What absorbs at 2919 cm⁻¹ in an FTIR spectrum?
A band near 2919 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 2919 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 | 63 | 53 | 1.0 |
| Hydroxyl (O-H) | 7 | 5 | 1.0 |
| N h | 4 | 4 | 1.0 |
| Methyl | 4 | 3 | 1.0 |
| Carbohydrate | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 3 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Lipid | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Aromatic ring | 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 |
|---|---|---|---|
| pectin | 2919, 1746, 1150 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| asphalt | 2919, 1600, 1376 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| silver nanoparticles | 2919, 1636, 1631 | Hydroxyl (O-H), Alkyl C-H, N 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 2919 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
-
Alkyl C-H confidence 1.0
“39.41 ± 0.22 -1.73 ± 0.04 17.36 ± 0.19 c a c cm-1 cm-1 GL 17.05 ± 0.27 27.08 ± 0.33 11.38 ±0.18 a d a (sp2) stretching 2918.92 and 2851.05 corresponding to the CH (sp3) stretching.”
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
“On the contrary, the content of and cm-1 CH group corresponding to peaks at 2919 and 2849 were not”
Effect of oxidation processing on the surface properties and floatability of Meizhiyou long-flame coal DOI: 10.1016/j.fuel.2017.08.053 -
Alkyl C-H confidence 1.0
“As can be deduced, the absorption bands cm-1, cm-1 at 2919.3 and 2850 are caused by stretching vibration of aliphatic C-H cm-1, cm-1 cm-1 while the peaks at 1468 1445 and 1437 are identified as bending”
Liang 等 - 2017 - Thermo-stability and aging performance of modified DOI: 10.1016/j.matdes.2017.04.060 -
Alkyl C-H confidence 1.0
“peaks at 2919, 2850, 1586, and 1031 were due to C-H methylene group of”
Manullang 等 - 2021 - Plant-extract-mediated biosynthesis of silver nano DOI: 10.13057/nusbiosci/n130216 -
Secondary amine confidence 1.0
“which was a result of an overlap of carboxylic - A clear observation of the relative spectra peak changes is O-H with primary and secondary amine -N-H stretching 2919cm(cid:2)1”
Mashingaidze 等 - 2013 - Exploration of the biomacromolecular interactions DOI: 10.1002/jbm.a.34664 -
Alkyl C-H confidence 1.0
“In the region 3700-2500 absorptions at 2964, 2931, and cm¡1 troscopy, employing the KBr technique, in the spectral range 2907 in DMS were ascribed to C-H-stretching vibrations of cm¡1 dimethylsilylgroups,whileastrongpeakat2919cm¡1intheDMPS”
Modification of Chrysotile Surface by Organosilanes: An IR–Photoacoustic Spectroscopy Study DOI: 10.1006/jcis.2001.7524 -
confidence 1.0
“The band at 2938 cm-1 and 2919 cm-1 corresponded to N-H cm-1 cm-1 with WPC in honey powder.”
Development and Characterization of a Nutritionally Rich Spray-Dried Honey Powder DOI: 10.3390/foods10010162 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Yuan 等 - 2015 - Hydrophobic effect of silica functionalized with s DOI: 10.1007/s12039-015-0965-0
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