What absorbs at 2861 cm⁻¹ in an FTIR spectrum?
A band near 2861 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 2861 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 | 9 | 9 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Alkene (C=C) | 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 |
|---|---|---|---|
| chitosan | 2861, 1650, 1655 | Alkyl C-H, Acetate, Methacrylate | 1 |
| polycaprolactone | 2861, 1580, 1751 | Methacrylate, Acetate, 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 2861 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 strong peak at 1750 cm-1, was attributed to the C=O stretching, and distinctive cm-1 cm-1 distinctive peaks at 2940 and 2861 were ascribed to the CH stretching in peaks at 2940 cm-1 and 2861 cm-1 were ascribed to the CH2 stretching in PCL”
Plasma-Induced Graft Polymerization of Polyethylenimine onto Chitosan/Polycaprolactone Composite Membrane for Heavy Metal Pollutants Treatment in Industrial Wastewater DOI: 10.3390/coatings12121966 -
Alkyl C-H confidence 1.0
“cm-1 cm-1 2861 was dispensed to C-H stretching.”
New Insight on Photoisomerization Kinetics of Photo-Switchable Thin Films Based on Azobenzene/Graphene Hybrid Additives in Polyethylene Oxide DOI: 10.3390/polym12122954 -
Acetate confidence 1.0
“cm-1, groups were identified by the peaks at 2950-2900 The peaks at 2861 and 2853 respectively, are caused by asymmetric CH3 stretching and both asymmetric and symmetric P.”
Do Red Seaweed Nanoparticles Enhance Bioremediation Capacity of Toxic Dyes from Aqueous Solution? DOI: 10.3390/gels8050310 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Musa 等 - 2017 - Development and evaluation of exemestane-loaded ly DOI: 10.15171/bi.2017.27 -
Alkyl C-H confidence 1.0
“Structural Analysis of Microspheres In the pure TRHC spectrum (Figure 8), characteristic peaks appeared at 3300.55 cm-1 for OH and 2929.68 and 2860.73 cm-1 for CH stretching.”
Prunus armeniaca Gum-Alginate Polymeric Microspheres to Enhance the Bioavailability of Tramadol Hydrochloride: Formulation and Evaluation DOI: 10.3390/pharmaceutics14050916 -
Acetate confidence 1.0
“The peak at 1748 correspond cm-1, cm-1 cm-1 to C=O stretching vibrations and the peaks at 2861 2921 and 3004 were associated with the -CH 2 cm-1 stretching, while the band at 3300 was ascribed to -O-H stretching vibrations.”
Phosphorylated microcapsules containing natural oil for potential self-healing use DOI: 10.1016/j.matpr.2021.05.093 -
Alkyl C-H confidence 1.0
“The hydroxyl group (OH) had an absorption peak at 3504.45 while 2860.79cm-1 cm-1 the band at was due to -CH stretching.”
Fabrication, In Vitro, and In Vivo Assessment of Eucalyptol-Loaded Nanoemulgel as a Novel Paradigm for Wound Healing DOI: 10.3390/pharmaceutics14091971 -
Ammonium confidence 1.0
“The two main characteristic bands at 2928 and 2861 cm-1 were assigned cm-1 3+ to the -NH3+ stretching vibrations [31,32].”
Spectroscopic and Molecular Docking Studies of Cu(II), Ni(II), Co(II), and Mn(II) Complexes with Anticonvulsant Therapeutic Agent Gabapentin DOI: 10.3390/molecules27134311
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