What absorbs at 650 cm⁻¹ in an FTIR spectrum?
A band near 650 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 |
|---|---|---|---|
| Metal oxygen | 7 | 7 | 0.9 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 0.9 |
| Carboxyl (COOH) | 1 | 1 | 0.9 |
| Silicon (Si) | 1 | 1 | 0.8 |
| Lipid | 1 | 1 | 0.8 |
| Phospholipid | 1 | 1 | 0.8 |
| Silicon silicon | 1 | 0 | 0.9 |
| Chlorine | 1 | 0 | 0.7 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Literature behind these assignments
-
Alkyl C-H confidence 1.0
“stretching), while the peaks within the range of 1000The pre-processing also significantly showed that the cm-1 could be seen through the absorption of alkenes 650 quantified FTIR spectra were distributed normally with functional group C-H”
Aziz 等 - 2020 - FTIR and HPLC-Based Metabolomics of Yacon Leaves E DOI: 10.22146/ijc.43453 -
confidence 1.0
“Due to vibrations of free water molecules”
Omar 等 - 2023 - Investigation of morphological, structural and ele DOI: 10.1007/s11082-023-04663-6 -
confidence 1.0
“Attributed to Pd-O stretching vibrations.”
Refat 等 - 2021 - SYNTHESIS, CHARACTERIZATION, AND PHOTOCATALYTIC EF DOI: 10.4314/bcse.v35i1.9 -
confidence 0.95
“Text: 'growing double peaks centered at 650 cm-1 and 555 in the ZIF-67 spectra are due to Co3O4'.”
Wu 等 - 2019 - Unveiling the thermolysis natures of ZIF-8 and ZIF DOI: 10.1039/C9CP02582K. -
confidence 0.9
“Explicitly stated as KBr band cutoff.”
Choe 等 - 2019 - Characterization of cotton fabric scouring by Four DOI: 10.1177/0040517518790976 -
Carboxyl (COOH) confidence 0.9
“Stretching vibration of Co-O bond, characteristic of Co3O4 spinel.”
Kouotou 和 Tian - 2017 - In situ Fourier Transform Infrared Spectroscopy Di DOI: 10.1063/1674-0068/30/cjcp1705097 -
Metal oxygen confidence 0.9
“Explicit assignment: 'broad cm-1 Sn-O peak was centered on 650'”
Saleh 等 - 2020 - Structural and frequency-dependent dielectric prop DOI: 10.1007/s11051-020-4763-3 -
Metal oxygen confidence 0.9
“Peak at 650 cm-1 assigned to Cd-O stretching.”
Selvi 等 - 2017 - Synthesis, Structural, Optical, Electrical and The DOI: 10.1007/s10904-017-0662-1
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