What absorbs at 813 cm⁻¹ in an FTIR spectrum?
A band near 813 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 813 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 |
| Silicon-oxygen (Si-O) | 4 | 4 | 1.0 |
| Silicon (Si) | 4 | 4 | 1.0 |
| Aromatic ring | 4 | 3 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Siloxane (Si-O-Si) | 2 | 2 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Metal oxygen | 2 | 2 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| N n bond | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 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 |
|---|---|---|---|
| lignin | 813, 1035, 1510 | Alkyl C-H, Aromatic ring | 1 |
| PMMA | 813, 1722, 1383 | 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 813 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
“785 Out-of-plane C H bending vibration 813 813 813 Para disubstituted benzene ring”
Chabukswar 等 - 2012 - Studies on Synthesis and Effect of Dopants on Cond DOI: 10.1080/10601325.2012.722850 -
Aromatic ring confidence 1.0
“LLM confirmed rule peak-group candidate”
Gangnaik 等 - 2015 - Correlation of lithographic performance of the ele DOI: 10.1116/1.4926387 -
confidence 1.0
“In the spectrum of the anhydrous powder, C3S is denoted by O-Si-O and Si-O-Ca stretching modes at 813 and 936 cm-1, respectively [31,37].”
The Application of 29Si NMR Spectroscopy to the Analysis of Calcium Silicate-Based Cement using Biodentine™ as an Example DOI: 10.3390/jfb10020025 -
Metal oxygen confidence 1.0
“LLM confirmed rule peak-group candidate”
Li 等 - 2021 - Mechanisms of arsenate and cadmium co-immobilized DOI: 10.1016/j.cej.2021.130410 -
Nitrogen heterocycle confidence 1.0
“cm-1, cm-1 the absorption peak of the triazine ring at 813 and the absorption peak of the stretching cm-1 vibration P-O at 1088 [33].”
Liang 等 - 2020 - Thermal Kinetics of a Lignin-Based Flame Retardant DOI: 10.3390/polym12092123 -
Silicon (Si) confidence 1.0
“DMPS showed a strong peak at 813 amethyldisiloxane are covalently bound through the silanols to cm¡1 assigned to a Si-phenyl vibration.”
Modification of Chrysotile Surface by Organosilanes: An IR–Photoacoustic Spectroscopy Study DOI: 10.1006/jcis.2001.7524 -
Amide confidence 1.0
“It was confirmed by FTIR that specific vibration cm-1, cm-1, amide B (N-H) 3069,396 amide I (C=O) at band peak amide A (N-H) at 3286,209 cm-1, cm-1, cm-1, amide II (N-H and CN) at 1538,949 amide III (C-N) at 1276,789 1643,813 cm-1, respecti”
Nasir 和 Apriani - 2018 - Synthesis and Property of Ag(NP)catechinGelatin DOI: 10.1088/1757-899X/293/1/012004 -
Metal oxygen confidence 1.0
“The bonding of O=Zr=O and the metal-oxygen interface was confirmed in the synthesized ZrO NPs by the bands of 813 and 734 [53-55].”
Chelliah 等 - 2023 - Photocatalytic Organic Contaminant Degradation of DOI: 10.3390/separations10030156
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