What absorbs at 824 cm⁻¹ in an FTIR spectrum?
A band near 824 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 320,000+ reference spectra and knowledge graph.
Backed by 7 cited sources
Quick answer
A band near 824 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 | 7 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Nitro (NO2) | 1 | 1 | 1.0 |
| Carbon dioxide | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Oxygen heterocycle | 1 | 1 | 1.0 |
| C=n | 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 |
|---|---|---|---|
| Polyurethane | 824, 2270, 1512 | Alkyl C-H | 1 |
| porous silicon | 824, 1030, 1108 | 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 824 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
-
Oxygen heterocycle
- Reported band
- 824 cm-1
- Assignment
- Oxygen heterocycle
- Material / context
- Polyurethane; Acrylate; Cycloaliphatic Isocyanate Effects on Physico-Chemical
-
Silicon (Si)
- Reported band
- 824 cm-1
- Assignment
- Silicon (Si)
- Material / context
- porous silicon
-
Alkyl C-H
- Reported band
- 824 cm-1
- Assignment
- Alkyl C-H
- Material / context
- Green Remediation to Polymer Hybrid Fabrication; polyphenol; copper complex
-
C c single bond
- Reported band
- 824 cm-1
- Assignment
- C c single bond
- Material / context
- human saliva
-
Alkyl C-H
- Reported band
- 824 cm-1
- Assignment
- Alkyl C-H
- Material / context
- finish; PPTA sequences; Technora aramid fibres
-
Alkyl C-H
- Reported band
- 824 cm-1
- Assignment
- Alkyl C-H
- Material / context
- Technora T240 aramid fibers
-
C-S single bond
- Reported band
- 824 cm-1
- Assignment
- C-S single bond
- Material / context
- Pyrene as Chemosensor; Conjugated Molecules Based on Dithienopyrrole Derivatives; EDP4HP
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