What absorbs at 3318 cm⁻¹ in an FTIR spectrum?
A band near 3318 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 3318 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 | 4 | 4 | 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 |
| Secondary amine | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 0.8 |
| Alkyl C-H | 1 | 1 | 0.5 |
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 |
|---|---|---|---|
| AuNPs | 3318, 1646, 1721 | Hydroxyl (O-H), Methacrylate | 1 |
| polymer | 3318, 1718, 1722 | Methacrylate, Hydroxyl (O-H), Methoxy (OCH3) | 1 |
| gold nanoparticles | 3318, 1638, 3252 | Methacrylate, 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 3318 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 stretching bands in Coated collagen Coated collagen 3 3318cm-1 3746cm-1 and are related to the OH and NH PHBVnanofiber nanofiber nanofiber”
Ai 等 - 2011 - Fabrication of Coated-Collagen Electrospun PHBV Na DOI: 10.1155/2011/123724 -
confidence 1.0
“Fourier Transform Infrared Spectroscopy (FTIR) characteristic peak of N-H at 3318 cm-1 and the N-H band at 1525 cm-1;”
Structural Conformation Comparison of Different Clear Aligner Systems: An In Vitro Study DOI: 10.3390/dj10050073 -
Hydroxyl (O-H) confidence 1.0
“A strong band at 2 cm-1 cm-1 3318 and 3339 is ascribed an O-H stretching vibration [27].”
An Investigation into the PVA:MC:NH4Cl-Based Proton-Conducting Polymer-Blend Electrolytes for Electrochemical Double Layer Capacitor (EDLC) Device Application: The FTIR, Circuit Design and Electrochemical Studies DOI: 10.3390/molecules27031011 -
Hydroxyl (O-H) confidence 1.0
“The related FTIR spectrum showed a sharp band cm-1 centered at 3318 assigned to stretching vibration of O-H from phenols groups.”
The “End Life” of the Grape Pomace Waste Become the New Beginning: The Development of a Virtuous Cycle for the Green Synthesis of Gold Nanoparticles and Removal of Emerging Contaminants from Water DOI: 10.3390/antiox11050994 -
confidence 1.0
“The peak at 3318 represents an N-H stretch, while cm-1 cm-1 the peak at 3185.51 indicates an O-H stretch.”
Biodegradation of Azo Dye Methyl Red by Pseudomonas aeruginosa: Optimization of Process Conditions DOI: 10.3390/ijerph19169962 -
Acetate confidence 1.0
“As to the spectra of the plasticized blends, the intensity of the bands at cm-1 3318, 2918, and 2850 increased, while the ratio of the C-O and C = O peak areas increased at the same time, especially for the PPLA 4000.”
Li 等 - 2018 - Preparation of plasticized poly (lactic acid) and DOI: 10.1371/journal.pone.0193520 -
Hydroxyl (O-H) confidence 0.95
“Text: 'cm-1 about 3318 attributed to the presence of bonded hydroxyl groups'”
Synthesis, characterization, and application of β-cyclodextrin-based ion-imprinted polymer for selective sequestration of Cr(VI) ions from aqueous media: Kinetics and isotherm studies DOI: 10.1016/j.molliq.2019.111991 -
confidence 0.95
“Same as above.”
Jadhav 等 - 2017 - Thermoresponsive copolymer-grafted SBA-15 porous s DOI: 10.3144/expresspolymlett.2017.11
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