What absorbs at 724 cm⁻¹ in an FTIR spectrum?
A band near 724 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 724 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.
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Alkyl C-H | 6 | 6 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Metal oxygen | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| starch | 724, 1650, 1540 | Alkyl C-H | 1 |
| PET | 724, 1408, 800 | 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 724 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.
Literature behind these assignments
-
confidence 1.0
“It shows two strong characteristic absorption 723.67eV correspond to Fe 2p1/2, these peaks can be attributed to bands at 592 cm-1 and 442 cm-1.”
Structural and magnetic properties of Gd-Zn substituted M-type Ba-Sr hexaferrites by sol-gel auto-combustion method DOI: 10.1016/j.jallcom.2019.06.348 -
Metal oxygen confidence 1.0
“The peaks appear on 724, 863 and 974 is corresponding to the stretching vibration of metal oxide (M-O) bonds in the BaMnO 3.”
Rani 和 Yadav - 2015 - Study of Optical Properties of BaMn1-xCrxO3 (x=0.0 DOI: 10.1063/1.4929284 -
Alkyl C-H confidence 1.0
“The band at 724 is due to the vibrational cm-1 C-H CeOeC [25-27].”
Structural and optical properties of Fe3+ doped ZnCdO nanostructures for luminescent application DOI: 10.1016/j.ijleo.2020.164283 -
Metal oxygen confidence 1.0
“~ 633 Bending vibrations of V-O bonds ~724 (Q1) ~ 762 Stretching vibrations of P-O-P bonds ~ 773 (Q0) ~ 908 Bending vibrations of P-O-P bonds”
Andronache 和 Racolta - 2014 - Structural Investigation of MO center dot P2O5 cen DOI: 10.1063/1.4903024 -
Alkyl C-H confidence 1.0
“cm-1 cm-1 2916/2914 and 2852/2847 correspond to the CH 2stretching vibration, while cm-1 the sharper peak around 724/722 can be attributed to the CH rocking mode of 2 the CH groups.”
Use of Fourier-Transform Infrared Spectroscopy for DNA Identification on Recycled PET Composite Substrate DOI: 10.3390/app12094371 -
Carboxyl (COOH) confidence 1.0
“In addition, the presence of characteristic bands at 1692 cm-1, 1530 cm-1, 1266 cm-1, and 724 cm-1 in the GA Raman spectrum Molecules2022,27,279 8of17 (Figure 2b) can be related to the carboxylic group in the non-polymerized molecule.”
Vibrational Study (Raman, SERS, and IR) of Plant Gallnut Polyphenols Related to the Fabrication of Iron Gall Inks DOI: 10.3390/molecules27010279 -
Acetate confidence 1.0
“The region of cm-1) cm-1 and C=O stretching C-H bond (724 and 1460 900 (C-C and C-O) in the IR spectrum is sensitive to”
Pourfarzad 等 - 2015 - Serish inulin and wheat biopolymers interactions i DOI: 10.1007/s13197-015-1939-4 -
Borate confidence 1.0
“The peak at around 724 is assigned to 3 the bending vibrations of B-O linkages.”
Rajesham 等 - 2022 - Synthesis, physical, optical and structural studie DOI: 10.21203/rs.3.rs-1495935/v1
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