What absorbs at 503 cm⁻¹ in an FTIR spectrum?
A band near 503 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 7 cited sources
Quick answer
A band near 503 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) | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Methacrylate | 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 |
| Acetate | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| polyaniline | 503, 1565, 1570 | Alkyl C-H, Methacrylate | 1 |
| nanocomposites | 503, 1717, 1630 | Alkyl C-H, Methacrylate | 1 |
| titanium dioxide | 503, 1716, 1724 | Alkyl C-H, Methacrylate | 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 503 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
“The band at 803 represented the stretching of C-H at 503 cm-1 was seen to be attributed to condensed octahedral AlO6 [18].”
Bekhoukh 等 - 2021 - Development, Investigation, and Comparative Study DOI: 10.3390/polym13193344 -
Acetate confidence 1.0
“Changes in C=O bands 503 in IR spectra were affected when the OM was heated with minerals.”
Hirakawa 等 - 2021 - Effects of minerals on metamorphism of organic mat DOI: 10.1016/0016-7037(89)90180-4 -
Water (H2O) confidence 1.0
“Increase in absorbability (A) and water absorption (WA), 503 synchronized with the increase in the viscosity of the mixture, the gas escapes to the outside.”
Liszkowska 等 - 2019 - The Effect of Accelerated Aging Conditions on the DOI: 10.3390/app9132663 -
Alkyl C-H confidence 1.0
“The small absorption peaks at 765.74, 698.23 and togram of condition (iv), exhibited peaks at retention time cm-1 503.42 12.4, 15.87 and 22.8 min which indicated that addition of were corresponding to CH deformations as well nanoparticles a”
Enhanced degradation of indeno(1,2,3-cd)pyrene using Candida tropicalis NN4 in presence of iron nanoparticles and produced biosurfactant: a statistical approach DOI: 10.1007/s13205-019-1623-x -
Carboxyl (COOH) confidence 1.0
“LLM confirmed rule peak-group candidate”
Priya 和 Azhagan - 2023 - Influence of succinic acid species on structural, DOI: 10.15251/DJNB.2023.181.55 -
Silicon-oxygen (Si-O) confidence 0.9
“Assigned to SiO4 vibration.”
Characterization of a calcium phospho-silicated apatite with iron oxide inclusions DOI: 10.1016/j.jcrysgro.2010.12.054 -
confidence 0.9
“Explicitly attributed to C-O-S coupled vibrations.”
Flotation Performance, Structure-Activity Relationship and Adsorption Mechanism of O-Isopropyl-N-Ethyl Thionocarbamate Collector for Elemental Sulfur in a High-Sulfur Residue DOI: 10.3390/met
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