What absorbs at 1545 cm⁻¹ in an FTIR spectrum?
A band near 1545 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 1545 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 |
|---|---|---|---|
| Amide | 54 | 47 | 1.0 |
| Carboxyl (COOH) | 16 | 12 | 1.0 |
| N h | 15 | 12 | 1.0 |
| Secondary amine | 11 | 10 | 1.0 |
| Methacrylate | 10 | 9 | 1.0 |
| Acetate | 10 | 9 | 1.0 |
| Carbonyl (C=O) | 10 | 8 | 1.0 |
| C n single bond | 9 | 8 | 1.0 |
| Ester | 8 | 7 | 1.0 |
| Bromine | 6 | 5 | 1.0 |
| Ketone | 6 | 5 | 1.0 |
| Protein | 6 | 5 | 1.0 |
| Nitrogen heterocycle | 5 | 4 | 1.0 |
| Methoxy (OCH3) | 4 | 4 | 1.0 |
| C-O single bond | 4 | 4 | 1.0 |
| Ring structure | 4 | 3 | 1.0 |
| Bronsted acid site | 4 | 2 | 1.0 |
| Lewis acid site | 4 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Protein alpha helix | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Urea | 1 | 1 | 0.8 |
| Carbonate | 1 | 1 | 0.8 |
| Silanol (Si-OH) | 1 | 0 | 1.0 |
| Silicon (Si) | 1 | 0 | 1.0 |
| Nitrate | 1 | 0 | 1.0 |
| Amino acid | 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 |
|---|---|---|---|
| Silver nanoparticles | 1545, 1636, 1631 | Amide, N h | 2 |
| ZnO | 1545, 1400, 3430 | Amide | 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 1545 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
“In the amide II region the absorption band around changes in amide I and amide II regions as represented 1545cm-1 𝛼-helix can be assigned to structure, and vibration in Figure 2(b) in which these regions were zoomed in, 1535cm-1 𝛽whereas no”
Calabro 等 - 2013 - 50 Hz Electromagnetic Field Produced Changes in FT DOI: 10.1155/2013/414393 -
Carbohydrate confidence 1.0
“Therefore, selection based on other related (1737.8, 1267.2, and 969.2 proteins (1688.6 and cm-1), characters such as FHB severity or percent scabby seed 1544.9 cellulose vibrations (1516, 1463.9, 1374.2, cm-1), has been proposed [7,59].”
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 -
Amide confidence 1.0
“LLM confirmed rule peak-group candidate”
Mackanos 等 - 2009 - Use of an endoscope-compatible probe to detect col DOI: 10.1117/1.3174387(cid:4) -
Ring structure confidence 1.0
“The peak at 1545 cm(cid:1)1 C@C attributed to ring stretching alkene, peak at 1441 CAH assigned to the bend of CH 2/CH arene-ethylbenzene, the 3”
Green synthesis of Silver nanoparticles using Streptomyces hirsutus strain SNPGA-8 and their characterization, antimicrobial activity, and anticancer activity against human lung carcinoma cell line A549 DOI: 10.1016/j.sjbs.2021.08.084 -
Acetate confidence 1.0
“The bands at 1545 and 1431 are attributed to asymmetric Photoluminescence and symmetric C O stretching vibration modes.”
Photoluminescence and thermoluminescence studies of Tb3+ doped ZnO nanorods DOI: 10.1016/j.mseb.2013.01.006 -
Carbonyl (C=O) confidence 1.0
“region, and Amide II vibration can be located at around 1500-1600 the band detected cm-1 at 1545 could indicate the frequency of the C=O carbonyl groups stretching vibrations cm-1 along the peptide bond [72].”
Green Synthesis of Silver Nanoparticles for Preparation of Gelatin Films with Antimicrobial Activity DOI: 10.3390/polym14173453 -
Ester confidence 1.0
“To understand the dynamics of imbibition, the proteins, lipids, and carbohydrates of the cotyledons and hilum region in mature soybean seeds were mapped using synchrotron Fourier transformed infrared microspectroscopy, based on characterist”
Pietrzak 和 Miller - 2005 - Microchemical structure of soybean seeds revealed DOI: 10.1021/jf050608x -
confidence 1.0
“The peak at 1545 At first the noise (root mean square - rms) of the deconvolution has been assigned to N-H bending vibration and C-N stretching”
Tarantilis 等 - 2012 - Monitoring of royal jelly protein degradation duri DOI: 10.3896/IBRA.1.51.2.07
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