What absorbs at 815 cm⁻¹ in an FTIR spectrum?
A band near 815 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 815 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 |
|---|---|---|---|
| Aromatic ring | 7 | 6 | 1.0 |
| Alkyl C-H | 7 | 6 | 1.0 |
| Amide | 4 | 4 | 1.0 |
| Methacrylate | 4 | 4 | 1.0 |
| Acetate | 4 | 4 | 1.0 |
| C-O single bond | 4 | 4 | 1.0 |
| Ring structure | 3 | 3 | 1.0 |
| Ester | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 3 | 3 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Silicon-oxygen (Si-O) | 3 | 3 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Metal oxygen | 2 | 2 | 1.0 |
| Siloxane (Si-O-Si) | 2 | 2 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 0.8 |
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 | 815, 2270, 1700 | Alkyl C-H, Methacrylate, Amide | 1 |
| SiO | 815, 800, 1745 | Methacrylate | 1 |
| graphite | 815, 1640, 1326 | Alkyl C-H, Methacrylate, Aromatic ring | 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 815 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
-
Amide confidence 1.0
“The absorption bands 1413 cm-1 3-, cm-1 cm-1 at 815.25 and 728.12 were assigned to the N-O bending vibration of NO and to C-N at 815.25 cm-1 and 728.12 cm-1 were assigned to the N-O bending vibration of NO3-, and to C-N stretching from the”
Effect of Ratio in Ammonium Nitrate on the Structural, Microstructural, Magnetic, and AC Conductivity Properties of BaFe12O19 DOI: 10.3390/ma11112190 -
Metal oxygen confidence 1.0
“FTIR band peaks were observed at 815 cm-1 corresponding to the stretching vibrations of Bi-O and Ti-O.”
Fabrication of the flexible nanogenerator from BTO nanopowders on graphene coated PMMA substrates by sol-gel method DOI: 10.1016/j.matchemphys.2017.02.002 -
N-O bond confidence 1.0
“There is no sharp cm-1 (structural OH and adsorbed water), a small peak at 1100 (sp 3and isolated characteristic Raman peak at 1332 cm-1 cm-1 due to C-O, and a large peak at around 815 bonded carbon) which is related to a nanodiamond phase”
Ito 等 - 2021 - Assessing the debris generated by the small carry- DOI: 10.2343/geochemj.2.0632 -
confidence 1.0
“cm(cid:50)1, correspond to Si-O stretching mode, 815, and 450 That is, the addition of high electronegativity fluorine atoms bending mode, and rocking mode, respectively.”
Lee 和 Park - 1996 - Effect of fluorine on dielectric properties of SiO DOI: 10.1063/1.363512 -
Alkene (C=C) confidence 1.0
“The characteristics of the acrylate group were determined by the absorption band of 1663 and 815 cm-1 which related to the acrylate double bond (-CH=CH2) and vinyl functionality of (CH2=CH-”
Mudri 等 - 2020 - Comparative Study of Aromatic and Cycloaliphatic I DOI: 10.3390/polym12071494 -
Alkyl C-H confidence 1.0
“(AOH) TA, exposure to MG resulted in shifts for the hydroxyl and cm(cid:1)1) C@O @CAH in esters (peaks at 1745.26 and bending in arocm(cid:1)1 cm(cid:1)1) (ANH) amine groups (from 3269.18 to 3272.13 and cm(cid:1)1) matic rings (peaks at 815”
Decolourization of malachite green dye by endolichenic fungi from the lichen Usnea sp.: A novel study on their dye removal potential DOI: 10.1016/j.jksus.2021.101579 -
Nucleic acid confidence 1.0
“When comparing the Raman spectra of atypical hyperplasia and cancer hyperplasia and cancer samples, in the first one, peaks corresponding to the proline, PO2samples, in the first one, peaks corresponding to the proline, hydroxyproline, tyro”
Simultaneous FTIR and Raman Spectroscopy in Endometrial Atypical Hyperplasia and Cancer DOI: 10.3390/ijms21144828 -
Acetate confidence 1.0
“cm-1 be seen near 1454 The absorption peaks near 815 appeared due to the in-plane bending Materials2020,13,2811 6of13 cm-1 (δ(C=O)).”
Cao 等 - 2020 - Synthesis and Effects of Two Novel Rare-Earth Ener DOI: 10.3390/ma13122811
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