What absorbs at 1653 cm⁻¹ in an FTIR spectrum?
A band near 1653 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 1653 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 | 41 | 37 | 1.0 |
| Carbonyl (C=O) | 18 | 16 | 1.0 |
| Protein alpha helix | 11 | 7 | 1.0 |
| Methacrylate | 10 | 9 | 1.0 |
| Carboxyl (COOH) | 10 | 9 | 1.0 |
| Acetate | 10 | 9 | 1.0 |
| N h | 8 | 8 | 1.0 |
| C-O single bond | 7 | 7 | 1.0 |
| Alkene (C=C) | 7 | 7 | 1.0 |
| Ketone | 7 | 6 | 1.0 |
| Ester | 7 | 6 | 1.0 |
| Hydroxyl (O-H) | 6 | 6 | 1.0 |
| Water (H2O) | 6 | 6 | 1.0 |
| Methoxy (OCH3) | 5 | 5 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| Protein | 3 | 3 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| S s | 1 | 1 | 1.0 |
| Fatty acid | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Protein beta turn | 1 | 1 | 1.0 |
| Anhydride | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Protein random coil | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 0.9 |
| Nucleic acid | 1 | 1 | 0.8 |
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 | 1653, 1100, 1080 | Methacrylate | 1 |
| rGO | 1653, 2358, 2930 | Methacrylate, Amide | 1 |
| hydrogels | 1653, 3281, 1700 | Amide, Methacrylate, Carbonyl (C=O) | 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 1653 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
-
Water (H2O) confidence 1.0
“Moreover, the interleaved may be observed at 1653 cm-1 cm-1 water molecules, bands exist at 3460 and 1631 process can be confirmed by vanishing the nitrate peak”
Bohari 等 - 2022 - Synthesis and Characterization of 2,4-Dichlorophen DOI: 10.22146/ijc.73546 -
Aromatic ring confidence 1.0
“The significant spectral features are the cm(cid:0) 1, it is evident that faster heating rates offset the end of the second carbonyl peak at 1653 the phenyl ring stretching bands at 1593 cm(cid:0) cm-1 cm-1 1, decomposition step at higher t”
Detecting, characterising and assessing PEEK’s and CF-PEEK’s thermal degradation in rapid high-temperature processing DOI: 10.1016/j.polymdegradstab.2022.110096 -
Amide confidence 1.0
“Peaks at 3294 (Amide A), 3060 (Amide B), 2871 (CH 3 1544cm-1 symmetric stretching), 1653 (Amide I) and The intensity or area of a particular FTIR absorption”
Igci 等 - 2017 - Application of Fourier transform infrared spectros DOI: 10.17219/acem/65784 -
Amide confidence 1.0
“After incubaondary structure than other amide bands, thus the amide I band cm-1 was shifted from tion for 35 h, the predominate peak at 1653 selected as a probe to differentiate the changes in secondary was”
Additives affecting thermal stability of salmon calcitonin in aqueous solution and structural similarity in lyophilized solid form DOI: 10.1016/j.procbio.2011.08.017 -
Hydroxyl (O-H) confidence 1.0
“FTIR spectra of GW3 loaded with PG, PG, acrylamide, and whey protein isolate cm-1, FTIR spectrum of rGO showed peaks at 1727, 1550, and stretching at 1653 and OH bending of carboxylic acid cm-1, cm-1 1049 from rGO was visible at 1445 and 14”
Owonubi 等 - 2018 - Characterization and in vitro release kinetics of DOI: 10.1007/s40090-018-0139-2 -
Carbonyl (C=O) confidence 1.0
“Vibrational modes 1653 Carbonyl Stretching 1488 Aromatic C-C vibration 1305”
Vibrational spectroscopic study of pure and silica-doped sulfonated poly(ether ether ketone) membranes DOI: 10.1016/j.saa.2014.12.004 -
Alkene (C=C) confidence 1.0
“LLM confirmed rule peak-group candidate”
Rout 等 - 2017 - A green approach to produce silver nano particles DOI: 10.1016/j.surfin.2017.03.004 -
Aromatic ring confidence 1.0
“And in rice straw, the per- (assigned to aromatic ring modes or peaks at 1653 cm21”
Effect of microbiological inoculants DN‐1 on lignocellulose degradation during co‐composting of cattle manure with rice straw monitored by FTIR and SEM DOI: 10.1002/ep.12222
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