What absorbs at 3311 cm⁻¹ in an FTIR spectrum?
A band near 3311 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 3311 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) | 5 | 5 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Phenolic | 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 |
|---|---|---|---|
| bio-based | 3311, 1720, 1740 | Carbonyl (C=O), Hydroxyl (O-H), N h | 1 |
| sodium alginate | 3311, 1636, 1080 | 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 3311 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
“5-FU-HBA cm-1 cm-1 There was a shift of the amino and carbonyl peaks to 3311 and 1753 in this cm-1 cm-1, cocrystal compared with the corresponding peaks of 5-FU at 3220.24 and 1662”
Synthesis, Characterization, Theoretical and Experimental Anticancer Evaluation of Novel Cocrystals of 5-Fluorouracil and Schiff Bases against SW480 Colorectal Carcinoma DOI: 10.3390/pharmaceutics15071929 -
confidence 1.0
“All the cm-1 3311 because of N-H stretching indicating formulations showed a sustained release pattern”
Bashir 等 - 2014 - In vitro Evaluation of Nateglinide-Loaded Microsph DOI: 10.4314/tjpr.v13i7.6 -
Hydroxyl (O-H) confidence 1.0
“al.28 cm-1 It was stated by Saif et that the broad absorption band at 3310.7 was linked to the hydroxyl (OH) functional groups in alcohols and phenolic compounds.”
Tea from the drinking to the synthesis of metal complexes and fabrication of PVA based polymer composites with controlled optical band gap DOI: 10.1038/s41598-020-75138-x -
Hydrogen bond confidence 1.0
“corresponds to an ansymmetric vibration of the free The broad and intense peak at 3311 O-H groups present in the cellulose I and OH groups that correspond to the intra-and intermolecular hydrogen bonds (Kargarzadeh et al.”
Coelho de Carvalho Benini 等 - 2017 - Characterization of a New Lignocellulosic Fiber fr DOI: 10.1080/15440478.2016.1167647 -
confidence 1.0
“It can be seen from Figure 4b,c Figure 4c that with increasing plasticization time, (i) a red shift occurs between the N-H stretching that with increasing plasticization time, (i) a red shift occurs between the N-H stretching from 3311”
Preparation of Bio-Based Polyamide Elastomer by Using Green Plasticizers DOI: 10.3390/polym8070257 -
confidence 1.0
“ν(NH), bands at 3311 originate from the stretching vibrations of side N-H bonds, with maxima shifted by 10 units to lower wavenumbers than in the spectrum of monomer.”
Semi-Crystalline Copolymer Hydrogels as Smart Drug Carriers: In Vitro Thermo-Responsive Naproxen Release Study DOI: 10.3390/pharmaceutics13020158 -
confidence 1.0
“The FTIR analysis (B/D) cm-1 content of nitrogen (N 446.7 kg/ha) and very high shows a broad band at around 3311 and 2918 which = Mohan et al.”
Mohan 等 - 2021 - Pharmaco-chemical profiling of Desmodium gangeticu DOI: 10.1186/s43094-021-00356-7 -
Hydroxyl (O-H) confidence 1.0
“Composts 1:2 -IMO have peaks that developed on 3311 cm and 3267 cm and have been ascribed to the -OH groups.”
Musa 等 - 2021 - Carbon Dynamics of Fruit and Vegetable Wastes and DOI: 10.3390/su131910869
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