What absorbs at 1381 cm⁻¹ in an FTIR spectrum?
A band near 1381 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 1381 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 | 9 | 8 | 1.0 |
| Amide | 7 | 5 | 1.0 |
| Methacrylate | 6 | 6 | 1.0 |
| Acetate | 6 | 6 | 1.0 |
| Methoxy (OCH3) | 5 | 5 | 1.0 |
| C-O single bond | 4 | 4 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Secondary amine | 3 | 2 | 1.0 |
| C n single bond | 3 | 2 | 1.0 |
| Carboxyl (COOH) | 3 | 2 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| C c single bond | 2 | 1 | 1.0 |
| Carbonyl (C=O) | 2 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Carbohydrate | 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 |
|---|---|---|---|
| chitosan | 1381, 1650, 1655 | Alkyl C-H, Amide, Acetate | 2 |
| graphene oxide | 1381, 1150, 3400 | Methacrylate, Acetate, Alkyl C-H | 1 |
| GO | 1381, 1720, 1182 | Methacrylate, Acetate, 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 1381 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
“There are two peaks at 1381 and 1060 linked to the asymmetric metric C-O in the copper oxide structure.”
Chitosan Capped Copper Oxide Nanocomposite: Efficient, Recyclable, Heterogeneous Base Catalyst for Synthesis of Nitroolefins DOI: 10.3390/catal12090964 -
Amide confidence 1.0
“moreover, the absorption band at 1381 corresponds to the cm(cid:0) COC-- 1 viscous to facilitate the formation of small droplets in the shearing amide II, and the peak at 1155 corresponds to the process, resulting in dispersion of that phas”
A composite chitosan derivative nanoparticle to stabilize a W1/O/W2 emulsion: Preparation and characterization DOI: 10.1016/j.carbpol.2020.117533 -
Hydroxyl (O-H) confidence 1.0
“Polymer changedpartsbeingremoved.10Eachdifferencespectrum concentration was determined from the relative intensities at shownhereisaspectrumgivenbythedifferencebetween (O-H (C-H cm-1 cm-1 bending band of water) and 1381 1648 twodistinctstat”
Maeda - 2001 - IR spectroscopic study on the hydration and the ph DOI: 10.1021/la001346q -
Amide confidence 1.0
“cm-1), H stretching (around 3431 C O group due to O cm-1), cm-1), (1616 C C and C N stretching (1381 O H cm-1) cm-1).”
Evaluation of different extracts and synthesised silver nanoparticles from leaves of Euphorbia prostrata against Haemaphysalis bispinosa and Hippobosca maculata DOI: 10.1016/j.vetpar.2012.02.001 -
Hydroxyl (O-H) confidence 1.0
“cm-1 • the 1381 band corresponds to deformation modes with participation of the OH, CH, and C-N groups;”
Vibrational Spectroscopy Fingerprinting in Medicine: from Molecular to Clinical Practice DOI: 10.3390/ma12182884 -
Acetate confidence 1.0
“The peak at 1381 cm-1 confirmed the C-O-H bending at the C-6 position [43].”
Pullulan Oxidation in the Presence of Hydrogen Peroxide and N-Hydroxyphthalimide DOI: 10.3390/ma15176086 -
Acetate confidence 1.0
“Molecules2019,24,1211 4of14 According to Figure 2d, peaks near 1624 and 1381 cm-1 belong to the stretching vibrations of C=O.”
Chen 等 - 2019 - In Vitro Toxicity Study of a Porous Iron(III) Meta DOI: 10.3390/molecules24071211 -
Alkene (C=C) confidence 1.0
“The peaks at the 1381 1220 and associated with the stretching vibration of C=C of the aromatic ring.”
New Insights into the Interaction between Graphene Oxide and Beta-Blockers DOI: 10.3390/nano9101429
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