What absorbs at 1366 cm⁻¹ in an FTIR spectrum?
A band near 1366 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 1366 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 | 10 | 10 | 1.0 |
| Amide | 5 | 5 | 1.0 |
| Secondary amine | 4 | 4 | 1.0 |
| C n single bond | 4 | 4 | 1.0 |
| Methacrylate | 4 | 4 | 1.0 |
| Acetate | 4 | 4 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| C-O single bond | 3 | 2 | 1.0 |
| Hydroxyl (O-H) | 3 | 1 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Aldehyde (CHO) | 1 | 1 | 1.0 |
| Fatty acid | 1 | 1 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 0.9 |
| Alkene (C=C) | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| pectin | 1366, 1746, 1150 | Alkyl C-H, Amide | 1 |
| LDPE | 1366, 1720, 1737 | Alkyl C-H | 1 |
| curcumin | 1366, 1063, 1153 | Amide, 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 1366 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
“LLM confirmed rule peak-group candidate”
Awal 等 - 2012 - Thermal analysis and spectroscopic studies of elec DOI: 10.1007/s10973-011-1875-0 -
Alkyl C-H confidence 1.0
“It was observed that ruminant cm(cid:0) 0.875 0.978 0.074 0.938 1.000 0.031 1.000 0.957 0.021 0.944 0.957 0.050 1 2900-2800 fat samples were positively correlated to the bands Beef cm(cid:0) cm(cid:0) (C-- 1 1 (C-H symmetric stretching), 17”
Comparison and chemical structure-related basis of species discrimination of animal fats by Raman spectroscopy using near-infrared and visible excitation lasers DOI: 10.1016/j.lwt.2020.110105 -
Carbonyl (C=O) confidence 1.0
“Varioius bands can be identified in both spectra cm(cid:1)1, including the SO stretching band at 1366 the carbonyl stretching 2 cm(cid:1)1,”
Quintas 等 - 2003 - An infrared method, with reduced solvent consumpti DOI: 10.1081/SL-120026637 -
Phosphate (PO4) confidence 1.0
“LLM confirmed rule peak-group candidate”
Rahim 等 - 2021 - Physicochemical properties of phosphate butyrate a DOI: 10.1088/1755-1315/681/1/012043 -
Fatty acid confidence 1.0
“- 1406 1414 in amino acid, fatty acids - - - - - Aldehydic C-H bending vibration 1366”
Sukprasert 等 - 2020 - Synchrotron FTIR Light Reveals Signal Changes of B DOI: 10.1155/2020/6149713 -
Alkyl C-H confidence 1.0
“The characteristic peak at cm-1 1366 is associated with the asymmetric H-C-H bending of the glycerol group's O-CH 2”
Dhal 等 - 2023 - Formulation and Characterization of Emulgel-Based DOI: 10.3390/gels9060466 -
Acetate confidence 1.0
“cm-1, C-C=C symmetric of aromatic ring at 1639.49 C=O cm-1, stretching of aldehyde group at 1735.93 peak at N=O cm-1, bend which corresponds to 1365.60 C-O stretching cm-1.”
Gajendiran 等 - 2016 - Microbial degradation of low-density polyethylene DOI: 10.1007/s13205-016-0394-x -
Alkyl C-H confidence 1.0
“at ~1366 cm-1 2 originate from CH 2-scissoring vibrations of Suc molecules [48].”
Stabilization of Dry Sucrose Glasses by Four LEA_4 Proteins from Arabidopsis thaliana DOI: 10.3390/biom11050615
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