What absorbs at 2991 cm⁻¹ in an FTIR spectrum?
A band near 2991 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
Réponse rapide
A band near 2991 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 |
|---|---|---|---|
| Alkyl C-H | 6 | 6 | 1,0 |
| Methyl | 3 | 3 | 1,0 |
Le classement reflète les preuves bibliographiques accumulées, et non une règle faisant autorité. Confirmez toujours dans le contexte de votre échantillon.
Matériaux possibles
| Matériel | Pics de support | Groupes chevauchants | Sources citées |
|---|---|---|---|
| TiO | 2991, 1730, 1699 | Alkyl C-H | 1 |
| rGO | 2991, 2358, 2930 | Alkyl C-H | 1 |
| PLA | 2991, 1650, 1073 | Alkyl C-H | 1 |
| PEG | 2991, 1650, 1342 | Alkyl C-H | 1 |
| PLLA | 2991, 1182, 921 | Alkyl C-H, Methyl | 1 |
Les matériaux sont affichés uniquement lorsque le même ensemble de littérature soutient cette bande et au moins un pic caractéristique supplémentaire.
Logique du spectre
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 2991 cm⁻¹ is usually not enough for material identification by itself.
Utilisation réelle
Ce type de requête est courant dans l＇identification des polymères, le criblage des plastiques inconnus, le dépannage du contrôle qualité, la vérification des matériaux recyclés et l＇examen de l＇attribution des pics appuyée par la littérature.
Erreurs courantes
- Traiter une bande isolée comme preuve d＇un matériau sans vérifier au moins un ou deux pics de support.
- Ignorer le chevauchement : plusieurs groupes fonctionnels peuvent contribuer près du même nombre d＇onde.
- Sauter la validation lorsque des additifs, des mélanges, l＇oxydation ou la contamination peuvent déformer le spectre.
Conseil de vérification
Lorsque l＇ambiguïté persiste, validez l＇hypothèse avec DSC, GC-MS ou TGA, en particulier pour les mélanges, les échantillons dégradés et les polymères chargés.
Bibliographie derrière ces attributions
-
Alkyl C-H confiance 1,0
“The two cm-1 bands at 2991 and 2948 can be attributed to the C-H bond stretching vibrations of the -CH and”
Awad 等 - 2020 - Experimental Investigation of Methyl Methacrylate DOI: 10.3390/ma13245793 -
Alkyl C-H confiance 1,0
“LLM confirmed rule peak-group candidate”
Structural and Surface Compatibility Study of Modified Electrospun Poly(ε-caprolactone) (PCL) Composites for Skin Tissue Engineering DOI: 10.1208/s12249-016-0500-8 -
Alkyl C-H confiance 1,0
“The characteristic band at 2991 cm-1 to 2976 cm-1 cm-1 cm-1 (C=C 2976 corresponds to C-H stretching vibrations, 1652 skeletal vibration), 1521”
Complex Permittivity and Electromagnetic Interference Shielding Effectiveness of OPEFB Fiber-Polylactic Acid Filled with Reduced Graphene Oxide DOI: 10.3390/ma13204602 -
Alkyl C-H confiance 1,0
“The asymmetric and symmetric C-H stretching (St.) cm1 cm1, of the methyl groups were attributed to the transmission bands at 2991 and 2943 respectively.”
Ragab - 2022 - Improved Physical, thermal, and conductivity stren DOI: 10.21203/rs.3.rs-1514992/v1 -
Alkyl C-H confiance 1,0
“The bands at 2991 and 2868 which were attributed to various C-H stretching vibrations, had opposite signs on the PC2 and PC3 loading curves.”
Ex Vivo Vibration Spectroscopic Analysis of Colorectal Polyps for the Early Diagnosis of Colorectal Carcinoma DOI: 10.3390/diagnostics11112048 -
Methyl confiance 0,9
“Explicit assignment: CH3 asymmetric stretching”
Differentiation in MALDI-TOF MS and FTIR spectra between two pathovars of Xanthomonas oryzae DOI: 10.1016/j.saa.2014.06.056 -
Methyl confiance 0,9
“Explicit assignment: 'absorption peak around 2991 ... stretching vibration peak of CH3'”
Li 等 - 2020 - Effect of molecular weight of polyethylene glycol DOI: 10.1039/d0ra08699a -
Alkyl C-H confiance 0,8
“Text: 'strong peak at 2991.3 cm-1 (Q is assigned as the center branch) ... R(2) transition of our 5ν C-H'”
Perez-Delgado 和 Manzanares - 2010 - Cavity Ring Down and Fourier Transform Infrared Sp DOI: 10.1021/jp105382p
Avez-vous un spectre avec cette bande ?
Téléchargez votre spectre FTIR et obtenez un rapport d＇interprétation complet — attributions de pics avec citations bibliographiques, correspondances de bibliothèque et une chaîne de preuves avec évaluation de la confiance — en quelques secondes.