What absorbs at 3009 cm⁻¹ in an FTIR spectrum?
A band near 3009 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 3009 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 | 16 | 14 | 1.0 |
| Alkene (C=C) | 12 | 11 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Fatty acid | 1 | 1 | 1.0 |
| Oxygen heterocycle | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 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 |
|---|---|---|---|
| polyethylene | 3009, 1737, 1720 | Alkyl C-H | 1 |
| polypropylene | 3009, 1030, 1600 | Alkyl C-H | 1 |
| MgO | 3009, 699, 874 | Alkyl C-H, N h | 1 |
| curcumin | 3009, 1063, 1153 | 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 3009 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 time and added enzyme effects were evaluated, cm-1) which resulted in the conversion of 50 and 45% of the unsaturation peak (3009 for the 24 h reactions with and without acrylic immobilization, respectively, in addition to cm-1), altera”
Montenegro 等 - 2023 - Enzymatic and Synthetic Routes of Castor Oil Epoxi DOI: 10.3390/polym15112477 -
Fatty acid confidence 1.0
“Another band appears at 3009 corresponding to the (H-C=) stretching vibration, which can be related to unsaturation in fatty acids, which is obviously greatest in the Brazilian coffee (B).”
Obeidat 等 - 2018 - Application of FTIR Spectroscopy for Assessment of DOI: 10.1007/s10812-018-0585-9 -
Aromatic ring confidence 1.0
“and 3009 aromatic C-H stretch was found at 3012 in NF-NDs/PAP/PANi/PTh and F-NDs/PAP/ An FTIR specPANi/PTh, respectively.”
Ashraf 等 - 2014 - Preparation and properties of multilayered polymer DOI: 10.1515/polyeng-2013-0297 -
Alkyl C-H confidence 1.0
“examined, including the regions between 3400 and cm-1 cm-1 MCR-ALS 2700 performed the spectral deconvolution of the exper- (C H/N H stretching), 3009 and 2909 (covercm-1 cm-1 imental ing data matrix [48] uncovering the temperature-dependent”
Calvo 等 - 2014 - A dynamic thermal ATR-FTIRchemometric approach to DOI: 10.1016/j.jpba.2013.12.036 -
Alkene (C=C) confidence 1.0
“a small peak was seen in all of the samples at 3009 This peak is caused by the symmetric stretching vibration of alkene double bonds, which suggests that all of the”
The Influence of Emulsifiers on the Physiochemical Behavior of Soy Wax/Rice Bran Oil-Based Oleogels and Their Application in Nutraceutical Delivery DOI: 10.3390/gels9010047 -
Alkene (C=C) confidence 1.0
“By analyzing and sesses two cis-alkene characteristic peaks which appear at 1660 and 3009 cm-1, representcomparing the spectra, it was found that the spectrum of the pristine jatropha possesses ing stretching vibrations of C=C and C=C-H, re”
Degradable Slow-Release Fertilizer Composite Prepared by Ex Situ Mixing of Inverse Vulcanized Copolymer with Urea DOI: 10.3390/agronomy12010065 -
Alkyl C-H confidence 1.0
“showed a more apparent minor peak at 3009 This peak was associated with the stretching vibration of CH cis-olefinic groups [45].”
Chemical Composition and Thermogravimetric Behaviors of Glanded and Glandless Cottonseed Kernels DOI: 10.3390/molecules27010316 -
Alkene (C=C) confidence 1.0
“LLM confirmed rule peak-group candidate”
Direct Polypropylene and Polyethylene Liquefaction in CO2 and N2 Atmospheres Using MgO Light and CaO as Catalysts DOI: 10.3390/ma15030844
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