What absorbs at 1613 cm⁻¹ in an FTIR spectrum?
A band near 1613 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 1613 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 |
|---|---|---|---|
| Carboxyl (COOH) | 6 | 6 | 1.0 |
| Amide | 6 | 5 | 1.0 |
| Carbonyl (C=O) | 5 | 4 | 1.0 |
| Methacrylate | 4 | 4 | 1.0 |
| Acetate | 4 | 4 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Ketone | 3 | 3 | 1.0 |
| Ester | 3 | 3 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 0.7 |
| Protein | 1 | 1 | 0.7 |
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 |
|---|---|---|---|
| Sodium alginate | 1613, 1636, 1080 | Methacrylate, Carboxyl (COOH), Amide | 1 |
| TiO2 | 1613, 1700, 1093 | Methacrylate, Carboxyl (COOH) | 1 |
| montmorillonite | 1613, 1637, 523 | Methacrylate, Amide, Carboxyl (COOH) | 1 |
| alginate | 1613, 1100, 1715 | Methacrylate, Carboxyl (COOH), 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 1613 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
-
N-O bond confidence 1.0
“The Raman spectra of SCT cm-1 cm-1 1710-1728 compared to no peak for the a peak at about also gave a peak at about 1613 [Figure 6 (bottom),”
Byaruhanga 等 - 2006 - Alteration of kafirin and kafirin film structure b DOI: 10.1021/jf052942z -
Acetate confidence 1.0
“The presence of the PAMAM layer is indicated The full FTIR spectra for the various samples after surface modifications are shown in by distinctive peaks, such as C=O stretching at 1613 cm-1 and N-H bending at 1563 cm-1.”
Surface Heparinization of a Magnesium-Based Alloy: A Comparison Study of Aminopropyltriethoxysilane (APTES) and Polyamidoamine (PAMAM) Dendrimers DOI: 10.3390/jfb13040296 -
Alkene (C=C) confidence 1.0
“C=C stretching band at 1613 While these are a very good forassistancewithexperiments,andM.J.Walter(UniversityofBristol) match,wecannotprovideamechanismofformationforthismolecule.”
Reactions between organic acids and montmorillonite clay under Earth-forming conditions DOI: 10.1016/j.chemgeo.2010.12.023 -
Water (H2O) confidence 1.0
“A swelling at 1613 cm-1 and a depression at 1660 might tentatively be attributed to a slight lower-energy shift of the bending mode of water at cm-1.”
Nakamura 等 - 2003 - In situ FTIR studies of primary intermediates of p DOI: 10.1021/ja029503q -
confidence 1.0
“A peak around 1613 was corresponding to the amine N-H ±”
Green synthesis and characterization of titanium dioxide nanoparticles using leaf extract of Pouteria campechiana and larvicidal and pupicidal activity on Aedes aegypti DOI: 10.1016/j.envres.2021.111333 -
Carboxyl (COOH) confidence 1.0
“Asymmetric carboxylate Symmetric stretching Symmetric COO1613 1417 1417”
El-Bana 等 - 2022 - MOLECULAR STRUCTURE AND OPTICAL ATTRIBUTES OF (Na- DOI: 10.4314/bcse.v36i3.19 -
C c single bond confidence 1.0
“range comes from skeletal vibrations (C-C at 1613 nevertheless, the signal related α,β-unsaturated to C=C vibration of ketones can also be found in this spectral region.”
A Novel FTIR-Based Chemometric Solution for the Assessment of Saffron Adulteration with Non-Fresh Stigmas DOI: 10.3390/molecules28010033 -
Hydroxyl (O-H) confidence 1.0
“FTIR spectrum of the native sodium alginate (Figure 2(a)) been observed for iron-crosslinked hydroxamic alginate 3000-3600cm-1 exhibited bands at [21], and it has been attributed to complexation of carboxylic corresponding to O-H 1613cm-1 1”
Furuyama Lima 等 - 2018 - Synthesis and Physicochemical Characterization of DOI: 10.1155/2018/4218270
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