What absorbs at 2141 cm⁻¹ in an FTIR spectrum?
A band near 2141 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 2141 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 |
|---|---|---|---|
| Adsorbed carbon monoxide | 2 | 2 | 1.0 |
| C#c | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| N n bond | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| water | 2141, 1018, 2945 | Methoxy (OCH3) | 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 2141 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
“2325.00 2349.47, 2817.79, 2124.28, 1905.70, 1444.61, 1123.54, and 529.99 were 2337.64 assigned to O-H stretching, alcohol, O-H stretching, carboxylic acid, - - 2140.59 2124.28 carbodiimide (N=C--N C-- = N N stretching, allene, C-H bending,”
Preparation and characterization of activated carbon from agricultural wastes and their ability to remove chlorpyrifos from water DOI: 10.1016/j.toxrep.2023.01.011 -
Silicon hydride confidence 1.0
“and SiH stretching vibration at 2141 The absorption peaks position and identification of SiH bonds in the spectral range 3 x cm-1 from 2050 to 2150 are listed in Tab.”
Kralik 和 Kopani - 2023 - Analysis of porous silicon structures using FTIR a DOI: 10.2478/jee-2023-0028 -
C#c confidence 1.0
“At peak with wave numbers 2140.99 cm-1 and 2059.98 , corresponds to the absorption caused by the triple bonds of C≡C (alkaline type cm-1”
Maulida 等 - 2018 - Utilization of mango seed starch in manufacture of DOI: 10.1088/1748-0221/5/10/P10010/pdf -
Adsorbed carbon monoxide confidence 1.0
“The relevant features of the spectrum of CO adsorbed at 60 K (Figure 3) are: a) a broad and highly cm-1 cm-1, reversible band at 2141 due to physically adsorbed CO;”
Mino 等 - 2012 - Particles Morphology and Surface Properties As Inv DOI: 10.1021/jp303942h -
Adsorbed carbon monoxide confidence 1.0
“The relevant features of the spectrum of CO adsorbed at 60 K (Figure 3) are: a) a broad and highly cm-1 cm-1, reversible band at 2141 due to physically adsorbed CO;”
Mino 等 - 2013 - Rutile Surface Properties Beyond the Single Crysta DOI: 10.1021/jp401916q
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