What absorbs at 1637 cm⁻¹ in an FTIR spectrum?
A band near 1637 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 1637 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 | 40 | 36 | 1.0 |
| Carbonyl (C=O) | 30 | 28 | 1.0 |
| Methacrylate | 26 | 26 | 1.0 |
| Acetate | 23 | 23 | 1.0 |
| Ester | 22 | 22 | 1.0 |
| Carboxyl (COOH) | 21 | 21 | 1.0 |
| Alkene (C=C) | 21 | 18 | 1.0 |
| Hydroxyl (O-H) | 20 | 20 | 1.0 |
| Ketone | 20 | 20 | 1.0 |
| Water (H2O) | 18 | 17 | 1.0 |
| N h | 12 | 12 | 1.0 |
| Secondary amine | 6 | 6 | 1.0 |
| Silicon-oxygen (Si-O) | 5 | 5 | 1.0 |
| Protein | 5 | 5 | 1.0 |
| Silicon (Si) | 4 | 4 | 1.0 |
| C c single bond | 4 | 4 | 1.0 |
| C n single bond | 4 | 4 | 1.0 |
| Methoxy (OCH3) | 4 | 4 | 1.0 |
| C-O single bond | 4 | 4 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Protein beta sheet | 4 | 4 | 0.9 |
| Siloxane (Si-O-Si) | 3 | 3 | 1.0 |
| Carbohydrate | 3 | 3 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| Protein alpha helix | 3 | 2 | 1.0 |
| Bronsted acid site | 2 | 2 | 1.0 |
| Bromine | 2 | 2 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Urethane | 2 | 2 | 1.0 |
| Carbon dioxide | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 1.0 |
| Anhydride | 1 | 1 | 1.0 |
| Oxalate | 1 | 1 | 1.0 |
| Aldehyde (CHO) | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 0.9 |
| Chitosan | 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 |
|---|---|---|---|
| starch | 1637, 1650, 1540 | Methacrylate, Acetate, Amide | 1 |
| montmorillonite | 1637, 523, 1743 | Methacrylate, Acetate, Amide | 1 |
| nanocomposites | 1637, 1717, 1630 | 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 1637 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
-
Acetate confidence 1.0
“Therefore, the very strong band in IR at 1637 and quency of C O stretching dependant on various factors.”
Arjunan 等 - 2007 - Fourier transform infrared and Raman spectral assi DOI: 10.1016/j.saa.2006.09.044 -
confidence 1.0
“cm(cid:0) 1 granules, including the amylose content, distribution of branch chains of Prominent peak in the region of 1637 revealed the presence of (-N-H) amylopectin, interactions of amylose-amylose and amylose-lipid could amine group (Ng”
Encapsulating probiotics in novel resistant starch wall material for production of rice flour extrudates DOI: 10.1016/j.lwt.2020.110839 -
Amide confidence 1.0
“cm-1 The FTIR band at 1637 corresponds to Amide I of collagen [25] that exists in the raw HAP of bovine bone powder and is completely removed in calcined HAP samples.”
XRD and FTIR study of A&B type carbonated hydroxyapatite extracted from bovine bone DOI: 10.1063/1.5089399 -
Hydroxyl (O-H) confidence 1.0
“The two bands observed cm-1 at 1637 and 1436 are associated with the deformation of the -OH groups of water”
Caliman 等 - 2023 - Gellan Gum-Montmorillonite Nanocomposites for Elec DOI: 10.3390/coatings13020350 -
Alkene (C=C) confidence 1.0
“lymerized, was determined by the ratio of the absorbance peak corresponding to the aliphatic carMethodology cm-1 bon-carbon double bond (1637 peak height)”
Collares 等 - 2014 - Discrepancies in degree of conversion measurements DOI: 10.1590/S1806-83242013000600002 -
Hydroxyl (O-H) confidence 1.0
“These cm-1 cm-1 two peaks at 3270-3273 (O-H stretching) and 1637 (approx.) (scissoring of two H atoms bonded with samples43-45.”
Analysis of the ex-vivo transformation of semen, saliva and urine as they dry out using ATR-FTIR spectroscopy and chemometric approach DOI: 10.1038/s41598-021-91009-5 -
Lignin confidence 1.0
“There were also no changes or shifts near 1514 and 1637 cm-1 wavenumbers which associated with lignin compounds [6].”
Firsoni 等 - 2019 - Fiber Content and Relative Feed Value Estimation o DOI: 10.1088/1757-899X/546/4/042008 -
Alkene (C=C) confidence 1.0
“LLM confirmed rule peak-group candidate”
Galvo 等 - 2010 - Influence of light guide tip used in the photo-act DOI: 10.1134/S1054660X10190059
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