022 - Design and Optimization of Lornoxicam Dispersible DOI: 10.3390/ph15121463 -
Hydroxyl (O-H) confidence 1.0
“Type and Origin of Vibration (cm-1) υ(O-H) 3281 in H 2O υ(C-H) υ(NH or/and 3) of free 2933, 2890 amino acids”
Rapid Detection of Thermal Treatment of Honey by Chemometrics-Assisted FTIR Spectroscopy DOI: 10.3390/foods10112892 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Egle 等 - 2022 - Injectable Platelet-Rich Fibrin as a Drug Carrier DOI: 10.3390/ijms23137407 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Development of a Novel Green Bio-Nanofluid from Sapindus Saponaria for Enhanced Oil Recovery Processes DOI: 10.3390/pr10061057 -
N h confidence 1.0
“inpurefurosemide, inphysical cm-1 cm-1 mixtures), and NH stretching vibration of sulphonamide (3281 in pure furosemide, 3285 in physical mixtures) [29,30] have disappeared in both nanofibrous samples containing furosemide.”
Kovacs 等 - 2020 - Influence of Aqueous Solubility-Enhancing Excipien DOI: 10.3390/pharmaceutics12040385 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Popa 等 - 2022 - Influence of Convective and Vacuum-Type Drying on DOI: 10.3390/molecules27134063
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