What absorbs at 3200 cm⁻¹ in an FTIR spectrum?
A band near 3200 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 3200 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) | 74 | 59 | 1.0 |
| N h | 29 | 26 | 1.0 |
| Amide | 11 | 11 | 1.0 |
| Alkyl C-H | 11 | 10 | 1.0 |
| Water (H2O) | 10 | 5 | 1.0 |
| Secondary amine | 9 | 8 | 1.0 |
| Carboxyl (COOH) | 7 | 4 | 1.0 |
| Hydrogen bond | 5 | 4 | 1.0 |
| Acetate | 4 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Silanol (Si-OH) | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 2 | 2 | 1.0 |
| Ammonium | 2 | 2 | 1.0 |
| Silicon (Si) | 2 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Protein random coil | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 0.8 |
| Oxygen heterocycle | 1 | 1 | 0.7 |
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 |
|---|---|---|---|
| silica | 3200, 1100, 1080 | Hydroxyl (O-H), Alkyl C-H | 1 |
| water | 3200, 1018, 2945 | Hydroxyl (O-H), Alkyl C-H | 1 |
| asphalt | 3200, 1600, 1376 | 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 3200 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
-
confidence 1.0
“Explicit: 'a negative band centered at 3200 cm-1 ... referred as solvent-shared ion-pair'.”
Ashraf 等 - 2021 - Identification and properties of ion-pairs in the DOI: 10.1016/j.molliq.2020.114891 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Effect of used motor oil as a rejuvenator on crumb rubber modifier’s released components to asphalt binder DOI: 10.1177/1477760620918600 -
Hydroxyl (O-H) confidence 1.0
“R.K.Deyetal./ColloidsandSurfacesA:Physicochem.Eng.Aspects324(2008)41-46 43 3200cm-1, between 3400 and assigned to the O H stretching frequency of the silanol groups bonded to the inorganic structure, as well as to the adsorbed water molecul”
Dey 等 - 2008 - Mesoporous silica functionalized with diethylenetr DOI: 10.1016/j.colsurfa.2008.03.030 -
Carboxyl (COOH) confidence 1.0
“An FTIR spectrum was measured with a dry sample to minimize the boric acid peak at Kubelka-Munk cm-1 3200 and better show other peaks between cm-1 cm-1.”
Garro Mena 和 Hohn - 2021 - Modification of hexagonal boron nitride by thermal DOI: 10.1007/s10853-020-05719-8 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Facile synthesis and characterization of Zno-HNT additive for enhancement of polysulfone membrane for Oil-In-Water separation DOI: 10.1016/j.matpr.2021.02.589 -
Hydroxyl (O-H) confidence 1.0
“cm-1 cm-1 1616 The wild absorption band between 3200 and 3700 can be observed for all tested samples, corresponding to the stretch vibrations of O-H.”
Liang 等 - 2017 - Thermo-stability and aging performance of modified DOI: 10.1016/j.matdes.2017.04.060 -
confidence 1.0
“Explicitly assigned to hydrogen-related bonds.”
Miyazaki 等 - 2005 - Properties of radio-frequency-sputter-deposited Ga DOI: 10.1063/1.1888027g -
Hydrogen bond confidence 1.0
“LLM confirmed rule peak-group candidate”
Moussa 等 - 2009 - Experimental and Theoretical Characterization of A DOI: 10.1021/jp808710n
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