What absorbs at 1166 cm⁻¹ in an FTIR spectrum?
A band near 1166 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 1166 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 |
|---|---|---|---|
| C-O single bond | 8 | 7 | 1.0 |
| Methoxy (OCH3) | 7 | 7 | 1.0 |
| Methacrylate | 7 | 7 | 1.0 |
| Acetate | 7 | 7 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| S s | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Chlorine | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 0.8 |
| Lipid | 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 |
|---|---|---|---|
| cellulose | 1166, 1735, 1650 | Acetate, Methacrylate, C-O single bond | 1 |
| hemicelluloses | 1166, 1735, 1270 | C-O single bond, Methacrylate, Acetate | 1 |
| polyaniline | 1166, 1565, 1570 | Methacrylate, Acetate | 1 |
| copolymer | 1166, 2921, 1540 | Methacrylate, Acetate | 1 |
| CS | 1166, 1645, 1720 | Methacrylate, C-O single bond, Acetate | 1 |
| lignin | 1166, 1035, 1510 | Methacrylate, Acetate, C-O single bond | 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 1166 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
-
Acetate confidence 1.0
“C-N bending + stretching) was located at 1522 while the cm(cid:2)1 The presence of a melting peak suggested that the crystalline C-O-C peak at 1166 was attributed to the stretching cm(cid:2)1 structure of the PCL is preserved due to its rel”
Cetina-Diaz 等 - 2014 - Physicochemical characterization of segmented poly DOI: 10.1039/c3tb21500h -
Ester confidence 1.0
“cm(cid:2)1 1380cm(cid:2)1 showed strong lipid spectral peaks at 1166 and Biological tissue is essentially made up of proteins, nucleic 1748cm(cid:2)1, including a very strong carbonyl-ester band at and a acids, carbohydrates and lipids each”
Das 等 - 2008 - FTIR of touch imprint cytology A novel tissue dia DOI: 10.1016/j.jphotobiol.2008.05.012 -
Alkyl C-H confidence 1.0
“1447 C C stretching in benzoid rings 2996 C H stretching N stretching 1166 N S bond 1291 C”
Dey Sadhu 等 - 2020 - Preparation and characterization of polyanilinea DOI: 10.1002/pc.25738 -
Acetate confidence 1.0
“In particular, cm-1 alcohol), while the absorption band at 1166 Ni/Zr-BTC thermogram exhibited a third mass decrease originated from the C-O stretching vibration (secondary”
Lestari 等 - 2022 - Zirconium(IV)-BTC-Based MOF Modified with Nickel a DOI: 10.17576/jsm-2022-5109-16 -
confidence 1.0
“Furthermore, the intensities of several peaks, the C O vibrations associated with the pyranose ring including The KAS method can be described by the following equation cm-1, cm-1 at 1166 the N H bending vibration at 1609 and the [30]:”
Study on the thermal degradation kinetics and pyrolysis characteristics of chitosan-Zn complex DOI: 10.1016/j.jaap.2016.03.021 -
Amide confidence 1.0
“The 1165.75 absorption band indicated the existence of cm-1, aromatic amine (C-N stretch).”
The Nutritional Quality and Structural Analysis of Black Soldier Fly Larvae Flour before and after Defatting DOI: 10.3390/insects13020168 -
C c single bond confidence 1.0
“C-C-O-C stretching vibration of AC was represented by a distinct band around 1166, 1195 RESULTS AND DISCUSSION cm-1.”
Zulkifli 等 - 2020 - Corrosion Resistance Evaluation of Acrylic Coating DOI: 10.17576/jkukm-2020-32(2)-14 -
Alkyl C-H confidence 1.0
“Also, the band present at cm-1 cm-1 CH in cellulose and the band at 1166 1417 is related to the C-H group and bending”
Allouch 等 - 2019 - CHARACTERIZATION OF COMPONENTS ISOLATED FROM ALGER DOI: 10.1016/j.pecs.2012.02.002
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