What absorbs at 805 cm⁻¹ in an FTIR spectrum?
A band near 805 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 805 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 |
|---|---|---|---|
| Silicon-oxygen (Si-O) | 6 | 6 | 1.0 |
| Silicon (Si) | 3 | 3 | 1.0 |
| Siloxane (Si-O-Si) | 3 | 3 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Sulfate (SO4) | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Metal oxygen | 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 |
| Boron nitrogen | 1 | 0 | 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 |
|---|---|---|---|
| SiC | 805, 791, 1136 | Silicon-oxygen (Si-O), Silicon (Si), Siloxane (Si-O-Si) | 1 |
| asphalt | 805, 1600, 1376 | 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 805 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
“In addition, the bands at 805.22 are occupied by the phosphate group of the binding cm(cid:0) 1 Si-O and the strong stretching silicon group of the binding.”
Biologically-induced synthetic manganese carbonate precipitate (BISMCP) for potential applications in heavy metal removal DOI: 10.1016/j.heliyon.2023.e15919 -
Sulfate (SO4) confidence 1.0
“LLM confirmed rule peak-group candidate”
Fauzi 等 - 2020 - Characterization, Disintegration, and Dissolution DOI: 10.1155/2020/3565931 -
Hydroxyl (O-H) confidence 1.0
“CR occurs at the peak of 1261 1094 1031 804.7 and 667 cm-1, cm-1 cm-1 The absorption peaks at 1261 1094 and 1031 are identified as the bending vibrations of O-H, stretching vibrations of C-O and stretching vibrations of 804.7cm-1 S=O, respe”
Liang 等 - 2017 - Thermo-stability and aging performance of modified DOI: 10.1016/j.matdes.2017.04.060 -
Metal oxygen confidence 1.0
“The cm-1 intense transmittance band at 805 is due to vibrating Figure 6 displays the UV-visible spectra of YVO4:5%Dy, modes of stretching frequency of V-O bonds in YVO Eu (1 mol%, 3 mol%, 5 mol% and 7 mol%) nanophosphor.”
Synthesis and luminescence properties of europium-codoped and dysorium-doped YVO4 nanophosphor for potential applications DOI: 10.1007/s00339-019-2990-1 -
confidence 1.0
“1.0 corresponded to the asymmetric vibration of the siloxane ml/min) to pH = 9 with 150 ml of 3.0 mol/L HNO containcm-1 bond Si-O-Si, and the band at 805 was assigned to the 3”
Adam 等 - 2012 - Liquid Phase Oxidation of Acetophenone over Rice H DOI: 10.1016/S1872-2067(11)60361-6 -
confidence 1.0
“(cid:2)460, vibration patterns of KIT-6 centered at 805, 970, and crystalline emulsion with the crystallization time of 24 h cm(cid:4)1.29 cm(cid:4)1 1080 The adsorption band around 460 represents could be easily assembled using a mesoporou”
Synthesis of ZSM-5/KIT-6 with a tunable pore structure and its catalytic application in the hydrodesulfurization of dibenzothiophene and diesel oil DOI: 10.1039/c8ra05675g -
Silicon carbon confidence 1.0
“5a, top plot) show a distinct (possibly crystalline) cm-1, which corresponds to the transverse optical vibrational mode of SiC, along with a shoulder where peak at 805 cm-1, which corresponds to the lateral optical vibrational mode of SiC [”
Henry 等 - 2018 - Characterization of Ceramic Matrix Composite Degra DOI: 10.1063/1.5031613 -
Hydroxyl (O-H) confidence 1.0
“It also shows reduced absorbance in the 805 and OH deformation vibrations and CO stretching vibrations (phecm-1 gion, which is associated with the sulfate group of the 3,6-anhynols) can be found.”
A novel biodegradable film based on κ‐carrageenan activated with olive leaves extract DOI: 10.1002/fsn3.1554
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a confidence-rated evidence chain — in seconds.