What absorbs at 2972 cm⁻¹ in an FTIR spectrum?
A band near 2972 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 2972 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 | 8 | 8 | 1.0 |
| Amide | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Aromatic ring | 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
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| polycaprolactone | 2972, 1580, 1751 | Methacrylate, Alkyl C-H, Amide | 1 |
| silver nanoparticles | 2972, 1636, 1631 | Hydroxyl (O-H), Alkyl C-H, Methacrylate | 1 |
| iron oxide nanoparticles | 2972, 528, 1628 | Hydroxyl (O-H), Alkyl C-H, Methacrylate | 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 2972 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
-
Hydroxyl (O-H) confidence 1.0
“Likewise, IR spectral bands at 2972, 2880, cm-1 178 and 2367 assigned to -OH, C-H and H-C=O stretching of hydroxyl groups of phenols, 179 carboxylic acids, alkanes and aldehydes (Yusefi et al., 2020;”
Bio-inspired synthesis of flower shaped iron oxide nanoparticles (FeONPs) using phytochemicals of Solanum lycopersicum leaf extract for biomedical applications DOI: 10.1016/j.bcab.2020.101698 -
Alkyl C-H confidence 1.0
“Between them, the cm-1 spectra of LBQ had two peaks at 2972 (C-H stretching of the methylene bridges) and Molecules 2022, 27, x FOR PEER REVIEW 4 of 20 Molecules2022,27,5842”
Comparative Analysis of the Phenolic Profile of Lycium barbarum L. Fruits from Different Regions in China DOI: 10.3390/molecules27185842 -
Hydroxyl (O-H) confidence 1.0
“(2020), the to O-H stretch, while the peaks at 2972, 1375, and 1218 cm-1 heating process to diatomite waste at 400 °C increases could be attributed to C-H stretching vibration.”
Hamdiani 和 Shih - 2021 - A Green Method for Synthesis of Silver-Nanoparticl DOI: 10.22146/ijc.63573 -
Alkyl C-H confidence 1.0
“Two other peaks at 2972 which corresponds to C-H Alkayl treated samples.”
Sultana 等 - 2023 - Investigation of the Effect of Atmospheric Plasma DOI: 10.3390/membranes13020231 -
Alkyl C-H confidence 1.0
“In 2 cm-1 pure PVC sample A, the C-H stretching peak at 2972 cm-1 and C-Cl stretching observed at 863 [33].”
Dynamic mechanical and optical characterization of PVC/fGO polymer nanocomposites DOI: 10.1007/s00339-018-2026-2 -
Hydroxyl (O-H) confidence 1.0
“Observed peak cm-1 intensity at 3324.6 was assigned to the -O-H structuring vibrations modes, 2971.6, cm-1, 2926.4, and 2881.2 which are attributed to the presence of asymmetric and symmetric structuring vibration modes of C-H aliphatic car”
Alamier 等 - 2022 - Thermodynamic and Spectroscopic Studies of SDS in DOI: 10.3390/app122312020 -
Amide confidence 1.0
“The amide A band at 3300 and cm-1 the amide B band peaks at 2972 are associated with N-H stretching vibrations and cm-1 the asymmetrical stretching of CH 2.”
A 3D-Printed Polycaprolactone/Marine Collagen Scaffold Reinforced with Carbonated Hydroxyapatite from Fish Bones for Bone Regeneration DOI: 10.3390/md20060344 -
Alkyl C-H confidence 1.0
“In an 1376, and 1450 are due to stretch, and the peaks at 2865 PPG.36 cm-1 βCD C-H attempt to develop a reusable platform, in this work we and 2972 arise from stretching groups of In βCD evaluated two different PPG surfaces, as a support, t”
Panahi 等 - 2022 - Nanostructured Cyclodextrin-Mediated Surface for C DOI: 10.1021/acsami.2c07701
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