What absorbs at 872 cm⁻¹ in an FTIR spectrum?
A band near 872 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 872 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 |
|---|---|---|---|
| Carbonate | 6 | 5 | 1.0 |
| Methoxy (OCH3) | 5 | 5 | 1.0 |
| Methacrylate | 5 | 5 | 1.0 |
| C-O single bond | 5 | 5 | 1.0 |
| Acetate | 5 | 5 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Silicon-oxygen (Si-O) | 4 | 4 | 1.0 |
| Phosphate (PO4) | 3 | 3 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| Silicate | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Water (H2O) | 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 |
|---|---|---|---|
| silica | 872, 1100, 1080 | Methacrylate | 1 |
| PVC | 872, 834, 1195 | Methoxy (OCH3), Methacrylate, C-O single bond | 1 |
| chitosan | 872, 1650, 1655 | Methacrylate, C-O single bond, Methoxy (OCH3) | 1 |
| chitin | 872, 1650, 1655 | Methacrylate, C-O single bond, Methoxy (OCH3) | 1 |
| CS | 872, 1645, 1720 | Methacrylate, C-O single bond, Methoxy (OCH3) | 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 872 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
-
C c single bond confidence 1.0
“cm-1) cm-1), cm-1).9, 10 CH stretching (954 and C-C vibration (868 -CHbending (754 and 1383 cm-1 The peak at 872 observed in all samples which is due to C-C stretching and featured for cm-1 amorphous properties of films.”
Ghosh 等 - 2020 - Blown films fabrication of poly lactic acid based DOI: 10.1016/j.mtcomm.2019.100737 -
Water (H2O) confidence 1.0
“For 3(b), there Absorption peak at 872, 1247 and 1251 was presence of hydrogen bonded O-H [27] which indicates the moisture.”
Ismail 等 - 2015 - Effect of Radiation on Properties of ENRPVCSiO2 DOI: 10.1063/1.4931308 -
Ring structure confidence 1.0
“1 pectin, water associated cellulose/lignin (2015) Band at 871.83 for influent wastewater was observed for and alkaloids CH2 ring stretching of 1,4-dioxane (ALVER and Parlak, 2016) which was”
Greenhouse gases emissions from duckweed pond system treating polyester resin wastewater containing 1,4-dioxane and heavy metals DOI: 10.1016/j.ecoenv.2020.111253 -
confidence 1.0
“A relatively weak and broader band at 872 corresponded to N - H bending vibrations of primary/secondary amines.”
Pai 等 - 2019 - Photocatalytic zinc oxide nanoparticles synthesis DOI: 10.1016/j.ijleo.2019.03.101 -
Acetate confidence 1.0
“The FTIR analysis confirmed the presence of NH out of plane bending (872 cm-1) cm-1) and C-O-C stretching (1016 for chitosan with 59.76% degree of deacetylation.”
Sudatta 等 - 2020 - Extraction, characterization and antimicrobial act DOI: 10.1016/j.ijbiomac.2020.06.291 -
Silicate confidence 1.0
“LLM confirmed rule peak-group candidate”
Optimization of primary sewage sludge and coal lignite by microwave assisted pyrolysis for the production of bio oil DOI: 10.1080/09593330.2020.1797903 -
Carbonate confidence 1.0
“LLM confirmed rule peak-group candidate”
Evidence for Mild Diagenesis in Archaeological Human Bones from the Fewet Necropolis (SW Libya): New Insights and Implications from ATR–FTIR Spectroscopy DOI: 10.3390/app13020687 -
Alkyl C-H confidence 1.0
“vibration of ether bond 777 817 and aer fastness of silk fabrics mordanting with six metal ions article cm-1 C-H 872 are the absorption peaks of the bond on the were conducted, the results are shown in Table 2.”
Extraction of pigments from camellia seed husks and their application on silk fabrics DOI: 10.1039/d2ra06793e
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