What absorbs at 851 cm⁻¹ in an FTIR spectrum?
A band near 851 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 851 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 | 4 | 4 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Phosphate (PO4) | 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 |
| Carbonate | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| C c single bond | 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 |
|---|---|---|---|
| PVA | 851, 1660, 2930 | Alkyl C-H, Hydroxyl (O-H) | 2 |
| starch | 851, 1650, 1540 | Hydroxyl (O-H), Alkyl C-H | 1 |
| sodium alginate | 851, 1636, 1080 | Hydroxyl (O-H), Alkyl C-H | 1 |
| NiO | 851, 1006, 1450 | Metal oxygen, Hydroxyl (O-H), Alkyl C-H | 1 |
| nanocomposite | 851, 2921, 3300 | Hydroxyl (O-H), Alkyl C-H, Metal oxygen | 1 |
| TiO2 | 851, 1700, 1093 | Metal oxygen, Hydroxyl (O-H), 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 851 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
“FTIR spectra of starch typically demonstrates bands at 1100-900 (C-O-H Pre-proof cm-1 bending and stretch vibration), 1100-1150 (C-O, C-C and C-O-H stretching), 840 and cm-1 cm-1 1077 (CH 2-O-CH stretching vibration), 851 (skeletal stretchi”
Pourmohammadi 和 Abedi - 2020 - The effect of pre and post-ultrasonication on the DOI: 10.1016/j.ijbiomac.2020.06.205 -
C c single bond confidence 1.0
“The vibrational peaks at 1260 and 2 851cm-1 are assigned to C-C stretching and CH rocking of PVA.”
Sathish 等 - 2013 - Nano Composite PVA-TiO2 Thin Films for OTFTs DOI: 10.4028/www.scientific.net/AMR.678.335 -
Aromatic ring confidence 1.0
“The additional bands at 970.19 850.61 cm-1 cm-1 721.38 and 626.87 are due to aromatic C-H bending mode [22].”
Al-Qahtani 等 - 2022 - Structural, morphological, optical and electrochem DOI: 10.15251/JOR.2022.182.187 -
confidence 1.0
“2 hydroxide.28,29 The three peaks of NiO/ZrO at 851.48, 854.68 2 which indicates that the addition of Zn species to the NiO/ZrO 2 Ni0/NiO, and 860.58 eV can be attributed to Ni(OH) and shakeZnO-ZrO NiO2 catalyst forms a solid solution and w”
Study on the performance of NiO/ZnxZr1−x catalysts for CO2 hydrogenation DOI: 10.1039/d0ra07660k -
Alkyl C-H confidence 1.0
“Practical application of BBSQ C-H and the vibration peak at 851 of the alkenyl group signicantly near the central squarate ring also changed The detection parameters of BBSQ and some reported probes”
NIR squaraine dyes for dual colorimetric and fluorescent determination of Fe3+, Cu2+, and Hg2+ ions DOI: 10.1039/d3ra02419a -
Carbonate confidence 1.0
“LLM confirmed rule peak-group candidate”
Fourier transform infrared spectroscopic studies of methane and liquefied natural gas reforming processes on Ni/CeO2 catalyst DOI: 10.1007/s11144-023-02362-7 -
Hydroxyl (O-H) confidence 1.0
“A peak in the absorption band at 851.4 has been ascribed to the O-H-O cm-1 bending vibration mode, while a smaller peak at 487 seems to represent the stretching cm-1.”
Venkatachalapathy 等 - 2022 - Synthesis, morphological, structural, functional, DOI: 10.15251/DJNB.2022.174.1441 -
Acetate confidence 1.0
“of PVA/SA evidenced for C-O-C at 1090 In the case of PMA incorporated PEMs cm-1 (Figure 1B,D) the peaks at 851 and 843, 966, 783 and 1060 are attributed to M=O d, MO b-M, M-O c-M and O=P=O, respectively [41,43].”
Fabrication of Eco-Friendly Polyelectrolyte Membranes Based on Sulfonate Grafted Sodium Alginate for Drug Delivery, Toxic Metal Ion Removal and Fuel Cell Applications DOI: 10.3390/polym13193293
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