What absorbs at 816 cm⁻¹ in an FTIR spectrum?
A band near 816 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 816 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 |
|---|---|---|---|
| Methoxy (OCH3) | 4 | 4 | 1.0 |
| Methacrylate | 4 | 4 | 1.0 |
| C-O single bond | 4 | 4 | 1.0 |
| Acetate | 4 | 4 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Nitro (NO2) | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
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 816 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
-
Silicon (Si) confidence 1.0
“The intense band at 755 cm-1 B-doped one, whereas a new band at 816 appears, which has been easily assigned to the Si-B cm-1).”
Borini 和 Ugliengo - 2003 - The Si-H-B complex in p(+)-type porous silicon a DOI: 10.1002/pssa.200306540 -
Hydroxyl (O-H) confidence 1.0
“were present in both FTIR spectra of plant extract and FeNPs, such as alkyl halides, alkynes, aromatics and aliphatic amines, esters, ethers, alcohol, carboxylic acids, and nitro Nanomaterials2022,12,2404 11of25 compounds with peaks at 526.”
Green Synthesis and Characterization of Iron Nanoparticles Synthesized from Aqueous Leaf Extract of Vitex leucoxylon and Its Biomedical Applications DOI: 10.3390/nano12142404 -
Metal oxygen confidence 1.0
“LLM confirmed rule peak-group candidate”
Saliu 等 - 2017 - Catalytic crosslinking of a regenerated hydrophobi DOI: 10.1515/epoly-2016-0289 -
Acetate confidence 1.0
“The band located at 816 attributed to the C-O cm-1 stretching of alcohol.”
Ahmed 等 - 2021 - STRUCTURAL AND OPTICAL CHARACTERISTICS OF POLY(VIN DOI: 10.4314/bcse.v35i3.12 -
confidence 1.0
“A wide, high, cm-1 and intense absorption band present at 1091 might suggest the stretching vibration of (Si-O-C) and (Si-O-Si) bonds present in the silane, while the two peaks around 816”
Enhanced Coating Protection of C-Steel Using Polystyrene Clay Nanocomposite Impregnated with Inhibitors DOI: 10.3390/polym15020372 -
Acetate confidence 1.0
“The two new peaks at 1365 cm-1 be related to the S=O group, and the peak at 816 can be related to the C-O-S bonds [19].”
Awada 和 Daneault - 2015 - Chemical Modification of Poly(Vinyl Alcohol) in Wa DOI: 10.3390/app5040840 -
Alkyl C-H confidence 1.0
“In the meantime, the FTIR spectrum displayed an out of plan bending peak, corresponding to the complexed arene C-H at 816 cm-1, while their stretching bands were observed at 3097, 469, and 553 cm-1.”
Cationic Cyclopentadienyliron Complex as a Novel and Successful Nucleating Agent on the Crystallization Behavior of the Biodegradable PHB Polymer DOI: 10.3390/molecules23102703 -
Acetate confidence 1.0
“1220, ment (16.3%) in comparison with the control (9.8%), RC 1105, 1064 and 1017 (C-O-C stretching) 816 and 770 (11%) and ST (8.6%).”
Iliadi 等 - 2022 - Epsilon ffect of cleansers on the composition and DOI: 10.1186/s40510-022-00449-w
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