What absorbs at 1991 cm⁻¹ in an FTIR spectrum?
A band near 1991 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 6 cited sources
Quick answer
A band near 1991 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.
Attributions possibles de groupes fonctionnels
| Groupe fonctionnel | Faits à l＇appui | Sources citées | Confiance maximale |
|---|---|---|---|
| Aromatic ring | 2 | 2 | 1,0 |
| Carbonyl (C=O) | 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 |
Le classement reflète les preuves bibliographiques accumulées, et non une règle faisant autorité. Confirmez toujours dans le contexte de votre échantillon.
Possible materials
| Matériel | Pics de support | Overlapping groups | Sources citées |
|---|---|---|---|
| lignin | 1991, 1035, 1510 | Methacrylate, Aromatic ring, Methoxy (OCH3) | 2 |
| wood | 1991, 1740, 1730 | Methacrylate, Methoxy (OCH3), Aromatic ring | 2 |
| cellulose | 1991, 1735, 1650 | Methacrylate, Methoxy (OCH3) | 1 |
| hemicellulose | 1991, 1730, 897 | Methacrylate, Methoxy (OCH3), Carbonyl (C=O) | 1 |
| TiO2 | 1991, 1700, 1093 | Methacrylate, 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 1991 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.
Bibliographie derrière ces attributions
-
Alkyl C-H confiance 1,0
“The intensity of this peak is inversely Caesalpiniaceae, Annonaceae, Bombacaceae, Dipterocarpaceae, proportional to CH stretching vibration (Rochdi and Landias, 1991;”
Mathews 等 - 2018 - Characterization of Panandhro Lignite Deposits (Ka DOI: 10.1007/s12594-018-851-8 -
Aromatic ring confiance 1,0
“Pandey (1999) CsO 3 1596 Aromatic skeletal vibration plus stretch Faix (1991), Faix et al.”
Rana 等 - 2008 - FTIR spectroscopy in combination with principal co DOI: 10.1515/HF.2008.104 -
Aromatic ring confiance 1,0
“cm1, For hemicelluloses and lignin, the characteristic peaks at 1735 1510 and 810 belonged to C = O stretching vibrations in the O = C-OH group of the glucuronic acid unit in xylan (Åkerholm and Salmén, 2001), to the aromatic skeletal vibra”
Wang 等 - 2022 - Molecular-level characterization of changes in the DOI: 10.21203/rs.3.rs-882939/v1 -
confiance 1,0
“2,921cm-1 groups,whilethe2,877cm-1 acetylene, whose formation is accompanied by the complete isduetoaliphatic-CH 3 erosion of the OH groups features with maxima at 3,716 and (Colthup et al., band may be due to -CH of alkanes, respectively c”
Carbon Domains on MoS2/TiO2 System via Catalytic Acetylene Oligomerization: Synthesis, Structure, and Surface Properties DOI: 10.3389/fchem.2017.00091 -
Acetate confiance 1,0
“Hemicellulose 1245 C-O stretch (Faix, 1991) Hemicellulose D 1735-1740 C=O stretching in glucuronic acid (xylan) (Marchessault, 1962;”
Dinant 等 - 2019 - Synchrotron FTIR and Raman spectroscopy provide un DOI: 10.1093/jxb/ery396 -
Carbonyl (C=O) confiance 1,0
“In addition, 1601 is also associated with the C=O asymmetric stretching vibration (Faix 1991).”
Zhu 等 - 2022 - The spatial orientation and interaction of cell wa DOI: 10.21203/rs.3.rs-1076632/v1
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