What absorbs at 1568 cm⁻¹ in an FTIR spectrum?
A band near 1568 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 1568 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 | 5 | 5 | 1.0 |
| Ring structure | 5 | 4 | 1.0 |
| Carbonyl (C=O) | 4 | 4 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Aromatic ring | 4 | 3 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Ester | 3 | 3 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| C=n | 2 | 2 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 1.0 |
| Sulfate (SO4) | 1 | 1 | 1.0 |
| Quinone | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 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 |
|---|---|---|---|
| ZnO | 1568, 1400, 3430 | Amide | 1 |
| polyaniline | 1568, 1565, 1570 | Amide, Ring structure | 1 |
| ZnO nanoparticles | 1568, 1219, 1726 | Amide, Carboxyl (COOH) | 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 1568 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
“cm-1 sample at 1729 and 1568 The peak at 1729 described a stretch vibration of the cm-1 C=O ester group, while the peak at 1568 showed an asymmetrical stretch vibration of the carboxyl group [6,50,51,66].”
Dual Modification of Sago Starch via Heat Moisture Treatment and Octenyl Succinylation to Improve Starch Hydrophobicity DOI: 10.3390/polym14061086 -
confidence 1.0
“is 60◦C, for transition metal complexes, appearing in only four crystalloAt the intensity of DRIFTS peaks at 1568, 1440, 1380, and cm-1always characterized complexes.”
Gaur 等 - 2013 - CO oxidation studies over cluster-derived AuTiO2 DOI: 10.1016/j.cattod.2012.10.029 -
Water (H2O) confidence 1.0
“The bands observed at 3450 and cm-1are the band in 1568 due to the fact that the calcined nanoparticles tends to physically absorb water and carbon dioxide from air.”
Synthesis of nickel oxide nanoparticles using pulsed laser ablation in liquids and their optical characterization DOI: 10.1016/j.apsusc.2012.03.147 -
N-O bond confidence 1.0
“N-O stretching and bending modes were found in all as-burnt cm-1 BCZT powders due to the appearance of the peaks at 1568, 1383, 856 and 818 for pH 5, MANUSCRIPT cm-1 cm-1 at 1559, 1375, 857 and 691 for pH 7 and at 1560, 1380 and 854 for pH”
Influence of pH values on the surface and properties of BCZT nanopowders synthesized via sol-gel auto-combustion method DOI: 10.1016/j.surfcoat.2016.03.091 -
Quinone confidence 1.0
“The characteristic peak at 1568 corresponds to vibration of skeleton of quinone ring.”
Jin 等 - 2018 - Polymer anode used in hydrometallurgy Anodic beha DOI: 10.1016/j.hydromet.2018.01.020 -
Sulfate (SO4) confidence 1.0
“The spectrum of a dry PANI-sulfate film exhibits main peaks cm-1 corresponding to quinone and benzene at 1568 and 1482 ring-stretching deformations, respectively (Fig.”
Sedenkova 等 - 2006 - In-situ polymerized polyaniline films. Preparation DOI: 10.1016/j.tsf.2006.05.038 -
Carboxyl (COOH) confidence 1.0
“1568cm-1 and The peak at was attributed to asymmetric stretching of vibration of a carboxyl group, whereas the 1726cm-1”
Structural properties of lotus seed starch prepared by octenyl succinic anhydride esterification assisted by high hydrostatic pressure treatment DOI: 10.1016/j.lwt.2019.108698 -
Acetate confidence 1.0
“The peaks 2934, 2857, and 2854 cm-1 around 1634, 1550, and 1568 cm-1 correspond to the C=O amide group.”
Innovative Investigation of Zinc Oxide Nanoparticles Used in Dentistry DOI: 10.3390/cryst12081063
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