What absorbs at 1380 cm⁻¹ in an FTIR spectrum?
A band near 1380 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 1380 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 | 41 | 33 | 1.0 |
| Amide | 16 | 14 | 1.0 |
| Secondary amine | 13 | 11 | 1.0 |
| Methacrylate | 12 | 10 | 1.0 |
| Acetate | 12 | 10 | 1.0 |
| Methyl | 11 | 10 | 1.0 |
| C n single bond | 10 | 8 | 1.0 |
| Methoxy (OCH3) | 10 | 8 | 1.0 |
| Carboxyl (COOH) | 8 | 8 | 1.0 |
| C-O single bond | 8 | 6 | 1.0 |
| Hydroxyl (O-H) | 8 | 6 | 1.0 |
| Aromatic ring | 6 | 6 | 1.0 |
| Ester | 6 | 6 | 1.0 |
| Carbonyl (C=O) | 6 | 6 | 1.0 |
| N h | 5 | 5 | 1.0 |
| Carbonate | 5 | 5 | 1.0 |
| Ketone | 4 | 4 | 1.0 |
| Ring structure | 4 | 3 | 1.0 |
| Lipid | 3 | 3 | 1.0 |
| C c single bond | 3 | 2 | 1.0 |
| Carbohydrate | 3 | 2 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Imide | 2 | 1 | 1.0 |
| Boron nitrogen | 2 | 0 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
| Triglyceride | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Nitro (NO2) | 1 | 1 | 1.0 |
| Fatty acid | 1 | 1 | 0.7 |
| Siloxane (Si-O-Si) | 1 | 0 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 0 | 1.0 |
| Silicon (Si) | 1 | 0 | 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 |
|---|---|---|---|
| ZnO | 1380, 1400, 3430 | Alkyl C-H, Methacrylate, Amide | 1 |
| silver nanoparticles | 1380, 1636, 1631 | Alkyl C-H, Methacrylate, Amide | 1 |
| SnO2 | 1380, 2800, 1547 | Alkyl C-H, Methacrylate, Amide | 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 1380 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
“The vibration at 1380 is assigned to the C O (cid:4)+ (cid:4)+ (cid:4)+ (cid:4)+ (cid:4)- (cid:4) = + + + + (A 1g) (A 2g) (B 1g) (B 2g) (Eg) mode related to the citrate complex.”
Azam 等 - 2012 - Effect of Mn doping on the structural and optical DOI: 10.1016/j.jallcom.2012.01.072 -
Nitro (NO2) confidence 1.0
“The peaks at 1380, 1529 tromagnetic spectrum, molecules undergo electronic tranindicates the presence of nitro compounds.”
Synthesis of Phytonanocomposite of Zinc Oxide by Ixora coccinea Linn for Cancer Treatment DOI: 10.1007/s10904-016-0382-y -
Alkyl C-H confidence 1.0
“mean.Mean FTIR spectra for each pathologygroup were calculated Lipids have long hydrocarbon chains and therefore their peaks (1380cm(cid:2)1), and empirical peak analysis of the spectra from the four tissue are attributed vibrations of CH C”
Das 等 - 2008 - FTIR of touch imprint cytology A novel tissue dia DOI: 10.1016/j.jphotobiol.2008.05.012 -
Lipid confidence 1.0
“This suggests that an increase in CH intensity for NP4 is not just attributable to lipids, but could also be due to proteins, as evidenced by the significant increase cm-1 in the intensity of the peak at ~1380 sCH 3) exclusively for the rep”
Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy DOI: 10.1016/j.saa.2021.120830 -
Alkyl C-H confidence 1.0
“The peaks at 2934 and cm-1 1380 were attributed to the stretching and bending of C-H bond.”
Hu 等 - 2021 - Properties and Structure of Modified Taro Starch DOI: 10.1002/star.202000252. -
Ester confidence 1.0
“In the fingerprint region peaks 1380observed strong diffraction peaks (10 0), (00 2), (10 2), (110), 903cm(cid:1)1 indicates strong presence of esters (aromatic hence the (10 3), (1 12), (20 0) and (20 1).”
Green synthesis of ZnO doped Moringa oleifera leaf extract using Titon yellow dye for photocatalytic applications DOI: 10.1016/j.matpr.2020.05.119 -
Alkyl C-H confidence 1.0
“From left to right, both spectra show the carbon-carbondoublebondstretchingvibrationpeakat1645cm(cid:1)1 band, the bending vibration peak of the methyl and methylene at cm(cid:1)1 cm(cid:1)1 1450 band, the methyl bending vibrationpeaks at 1”
Liu 等 - 2017 - Determination of the content of Eucommia ulmoides DOI: 10.1016/j.polymertesting.2017.09.023 -
Aromatic ring confidence 1.0
“LLM confirmed rule peak-group candidate”
Synthesis and Catalytic Evaluation of Silver Nanoparticles Synthesized with Aloysia triphylla Leaf Extract DOI: 10.1007/s10876-016-1062-3
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