What absorbs at 1391 cm⁻¹ in an FTIR spectrum?
A band near 1391 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 1391 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 | 5 | 4 | 1.0 |
| Hydroxyl (O-H) | 4 | 3 | 1.0 |
| C-O single bond | 3 | 2 | 1.0 |
| Carbonate | 2 | 2 | 1.0 |
| Borate | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 1 | 1.0 |
| Methacrylate | 2 | 1 | 1.0 |
| Acetate | 2 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 0.7 |
| Carboxyl (COOH) | 1 | 0 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
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 1391 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
-
Borate confidence 1.0
“acid.8 al.,51 to the bond in the As suggested by Liu et the (cid:3)1 B-O band at 1391 cm can be correlated with linkage in cm(cid:3)1 borate.”
Reticulated three-dimensional network ablative composites for heat shields in thermal protection systems DOI: 10.1039/c4ra05811a -
Phosphate (PO4) confidence 1.0
“COOcm-1 the symmetric stretch band at 1391 and 4885 9545 2the PO symmetric stretching;”
Wang 等 - 2012 - Differentiation in MALDI-TOF MS and FTIR spectra b DOI: 10.1186/1471-2180-12-182 -
Hydroxyl (O-H) confidence 1.0
“1391-G3.1 0.46 0.21 0.0034 0.85 0.29 1.13 clude the fundamental OH stretching vibration (v1) at 1391-G4.1 0.51 0.22 0.0036 0.85 0.35 1.20 3550cm-1,andthefundamentalHOHbendingvibration 1391-G5.1 0.48 0.22 0.0036 0.83 0.29 1.13 cm-1 1391-G6.1”
Wysoczanski 和 Tani - 2006 - Spectroscopic FTIR imaging of water species in sil DOI: 10.1016/j.jvolgeores.2006.03.024 -
Alkyl C-H confidence 1.0
“(2015) 1391cm-1 The C-H bending vibrations at indicates the presence of”
Co-pyrolysis of rice straw and water hyacinth_ Characterization of products, yields and biomass interaction effect DOI: 10.1016/j.biombioe.2019.105281 -
C-O single bond confidence 1.0
“C-OH In the region of the in-plane bending vibrations a new band appeared at 1391 in”
Budziak 等 - 2019 - Formation of Prenylated Chalcone Xanthohumol Cocry DOI: 10.3390/molecules24234245 -
Hydroxyl (O-H) confidence 1.0
“Parent alumina sample in (Figure 1(a)) shows 1460 In-plane scissoring of CH group 0.02 0.14 3334cm-1 2 corresponding to the hydroxyl broad band at 1391 In-plane O-H deformation of PEG 0.02 0.12 groups stretching on the alumina surface.”
El-Naggar - 2013 - Characterization of Modified and Polymer Coated Al DOI: 10.1155/2013/706960 -
Carbonate confidence 1.0
“The absorption peaks of calcite are related to the strong peak (CO3) at ~1391 cm-1 peaks.”
Archaeometric Investigations of the Chalcolithic Pottery from Topolița—Neamț County, Romania DOI: 10.3390/coatings13030488 -
Alkyl C-H confidence 1.0
“1 C=O 1799 stretching vibration in EC C=O 1740 stretching vibration in DEC 0.5 1391 C-H bending vibration in EC 1391 C-H bending vibration in DEC 0 1258 C-O asymmetric stretching vibration in DEC 0 50 100 150 200 250 300 350 400”
Matsui 等 - 2015 - In-operando FTIR Spectroscopy for Composite Electr DOI: 10.5796/electrochemistry.83.874
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