What absorbs at 2922 cm⁻¹ in an FTIR spectrum?
A band near 2922 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 2922 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 | 107 | 102 | 1.0 |
| Hydroxyl (O-H) | 11 | 10 | 1.0 |
| Methyl | 10 | 9 | 1.0 |
| Methacrylate | 7 | 7 | 1.0 |
| Acetate | 7 | 7 | 1.0 |
| Carboxyl (COOH) | 7 | 7 | 1.0 |
| Amide | 6 | 6 | 1.0 |
| Aromatic ring | 6 | 6 | 1.0 |
| Lipid | 5 | 5 | 1.0 |
| Carbonyl (C=O) | 5 | 4 | 1.0 |
| Methoxy (OCH3) | 4 | 4 | 1.0 |
| Ketone | 4 | 4 | 1.0 |
| Hydrogen bond | 4 | 4 | 1.0 |
| Ester | 3 | 3 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| Oxygen heterocycle | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Fatty acid | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Chlorine | 1 | 1 | 1.0 |
| Silicate | 1 | 1 | 1.0 |
| Triglyceride | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Nucleic acid | 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 |
|---|---|---|---|
| Polystyrene | 2922, 1020, 1600 | Alkyl C-H, Methacrylate, Hydroxyl (O-H) | 2 |
| PVP | 2922, 2983, 1648 | Alkyl C-H, Hydroxyl (O-H), Methacrylate | 1 |
| Polyethylene | 2922, 1737, 1720 | Alkyl C-H, Methacrylate, Hydroxyl (O-H) | 1 |
| nanotube | 2922, 1540, 1080 | Methacrylate, Hydroxyl (O-H), Alkyl C-H | 1 |
| TiO2 | 2922, 1700, 1093 | Hydroxyl (O-H), Alkyl C-H, Methacrylate | 1 |
| hydroxyapatite | 2922, 1620, 1639 | 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 2922 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
“Peaks at 2922 attributed to C-H and at 1105 is belong to C-O bond from ether or carboxylic acid groups.”
Arizka 等 - 2019 - Synthesis and Physical Properties Characterization DOI: 10.1088/1757-899X/546/4/042004 -
Alkyl C-H confidence 1.0
“cm-1 and 1635 due to stretching vibrations of O-H group, the bands assigned at 3275 cmcm-1, - 1 the band at 2922 due to vibrations of C H stretching thee band at 1213 1062cm-1,482cm-1,576cm-1,1535cm-1arethefollowingvibrationsC-Ostretching,N”
Bio-engineered TiO2 nanoparticles using Ledebouria revoluta extract: Larvicidal, histopathological, antibacterial and anticancer activity DOI: 10.1080/03067319.2020.1718668 -
Alkyl C-H confidence 1.0
“The peak of 2922.36 cm-1 attributed to C-H bonds with benzene, and the band at 3059.46 corresponded to (Ar-H) bond absorption [19].”
Hidayani 等 - 2022 - Acoustic and Mechanical Properties of Polystyrene DOI: 10.37358/Mat.Plast.1964 -
Alkyl C-H confidence 1.0
“The band at 2922.36 cm-1 and 3059.46 cm-1 corresponded to C-H bonds with benzene and Ar-H.”
Preparation and Characterization of Sound-Absorbent Based on Polystyrene Reinforced Primary Sludge and Fly Ash from Pulp Mill DOI: 10.14716/ijtech.v14i3.5131 -
Alkyl C-H confidence 1.0
“3240 C-H stretching 2922 2929 2923 2929 C=O stretching”
Investigations of biodegradable polymer blend electrolytes based on Cornstarch: PVP: NH4Cl and its potential application in solid-state batteries DOI: 10.1007/s10854-021-05266-1 -
Alkyl C-H confidence 1.0
“a small peak at 2921.63 in both the films showed good C-H stretch, while a sharp peak”
Synthesis and characterization of eco-friendly bioplastic from low-cost plant resources DOI: 10.1007/s42452-019-1460-x -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
60MeV Ni ion induced modifications in nano-CdS/polystyrene composite films DOI: 10.1016/j.radphyschem.2013.06.022 -
Alkyl C-H confidence 1.0
“[41-42] IR analysis of the whole plant extract of Gotu kola revealed that the presence of different functional groups ranging from O-H stretching, hydroxyl (3319.26 cm-1), C-H stretching, carbonyl (2921.96 cm-1), C=C”
Kumar 等 - 2021 - Centella asiatica mediated facile green synthesis DOI: 10.1016/j.inoche.2021.108865
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