What absorbs at 3236 cm⁻¹ in an FTIR spectrum?
A band near 3236 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 6 cited sources
Quick answer
A band near 3236 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) | 3 | 3 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| Epoxy | 3236, 1660, 1735 | Alkyl C-H | 1 |
| polyurethane | 3236, 2270, 1700 | Alkyl C-H, N h | 1 |
| epoxy resin | 3236, 905, 1100 | Alkyl C-H | 1 |
| alginate | 3236, 1100, 1715 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| activated carbon | 3236, 1575, 1210 | Hydroxyl (O-H), Alkyl C-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 3236 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
-
Aromatic ring confidence 1.0
“The bands at 3236, 1637, 1569, 1444, is observed for the quinonoid ring-stretching vibrations”
Blaha 等 - 2019 - Role of p-Benzoquinone in the Synthesis of a Condu DOI: 10.1021/acsomega.9b00542 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Optimization of Cr (VI) removal from aqueous solution with activated carbon derived from Eichhornia crassipes under response surface methodology DOI: 10.1186/s13065-023-00913-6 -
N h confidence 1.0
“Assigned to N-H stretching vibration.”
The Influence of Initiator Concentration on Selected Properties of Thermosensitive Poly(Acrylamide-co-2-Acrylamido-2- Methyl-1-Propanesulfonic Acid) Microparticles DOI: 10.3390/polym -
confidence 1.0
“12 (Figure 5) the first changes appear in all samples in the range of wave numbers amounting to approximately 3236 cm-1, and this is the occurrence of stretching vibrations of the amino group N-H.”
Markowicz 和 Szymanska-Pulikowska - 2021 - Assessment of the Decomposition of Oxoand Biodeg DOI: 10.3390/ma14216449 -
Hydroxyl (O-H) confidence 1.0
“Meanwhile, salicylic acid exhibited distinctive peaks at 3236 and around 3008-2858 C=O which indicate O-H and C-H stretch, respectively.”
Nugrahani 等 - 2020 - A Comprehensive Study of a New 1.75 Hydrate of Cip DOI: 10.3390/cryst10050349 -
Hydroxyl (O-H) confidence 1.0
“7 the FTIR absorption between 3236 and 3250 is due to hydroxyl ions of the clay minerals, cm-1 and the peak at 3140 can be attributed to hydrated ferric oxide.”
Sanchez-Polo 等 - 2019 - An Archaeometric Characterization of Ecuadorian Po DOI: 10.1038/s41598-018-38293-w
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