What absorbs at 2270 cm⁻¹ in an FTIR spectrum?
A band near 2270 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 2270 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 |
|---|---|---|---|
| N c o | 19 | 18 | 1.0 |
| Isocyanate | 15 | 13 | 1.0 |
| Methacrylate | 5 | 5 | 1.0 |
| Carboxyl (COOH) | 5 | 5 | 1.0 |
| Carbonyl (C=O) | 5 | 5 | 1.0 |
| Amide | 5 | 5 | 1.0 |
| Acetate | 5 | 5 | 1.0 |
| Ketone | 4 | 4 | 1.0 |
| Ester | 4 | 4 | 1.0 |
| N-O bond | 4 | 3 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| C=n | 2 | 2 | 1.0 |
| Adsorbed carbon monoxide | 1 | 1 | 1.0 |
| Carbon dioxide | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 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 |
|---|---|---|---|
| polyurethane | 2270, 1700, 1100 | Methacrylate | 2 |
| polyurethanes | 2270, 1740, 1728 | Methacrylate | 1 |
| polyvinyl alcohol | 2270, 1141, 1640 | Methacrylate, Carboxyl (COOH) | 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 2270 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
“Samples were canbeobserved[17].Thereactionbetweenurethaneprepolymerand dehydratedingradedalcohols(10,30,50,70,80,85,90,95,and100%) polyvinyl alcohol indicates the absence of isocyanate peaks (NCO) at 2270cm-1.”
Preparation and characterization of polyvinyl alcohol hydrogels crosslinked by biodegradable polyurethane for tissue engineering of cartilage DOI: 10.1016/j.msec.2010.02.017 -
N c o confidence 1.0
“troscopy is from the disappearance of the NCO peak at 2270 still observed even after 7 days of RT curing followed by 545 h 50◦C composition, time for complete cure, hard segment content curing at at 25% RH.”
Hydrogen bonding and thermomechanical properties of model polydimethylsiloxane based poly(urethane-urea) copolymers: Effect of hard segment content DOI: 10.1016/j.porgcoat.2015.06.015 -
C=n confidence 1.0
“Obviously, the characteristic is interesting that the viscosity of the HTPE/HDIB system cm-1 peak height at 2270 corresponding to-N=C=O”
Curing reaction kinetics of HTPE polymer studied by simultaneous rheometry and FTIR measurements DOI: 10.1007/s10973-016-5485-8 -
N c o confidence 1.0
“cm-1 cm-1 Previous studies had reported that the C-O is stretching at 1062 and 1220 and no NCO absorption at 2270 were observed showing that the reaction was complete [16].”
Preparation of one-shot and two-shot method of semi-rigid polyurethane film based on functionalized liquid natural rubber DOI: 10.1063/1.5047200 -
confidence 1.0
“The FTIR spectrum of the resulting product DRICP/silica sphere (DRICPSS) shows no cm-1 characteristic isocynate absorption peak at 2270 and shows a new absorption peat at cm-1 1700 corresponding the C=O stretching vibration.”
Kim 和 Kang - 2012 - Optical properties of azo-chromophore attached on DOI: 10.1117/12.999810 -
N c o confidence 1.0
“LLM confirmed rule peak-group candidate”
Preparation and Characterization of Self-Colored Waterborne Polyurethane and Its Application in Eco-Friendly Manufacturing of Microfiber Synthetic Leather Base DOI: 10.3390/polym10030289 -
Isocyanate confidence 1.0
“cm-1 cm-1 N=C=O peak at 2270 was ascribed to bonds.”
Novel Polyvinyl Alcohol (PVA)/Cellulose Nanocrystal (CNC) Supramolecular Composite Hydrogels: Preparation and Application as Soil Conditioners DOI: 10.3390/nano9101397 -
Isocyanate confidence 1.0
“reported.16,29,33-36 appearance of the strong isocyanate absorption By time-dependent FTIR studcm(cid:2)1 peak around 2270 ies we demonstrated that, following a heating with an FTIR spectropho- (cid:1)C for 30 min) the development of step (”
Time-dependent morphology development in segmented polyetherurea copolymers based on aromatic diisocyanates DOI: 10.1002/polb.21652
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