What absorbs at 2050 cm⁻¹ in an FTIR spectrum?
A band near 2050 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 2050 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 | 4 | 3 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| C=n | 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 |
| Nitrile | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 0.5 |
| Alkyl C-H | 1 | 0 | 1.0 |
| Thiocyanate | 1 | 0 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed 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 2050 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
-
Nitrile confidence 1.0
“(cid:4)C 500 Following the heating of 4 at 500 for 0.2 h, the ATR FTIR C≡N revealed that the stretching frequencies between 2050 and cm(cid:3)1 confirming 2200 disappeared, thereby that the third stage of masslossduringtheTGAbelongstothedec”
Gerber 和 Erasmus - 2018 - Electronic effects of metal hexacyanoferrates An DOI: 10.1016/j.matchemphys.2017.09.029 -
confidence 1.0
“the absolute FTIR spectra also showed a significant peak at 2050 Analysis of the "light' cm-1, minus 'dark' difference spectra showed four very sharp CO stretching bands at 1970 1977 cm-1, cm-1, cm-1, 1981 and 1985 previously assigned to th”
Liu 等 - 2012 - Structural changes that occur upon photolysis of t DOI: 10.1016/j.bbabio.2011.12.010. -
Adsorbed carbon monoxide confidence 1.0
“A weak band was also observed at below 0.15V by SFG measurements as adsorbed CO derived from methanol on Pt(100) in addition to the main atop CO band at 2050cm-1.”
Sato 等 - 2007 - Adsorptionoxidation of CO on highly dispersed Pt DOI: 10.1016/j.electacta.2007.05.007 -
confidence 1.0
“An additional FTIR band at 2050 1 assigned to CO was detected and was found to increase during UV irradiation due to the adsorption of molecular CO on Pt/TiO 2.”
Belhadj 等 - 2017 - Mechanisms of Simultaneous Hydrogen Production and DOI: 10.1021/acscatal.7b01312 -
Adsorbed carbon monoxide confidence 1.0
“LLM confirmed rule peak-group candidate”
Buso-Rogero 等 - 2014 - Formic acid electrooxidation on thallium-decorated DOI: 10.1039/c4cp00304g -
Acetate confidence 1.0
“The broad and very weak band centered at 2050 has been assigned to 2 C-O-S impurity groups due to contamination of the raw materials [10,12].”
Pamukchieva 等 - 2012 - IR studies of impurities in chalcogenide glasses a DOI: 10.1088/1742-6596/356/1/012047 -
C=n confidence 1.0
“The C=N stretching vibrations in the polyaniline's quinonoid and benzenoid rings account for the 2135 cm-1 and 2050 cm-1 peaks, while the C-N stretching vibration was responsible for the 1875 cm-1 peak.”
Fabrication of Enhanced UV Protective Cotton Fabric Using Activated Nano-Biocarbon Derived from Teff Hay Grafted by Polyaniline: RSM-Based Optimization and Characterization DOI: 10.3390/molecules28135142 -
Adsorbed carbon monoxide confidence 1.0
“On the Pt(111) without nickel two main CO bands are observed, at 2050 and 1825 that can be ascribed to on top and bridge CO, respectively [41].”
Sarabia 等 - 2018 - Underpotential deposition of Nickel on platinum si DOI: 10.1016/j.jelechem.2017.11.033
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