What absorbs at 2849 cm⁻¹ in an FTIR spectrum?
A band near 2849 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 2849 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 | 37 | 36 | 1.0 |
| Hydroxyl (O-H) | 6 | 5 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| C-O single bond | 2 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Aldehyde (CHO) | 1 | 1 | 0.95 |
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 |
|---|---|---|---|
| cellulose | 2849, 1735, 1650 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| hemicellulose | 2849, 1730, 897 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| lignin | 2849, 1035, 1510 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| biomass | 2849, 1082, 1282 | 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 2849 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
“Two consecutive peaks found at 2849 and cm-1 2931 may be attributed to the C-H stretching [62].”
Punia 等 - 2021 - Microstructural, Optical and Magnetic Study of Ni- DOI: 10.1007/s10948-021-05967-y -
C-O single bond confidence 1.0
“3299.09 3530.15 3565.78 C-H actions between the anti-Alzheimer's drugs (PC-37 and tacrine) Alkenyl stretching 2920.30 2918.84 2917.80 Open C-OH stretching 2848.72 2480.15 2849.57 and AIL (4-PyC8).”
Multi-spectroscopic monitoring of molecular interactions between an amino acid-functionalized ionic liquid and potential anti-Alzheimer's drugs DOI: 10.1039/d0ra06323a -
Alkyl C-H confidence 1.0
“CH2 antisymmetric stretching, combination Small - 2849 Weak CH2 symmetric stretching, combination C¼O 1732 Strong stretching Large - 1487 Weak CH2 scissors”
Vibrational Stark effect (VSE) on the infrared spectrum of a poly(methyl methacrylate) thin film DOI: 10.1016/j.vibspec.2015.03.006 -
Hydroxyl (O-H) confidence 1.0
“1527cm-1 assigned to hydroxyl (-OH) groups before adsorption, and The amide (-NH) peak observed at 1528cm-1, 2849cm-1 the two sharp peaks at 2918 and shifted to whilst the (-COO) group shifted to (-CH and 3 1405cm-1 2852cm-1 -CH after the a”
Thabede 等 - 2021 - Magnetite Functionalized Nigella Sativa Seeds for DOI: 10.1155/2021/6655227 -
Alkyl C-H confidence 1.0
“In the aliphatic stretching region, there were two cm-1 cm-1 distinct peaks at 2849 and 2917 which is attributed to symmetric and asymmetric -CH 2 14”
Optimization of primary sewage sludge and coal lignite by microwave assisted pyrolysis for the production of bio oil DOI: 10.1080/09593330.2020.1797903 -
Alkyl C-H confidence 1.0
“The second prominent peaks -CH which represent the stretching vibrations due to the presence of methyl/methylene are at 3050 and 2849 cm-1, and 3075, 2925 cm-1, only shown by TSW and MSW bio-chars, cm-1 group.”
Bio-Char Characterization Produced from Walnut Shell Biomass through Slow Pyrolysis: Sustainable for Soil Amendment and an Alternate Bio-Fuel DOI: 10.3390/en15010001 -
Alkyl C-H confidence 1.0
“Te average size of the nanospectively, asymmetric and symmetric C-H stretching 2849cm-1, particles in the Sn(Fe:Ni)O peaks were at 2917 and respectively.”
Aloufi - 2023 - Assessment of Structural, Optical, and Antibacteri DOI: 10.1155/2023/5494592 -
Carbohydrate confidence 1.0
“groups of the polysaccharide fraction and residual carboxylic acids, and intense bands at 2918 and groups of the polysaccharide fraction and residual carboxylic acids, and intense bands at 2918 and 2849 cm-1 attributed to the asymmetrical a”
Structural Studies of the Cutin from Two Apple Varieties: Golden Delicious and Red Delicious (Malus domestica) DOI: 10.3390/molecules25245955
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