What absorbs at 2957 cm⁻¹ in an FTIR spectrum?
A band near 2957 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 2957 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 | 23 | 22 | 1.0 |
| Methyl | 5 | 5 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 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 |
|---|---|---|---|
| lipids | 2957, 1735, 810 | Alkyl C-H, Amide | 1 |
| chitosan | 2957, 1650, 1655 | Alkyl C-H, Amide, N h | 1 |
| PMMA | 2957, 1722, 1383 | Alkyl C-H | 1 |
| glycerol | 2957, 1585, 1630 | 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 2957 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
“Moreover, the bands located cm-1 cm-1 at 2957 and 2895 in CSMCD1 are due to the C-H stretching, symmetrically and asymmetrically [21,65].”
Structural, Electrical and Electrochemical Properties of Glycerolized Biopolymers Based on Chitosan (CS): Methylcellulose (MC) for Energy Storage Application DOI: 10.3390/polym13081183 -
Alkyl C-H confidence 1.0
“2888.93 Alkene C-H stretching stretching asymmetric 2956.67 2946 2949.92 CH 3 stretching asymmetric 3002 3000 2998.14 CH 3 3027.07 3026.1”
Ganesan 等 - 2018 - The effect of titanium dioxide nano-filler on the DOI: 10.1007/s10854-018-8815-8 -
Alkyl C-H confidence 1.0
“CH asymmetric stretching (2957 research rather than to understand the molecular mecha-”
Igci 等 - 2017 - Application of Fourier transform infrared spectros DOI: 10.17219/acem/65784 -
Alkyl C-H confidence 1.0
“The spectrum cm-1 TEL demonstrated the characteristic peaks at 3059 (aroof cm-1 cm-1 matic C H stretch), 2957 (aliphatic C H stretch), 1699 cm-1 (carboxylic acid), 1599 (aromatic C C bending and stretchcm-1”
Telmisartan complex augments solubility, dissolution and drug delivery in prostate cancer cells DOI: 10.1016/j.carbpol.2013.09.077 -
Amide confidence 1.0
“3089 (w) 3081 (w) 3079 (w) Amide B: N-H stretching of proteins asymmetric stretching, mainly lipids 2957 (s) 2953 (m) 2955 (m) CH 3”
Spectral profile index changes as biomarker of toxicity in Catla catla (Hamilton, 1822) edible fish studied using FTIR and principle component analysis DOI: 10.1007/s42452-020-3001-z -
Alkyl C-H confidence 1.0
“C-C stretching in benzoic ring and C-H wagging 2872 C-H stretching at imidazole ring 2957 C-H stretching in alkyl chain Table 3.”
Degradation of Losartan Potassium Highlighted by Correlated Studies of Photoluminescence, Infrared Absorption Spectroscopy and Dielectric Spectroscopy DOI: 10.3390/pharmaceutics14112419 -
Alkyl C-H confidence 1.0
“(trans is highly ordered conformation), the bands appear those of CH stretching bands near 2957 and 2873 3 cm(cid:2)1, at 2918 and 2848”
Topacli 等 - 2006 - Infrared studies of pyroelectric Langmuir-Blodgett DOI: 10.1016/j.molstruc.2006.03.083 -
Alkyl C-H confidence 1.0
“Assignment DPPC Major Peaks Assignment SM Major Peaks Assignment 2957 C-H stretch 2919 C-H stretch 2957 2919”
Prediction of Neonatal Respiratory Distress Biomarker Concentration by Application of Machine Learning to Mid-Infrared Spectra DOI: 10.3390/s22051744
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