What absorbs at 1683 cm⁻¹ in an FTIR spectrum?
A band near 1683 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 1683 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) | 13 | 12 | 1.0 |
| Methacrylate | 6 | 6 | 1.0 |
| Carboxyl (COOH) | 6 | 6 | 1.0 |
| Amide | 6 | 6 | 1.0 |
| Acetate | 6 | 6 | 1.0 |
| Ketone | 5 | 5 | 1.0 |
| Ester | 5 | 5 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Protein beta sheet | 2 | 2 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| Protein beta turn | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Protein alpha helix | 1 | 1 | 0.3 |
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 |
|---|---|---|---|
| zinc oxide | 1683, 1627, 1638 | Methacrylate, Carboxyl (COOH), Amide | 1 |
| ZnO | 1683, 1400, 3430 | Methacrylate, Amide | 1 |
| polypropylene | 1683, 1030, 1600 | Methacrylate, Carbonyl (C=O), Amide | 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 1683 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
-
Protein beta sheet confidence 1.0
“1652 and 1667 due to α helix and 1683 cm-1 due to antiparallel β sheet.”
Spectral profile index changes as biomarker of toxicity in Catla catla (Hamilton, 1822) edible fish studied using FTIR and principle component analysis DOI: 10.1007/s42452-020-3001-z -
Aromatic ring confidence 1.0
“C¼O 1692 Stretching of benzoyl C¼O 1734 bonded acid Non-H nC¼C C¼O Amorphous 123 INDO 1591 of aromatic ring Stretching of benzoyl (Exo) C¼O 1683 H-bonded 44 acid in a cyclic dimer (Tg),”
Thermoanalytical and Fourier transform infrared spectral curve-fitting techniques used to investigate the amorphous indomethacin formation and its physical stability in Indomethacin-Soluplus® solid dispersions DOI: 10.1016/j.ijpharm.2015.10.042 -
Acetate confidence 1.0
“increasedfrom300to500,700and900◦ C,onlyabroadbandof The peaks at 1683 and 1624 represents the C O and C O in”
Wahab 等 - 2008 - Synthesis and characterization of hydrozincite and DOI: 10.1016/j.jallcom.2007.07.029 -
Protein beta sheet confidence 1.0
“As discussed in the cm(cid:4)1, b-sheet and the main native band shifted to ~1683 following section, the differences in aggregation propensity cm(cid:4)1 b showed decreased intensity, suggesting a 2m variants are at ~1636 detected by FTIR s”
Structure, Stability, and Aggregation of β-2 Microglobulin Mutants: Insights from a Fourier Transform Infrared Study in Solution and in the Crystalline State DOI: 10.1016/j.bpj.2012.02.045 -
Carbonyl (C=O) confidence 1.0
“1683cm-1 at is assigned to the carbonyl group stretching”
Bulut 和 Karagoz - 2013 - Pyrolysis of Table Sugar DOI: 10.1155/2013/172039 -
Carbonyl (C=O) confidence 1.0
“cm-1 C=O and 1439 and the bond in the carboxylic acid group is 1683 The peak at 1388 infrared spectrum of EDTA (curve a in Figure 2A), the stretching vibration peaks of -CH2are 3017 cm-1 cm-1 is the C-N bond, 1310 is the bending vibration o”
Inhibition of Poly(ethylenediaminetetraacetic acid-diethanolamine) on Deposition of Calcium Sulfate Crystal in Simulated Industrial Water DOI: 10.3390/cryst10060544 -
Acetate confidence 1.0
“cm-1 The 1683 peak, which is hardly noticeable and visible only for S1, belongs to the C=O band, which indicates cellulose hydrolysis and oxidation [34].”
Determination of the Conservation State of Some Documents Written on Cellulosic Support in the Poni-Cerntescu Museum, Iași City in Romania DOI: 10.3390/app11188726 -
Acetate confidence 1.0
“Also, the observation of the bands at 3674 and 3653cm-1 1683cm-1 C=O confirms that the used kaolinite is a highly is due to the free vibration since the at”
Guessoum 等 - 2012 - Effects of Kaolin Surface Treatments on the Thermo DOI: 10.1155/2012/549154
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