What absorbs at 3393 cm⁻¹ in an FTIR spectrum?
A band near 3393 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 3393 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 | 2 | 2 | 0.9 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Oxygen heterocycle | 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 |
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 |
|---|---|---|---|
| polypropylene | 3393, 1030, 1600 | Alkyl C-H, 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 3393 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 main cm-1 an OH band at 3393 for natural F-bearing clinohumite.”
In-situ high-temperature vibrational spectra for synthetic and natural clinohumite: Implications for dense hydrous magnesium silicates in subduction zones DOI: 10.2138/am-2019-6604 -
Hydroxyl (O-H) confidence 1.0
“5 of 15 Polymers2023,15,2477 5of15 cm-1 peak characteristic of the epoxy ring, the conversion of the peak at 3009 is related cm-1 to hydroxyl stretching, which is verified at 3393 (Figure 2b), and C-O absorption cm-1), (1157 indicating modi”
Montenegro 等 - 2023 - Enzymatic and Synthetic Routes of Castor Oil Epoxi DOI: 10.3390/polym15112477 -
Alkyl C-H confidence 1.0
“The Fourier transform infrared spectroscopy (FT-IR) analysis measures the selective absorption of light by the vibration modes of specific chemical bonds in the sample determining several functional groups such as OHcm-1), hydroxyl and amid”
Koutb 等 - 2021 - Paclitaxel production by endophytic fungus, Neopes DOI: 10.30955/gnj.003839 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Facile Synthesis of Magnetic Nigella Sativa Seeds: Advances on Nano-Formulation Approaches for Delivering Antioxidants and Their Antifungal Activity against Candida albicans DOI: 10.3390/pharmaceutics15020642 -
Hydroxyl (O-H) confidence 1.0
“Wavenumber Peak assignment cm-1 hydroperoxide, alcohol and acid O-H stretch ~3393 cm-1 alkyl CH-CH C-H stretch 2919 2”
Morsch 等 - 2017 - Investigating the Photocatalytic Degradation of Oi DOI: 10.1021/acsami.7b00638 -
Hydrogen bond confidence 1.0
“However, the stretching shift of piroxicam C in conjunction with these RDF 7 cm-1 calculations indicate that the hydrogen bond between the vibration of piroxicam at 3393 or 3339 was not observed”
Tantishaiyakul 等 - 2010 - Characterization of Cimetidine-Piroxicam Coprecipi DOI: 10.1208/s12249-010-9461-5 -
N h confidence 0.9
“Explicit assignment in text”
Chao Dan-Ming 等 - 2013 - Synthesis and Properties of Novel Poly(amic acid) DOI: 10.7503/cjcu20130297 -
Hydroxyl (O-H) confidence 0.9
“Characteristic absorption peaks of (P=O)-OH at 3393 cm-1.”
He 等 - 2019 - Novel Intumescent Flame Retardant Masterbatch Prep DOI: 10.3390/polym11010050
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