What absorbs at 1239 cm⁻¹ in an FTIR spectrum?
A band near 1239 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 1239 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 |
|---|---|---|---|
| Methacrylate | 8 | 8 | 1.0 |
| Acetate | 8 | 8 | 1.0 |
| C-O single bond | 7 | 7 | 1.0 |
| Methoxy (OCH3) | 6 | 6 | 1.0 |
| Amide | 5 | 5 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Sulfate (SO4) | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Phosphate (PO4) | 2 | 2 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Fluorine (C-F) | 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 | 1239, 1650, 1655 | Acetate, Methacrylate, 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 1239 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
“The Au/TiO The band centered at 1239 and 1416 is catalyst calcined at 450 2 C-H due to deformation vibrations.”
Du 等 - 2014 - Influence of Au Particle Size on AuTiO2 Catalysts DOI: 10.1021/jp504681f -
Carbonate confidence 1.0
“The peaks at 1457 and 1239 cm-1 also appear, indicative of the presence of CO3.”
Remineralization Potential of Three Restorative Glass Ionomer Cements: An In Vitro Study DOI: 10.3390/jcm12062434 -
Phosphate (PO4) confidence 1.0
“and C-N and C-C stretching (1122 cm-1 The band located at 1239 is assigned to the asymmetric PO stretching from phosphodiester”
Mostaco-Guidolin 等 - 2010 - Molecular and chemical characterization by Fourier DOI: 10.3233/SPE-2010-0466 -
C-O single bond confidence 1.0
“The ATR-FTIR spectrum of synthesized product (SPES) showed charactercm-1 istic peaks at the wavenumbers of 1239.4 corresponded to the stretching vibration of ether functional groups (-C-O-C-);”
The synthesis of sulfonated polyethersulfone (SPES) and the preparation of its membranes as matrix in the immobilization of Candida antarctica lipase B (Cal-B) DOI: 10.1007/s00289-019-02932-7 -
Sulfate (SO4) confidence 1.0
“cm(cid:0) cm(cid:0) 1 1) band at 1239 (and 1234 is interpreted as a sulfate band.”
Organic biopolymers of venus clams: Collagen-related matrix in the bivalve shells with crossed-lamellar ultrastructure DOI: 10.1016/j.bbrep.2021.100939 -
Acetate confidence 1.0
“Owing to the intermolecular bonds (seen in samples 2 and 3), the 1271 band cm-1 decreases while the 1239 band rises (non-bonded and bonded C-O stretching).”
HPTLC and ATR/FTIR Characterization of Antioxidants in Different Rosemary Extracts DOI: 10.3390/molecules26196064 -
Acetate confidence 1.0
“The vibrational stretching observed at 1229.99 cm-1 revealed a redshift from 1239 cm-1 for C-O-C stretching [39].”
Novel Hemocompatible Imine Compounds as Alternatives for Antimicrobial Therapy in Pharmaceutical Application DOI: 10.3390/pr8111476 -
Amide confidence 1.0
“FTIR spectra (Figure 2) showed the characteristic absorption bands assigned to the peptide bonds FTIR spectra (Figure 2) showed the characteristic absorption bands assigned to the peptide cm-1 cm-1 in collagen [31]: 3298 for amide A (stretc”
A Green Approach towards Native Collagen Scaffolds: Environmental and Physicochemical Assessment DOI: 10.3390/polym12071597
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