What absorbs at 1724 cm⁻¹ in an FTIR spectrum?
A band near 1724 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 1724 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 |
|---|---|---|---|
| Carbonyl (C=O) | 45 | 40 | 1.0 |
| Ester | 21 | 20 | 1.0 |
| Carboxyl (COOH) | 20 | 19 | 1.0 |
| Amide | 18 | 16 | 1.0 |
| Methacrylate | 16 | 15 | 1.0 |
| Acetate | 16 | 15 | 1.0 |
| Ketone | 14 | 13 | 1.0 |
| C-O single bond | 7 | 7 | 1.0 |
| Hydroxyl (O-H) | 7 | 7 | 1.0 |
| Methoxy (OCH3) | 6 | 6 | 1.0 |
| Alkyl C-H | 6 | 6 | 1.0 |
| Hydrogen bond | 3 | 3 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| N h | 2 | 1 | 1.0 |
| Fatty acid | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Chlorine | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Imide | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 0.9 |
| Aldehyde (CHO) | 1 | 0 | 1.0 |
| Secondary amine | 1 | 0 | 1.0 |
| N n bond | 1 | 0 | 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 |
|---|---|---|---|
| PHB | 1724, 3440, 1720 | Carbonyl (C=O), Ester | 1 |
| GO | 1724, 1720, 1182 | Amide, Carboxyl (COOH) | 1 |
| polyimide | 1724, 1720, 1778 | Amide, Carbonyl (C=O), Carboxyl (COOH) | 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 1724 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
-
Alkene (C=C) confidence 1.0
“2, the main IR bands of the GO sheets are peaked at 1041, 1230, 1373, 1614, 1724 and cm-1, C=C, 3604 these being assigned to the following vibrational modes: OH groups from the GO sheet edges, stretching8.”
Baibarac 等 - 2019 - Adsorption of 1,4-phenylene diisothiocyanate onto DOI: 10.1038/s41598-019-48314-x -
Imide confidence 1.0
“hr, the 1 in 2(b), shown Figure after hard baking at 275°C for As 1724 characteristic imide peaks appeared at 1780, and 1375cm-I.”
Ha 等 - 1998 - Polarized Infrared Spectroscopic Studies of Polari DOI: 10.1080/10587259808025380 -
Ester confidence 1.0
“FT-IR analysis showed a strong band at 1724 cm which attributed to the ester group's carbonyl - while NMR analysis has different peaks at 169.15, 67.6, 40.77, and 19.75 ppm that were corresponding to carbonyl, methine, methylene, and methyl”
Production and optimization of bioplastic (Polyhydroxybutyrate) from DOI: 10.1186/s12866-022-02593-z -
Carboxyl (COOH) confidence 1.0
“COO(cid:3) may be assigned to group vibration of the citrate 1724cm(cid:3)1 complex, the shoulder at might be corresponds to the COOR groups, caused by the dimer of free citric acid.”
Synthesis characterization and luminescence studies of 100MeV Si8+ ion irradiated sol gel derived nanocrystalline Y2O3 DOI: 10.1016/j.nimb.2014.02.128 -
Carbonyl (C=O) confidence 1.0
“LLM confirmed rule peak-group candidate”
Electrospun biodegradable calcium containing poly(esterurethane)urea: Synthesis, fabrication, in vitro degradation, and biocompatibility evaluation DOI: 10.1002/jbm.a.34490 -
Ester confidence 1.0
“cm-1 vibration of the C-O The bands at 2929 and 3403 are characteristic of 233 vibration.31,32 the C-H and O-H stretching Compared with β-cyclodextrin, the OCD 234 cm-1, showed a new stretching vibration peak at 1724 which was attributed to”
Niu 等 - 2019 - Preparation and Characterization of a Modified-bet DOI: 10.1021/acs.jafc.9b05467 -
Amide confidence 1.0
“LLM confirmed rule peak-group candidate”
Nugrahani 等 - 2020 - FTIR Method for Peptide Content Estimation and Deg DOI: 10.14499/indonesianjpharm31iss2pp78 -
Carbonyl (C=O) confidence 1.0
“The Folpet spectrum has three absorption bands, at 1724, 1271cm-1 Folpet band at also could not be used be1798cm-1, 1757 and due to carbonyl in-phase and”
Quintas 等 - 2003 - Simultaneous determination of Folpet and Metalaxyl DOI: 10.1016/S0003-2670(02)01596-9
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