What absorbs at 3261 cm⁻¹ in an FTIR spectrum?
A band near 3261 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 3261 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) | 6 | 6 | 1.0 |
| N h | 5 | 4 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Water (H2O) | 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 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| C#c | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 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 |
|---|---|---|---|
| HCl | 3261, 1708, 1032 | Hydroxyl (O-H), N h | 1 |
| graphite | 3261, 1640, 1326 | Alkyl C-H, Hydroxyl (O-H), 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 3261 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
-
Carboxyl (COOH) confidence 1.0
“This new peak at 3261 cm-' may be due to -COOH -N group, which can be formed by breaking the -C -”
Ha 等 - 1998 - Polarized Infrared Spectroscopic Studies of Polari DOI: 10.1080/10587259808025380 -
C#c confidence 1.0
“The absorption peaks of FTIR are contained of cm-1, cm-1, cm-1, cm-1 3261 2136 1635 and 1230 peaks that are assigned and fitted to C≡C, O-H, C=C, and C-O-H/O-H, respectively [20,21].”
Surface Enhanced Raman Scattering in Graphene Quantum Dots Grown via Electrochemical Process DOI: 10.3390/molecules26185484 -
Hydroxyl (O-H) confidence 1.0
“The cm-1 cm-1 broad band at 3261 may be assigned to the O-H stretching vibration.”
Structural and UV-blocking properties of carboxymethyl cellulose sodium/CuO nanocomposite films DOI: 10.1038/s41598-023-28032-1 -
N h confidence 1.0
“There are an additional very sharp bands at 3261 for and 3328 for that are suspected to be due to the NH stretching mode.”
Developing Further Versatility in Benzoxazine Synthesis via Hydrolytic Ring-Opening DOI: 10.3390/polym12030694 -
confidence 1.0
“Cell Component Peak Maxima Molecular Vibration Chitin/chitosan 3261 N-H stretching 3105”
Metal and Phosphate Ions Show Remarkable Influence on the Biomass Production and Lipid Accumulation in Oleaginous Mucor circinelloides DOI: 10.3390/jof6040260 -
Hydroxyl (O-H) confidence 1.0
“of all the batches was found to be in between -6.01 to The optimized batch (P1) indicated principal peaks -18.8mV, optimized batch shows -18.8mV mean zeta cm-1 observed at 3260.94 (OH stretching), a band peak potential which means optimized”
Giri 等 - 2019 - Hydrochlorothiazide Nanocrystals Stabilization by DOI: 10.5530/ijper.53.3.81 -
Alkyl C-H confidence 1.0
“3261.67 O-H stretching 3261.42 C-H stretching 2937.98 C-H stretching”
Development of Flexible Plasticized Ion Conducting Polymer Blend Electrolytes Based on Polyvinyl Alcohol (PVA): Chitosan (CS) with High Ion Transport Parameters Close to Gel Based Electrolytes DOI: 10.3390/gels -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Behavior and Mechanism of a Novel Hydrophobic Collector in the Flotation of Bastnaesite DOI: 10.3390/min12070817
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