What absorbs at 1623 cm⁻¹ in an FTIR spectrum?
A band near 1623 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 1623 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 |
|---|---|---|---|
| Amide | 12 | 12 | 1.0 |
| Carboxyl (COOH) | 10 | 10 | 1.0 |
| Carbonyl (C=O) | 10 | 9 | 1.0 |
| Methacrylate | 9 | 9 | 1.0 |
| Acetate | 9 | 9 | 1.0 |
| Ester | 8 | 8 | 1.0 |
| Water (H2O) | 7 | 7 | 1.0 |
| Ketone | 7 | 7 | 1.0 |
| Aromatic ring | 7 | 6 | 1.0 |
| Hydroxyl (O-H) | 6 | 6 | 1.0 |
| Alkene (C=C) | 6 | 6 | 1.0 |
| Protein beta sheet | 6 | 4 | 1.0 |
| N h | 4 | 4 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| C-O single bond | 3 | 3 | 1.0 |
| Protein | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Amine primary | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C=n | 2 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Urea | 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 |
|---|---|---|---|
| chitosan | 1623, 1650, 1655 | Amide, Methacrylate | 1 |
| silk fibroin | 1623, 1050, 1511 | Amide, Methacrylate | 1 |
| coal | 1623, 1600, 3030 | Carboxyl (COOH), Methacrylate | 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 1623 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
-
Amine primary confidence 1.0
“Because urea and ChCL intermolecular hydrogen interactions are formed, the stretching vibration of NH2 at 1662 cm-1 and the asymmetric vibration of NH2 at 1606 cm-1 in the FTIR spectra of urea shifted to 1663 and 1623 cm-1, respectively, in”
Can 等 - 2023 - Choline Chloride-Based Deep Eutectic Solvent-Treat DOI: 10.3390/f14030569 -
Acetate confidence 1.0
“The peak at 1623 (C O band) is in two spectra, but it is cm-1 18 samples each day.”
Carboxymethyl chitosan bounded iron oxide nanoparticles and gamma‐irradiated avian influenza subtype H9N2 vaccine to development of immunity on mouse and chicken DOI: 10.1002/vms3.680 -
N h confidence 1.0
“Morphology spectra of INA showed N-H stretching at 3368 cm-1, and 3184 C=O stretching of carboxylic acid Figure 4 shows SEM images of AC, INA and cm-1, cm-1, at 1658 NH stretching at 1623 C-N 2”
Wicaksono 等 - 2017 - Enhancement of solubility and dissolution rate of DOI: 10.4314/tjpr.v16i7.6 -
Acetate confidence 1.0
“Bands attributed to C=O vibrations were detected near cm-1 1623 (stretching) [34].”
Benjamin Ortega-Lazcano 等 - 2021 - Study of Pigments from the Colonial Convent of Act DOI: 10.3390/min11080852 -
Ester confidence 1.0
“1623 and the ester group vibration (located at 1760”
Bratu 等 - 2009 - Inclusion compound of Fosinopril with beta-cyclode DOI: 10.3233/SPE-2009-0373 -
Hydroxyl (O-H) confidence 1.0
“The stretch in aromatic ring and stretch in cm-1 polyphenols can be associated with a strong band at 1623 [17,19].”
From Green Remediation to Polymer Hybrid Fabrication with Improved Optical Band Gaps DOI: 10.3390/ijms20163910 -
Amide confidence 1.0
“LLM confirmed rule peak-group candidate”
Callone 等 - 2016 - Processing Influence on Molecular Assembling and S DOI: 10.1021/acsbiomaterials.5b00507 -
Water (H2O) confidence 1.0
“a band at 1623 (v) attributed to angular deformation of hydration water;”
Dick 等 - 2017 - Impact of HNO3 Solution Treatment of South Brazil DOI: 10.21577/0103-5053.20160230
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