What absorbs at 1626 cm⁻¹ in an FTIR spectrum?
A band near 1626 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 1626 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 | 18 | 15 | 1.0 |
| Carbonyl (C=O) | 13 | 11 | 1.0 |
| Carboxyl (COOH) | 9 | 7 | 1.0 |
| Methacrylate | 7 | 5 | 1.0 |
| Ketone | 7 | 5 | 1.0 |
| Ester | 7 | 5 | 1.0 |
| Acetate | 7 | 5 | 1.0 |
| Protein beta sheet | 7 | 5 | 1.0 |
| Hydroxyl (O-H) | 5 | 5 | 1.0 |
| Alkene (C=C) | 5 | 3 | 1.0 |
| N h | 4 | 4 | 1.0 |
| Aromatic ring | 4 | 3 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Protein | 3 | 3 | 1.0 |
| Carbonate | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| C=n | 2 | 2 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Amino acid | 2 | 2 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Carbon dioxide | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 0.9 |
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 | 1626, 1400, 3430 | Methacrylate, Amide | 1 |
| PVA | 1626, 1660, 2930 | 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 1626 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
-
Amino acid confidence 1.0
“The observed cm-1 cm-1 1361 (amide, -CN-) aliphatic absorption peaks and 1626 (>C=O) amino acid cysteine absorption peaks were typical effects of external factors on polypeptide hair fibers.”
Chang 等 - 2017 - Material Characteristics of Hair Cuticles after Ha DOI: 10.18494/SAM.2017.1707 -
C c single bond confidence 1.0
“PANpowder Thiswork Literature LiBOBpowder Thiswork Literature C_Ostretch 1830-1767[39](ionpairs) CNstretchingvibration 2245(sh) 2245[35] 1808,1795,1789,1769 2243[36,41] 1804[40] 2244[37,38] 1780[40] C\\Hstretching B\\Oextra-ringstretch 2930”
Effect of gamma radiation on the transport and structural properties of polyacrylonitrile-lithium bis(oxalato)borate films DOI: 10.1016/j.ssi.2017.03.003 -
confidence 1.0
“Explicit assignment: 'and 1626 corresponds to the ... bending'”
Influence of pH on the structural, spectral, optical, morphological and photocatalytic properties of ZrO2 nanoparticles synthesized by sol–gel technique DOI: 10.1007/s10854-020-04134-8 -
Amide confidence 1.0
“like 1626, 1632 and The amide II bands are absent in human HbA monoclonal antibody (R2) binds to particle bound 1c non-diabetic specimens.”
Farhan 等 - 2011 - Comparative study on secondary structural changes DOI: 10.1016/j.cca.2010.11.016 -
Hydroxyl (O-H) confidence 1.0
“The peaks at and 1626 more prominent when the size of the nano crystallites is less than are attributed to O-H stretching vibration and H-O-H bending the bulk exciton Bohr radius.”
Combustion synthesis, characterization and Raman studies of ZnO nanopowders DOI: 10.1016/j.saa.2011.05.043 -
Protein beta sheet confidence 1.0
“cm-1, β-sheets An intense band was also observed at 1626 which is associated to the intermolecular”
Sadat 和 Joye - 2020 - Peak Fitting Applied to Fourier Transform Infrared DOI: 10.3390/app10175918 -
Amide confidence 1.0
“Similarly, HSA's amide I shift to 1647.21 the position of aromatic amino acid residues such as phenylalanine, bandat1625.99cm-1 asshown in Fig.”
Probing the interaction of neem oil based nanoemulsion with bovine and human serum albumins using multiple spectroscopic techniques DOI: 10.1016/j.molliq.2015.09.022 -
Hydrogen bond confidence 1.0
“The peak at 1626 in the and The first one has a clear crystalline peak at 20.5◦ 2(cid:2) CG scattering spectrum can be assigned to the hydrogen bonding coupled angles of = in which the first one has a clear COO-1 20.5◦ 2(cid:2) stretching.”
Synthesis and properties of carrageenan grafted copolymer with poly(vinyl alcohol) DOI: 10.1016/j.carbpol.2013.06.047
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