What absorbs at 1685 cm⁻¹ in an FTIR spectrum?
A band near 1685 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) | 2 | 2 | 0.9 |
| Carboxyl (COOH) | 1 | 1 | 0.9 |
| Protein beta sheet | 1 | 1 | 0.9 |
| Alkene (C=C) | 1 | 1 | 0.9 |
| Hydroxyl (O-H) | 1 | 1 | 0.8 |
| Amide | 1 | 1 | 0.6 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Literature behind these assignments
-
confidence 0.9
“Text: 'absorption of C=O amida is at 1685'”
Suhendra 等 - 2018 - Optimization of Lipase-catalyzed Synthesis of Fatt DOI: 10.13005/ojc/340518 -
confidence 0.9
“Explicit assignment: 'band at 1685 cm-1 for the conjugated carbonyl compounds'”
Agatonovic-Kustrin 等 - 2021 - HPTLC and FTIR Fingerprinting of Olive Leaves Extr DOI: 10.3390/molecules26226892 -
confidence 0.9
“Large peak at 1685 caused by carbon-oxygen double bonds and deriving from PVP.”
Andersen 等 - 2016 - Nanomechanical IR spectroscopy for fast analysis o DOI: 10.1016/j.snb.2016.04.002 -
Carbonyl (C=O) confidence 0.9
“C=O stretching”
Araujo 等 - 2021 - Comparison of Different Methods for Spongin-like C DOI: 10.3390/membranes11070522 -
confidence 0.9
“Text: 'shoulder around 1685 characteristic features of antiparallel sheet'”
Kleiren 等 - 2010 - Development of a quantitative and conformation-sen DOI: 10.3233/SPE-2010-0405 -
Protein beta sheet confidence 0.9
“Explicit assignment: 'At 1685, 1637 and 1629 the β-sheets'”
Kristo 等 - 2021 - Optimization of layering technique and secondary s DOI: 10.1371/journal.pone.0260603 -
Carbonyl (C=O) confidence 0.9
“Explicit assignment in text”
Saucedo-Balderas 等 - 2015 - Synthesis, Molecular Structure of Diethyl Phenylen DOI: 10.5935/0103-5053.20140289 -
Carboxyl (COOH) confidence 0.9
“Explicit assignment: associated with vibrations of -COO-”
Selin 等 - 2018 - Ionically Paired Layer-by-Layer Hydrogels Water a DOI: 10.3390/gels4010007
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a confidence-rated evidence chain — in seconds.
Interpret my spectrum