What absorbs at 789 cm⁻¹ in an FTIR spectrum?
A band near 789 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 3 cited sources
Quick answer
A band near 789 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 |
|---|---|---|---|
| Silicon carbon | 2 | 2 | 1,0 |
| Ring structure | 1 | 1 | 1,0 |
| Carbohydrate | 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 |
|---|---|---|---|
| PE | 789, 1414, 1700 | Alkyl C-H | 1 |
| PP | 789, 1700, 1043 | Alkyl C-H | 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 789 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
-
Silicon carbon confiance 1,0
“LLM confirmed rule peak-group candidate”
Chen 等 - 2007 - Structural characterization and corrosion properti DOI: 10.4028/www.scientific.net/MSF.546-549.1111 -
Silicon carbon confiance 1,0
“2g) were located at 490 (symmetric Si-O stretch vibration) of the cm-1 cm-1 Si-O-Si chain and 710 (symmetric C-Si-C stretch vibration) and 789 (antisymmetric C-Si-C stretch cm-1 vibration) of the CH 3-Si-CH moieties.”
Optical photothermal infrared spectroscopy with simultaneously acquired Raman spectroscopy for two-dimensional microplastic identification DOI: 10.1038/s41598-022-23318-2 -
Alkyl C-H confiance 1,0
“in both ester and ether overlapping modes from polysaccharides and alginates in cm-1 The bands at 789 and 840 are attributed to out-of-plane C-H bending (mannose and Aloe) or pyranose ring in [56] and -CH twisting [57-59].”
High-Content Aloe vera Based Hydrogels: Physicochemical and Pharmaceutical Properties DOI: 10.3390/polym15051312
Avez-vous un spectre avec cette bande ?
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