What absorbs at 1260 cm⁻¹ in an FTIR spectrum?
A band near 1260 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 1260 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 | 22 | 19 | 1.0 |
| Methacrylate | 18 | 17 | 1.0 |
| Acetate | 18 | 17 | 1.0 |
| Methoxy (OCH3) | 16 | 15 | 1.0 |
| C-O single bond | 16 | 13 | 1.0 |
| Silicon carbon | 13 | 12 | 1.0 |
| Amide | 11 | 11 | 1.0 |
| Silicon (Si) | 8 | 8 | 1.0 |
| Secondary amine | 6 | 6 | 1.0 |
| C n single bond | 6 | 6 | 1.0 |
| Phosphate (PO4) | 6 | 4 | 1.0 |
| Carboxyl (COOH) | 5 | 5 | 1.0 |
| Hydroxyl (O-H) | 4 | 4 | 1.0 |
| Ring structure | 4 | 4 | 1.0 |
| Silicon-oxygen (Si-O) | 4 | 4 | 1.0 |
| Aromatic ring | 4 | 3 | 1.0 |
| Methyl | 3 | 3 | 1.0 |
| Carbohydrate | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Siloxane (Si-O-Si) | 3 | 3 | 1.0 |
| Phosphorus | 3 | 2 | 1.0 |
| N-O bond | 3 | 2 | 1.0 |
| Oxygen heterocycle | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Sulfate (SO4) | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| N n bond | 1 | 1 | 1.0 |
| Fluorine (C-F) | 1 | 1 | 1.0 |
| Chlorine | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| S s | 1 | 1 | 1.0 |
| Alkene (C=C) | 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 |
|---|---|---|---|
| humic acid | 1260, 1660, 1220 | Alkyl C-H, Methacrylate, Acetate | 1 |
| TiO | 1260, 1730, 1699 | Alkyl C-H, Methacrylate, Acetate | 1 |
| SiO | 1260, 800, 1745 | Methacrylate, Acetate, Methoxy (OCH3) | 1 |
| TiO2 | 1260, 1700, 1093 | Alkyl C-H, Methacrylate, Acetate | 1 |
| PVA | 1260, 1660, 2930 | Alkyl C-H, Acetate, Methacrylate | 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 1260 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
-
Silicon carbon confidence 1.0
“Due to LiTFSI/ PSx interactions, a slight shifting of 1260cm-1 atῦ Si-CH bending mode = to higher wavenumbers was membrane due to stiffening.”
Cznotka 等 - 2016 - Characterization of semi-interpenetrating polymer DOI: 10.1016/j.ssi.2016.02.016 -
Acetate confidence 1.0
“Absent ≅350+1000 combination band [60] ≅450+795 C-O combination band amide III, stretch of aromatic rings and carboxylic Medium shoulder Absent 1260 SiO2 C-O acids [38], stretching ≅”
FTIR photoacoustic spectroscopy for identification and assessment of soil components_ Chernozems and their size fractions DOI: 10.1016/j.pacs.2020.100162 -
N-O bond confidence 1.0
“At around 1260~1220 the band was assigned indicative of -NO group retention during nitration reaction [37].”
Co-Thermal Oxidation of Lignite and Rice Straw for Synthetization of Composite Humic Substances: Parametric Optimization via Response Surface Methodology DOI: 10.3390/ijerph192416875 -
Carboxyl (COOH) confidence 1.0
“FTIR spectra of water with strong absorbance bands at 3294 and 1640 (a), fulvic acid (SBFA) in solution (b), and the cm-1 difference spectrum revealing a protonated carboxyl band at 1260 (c).”
Lumsdon 和 Fraser - 2005 - Infrared spectroscopic evidence supporting heterog DOI: 10.1021/es050180iCCC -
Alkyl C-H confidence 1.0
“The cm-1 (CH symmetric bending in Sifilms are sufficiently stable if the absorption at 1260 3 2 ACCEPTED MANUSCRIPT cm-1 (CH 3) x) is lower than about 100 [10].”
Peter 等 - 2013 - FTIR analysis of a-SiCNH films deposited by PECVD DOI: 10.1016/j.vacuum.2013.04.014 -
C c single bond confidence 1.0
“LLM confirmed rule peak-group candidate”
Sathish 等 - 2013 - Nano Composite PVA-TiO2 Thin Films for OTFTs DOI: 10.4028/www.scientific.net/AMR.678.335 -
confidence 1.0
“Attribute to C-N stretch.”
Improvement of anti-corrosion performance of an epoxy coating using hybrid UiO-66-NH2/carbon nanotubes nanocomposite DOI: 10.1038/s41598-022-14854-y -
Alkyl C-H confidence 1.0
“All of these 1260 cm-1 can be also assigned to C-H bond vibration in the Si-CH group.”
The Influence of Different Types of SiO2 Precursors and Ag Addition on the Structure of Selected Titania-Silica Gels DOI: 10.3390/cryst13050811
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