What absorbs at 1619 cm⁻¹ in an FTIR spectrum?
A band near 1619 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 1619 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 | 10 | 10 | 1.0 |
| Methacrylate | 7 | 7 | 1.0 |
| Acetate | 7 | 7 | 1.0 |
| Ester | 6 | 6 | 1.0 |
| Carbonyl (C=O) | 6 | 6 | 1.0 |
| Ketone | 5 | 5 | 1.0 |
| Carboxyl (COOH) | 5 | 5 | 1.0 |
| Water (H2O) | 3 | 3 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Alkyl C-H | 3 | 2 | 1.0 |
| Alkene (C=C) | 3 | 1 | 1.0 |
| Urea | 2 | 2 | 1.0 |
| Amine primary | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 0 | 1.0 |
| Phosphate (PO4) | 1 | 0 | 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 |
|---|---|---|---|
| polyimide | 1619, 1720, 1778 | Amide, 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 1619 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
-
Alkene (C=C) confidence 1.0
“The peak at 1718.82 cm shows C=C stretching that indicated the presence cm-1 presence of carboxylic groups, while the peak at 1618.82 indicated the C=C stretching presence of peaks at the range of 3300-3700 cm indicated the OH stretching an”
Fatima 等 - 2021 - Extraction and Chemical Characterization of Humic DOI: 10.3390/su13168969 -
Acetate confidence 1.0
“1a), O 30cm-1 down-shift of the 13-keto stretching band about a 4=1655cm-1) ((cid:3) 2=1684→(cid:3) 18O-labelling was observed by of the Hydrogen-bonding of a carbonyl group with a hydroxy or an oxygenatom,whilethechlorinskeletalvibrationsw”
Morishita 和 Tamiaki - 2009 - Specific coupling between the 13-keto carbonyl and DOI: 10.1016/j.saa.2008.09.016 -
Hydroxyl (O-H) confidence 1.0
“3318.91 strong,broad O-H alcohol stretching 1619.25”
Phytochemical Composition of Combretum molle (R. Br. ex G. Don.) Engl. & Diels Leaf and Stem Extracts DOI: 10.3390/plants12081702 -
Aromatic ring confidence 1.0
“The characteristic peaks of aromatic ring cm-1, cm-1 (FTIR), TGA, DSC, tensile properties, dielectric constant skeletal vibrations occurred at 1619 1497 and cm-1.”
Purushothaman 和 Bilal - 2014 - Development and characterization of homo, co and t DOI: 10.1515/polyeng-2013-0167 -
confidence 1.0
“The N-H bending vibrations are also absorbing at 1619 and cm-1.”
Potency of Urea-Treated Halloysite Nanotubes for the Simultaneous Boosting of Mechanical Properties and Crystallization of Epoxidized Natural Rubber Composites DOI: 10.3390/polym13183068 -
Ester confidence 1.0
“The appearance of peak at 1618.53 (CO, amide) and 1455.47 (CN, amide), and the disappearance of ester bands is related to amidation of CA oil to form CADFA [5,17].”
Development of Hydrophobic, Anticorrosive, Nanocomposite Polymeric Coatings from Canola Oil: A Sustainable Resource DOI: 10.3390/polym12122886 -
Hydroxyl (O-H) confidence 1.0
“The band at roughly 3427 corresponds to the stretching cm(cid:0) 1 O-H vibration of water molecules, while the smaller band at approximately 1619 may be caused by the stretching and bending modes of water molecules.”
Enhancing pseudocapacitive properties of cobalt oxide hierarchical nanostructures via iron doping DOI: 10.1016/j.heliyon.2023.e13817 -
N h confidence 1.0
“deformations of the amine bound to the metal-0.933 for 1589/1581cm-1 1586cm-1 A red shift of the amine scissoring modes, occurring at (Raman), 1588/1573cm-1 (FTIR) and (INS), was detected relative to the free diaminopropane ligand and simil”
Batista de Carvalho 等 - 2012 - Pt(II) Complexes with Linear Diamines-Part I Vibr DOI: 10.1155/2012/206297
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