What absorbs at 2955 cm⁻¹ in an FTIR spectrum?
A band near 2955 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 2955 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 | 26 | 25 | 1.0 |
| Methacrylate | 4 | 4 | 1.0 |
| Acetate | 4 | 4 | 1.0 |
| Methyl | 4 | 4 | 1.0 |
| Methoxy (OCH3) | 3 | 3 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Lipid | 2 | 2 | 1.0 |
| Sulfate (SO4) | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Fatty acid | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
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 2955 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
“cm(cid:2)1 3400 region with a number of prominent peaks due to - A + B P (P = product), when reactant A (limited) is present in -OH stretching in the intermolecular hydrogen-bonding structure reactant B (in excess), the rate equation can be”
Gao 等 - 2018 - A kinetics study of the heterogeneous reaction of DOI: 10.1039/c8cp01914b -
Alkyl C-H confidence 1.0
“Alcohol, carboxyl, water 3060 C-H stretch Aromatic CH 2955 C-H asymmetric stretch”
Compositional diversity in insoluble organic matter in type 1, 2 and 3 chondrites as detected by infrared spectroscopy DOI: 10.1016/j.gca.2011.03.037 -
Alkyl C-H confidence 1.0
“3.2.2.2 SC lipid structure C Lipid components of the SC exhibit four fine peaks at around 2955, 2920, 2870 and 2850 A cm-1 which are assigned to asymmetric CH stretching, asymmetric CH stretching,”
Mansour 等 - 2017 - Elucidation of penetration enhancement mechanism o DOI: 10.1016/j.saa.2017.05.026 -
Alkyl C-H confidence 1.0
“1731 1727 -4 C-H stretching in CH 2955 2947”
Naik 等 - 2019 - Optical and Electrical Properties of TCNQ Doped PM DOI: 10.1063/1.5100466 -
Alkyl C-H confidence 1.0
“relative abundances of some molecular substructures, and it Ibarra and Miranda, 1995) have attempted to use the ratio of the area has been demonstrated as a viable tool for the characterization of coal cm-1) to the area under under the asym”
Geochemical and petrographic alteration of rapidly heated coals from the Herrin (No. 6) Coal Seam, Illinois Basin DOI: 10.1016/j.coal.2016.08.022 -
N h confidence 1.0
“The presence of OLA group on CZTSe nanocrystals is indicated by NH bending modes at 909, 964 and 2 993cm-1, 1468cm-1, C-H bending mode at NH scissor mode at 2 1568cm-1 2955cm-1.”
Hot-injection synthesis and characterization of quaternary Cu2ZnSnSe4 nanocrystals DOI: 10.1016/j.matlet.2010.03.034 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Zhao 等 - 2015 - Evaluation of Oil Yield of Oil Shale by Infrared S DOI: 10.1007/s40242-015-4364-3 -
Alkyl C-H confidence 1.0
“cm-1 ν ν at 2852 and 2955 that arose from the s(CH 2) and as(CH 2), showed stronger absorption than bands at 2852 and 2955 cm-1 that arose from the νs(CH2) and νas(CH2), showed stronger absorption than the SSMC spectrum.”
Application of FTIR and LA-ICPMS Spectroscopies as a Possible Approach for Biochemical Analyses of Different Rat Brain Regions DOI: 10.3390/app8122436
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