What absorbs at 2161 cm⁻¹ in an FTIR spectrum?
A band near 2161 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 2161 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 |
|---|---|---|---|
| Nitrile | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Adsorbed carbon monoxide | 1 | 1 | 1.0 |
| C#c | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
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 2161 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
“The absorption characteristics of chitosan with OH stretching were found at 3002 cm-1, C-H at 2161 cm-1, and C=O at”
Synthesis and Optimization of Superhydrophilic-Superoleophobic Chitosan–Silica/HNT Nanocomposite Coating for Oil–Water Separation Using Response Surface Methodology DOI: 10.3390/nano12203673 -
C#c confidence 1.0
“3276 Strong, broad Alcohol Alkyne C≡C terminal alkyne (monosubstiOH stretch 2161 Weak”
The Antimicrobial Activities of Silver Nanoparticles from Aqueous Extract of Grape Seeds against Pathogenic Bacteria and Fungi DOI: 10.3390/molecules26196081 -
Adsorbed carbon monoxide confidence 1.0
“cm-1) other two bands at higher frequencies (2161 and 2152 required more time for complete The other two bands at higher frequencies (2161 cm-1 and 2152 cm-1) required more time for complete desorption, and for this reason they can be assig”
Atzori 等 - 2020 - Adsorption Properties of Ce-5(BDC)(7.5)(DMF)(4) MO DOI: 10.3390/inorganics8020009 -
Silanol (Si-OH) confidence 1.0
“The cm-1 remaining band at 2161 is related to silanol groups present in large quantity in Mn 2.0SiBEA in line with earlier”
Influence of the nature and environment of manganese in Mn-BEA zeolites on NO conversion in selective catalytic reduction with ammonia DOI: 10.1039/C7CP02096A -
Nitrile confidence 1.0
“ice is warmed, a nitrile band at 2161 AAN is diluted in water ice, a large amount of AAN is driven”
Borget 等 - 2012 - Aminoacetonitrile characterization in astrophysica DOI: 10.1051/0004-6361/201218949
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