What absorbs at 1723 cm⁻¹ in an FTIR spectrum?
A band near 1723 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 1723 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) | 35 | 28 | 1.0 |
| Methacrylate | 16 | 15 | 1.0 |
| Acetate | 16 | 15 | 1.0 |
| Ester | 15 | 14 | 1.0 |
| Carboxyl (COOH) | 15 | 14 | 1.0 |
| Ketone | 13 | 12 | 1.0 |
| Amide | 13 | 12 | 1.0 |
| Alkyl C-H | 7 | 7 | 1.0 |
| Methoxy (OCH3) | 5 | 5 | 1.0 |
| C-O single bond | 5 | 5 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| Urethane | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Secondary amine | 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 |
|---|---|---|---|
| Polyurethane | 1723, 2270, 1700 | Methacrylate, Acetate, Carbonyl (C=O) | 1 |
| lignin | 1723, 1035, 1510 | Methacrylate, Acetate | 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 1723 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
-
Ester confidence 1.0
“The other cm21 longed TC-HCl release, PHT-Na release behavior revealed that it peaks such as 1723 and 2941 corresponding to ester and can help the wound dressings to heal the wounds during 24 h carbon-hydrogen bonds in the chemical structur”
Askari 等 - 2016 - Three-layered electrospun PVAPCLPVA nanofibrous DOI: 10.1002/app.43309 -
Acetate confidence 1.0
“1425, 780 W-DO had characteristic peaks at 1723(C=O vibration), 1644, 1420, 1396, 1378, cm-1 1339, 1248, 1227, 1158,1103, 1074, 775 and 713 corresponding to the characteristic peaks of cm-1.”
Discrimination and similarity evaluation of tissue-cultured and wild Dendrobium species using Fourier Transform Infrared Spectroscopy DOI: 10.1016/j.molstruc.2015.01.027 -
Acetate confidence 1.0
“∼1723 C-O at The stretching vibration can be identified cm-1.”
Farrag 等 - 2012 - Preparation and Spectroscopic Properties of Monola DOI: 10.1021/jp210453v -
Carbonyl (C=O) confidence 1.0
“LLM confirmed rule peak-group candidate”
Characterization of chemically modified wood fibers using FTIR spectroscopy for biocomposites DOI: 10.1002/app.31746 -
Ester confidence 1.0
“are shown in Figure 3 (1850-1500 Characteristic vibrational bands at 1723, 4 cm-1 1690, and 1537 were observed and were attributed to the free ester structure 5 in polyol, the isocyanurate structure, and amide II band (C-NH at the crosslink”
A study of molecular architectural dynamics of crosslinked urethane during photo-aging by two-dimensional infrared correlation spectroscopy DOI: 10.1016/j.polymdegradstab.2020.109242 -
Carbonyl (C=O) confidence 1.0
“LLM confirmed rule peak-group candidate”
Jacob 等 - 2013 - Green Synthesis for Lignin Plasticization Aqueous DOI: 10.7569/JRM.2012.634107 -
N h confidence 1.0
“FTIR spectra 298 to 318 K gave an activation energy of 22.4 kJ 2+ cm-1 COOof the catalysts displayed peaks at 1723.23 and 1666.12 assigned to and NH groups, respectively, for both fresh and used specimens.”
Mahmud 等 - 2010 - Kinetic Analysis of Oleic Acid Esterification Usin DOI: 10.1021/ie900704n -
Acetate confidence 1.0
“The peak at 1723 cm-1 corresponds to free C=O groups and”
Additive Manufacturing Polyurethane Acrylate via Stereolithography for 3D Structure Polymer Electrolyte Application DOI: 10.3390/gels8090589
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