What absorbs at 1280 cm⁻¹ in an FTIR spectrum?
A band near 1280 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 1280 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 |
|---|---|---|---|
| C-O single bond | 18 | 16 | 1.0 |
| Methacrylate | 16 | 14 | 1.0 |
| Acetate | 16 | 14 | 1.0 |
| Methoxy (OCH3) | 15 | 13 | 1.0 |
| Alkyl C-H | 7 | 7 | 1.0 |
| Hydroxyl (O-H) | 7 | 7 | 1.0 |
| Amide | 6 | 6 | 1.0 |
| Carbonyl (C=O) | 4 | 4 | 1.0 |
| C c single bond | 4 | 4 | 1.0 |
| Carboxyl (COOH) | 4 | 3 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Protein | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Anhydride | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 0.9 |
| Phosphate (PO4) | 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 |
|---|---|---|---|
| silica | 1280, 1100, 1080 | Methacrylate, Acetate | 1 |
| PHB | 1280, 3440, 1724 | Methacrylate, Acetate, Methoxy (OCH3) | 1 |
| PEG | 1280, 1650, 1342 | Methacrylate, Acetate, C-O single bond | 1 |
| polypropylene | 1280, 1030, 1600 | Methacrylate, Acetate, Methoxy (OCH3) | 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 1280 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
“Figure 6b shows the peak heights of the CH rocking bands at about 1280”
Hauswirth 等 - 2022 - Spectroscopic Investigation of the Impact of Cold DOI: 10.3390/foods11182786 -
Anhydride confidence 1.0
“of the first peak decreases greatly from 179.0 to 880cm(cid:3)1) peaks (1280, 1080, and are attributed to phosphoric Theresiduesafter theconecalorimeter testwereexaminedfor species.[21] (--O)-O-P) anhydride (P changes in char appearance by”
Synergistic effects of ferric pyrophosphate (FePP) in intumescent flameretardant polypropylene DOI: 10.1002/pat.1590 -
C-O single bond confidence 1.0
“The band at 1305 is associated with the carbonyl group of the ketone linkage in the cm-1 PEEK repeat unit, while the band at 1280 is observed due to the resonance of the cm-1 cm-1 diphenyl ether group [31].”
Vibrational spectroscopic study of pure and silica-doped sulfonated poly(ether ether ketone) membranes DOI: 10.1016/j.saa.2014.12.004 -
Acetate confidence 1.0
“1280 The possible absorption due to C-O vibrations from carbonyl components of the bio”
Optimization of primary sewage sludge and coal lignite by microwave assisted pyrolysis for the production of bio oil DOI: 10.1080/09593330.2020.1797903 -
Amide confidence 1.0
“Amide III (appearing at band 1280 with an intensity of 0.053 for the new vegetable-tanned leather, but which disappeared for the historical binding) was associated with N-H in-plane bending and CH wagging vibration of glycine 2”
Fungal Biodeterioration of a Historical Manuscript Dating Back to the 14th Century: An Insight into Various Fungal Strains and Their Enzymatic Activities DOI: 10.3390/life12111821 -
Carbonyl (C=O) confidence 1.0
“LLM confirmed rule peak-group candidate”
Production kinetics of polyhydroxyalkanoates by using Pseudomonas aeruginosa gamma ray mutant strain EBN-8 cultured on soybean oil DOI: 10.1007/s13205-016-0452-4 -
C c single bond confidence 1.0
“The bands at cm-1 C-C 1280 and 1232 correspond to the stretching Table 2 summarizes the contact angles of sessile drops of cm-1 films.”
Effect of PEG grafting density on surface properties of polyurethane substrata and the viability of osteoblast and fibroblast cells DOI: 10.1007/s10856-022-06668-1 -
Acetate confidence 1.0
“A weak band of the region 1280 is related to stretching vibrations of C-O and cm-1 wagging of OH.”
HPTLC and FTIR Fingerprinting of Olive Leaves Extracts and ATR-FTIR Characterisation of Major Flavonoids and Polyphenolics DOI: 10.3390/molecules26226892
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