What absorbs at 3000 cm⁻¹ in an FTIR spectrum?
A band near 3000 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 3000 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 |
|---|---|---|---|
| Alkyl C-H | 136 | 126 | 1.0 |
| Hydroxyl (O-H) | 109 | 102 | 1.0 |
| N h | 25 | 24 | 1.0 |
| Aromatic ring | 19 | 18 | 1.0 |
| Hydrogen bond | 15 | 15 | 1.0 |
| Methyl | 12 | 10 | 1.0 |
| Carboxyl (COOH) | 11 | 10 | 1.0 |
| Methacrylate | 10 | 10 | 1.0 |
| Amide | 10 | 10 | 1.0 |
| Acetate | 10 | 10 | 1.0 |
| Water (H2O) | 10 | 9 | 1.0 |
| Carbohydrate | 8 | 8 | 1.0 |
| Carbonyl (C=O) | 8 | 7 | 1.0 |
| Ester | 7 | 7 | 1.0 |
| Methoxy (OCH3) | 6 | 6 | 1.0 |
| Ketone | 5 | 5 | 1.0 |
| C-O single bond | 5 | 5 | 1.0 |
| N-O bond | 5 | 3 | 1.0 |
| Lipid | 4 | 3 | 1.0 |
| Alkene (C=C) | 4 | 3 | 1.0 |
| Secondary amine | 3 | 3 | 1.0 |
| C c single bond | 3 | 3 | 1.0 |
| Metal oxygen | 3 | 3 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Phosphorus | 2 | 2 | 1.0 |
| Chitosan | 2 | 2 | 1.0 |
| Phosphate (PO4) | 2 | 2 | 1.0 |
| Chlorine | 2 | 2 | 1.0 |
| Fluorine (C-F) | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Styrene | 1 | 0 | 0.8 |
| Protein | 1 | 0 | 0.7 |
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 |
|---|---|---|---|
| cotton fabric | 3000, 900, 862 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| HDPE | 3000, 1369, 1216 | Alkyl C-H, Hydroxyl (O-H), Aromatic ring | 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 3000 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
“3000cm-1 the region In the present case, the very strong rise to three bands above for aromatic C H and 1164cm-1 modes observed at 1289 and in IR corresponds to H stretching observed in the region between one aliphatic C 2900cm-1.”
Arjunan 等 - 2007 - Fourier transform infrared and Raman spectral assi DOI: 10.1016/j.saa.2006.09.044 -
Carboxyl (COOH) confidence 1.0
“While in cobalt stearate, the absorption peak at wave number of 1554 cm-1indicate the presence of asymmetric vibrations of carboxylate groups absorption peak at the wave numbers of 3000”
Asriza 和 Arcana - 2015 - SYNTHESIS OF COBALT STEARATE AS OXIDANT ADDITIVE F DOI: 10.1063/1.4930711 -
Hydroxyl (O-H) confidence 1.0
“9) showed that the peaks were cm-1 of C-H stretching, free O-H stretching, O-H 3000”
Aziz 等 - 2020 - FTIR and HPLC-Based Metabolomics of Yacon Leaves E DOI: 10.22146/ijc.43453 -
Hydroxyl (O-H) confidence 1.0
“OH-stretching contribution in the region between ~3700 cm-1 and ~3000 cm-1.”
Hydrating Capabilities of the Biopolymers Produced by the Marine Thermophilic Bacillus horneckiae SBP3 as Evaluated by ATR-FTIR Spectroscopy DOI: 10.3390/ma15175988 -
Alkyl C-H confidence 1.0
“the region 3000 cm-1 and 1740 cm-1 were related to CH2 symmetric stretching Also, the wavenumbers 2851 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
“The stronger CH stretching vibrations over2 3000cm-1.”
Caroline 等 - 2009 - Growth, optical, thermal and dielectric studies of DOI: 10.1016/j.matchemphys.2008.09.070 -
Alkyl C-H confidence 1.0
“n a-Si 12xC :H deposited under high microwave powers cm21 groups.7 sp2 x The C-H bands expected above 3000 n ~>800 W! have also shown a diamondlike phase in the C films.17 are not found in our This may be because H is pref-”
Chew 等 - 2002 - Hydrogenated amorphous silicon carbide deposition DOI: 10.1063/1.1500418 -
Alkyl C-H confidence 1.0
“cotton.14-17 and (c) treating greige fabric in 2g/L of aqueous NaOH In our previous report, the C-H stretching 3000cm(cid:2)1 solution and then 2g/L of scouring agent (AZ-100, region of 2800 to and the carbonyl stretching 1800cm(cid:2)1 98(”
Characterization of cotton fabric scouring by Fourier transform-infrared attenuated total reflectance spectroscopy, gas chromatography-mass spectrometry and water absorption measurements DOI: 10.1177/0040517518790976
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