What absorbs at 2961 cm⁻¹ in an FTIR spectrum?
A band near 2961 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 2961 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 | 12 | 12 | 1.0 |
| Methyl | 3 | 3 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| polypropylene | 2961, 1030, 1600 | Alkyl C-H, Amide | 1 |
| lignin | 2961, 1035, 1510 | Alkyl C-H | 1 |
| polypyrrole | 2961, 1700, 400 | Alkyl C-H, Amide | 1 |
| PPy | 2961, 1043, 910 | Alkyl C-H, Amide | 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 2961 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
“The peak at 2961 Polarization measurements of PPy and PPy/ZnO nanocomposites attributed to stretching vibration of C H bond in CH [20,21].”
Structural and electrochemical study of polypyrrole/ZnO nanocomposites coating on nickel sheet synthesized by electrochemical method DOI: 10.1016/j.synthmet.2012.12.013 -
Alkyl C-H confidence 1.0
“and symmetric CH stretching of mainly lipids at 2961 and 2873 asymmetric 3”
Specific Mycoparasite-Fusarium Graminearum Molecular Signatures in Germinating Seeds Disabled Fusarium Head Blight Pathogen’s Infection DOI: 10.3390/ijms22052461 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Improvement of stability due to a cyclamen aldehyde/β-cyclodextrin inclusion complex DOI: 10.1016/j.molstruc.2020.128161 -
Alkyl C-H confidence 1.0
“a group of bands at 2961, 2932 and DandHatomsareshowninFig.3(panelB,1-3).Thespectra obviously belongs to the CH group of the furanosic ring 2 ofD-dopeduridineinthestretchingrangeofN(O)Dgroupat (Fig.”
Rozenberg 等 - 2005 - Low-temperature FTIR spectra and hydrogen bonds in DOI: 10.1016/j.saa.2004.05.024 -
Alkyl C-H confidence 1.0
“The cm-1) A bar graph of the total CH 2:CH peak area, which CH asym (2961 band shifted gradually towards higher”
Shi 等 - 2018 - Biochemical alterations of Candida albicans during DOI: 10.1039/c8an01452c -
Alkyl C-H confidence 1.0
“The observed peaks at 2961 cm-1 and 2873 were due to C-H stretching in the methyl and methylene groups [58].”
Preparation, Thermal, and Mechanical Characterization of UV-Cured Polymer Biocomposites with Lignin DOI: 10.3390/polym12051159 -
Acetate confidence 1.0
“At 2961 there is another band corresponding to CH 3.”
Valoration of the Synthetic Antioxidant Tris-(Diterbutyl-Phenol)-Phosphite (Irgafos P-168) from Industrial Wastewater and Application in Polypropylene Matrices to Minimize Its Thermal Degradation DOI: 10.3390/molecules28073163 -
Alkyl C-H confidence 1.0
“A noticeable growth of absorbance at bands 2960.96 cm-1, and 2925.90 respectively, was attributed to CH and CH groups.”
The Influence of Essential Oil Compounds on Antibacterial Activity of Mupirocin-Susceptible and Induced Low-Level Mupirocin-Resistant MRSA Strains DOI: 10.3390/molecules24173105
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