What absorbs at 2157 cm⁻¹ in an FTIR spectrum?
A band near 2157 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 5 cited sources
Quick answer
A band near 2157 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 | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Adsorbed carbon monoxide | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 1.0 |
| Hydroxyl (O-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 |
|---|---|---|---|
| Fe3O4 | 2157, 2358, 1673 | Alkyl C-H | 1 |
| iron oxide | 2157, 1130, 891 | Alkyl C-H | 1 |
| zeolite | 2157, 1013, 1245 | Alkyl C-H, Adsorbed carbon monoxide | 1 |
| Fe3O4 nanoparticles | 2157, 1673, 1470 | Alkyl C-H, Carbonyl (C=O) | 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 2157 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
“However, with the cm-1 reduced sample the band at 2157 is observed even after restoration of the silanol OH band.”
Penkova 等 - 2007 - Effect of the preparation method on the state of n DOI: 10.1021/jp071927p -
Silicon hydride confidence 1.0
“9.2 - N-H 2 Si-H rock 673 105 Si-H(N 2Si) stretching 2157”
Ay 和 Aydinli - 2004 - Comparative investigation of hydrogen bonding in s DOI: 10.1016/j.optmat.2003.12.004 -
Adsorbed carbon monoxide confidence 1.0
“band corresponds to linear CO complexes, the band at 2157 Tvaruˇzkov´a Wichterlov´a, 12 Z.”
Remarkable acid strength of ammonium ions in zeolites: FTIR study of low-temperature CO adsorption on NH4FER DOI: 10.1039/c4ra12504e -
Carbonyl (C=O) confidence 1.0
“The IR bands from 2860, 2926, and 2966 The strong IR band from 2157 cm-1 is specific to Fe-CO metal carbonyl vibration are specific to symmetric/asymmetric stretch C-H vibrations in the methyl group [51].”
Preparation and Characterization of Dextran Coated Iron Oxide Nanoparticles Thin Layers DOI: 10.3390/polym13142351 -
confidence 0.7
“Peak at 2157 confirms existence of carbon.”
Mahmood 等 - 2022 - Self-Healing Bio-Concrete Using Bacillus subtilis DOI: 10.3390/ma15217731
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a literature-backed analysis — in seconds.