What absorbs at 644 cm⁻¹ in an FTIR spectrum?
A band near 644 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 5 cited sources
Quick answer
A band near 644 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 |
| Alkyl C-H | 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 |
| Metal oxygen | 1 | 1 | 1,0 |
| Sulfur | 1 | 1 | 0,9 |
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 |
|---|---|---|---|
| PVC | 644, 834, 1195 | Alkyl C-H, Methoxy (OCH3), Methacrylate | 1 |
| DNA | 644, 1712, 1660 | Methacrylate, Methoxy (OCH3) | 1 |
| plasma | 644, 1656, 1650 | Alkyl C-H, 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 644 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
-
Metal oxygen confiance 1,0
“at octahedral sites and consequently results in a decrease in the saturation magnetization [50] symmetric stretching of M - O at medium 644 [62], and an increase in the coercivity according to equation (6) [63]: octahedral sites 2 K”
Low-temperature synthesis of Sr2FeMoO6 double perovskite; structure, morphology, and magnetic properties DOI: 10.1016/j.ceramint.2020.03.264 -
Aromatic ring confiance 1,0
“Smaller peak at 643.806 corresponds to the substituted benzene group [3, 12, 16].”
Treated Rhizophora mucronata tannin as a corrosion inhibitor in chloride solution DOI: 10.1371/journal.pone.0200595 -
Acetate confiance 1,0
“plane bend), (C-O stretching of alcoholic 644cm-1 Te prepared Sn(Fe:Ni)O groups), and (aromatic C-H out-of-plane bendnanoparticles were well crys-”
Aloufi - 2023 - Assessment of Structural, Optical, and Antibacteri DOI: 10.1155/2023/5494592 -
Sulfur confiance 0,9
“Text: 's(SO3) ... peaks at 644'”
Ramesh 和 Yi - 2009 - FTIR spectra of plasticized high molecular weight DOI: 10.1007/s11581-008-0279-z -
confiance 0,8
“Part of range 637-644 assigned to ring breathing modes.”
Vibrational Spectroscopy of Liquid Biopsies for Prostate Cancer Diagnosis DOI: 10.1177/1758835920918499
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