What absorbs at 420 cm⁻¹ in an FTIR spectrum?
A band near 420 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 420 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 |
|---|---|---|---|
| Metal oxygen | 11 | 10 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Aromatic ring | 3 | 2 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| N n bond | 1 | 1 | 0.6 |
| C-S single bond | 1 | 1 | 0.6 |
| Carbonyl (C=O) | 1 | 1 | 0.6 |
| Amide | 1 | 0 | 1.0 |
| Silicon (Si) | 1 | 0 | 0.7 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| ZnO | 420, 1400, 3430 | Metal oxygen, Hydroxyl (O-H), Alkyl C-H | 2 |
| polyethylene | 420, 1737, 1720 | Alkyl C-H, Hydroxyl (O-H), Aromatic ring | 1 |
| SiO | 420, 800, 1745 | Hydroxyl (O-H) | 1 |
| GO | 420, 1720, 1182 | Hydroxyl (O-H), 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 420 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
-
confidence 1.0
“peak at 420 may be attributed to the stretching vibration of the Ni-O bond As the AC calcination temperature increased, the absorption peak decreased rapidly and then increased.”
The preparation and characterization of the Ni-NiO/TiO2 hollow composite materials on micro-nano cellulose fibers DOI: 10.1016/j.vacuum.2018.06.044 -
Metal oxygen confidence 1.0
“The corresponding cm-1 cm-1 peak to the Ce-O stretching is observed at 420 and the band at 1080 and 1250”
Biosynthesis, characterization and cytotoxic activity of CeO2 nanoparticles DOI: 10.1016/j.ceramint.2018.04.063 -
Metal oxygen confidence 1.0
“4, AZO 0%, 2%, 3% and 4% gave the same weak absorption spectras at a wavenumber of 420 cm-1 atribute as a bending of Zn-O-Zn.”
conferenceseries.iop.org materials science and engineering open access proceedings IOP Conferences Series: Materials Science and Engineering DOI: 10.1088/1757-899X/176/1/012049 -
Metal oxygen confidence 1.0
“cm-1 1403 1085 and 1040 ZnO nanodrums gives the absorption at the wavenumber of 420 which is cm-1 the vibration of Zn-O-Zn and at 3450 which is the O-H functional group.”
The photocatalytic degradation of methylene blue using graphene oxide (GO)/ZnO nanodrums DOI: 10.1063/1.5054523 -
Alkyl C-H confidence 1.0
“In this present work, the bands due to C-H in-plane ring 280cm-1 420, are assigned to C-C-C stretching and out-of-plane vibration interacting somewhat with C-C stretching vibration are vibrations respectively.”
FTIR and FT Raman, molecular geometry, vibrational assignments, ab initio and density functional theory calculations for 1,5-methylnaphthalene DOI: 10.1016/j.saa.2010.09.002 -
Metal oxygen confidence 1.0
“LLM confirmed rule peak-group candidate”
Abd El-Moneim 等 - 2023 - XRD, FTIR and ultrasonic investigations of cadmium DOI: 10.1038/s41598-023-39489-5 -
Metal oxygen confidence 1.0
“The assignment of bands at 420 cm-1, 580 cm-1 and 650 cm-1 to the stretching vibrations of Zr-O bonds is more probable due to the progressive crystallization of different forms of zirconia in these samples, which agrees with the X-ray analy”
Adamczyk - 2022 - The Study of the Influence of ZrO2 Precursor Type DOI: 10.3390/gels8110724 -
Alkyl C-H confidence 1.0
“Figure 2: ATR-FTIR 375 Comparative study of carbonyl index methods for transmission and 1,420cm-1 C-H as the stretching modes between 1,500 and CI calculations used to compare against the SAUB method Table 3:”
Almond 等 - 2020 - Determination of the carbonyl index of polyethylen DOI: 10.1515/epoly-2020-0041
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