What absorbs at 1250 cm⁻¹ in an FTIR spectrum?
A band near 1250 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 1250 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 | 42 | 39 | 1.0 |
| Acetate | 42 | 39 | 1.0 |
| C-O single bond | 41 | 39 | 1.0 |
| Methoxy (OCH3) | 39 | 37 | 1.0 |
| Amide | 27 | 25 | 1.0 |
| Alkyl C-H | 19 | 19 | 1.0 |
| Secondary amine | 14 | 12 | 1.0 |
| Hydroxyl (O-H) | 13 | 11 | 1.0 |
| C n single bond | 12 | 10 | 1.0 |
| Carboxyl (COOH) | 11 | 10 | 1.0 |
| Ester | 8 | 7 | 1.0 |
| N h | 8 | 7 | 1.0 |
| C c single bond | 6 | 6 | 1.0 |
| Ring structure | 5 | 5 | 1.0 |
| Sulfate (SO4) | 5 | 5 | 1.0 |
| Carbonyl (C=O) | 5 | 4 | 1.0 |
| Phosphate (PO4) | 5 | 4 | 1.0 |
| Lignin | 4 | 4 | 1.0 |
| Ketone | 4 | 3 | 1.0 |
| Silicon-oxygen (Si-O) | 4 | 3 | 1.0 |
| Oxygen heterocycle | 4 | 3 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| Protein | 3 | 3 | 1.0 |
| Amine primary | 3 | 3 | 1.0 |
| Silicon (Si) | 3 | 2 | 1.0 |
| Silicon carbon | 3 | 2 | 1.0 |
| Chlorine | 2 | 2 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Metal oxygen | 2 | 2 | 1.0 |
| Siloxane (Si-O-Si) | 2 | 1 | 1.0 |
| S eq o | 2 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Thiol | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| Boron nitrogen | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Fluorine (C-F) | 1 | 1 | 0.9 |
| Sulfonyl | 1 | 0 | 1.0 |
| Phosphorus | 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 |
|---|---|---|---|
| polyaniline | 1250, 1565, 1570 | Methacrylate, Acetate | 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 1250 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
-
Amide confidence 1.0
“Further, the reduction in the intensity of the bands at positions 1250 and 1390cm-1 cm-1 (C-N stretch) and their shifting to the positions 1260 and 1410 respectively have been observed.”
Chhokkar 等 - 2020 - Electrical and Structural Characterization of 100 DOI: 10.1063/5.0023335 -
Aromatic ring confidence 1.0
“LLM confirmed rule peak-group candidate”
Effect of ultrasonication on particle size and magnetic properties of polyaniline NiCoFe2O4 nanocomposites DOI: 10.1016/j.jmmm.2014.04.024 -
Acetate confidence 1.0
“2230 2017, Vol.18, No.11 cm-1 The band around 1250 in both spectra is related to C-O stretching or O-H deformation of COOH or O-H phenolic”
Das 等 - 2017 - Extraction of xylem fibers from Musa sapientum and DOI: 10.1007/s12221-017-1187-5 -
S eq o confidence 1.0
“LLM confirmed rule peak-group candidate”
Sulfated polysaccharides (fucoidan) from the brown seaweed Silvetia compressa (J. Agardh) E. Serrão, T.O. Cho, S.M. Boo & Brawley DOI: 10.1007/s10811-019-01870-1 -
Amide confidence 1.0
“cm-1 1250 is the amide III band and is due to the”
Fabrication of pristine electrospun kafirin nanofiber mats loaded with thymol and carvacrol DOI: 10.1007/s10853-020-05663-7 -
Alkyl C-H confidence 1.0
“In this spectrum, the band pointing at 1250 correspond 2 cm-1 to C-H, C-N, N-H, and N-N vibrations.”
Mechanical and tribological characterization of CNx films deposited by d.c. magnetron sputtering DOI: 10.1002/pssc.200675911 -
Ring structure confidence 1.0
“The peak appeared at 1250, 1500, and 1600 are assigned to in-plane and ring stretching modes of the 1C.”
Kato 等 - 2005 - X-ray photoemission spectroscopy and Fourier trans DOI: 10.1116/1.1914816 -
Alkyl C-H confidence 1.0
“band appears at 1250 The C-H asymmetric bending”
Katiyar 等 - 2017 - Fullerene (C-60) Containing Cross-Linked Polyacryl DOI: 10.1166/jnn.2017.12880
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