What absorbs at 1747 cm⁻¹ in an FTIR spectrum?
A band near 1747 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 1747 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) | 21 | 21 | 1.0 |
| Methacrylate | 15 | 14 | 1.0 |
| Acetate | 15 | 14 | 1.0 |
| Carboxyl (COOH) | 14 | 13 | 1.0 |
| Ester | 13 | 12 | 1.0 |
| Ketone | 10 | 10 | 1.0 |
| Amide | 10 | 10 | 1.0 |
| Methoxy (OCH3) | 6 | 5 | 1.0 |
| C-O single bond | 5 | 4 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Protein | 2 | 2 | 1.0 |
| Lipid | 2 | 2 | 1.0 |
| Hydrogen bond | 2 | 1 | 1.0 |
| Hydroxyl (O-H) | 2 | 1 | 1.0 |
| Carbonate | 2 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Lignin | 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 |
|---|---|---|---|
| silica | 1747, 1100, 1080 | 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 1747 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
-
Carboxyl (COOH) confidence 1.0
“It CAP, resulting in the formation of stearic acid due to the 1541cm(cid:2)1 was also found that both IR peak intensities at 1747 and degradation of MgSt caused by neutralization of acidic CAP.”
Cheng 等 - 2008 - Effect of moisture content on solid-state interact DOI: 10.1016/j.apsusc.2008.08.009 -
Carbonate confidence 1.0
“stretch for linear poly(propylene carbonate) with waveassigned to the stretching vibration for the cm(cid:4)1.42 a-pinane number at 1747 This peak was conspicuously absent in the carbonate Apart from the characteristic FTIR cm(cid:4)1 cm(ci”
Synthesis of cyclic α-pinane carbonate – a potential monomer for bio-based polymers DOI: 10.1039/d1ra07943c -
Alkyl C-H confidence 1.0
“2660 δ(C-H) Stretching vibration δ(COH), δ(CCH), δ(OCH), Stretching and bending 1747 β-Sheet of amide I”
Hssaini 等 - 2022 - Do Pollination and Pollen Sources Affect Fig Seed DOI: 10.1155/2022/3969165 -
Ester confidence 1.0
“Neat PLA D cm-1 was found with characteristic bands that were displayed at approximately 1180 and 1747 cm-1, CEPTE which were assigned to stretching of the ester (C-O-C) and carbonyl functional groups (C=O) as reported in the literature[27,”
Effect of silica resources on the biodegradation behavior of poly (lactic acid) and chemical crosslinked poly (lactic acid) composites DOI: 10.1016/j.polymertesting.2018.08.026 -
Carbonyl (C=O) confidence 1.0
“The weak peak at 1747 is the characteristic band for carbonyl (C=O) T stretching that represents the ester linkage of lignin and hemicellulose.”
Rout 等 - 2017 - A green approach to produce silver nano particles DOI: 10.1016/j.surfin.2017.03.004 -
Aromatic ring confidence 1.0
“The peak at 1747 cm-1 was flavonoids and aromatic ring deformations), 1571 (N-H bending and C-N stretching in the amide”
Pleurotus Mushrooms Content in Glucans and Ergosterol Assessed by ATR-FTIR Spectroscopy and Multivariate Analysis DOI: 10.3390/foods9040535 -
Carbonyl (C=O) confidence 1.0
“firmed because if the spectra of the PLA and the PHB are (14824 00 ±508 45MPa), mixture PLA/PHB/Ag 74.5/24.5/1 observed separately, it is noted that for the PLA (4032), the an approximate increase of 264.56% is evidenced, whereas if carbony”
Cardenas-Trivino 等 - 2019 - Synthesis and Properties of Bionanocomposites of P DOI: 10.1155/2019/4520927 -
Carbonyl (C=O) confidence 1.0
“The ester carbonyl band in CCA appeared at 1747”
Detection of Human Cholangiocarcinoma Markers in Serum Using Infrared Spectroscopy DOI: 10.3390/cancers13205109
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