What absorbs at 1690 cm⁻¹ in an FTIR spectrum?
A band near 1690 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
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Carbonyl (C=O) | 10 | 9 | 1.0 |
| Amide | 9 | 9 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 0.9 |
| Protein beta sheet | 2 | 2 | 0.9 |
| Protein beta turn | 2 | 2 | 0.9 |
| Ester | 1 | 1 | 0.9 |
| Alkene (C=C) | 1 | 1 | 0.9 |
| Ketone | 1 | 1 | 0.9 |
| Hydroxyl (O-H) | 1 | 1 | 0.9 |
| Imide | 1 | 1 | 0.9 |
| Carbonate | 1 | 1 | 0.8 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Literature behind these assignments
-
Carbonyl (C=O) confidence 1.0
“Explicit assignment in text.”
Kharazmi 等 - 2015 - Structural, optical, opto-thermal and thermal prop DOI: 10.3762/bjnano.6.55 -
confidence 1.0
“explicit assignment”
Roy 等 - 2010 - Differentiation and mineralization of murine mesen DOI: 10.1016/j.diff.2010.03.003. -
Amide confidence 1.0
“amide I band occurs in 1690-1600 cm-1, mostly C=O stretching”
Swiadro-Pieton 等 - 2022 - Fast and Noninvasive Hair Test for Preliminary Dia DOI: 10.3390/molecules27165318 -
Carbonyl (C=O) confidence 0.95
“Explicit assignment: 'C=O vibration (1,690 cm-1)'”
Li 等 - 2018 - Decoloration of waste PET alcoholysis liquid by an DOI: 10.2166/wst.2018.191 -
Carbonyl (C=O) confidence 0.9
“Range 1690-1810 cm-1 assigned to carbonyl groups.”
Campanale 等 - 2023 - Fourier Transform Infrared Spectroscopy to Assess DOI: 10.3390/polym15040911 -
Amide confidence 0.9
“Explicit assignment: amide I band at 1690 cm-1.”
Vidal 和 Mello - 2011 - Collagen type I amide I band infrared spectroscopy DOI: 10.1016/j.micron.2010.09.010 -
Carbonyl (C=O) confidence 0.9
“Explicit assignment for β-CarhNPs.”
Bosio 等 - 2014 - Synthesis and characterization of CaCO3-biopolymer DOI: 10.1016/j.colsurfb.2014.09.011 -
Amide confidence 0.9
“Amide I C=O stretching between 1600-1690 cm-1.”
Elgamouz 等 - 2020 - Dataset in the characterization of black spot Ehre DOI: 10.1016/j.dib.2019.104927
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