What absorbs at 1433 cm⁻¹ in an FTIR spectrum?
A band near 1433 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 1433 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 |
|---|---|---|---|
| Alkyl C-H | 7 | 6 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Carbonate | 3 | 3 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Protein | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 1 | 1.0 |
| N h | 2 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 0.9 |
| Hydroxyl (O-H) | 1 | 1 | 0.6 |
| Ammonium | 1 | 0 | 1.0 |
| Silicon fluorine | 1 | 0 | 1.0 |
| Silicon (Si) | 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 |
|---|---|---|---|
| CS | 1433, 1645, 1720 | Methacrylate, Acetate, Alkyl C-H | 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 1433 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 h confidence 1.0
“N-H peaks in the complexed materials are the stretching shifts in 3126cm-1 3028cm-1 4+ NH from to and that of the bending mode 1441cm-1 1433cm-1 H-N-H 0.001 of from to when 30 wt.”
Synthesis and characterizations of phthaloyl chitosan-based polymer electrolytes DOI: 10.1016/j.jnoncrysol.2012.04.019 -
Acetate confidence 1.0
“The calculated vibration frequency of C-H cm-1, bending deformation, C-O-H bending and C-O stretching for 2-HEC have been obtained at 1433 cm-1”
Solid polymer electrolyte production from 2-hydroxyethyl cellulose: Effect of NH4NO3 composition on its structural properties DOI: 10.1016/j.carbpol.2017.02.033 -
Alkene (C=C) confidence 1.0
“cm-1 The increase of the peak at 1433 can be attributed to the C=C bond in the”
Spectroscopic Investigations of Porphyrin-TiO2 Nanoparticles Complexes DOI: 10.3390/molecules28010318 -
Carbonate confidence 1.0
“band at 3625 11 cm-1 Mohamedbakr and Burkitbaev, 2009), the band at 1633 to the flexural vibration Hcm-1 O-H of water, while the band located around 1433 could be attributed to the cm-1 carbonate issued from the calcite fraction of the diat”
El Ouardi 等 - 2020 - An insight of enhanced natural material (calcined DOI: 10.1016/S0043-1354(01)00071-9 -
Acetate confidence 1.0
“The peaks at 1433 and 1275 Cm-1 (b) are related to the stretching vibration of C-O in the”
Radiation Synthesis of Edible Coating Films of Nanocurcumin Based on Carboxymethyl Chitosan/Polyvinyl Alcohol to Extend the Shelf Life of Sweet Orange "Valencia" DOI: 10.1007/s10924-023-02854-6 -
Alkyl C-H confidence 1.0
“The bending wagging of This can be attributed to the formation of new carbonyl 1433cm-1 1375cm-1 CH2 vibrations is observed at and , groups within the doped PVA samples.”
Hamdalla 等 - 2015 - Influence of Erbium Ions on the Optical and Struct DOI: 10.1155/2015/204867 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Hanafy - 2012 - Dielectric relaxation and alternating current cond DOI: 10.1063/1.4739752 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Lefroy 等 - 2021 - A natural, cellulose-based microgel for water-in-o DOI: 10.1016/j.foodhyd.2020.106408
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