What absorbs at 2250 cm⁻¹ in an FTIR spectrum?
A band near 2250 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 2250 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 |
|---|---|---|---|
| Isocyanate | 7 | 5 | 1.0 |
| Amide | 6 | 5 | 1.0 |
| Nitrile | 3 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Ketone | 3 | 3 | 1.0 |
| Ester | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Silicon hydride | 3 | 2 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| N n bond | 1 | 1 | 1.0 |
| Urethane | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| C#c | 1 | 1 | 0.9 |
| Carbon dioxide | 1 | 1 | 0.6 |
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 |
|---|---|---|---|
| polyurethane | 2250, 2270, 1700 | Methacrylate, Amide | 1 |
| DNA | 2250, 1712, 1660 | Amide, 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 2250 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
-
N-O bond confidence 1.0
“A.M.Giovannozzi,M.Rocchia/SensorsandActuatorsB130(2008)795-801 797 2250cm-1, no signals at 2200 and due to the Si-H stretching withoxygenatomsinback-bondingconfiguration(O ySiH with x”
Giovannozzi 和 Rocchia - 2008 - Effect of the reaction time, reagent concentration DOI: 10.1016/j.snb.2007.10.043 -
Silicon (Si) confidence 1.0
“Porous silicon is more susceptible to oxidation than single crystal Lomonosov wafer and the spectra show evidence of substantial oxidation of the porous silicon after synthesis cm(cid:1)1 with the appearance of the absorbance peak at 2250 d”
Lie 等 - 2004 - Immobilisation and synthesis of DNA on Si(111), na DOI: 10.1039/b302845c -
Isocyanate confidence 1.0
“LLM confirmed rule peak-group candidate”
Degradation of polyester polyurethane by an indigenously developed consortium of Pseudomonas and Bacillus species isolated from soil DOI: 10.1016/j.polymdegradstab.2016.11.003 -
Silicon hydride confidence 1.0
“2158 2157 2162 [27] (6) Si-H(N (7) Si-H(N 3) stretching 2250 2224”
Ay 和 Aydinli - 2004 - Comparative investigation of hydrogen bonding in s DOI: 10.1016/j.optmat.2003.12.004 -
N n bond confidence 1.0
“= lab(AAN)×40 = 5×1017 N N limit(AAN) limit moleculecm-2 1×1016 detection is using the CN stretching around2250cm-1.”
Borget 等 - 2012 - Aminoacetonitrile characterization in astrophysica DOI: 10.1051/0004-6361/201218949 -
C c single bond confidence 1.0
“The bands at 1767 and 1665 were associated cm-1 -CN C-C band's absence at around 2250 due to the stretch with C=O stretching vibrations, and aromatic ring chain”
Bouchmella 等 - 2023 - Impact of Mesoporous Silica Functionalization Fine DOI: 10.1021/acsomega.2c08065 -
Isocyanate confidence 1.0
“LLM confirmed rule peak-group candidate”
Gregori Valdes 等 - 2018 - Synthesis and Characterization of Isosorbide-Based DOI: 10.3390/polym10101170 -
Hydroxyl (O-H) confidence 1.0
“The peak at 2250 is due to O-H stretching of the hydroxyl cm-1 cm-1 groups [29].”
Physicochemical Characterization and Antibacterial Activity of Titanium/Shellac-Coated Hydroxyapatite Composites DOI: 10.3390/coatings12050680
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