What absorbs at 3100 cm⁻¹ in an FTIR spectrum?
A band near 3100 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 3100 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) | 36 | 29 | 1.0 |
| Alkyl C-H | 27 | 26 | 1.0 |
| Amide | 8 | 8 | 1.0 |
| N h | 8 | 7 | 1.0 |
| Aromatic ring | 6 | 5 | 1.0 |
| Water (H2O) | 5 | 5 | 1.0 |
| Hydrogen bond | 5 | 5 | 1.0 |
| Carboxyl (COOH) | 4 | 4 | 1.0 |
| Secondary amine | 3 | 3 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Carbohydrate | 3 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Urea | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| Sulfur heterocycle | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Protein | 1 | 0 | 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 | 3100, 1030, 1600 | Alkyl C-H, Hydroxyl (O-H), Amide | 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 3100 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
“cm-1 area-1 µmol-bond is hydroxyl group absorption between 3100 and 3400 for n-propyl 3,4,5a slope of 0.092 anarrowabsorptionpeakat3500cm-1,whichhasnotbeen ) trihydroxybenzoate (with correlation coefficient, R 0.97) and0.154µmol-bondarea-1f”
Bahadur 等 - 2010 - Phenol Groups in Northeastern US Submicrometer Aer DOI: 10.1021/es9032277 -
Alkyl C-H confidence 1.0
“They found stretching bands corresponding to the -C-H and = C-H functional groups at 2964.37 and 3100.08 cm-1.”
The Effect of High-Intensity Ultrasound and Natural Oils on the Extraction and Antioxidant Activity of Lycopene from Tomato (Solanum lycopersicum) Waste DOI: 10.3390/antiox11071404 -
Alkyl C-H confidence 1.0
“(cid:2870)(cid:2868) (cid:2870)(cid:2868) 3100cm-1 3100cm-1 (cid:2925)(cid:2931)(cid:2930)(cid:11)(cid:2925)(cid:2931)(cid:2930) is detected for the C-H stretch mode, however for there is extra peak at and (cid:6) (cid:2870)(cid:2868)(cid:1”
EL-Barbary - 2016 - Hydrogenated Fullerenes in Space FT-IR Spectra an DOI: 10.1063/1.4953126 -
N h confidence 1.0
“The raw material of GBP existed as a large rod shaped crystal, but the evaporated GBP-L was found to be a thin plateshapedcrystalsimilartootherreport[20].SinceGBPdisplays a zwitterion in the solid state [13,21], thus there was no IR peak (3”
Hsu 和 Lin - 2009 - Rapid examination of the kinetic process of intram DOI: 10.1016/j.tca.2008.12.008 -
Ring structure confidence 1.0
“The cell was put under potentiostatic correspond to in-plane and ring stretching modes, respec- (cid:1)Hokuto by employing a potentiostat HZ-5000 HAG 3100 cm-1 tively.”
Kato 等 - 2007 - X-ray photoemission spectroscopy and Fourier trans DOI: 10.1116/1.2731347 -
Carbonyl (C=O) confidence 1.0
“degree of MAH was confirmed by the existence of carbonyl group (C=O) stretching peak at 3100 Thermal properties of MAH-g-PP and PP/MAH-g-PP/pulp composites were investigated by DSC and TGA.”
Lee 等 - 2014 - Effect of Maleic Ahydride Grafted PP on the Physic DOI: 10.7317/pk.2014.38.5.566 -
Aromatic ring confidence 1.0
“The aromatic C-H absorption band at 3100in the absorption peak from several functional groups cm-1 cm-1 3050 and aliphatic C-H at 3000-2850 originated ligands, as shown in Figure 1.”
Lestari 等 - 2022 - Zirconium(IV)-BTC-Based MOF Modified with Nickel a DOI: 10.17576/jsm-2022-5109-16 -
Hydroxyl (O-H) confidence 1.0
“Text: 'medium hydroxyl (OH) band in the region 3600-3100 cm-1.'”
Mathews 和 Singh - 2016 - Characterization of solid bitumen from Panandhro l DOI: 10.18520/cs/v111/i11/1842-1846
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