What absorbs at 638 cm⁻¹ in an FTIR spectrum?
A band near 638 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 638 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.
Possibili assegnazioni di gruppi funzionali
| Gruppo funzionale | Fatti di supporto | Fonti citate | Affidabilità massima |
|---|---|---|---|
| Metal oxygen | 4 | 3 | 1,0 |
| Chlorine | 1 | 1 | 1,0 |
| Sulfate (SO4) | 1 | 1 | 1,0 |
| Aromatic ring | 1 | 1 | 1,0 |
| Alkyl C-H | 1 | 1 | 1,0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1,0 |
| Silicon (Si) | 1 | 1 | 1,0 |
| Phosphate (PO4) | 1 | 1 | 0,95 |
La classifica riflette le prove bibliografiche accumulate, non una singola regola autorevole. Conferma sempre nel contesto del tuo campione.
Possible materials
| Materiale | Picchi di supporto | Overlapping groups | Fonti citate |
|---|---|---|---|
| iron oxide | 638, 1130, 891 | Metal oxygen | 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 638 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.
Letteratura dietro queste assegnazioni
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affidabilità 1,0
“Micro-Raman analysis of silica powder at an excitation wavelength of 532 nm laser showed cm-1, a spectrum having prominent peaks at 638, 802, and 1300 characteristic of Si particles.”
Dentin Bond Integrity of Filled and Unfilled Resin Adhesive Enhanced with Silica Nanoparticles—An SEM, EDX, Micro-Raman, FTIR and Micro-Tensile Bond Strength Study DOI: 10.3390/polym13071093 -
Alkyl C-H affidabilità 1,0
“demineralized dentin highlights together with the characteristic bands of apatite ~950 cm-1 cm-1 cm-1 and dentinal collagen 1637 (CC), 1455 (CH 2), specific bands of the monomer cm-1 cm-1 (CC), 1455 cm-1 (CH 2), specific bands of the monome”
Marginal Adaptation Assessment for Two Composite Layering Techniques Using Dye Penetration, AFM, SEM and FTIR: An In-Vitro Comparative Study DOI: 10.3390/app11125657 -
Sulfate (SO4) affidabilità 1,0
“Such spectral regions host features compatible with those of a sulfate (983, 1087, 1116, and 1182 cm-1), probably barite (BaSO4), to which the two uncertain peaks at 611 and 638 cm-1 also appear to be assigned.”
Degradation Products Assessment of the Wooden Painted Surfaces from a XVIIth Heritage Monastery DOI: 10.3390/app13042124 -
affidabilità 1,0
“The synthesized IONPs show characteristic absorption cm-1 around 638.4 which is attributed to vibration of Fe-O bonds.”
Kawish 等 - 2020 - Enhancement in Oral Absorption of Ceftriaxone by H DOI: 10.3390/pharmaceutics12060492 -
affidabilità 1,0
“FTIR Analysis cm-1 cm-1 The FTIR Peaks (KBr): 3323 (amine -NH 2, -NH stretch), 3378 (amine cm-1 cm-1 -NH 2, N-H stretch), 1046 (C-O-C ether linkage stretch), and 638 (C-Cl stretch).”
Copper-Treated Environmentally Friendly Antipathogenic Cotton Fabric with Modified Reactive Blue 4 Dye to Improve Its Antibacterial and Aesthetic Properties DOI: 10.3390/coatings13010133 -
Metal oxygen affidabilità 1,0
“396 cm-1 (B1g), 516 cm-1 (A1g+B1g), and 638 cm-1 (Eg) inThe minimum energy paths and corresponding activation barcreasingly demonstrated the fabrication of TiO2 on the surface riers for all elementary steps were calculated using the climbof”
Wei 等 - 2023 - Photoelectrocatalytic reduction of CO2 catalyzed b DOI: 10.1016/S1872-2067(23)64395-5 -
affidabilità 1,0
“the peak at 516 cm-1 was caused by the Si-O-Fe stretching vibrations whilst the peaks at 638 cm-1 and at 838 cm-1 were due to Si-O stretching vibrations and Si-O-Al stretching vibrations, respectively.”
Investigation on the Painting Materials and Profile Structures Used in Ancient Chinese Folk Architectural Paintings by Multiple Analytical Methods DOI: 10.3390/coatings12030320 -
Phosphate (PO4) affidabilità 0,95
“Explicit assignment in text.”
Preparation of LiFePO4 Powders by Ultrasonic Spray Drying Method and Their Memory Effect DOI: 10.3390/ma14123193
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