What absorbs at 1421 cm⁻¹ in an FTIR spectrum?
A band near 1421 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 1421 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 | 12 | 12 | 1.0 |
| Aromatic ring | 7 | 7 | 1.0 |
| Lignin | 6 | 5 | 1.0 |
| Acetate | 5 | 5 | 1.0 |
| Methoxy (OCH3) | 4 | 4 | 1.0 |
| Methacrylate | 4 | 4 | 1.0 |
| C c single bond | 4 | 4 | 1.0 |
| Ring structure | 4 | 4 | 1.0 |
| C-O single bond | 3 | 3 | 1.0 |
| Carbonate | 3 | 3 | 1.0 |
| Amide | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 3 | 3 | 1.0 |
| Carbohydrate | 3 | 3 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Nitrogen heterocycle | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Metal oxygen | 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 |
|---|---|---|---|
| AgNPs | 1421, 1232, 1048 | Alkyl C-H, 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 1421 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
-
Alkyl C-H confidence 1.0
“Cu-H C-H 2062 stretching 1421 bending 73.6423 0.4723 10.41 5.13 C-H 1632 N-H stretching 1372 bending”
El Bialy 等 - 2020 - Comparative Toxicological Effects of Biologically DOI: 10.2147/IJN.S241922 -
Aromatic ring confidence 1.0
“4.a, pMBA has two peaks at 1421 and 1590 that are related to cm-1 cm-1) 16 aromatic ring (C-C stretching) [42].”
Structural, optical and dielectric studies of Ag nanoparticles decorated by herceptin DOI: 10.1016/j.physe.2019.113562 -
Nitrogen heterocycle confidence 1.0
“20.16 (cid:4) (cid:4) (cid:4) 21, 22, and The peaks at 900, 1068, plane modes, Electrochemical polymerization and reduction were percm-1 1091, and 1121 can be assigned to pyrrole in-plane 0.05M 0.1M formed in acetonitrile containing thiophe”
Kato 等 - 2007 - X-ray photoemission spectroscopy and Fourier trans DOI: 10.1116/1.2731347 -
Nitrate confidence 1.0
“cm-1 existence of C=O bond is observed at 1653 The peak observed at 1421 is due to the cm-1 residual nitrate and organic matter in YVO 4:Dy.”
Rajendra 等 - 2018 - Luminescence properties of dysprosium doped YVO4 p DOI: 10.1016/j.jre.2018.07.001 -
Acetate confidence 1.0
“The cm-1 intense band observed at 1421 and 1382 are corresponds to stretching vibrations of C=O cm-1 and the band at ~ 1013 is due to the C-C bonding [51].”
Hydrothermal synthesis of surfactant assisted Zn doped SnO2 nanoparticles with enhanced photocatalytic performance and energy storage performance DOI: 10.1016/j.jpcs.2020.109407 -
Acetate confidence 1.0
“LLM confirmed rule peak-group candidate”
Tangwiwat 和 Milne - 2005 - Barium titanate sols prepared by a diol-based sol- DOI: 10.1016/j.jnoncrysol.2004.12.008 -
Alkyl C-H confidence 1.0
“The peaks at 1421 2) and 1373 + cm-1, δC-CH 3) are due to C-H groups.”
Optimization and Characterization of a Novel Exopolysaccharide from Bacillus haynesii CamB6 for Food Applications DOI: 10.3390/biom12060834 -
Alkyl C-H confidence 1.0
“cm-1 The bands at 1421, 1367, and 1316 are assigned as -CH bending, -CH bending, and”
Bian 等 - 2021 - Crystalline Structure Analysis of All-cellulose Na DOI: 10.1007/s10570-017-1259-0
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