What absorbs at 2150 cm⁻¹ in an FTIR spectrum?
A band near 2150 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 2150 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 |
|---|---|---|---|
| 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 |
| Amide | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| Adsorbed carbon monoxide | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Bronsted acid site | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 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 |
|---|---|---|---|
| cotton | 2150, 1030, 1638 | Methacrylate, Ester | 1 |
| goethite | 2150, 1470, 696 | Carboxyl (COOH) | 1 |
| biomass | 2150, 1082, 1282 | Methacrylate | 1 |
| silver nanoparticles | 2150, 1636, 1631 | Methacrylate | 1 |
| PLLA | 2150, 1182, 921 | 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 2150 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
-
Alkene (C=C) confidence 1.0
“tracts showed an olefinic peak at 2150 which by Bar and co-workers they synthesized silver Jatropa curcas disappeared in spectrum of shoot and seed extract nanoparticles using seed extract of”
Siraj 等 - 2020 - Biosynthesized silver nanoparticles from shoot and DOI: 10.2306/scienceasia1513-1874.2020.097 -
confidence 1.0
“[10]reporteda sim2 cm(cid:2)1 (cid:3)950-1350 ilar microstructural change during the oxidation of SiNWs at temvibration is associated with Si-O-Si vibration 2150cm(cid:2)1 peratures between 800 and 950(cid:3)C.”
Effect of H2 ambient annealing on silicon nanowires prepared by atmospheric pressure chemical vapor deposition DOI: 10.1016/j.cplett.2010.06.028 -
Water (H2O) confidence 1.0
“within the restricted sampling area illuminated by the IR radiation Upon water sorption, the PVOH spectrum begins to exhibit a duetothefixedaperturesize.Thissuggeststhatthedominantprobroad, symmetric, and relatively weak band centered near”
Time series Fourier transform infrared spectroscopy for characterization of water vapor sorption in hydrophilic and hydrophobic polymeric films DOI: 10.1016/j.saa.2020.119371 -
Bronsted acid site confidence 1.0
“The CO adsorption NMR spectroscopy is a reliable method for the quantification centers.11,47 15Nexperiments shown on the previous section do not give any of Lewis and Brønsted acid The adsorption of indication for these Brønsted acid sites,”
Comparative study of the strongest solid Lewis acids known: ACF and HS-AlF3 DOI: 10.1039/c8dt03279c -
Alkene (C=C) confidence 1.0
“and a peak at 2150 indicates the cm-1 stretching C=C=O of the bond that is present in ketenes.”
Grgac 等 - 2022 - The Effect of Ultrasonic Treatment on the Binding DOI: 10.3390/ma15020470 -
N h confidence 1.0
“The peak at 2150 cm-1 was for the CN group assigned to the -NH stretching vibrations [31,32].”
Spectroscopic and Molecular Docking Studies of Cu(II), Ni(II), Co(II), and Mn(II) Complexes with Anticonvulsant Therapeutic Agent Gabapentin DOI: 10.3390/molecules27134311 -
Acetate confidence 1.0
“O-H stretching in cellulose and lignin 3600-3000 C-H stretching in aliphatic formation 2960-2850 C=C=O stretching ketene 2150”
Acacia Holosericea: An Invasive Species for Bio-char, Bio-oil, and Biogas Production DOI: 10.3390/bioengineering6020033 -
Carbonate confidence 1.0
“The spectra cm-1, recorded on the bluish-green areas exhibited the Raman lines of Prussian blue, observed at 276, 532, 2094, 2150 cm-1 together with lines at 988 and 1050 due to sulphate and carbonate stretching modes of barite, and lead wh”
Hidden colours in stuccowork damaged by fire: A multi-analytical investigation for revealing the original decorative pattern DOI: 10.1016/j.culher.2015.11.002
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.