What absorbs at 1257 cm⁻¹ in an FTIR spectrum?
A band near 1257 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 1257 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 |
|---|---|---|---|
| Methoxy (OCH3) | 8 | 8 | 1.0 |
| Methacrylate | 8 | 8 | 1.0 |
| Acetate | 8 | 8 | 1.0 |
| C-O single bond | 7 | 7 | 1.0 |
| Amide | 4 | 4 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 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 |
|---|---|---|---|
| PDMS | 1257, 873, 1080 | Methoxy (OCH3), Methacrylate | 1 |
| cellulose | 1257, 1735, 1650 | 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 1257 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
-
confidence 1.0
“± to Si O Si , two peaks at 1257 and 810 attributable to of 22 1 One notable feature of the urea hydrowidths cm-1 Si(CH 3) O , besides the peaks at 2800-3000 due to CH gen bonding in the present case is the presence of two peaks for 2 cm-1”
Hydrogen bonding and thermomechanical properties of model polydimethylsiloxane based poly(urethane-urea) copolymers: Effect of hard segment content DOI: 10.1016/j.porgcoat.2015.06.015 -
Amide confidence 1.0
“tively large shifts in characteristic peaks of amide III, cm-1, At 4 DAI, spectra of diseased and healthy floret of cellulose, and phosphate (1246.5 shift to 1256.8 cm-1, different wheat cultivars are shown in Figure 5A.”
Synchrotron based phase contrast X-ray imaging combined with FTIR spectroscopy reveals structural and biomolecular differences in spikelets play a significant role in resistance to Fusarium in wheat DOI: 10.1186/s12870-014-0357-5 -
Nitrate confidence 1.0
“1625-1100 these features are within the range which 2.37 corresponds to coordinated nitrates on TiO Within the nitrate cm-1 category, the peak at 1160 can be assigned to the stretching mode (ø(NO)) of the protonated anionic nitrosyl NOH spe”
Pena 等 - 2004 - Identification of surface species on titania-suppo DOI: 10.1021/jp0313122 -
Phosphate (PO4) confidence 1.0
“FTIR spectrum results for PTFE 0.5 pore cm-1, cm-1 1031 and 794.7 size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm-1 for P=O stretching and stretching POC from group -OP =O.”
Saefurohman 等 - 2014 - Potentiometric Measurement Of Polymer-Membrane Ele DOI: 10.1063/1.4868773 -
Acetate confidence 1.0
“The presence of C-O-C ether stretching at a peak of 1257 cm-1 for CAC and C-MCC is an indication that the bleaching treatment used during the isolation of the cellulose did not effectively remove lignin from the cellulose.”
Characterizations of Alpha-Cellulose and Microcrystalline Cellulose Isolated from Cocoa Pod Husk as a Potential Pharmaceutical Excipient DOI: 10.3390/ma15175992 -
Alkyl C-H confidence 1.0
“the band at 1256.81 can be 2 indicates CH symmetrical and CH2 asymmetrical stretching;”
Efficient Degradation of High-Molecular-Weight Hyaluronic Acid by a Combination of Ultrasound, Hydrogen Peroxide, and Copper Ion DOI: 10.3390/molecules24030617 -
Alkyl C-H confidence 1.0
“The absorption band at 1257 represents CH symmetric bending 3 SiMe (Me used as abbreviation for the methyl bond CH 3).”
Comparative study of bulk and surface compositions of plasma polymerized organosilicon thin films DOI: 10.1002/ppap.201900024. -
Alkyl C-H confidence 1.0
“located at 2964 and the asymmetric stretching CH2 of ethyl ester is at 2937 cm-1 Table 1 for PEA shows, at 1726 due to the O=C stretching vibration of the ester cm-1 cm-1 group [25], at 1469 due to CH deformation vibration of ethyl ester, a”
Flores-Hernandez 等 - 2021 - Synthesis of a Biodegradable Polymer of Poly (Sodi DOI: 10.3390/polym13040504
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