What absorbs at 2846 cm⁻¹ in an FTIR spectrum?
A band near 2846 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 2846 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 | 17 | 17 | 1.0 |
| Methyl | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 0.8 |
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 | 2846, 1737, 1720 | Alkyl C-H, Methacrylate, Methoxy (OCH3) | 1 |
| polypropylene | 2846, 1030, 1600 | Alkyl C-H, Methacrylate, Methoxy (OCH3) | 1 |
| Starch | 2846, 1650, 1540 | Methacrylate, Alkyl C-H, Methoxy (OCH3) | 1 |
| cellulose | 2846, 1735, 1650 | Alkyl C-H, Methacrylate, Methoxy (OCH3) | 1 |
| silver nanoparticles | 2846, 1636, 1631 | Alkyl C-H, Methacrylate, Methoxy (OCH3) | 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 2846 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
“A difference between the inexistence of CH vibrations at 2846.4 and 2 experimental and calculated XRD diagrams is observed (such indicates that the surfactant is not present in the as-synthesized cm-1 3609.4 as (002), (101), (102), (100) pl”
Mu 等 - 2009 - Synthesis, characterization and photoluminescence DOI: 10.1088/0957-4484/20/34/345602 -
Alkyl C-H confidence 1.0
“The symmetric and asymmetric stretching vibrations of C-H groups are confirmed with two cm-1 cm-1, peaks at 2846 and 2919 respectively [40].”
Cellulose‐reinforced starch biocomposite: optimization of the effects of filler and various plasticizers using Design‐Expert method DOI: 10.1002/star.202000028. -
Alkyl C-H confidence 1.0
“Finally, cm-1, cm-1, 2846.1 and 2924.3 and 2850 assigned to asymmetrical and symmetrical stretching CH the bands at 2919.6 and 2846.1 cm-1, and 2924.3 and 2850 cm-1, assigned to asymmetrical and groups for CIP and CSP, respectively, were al”
Preparation of Renewable Bio-Polyols from Two Species of Colliguaja for Rigid Polyurethane Foams DOI: 10.3390/ma11112244 -
Alkyl C-H confidence 1.0
“The two sharp peaks visible at 2914 and 2846 cm-1 were attributed to the C-H bond stretching vibrations of methyl groups.”
In Situ Gel with Silver Nanoparticles Prepared Using Agrimonia eupatoria L. Shows Antibacterial Activity DOI: 10.3390/life13020573 -
Alkyl C-H confidence 1.0
“2911 CH2 Asymmetric stretching Polyethylene 2846 CH2 Symmetric stretching 3230”
Modification of surface characteristic and tribo-electric properties of polymers by DBD plasma in atmospheric air DOI: 10.1051/epjap/2017170149 -
Alkyl C-H confidence 1.0
“The Raman spectra of all waxes (Figure 2a,b) are dominated by the strong bands stretching vibrations: the bands at 2879 cm-1 and 2846 cm-1 are atrelated to the CHx”
Characterization of Waxes in the Roman Wall Paintings of the Herculaneum Site (Italy) DOI: 10.3390/app122111264 -
Alkyl C-H confidence 1.0
“cm-1 by opposed peaks at 2916 and 2937 capturing a widening of the CH asymmetric stretching peak, and by opposed peaks 2 cm-1 at 2846 and 2860 capturing a shift of the CH symmetric 2 stretching peak.”
Biophysical Stress Responses of the Yeast Lachancea thermotolerans During Dehydration Using Synchrotron-FTIR Microspectroscopy DOI: 10.3389/fmicb.2020.00899 -
Protein confidence 1.0
“(2006) found two intense 2915cm-1 2846cm-1 bands occurring at and associated with methyVariation in the physical-chemical parameters (protein, moisture, fat Fig.”
FTIR-ATR spectroscopy as a tool for the rapid detection of adulterations in butter cheeses DOI: 10.1016/j.lwt.2019.04.017
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