What absorbs at 698 cm⁻¹ in an FTIR spectrum?
A band near 698 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 698 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 |
|---|---|---|---|
| Aromatic ring | 5 | 4 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Ring structure | 3 | 2 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Styrene | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Aldehyde (CHO) | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 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 |
|---|---|---|---|
| silver nanoparticles | 698, 1636, 1631 | Hydroxyl (O-H), Alkyl C-H | 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 698 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
-
Hydroxyl (O-H) confidence 1.0
“The are mainly enclosed in the cavities of the axially oriented 698cm-1 peak, which increases with a reduction in dichroism of the cm-1 O-H confirms CC phase), while the out-of-plane 717 peak is”
Golla 等 - 2021 - Isolated and aggregated carvacrol guest molecules DOI: 10.1038/s41428-021-00511-0 -
Aromatic ring confidence 1.0
“2 cm-1 cm-1 at 3026 and 3060 corresponded to aromatic C-H cm-1 cm-1 At the same time, the hydroxyl ion was produced in the stretching and the two peaks at 698 and 756 showed decomposition reaction and hydrogen was abstracted the pattern of”
Jamarosliza 等 - 2014 - Effect of reaction conditions on the thermal stabi DOI: 10.1515/polyeng-2013-0117 -
Aromatic ring confidence 1.0
“In FTIR spectra, the peaks appeared at 698 and 740 which indicates cm-1, the aromatic C-C angular deformation.”
Uner 等 - 2016 - Wood Waste Turned Into Value Added Products Therm DOI: 10.5552/drind.2016.1534 -
Aldehyde (CHO) confidence 1.0
“Finally, the band at 698 represents cho- /term”
Comparison of the Effects of Statins on A549 Nonsmall‐Cell Lung Cancer Cell Line Lipids Using Fourier Transform Infrared Spectroscopy: Rosuvastatin Stands Out DOI: 10.1002/lipd.12296 -
Amide confidence 1.0
“The 697.86 and C-N (amines), absorption peaks were assigned for stretch Figure 3a presents the UV spectra of”
Al-Zahrani 等 - 2021 - Green-synthesized silver nanoparticles with aqueou DOI: 10.1515/gps-2021-0067 -
Aromatic ring confidence 1.0
“Out-of-plane bending vibration 757 cm-1 C-H Aromatic ring bending 698 cm-1 Fe-O”
Influence of Waste Toner on Asphalt Binder: Chemical and Rheological Characterization DOI: 10.3390/molecules28062794 -
confidence 1.0
“Si or Al, symmetric stretching vibration of CO at about 2 cm-1, 873 symmetrically stretching vibration of Si-O at 698 cm-1,bendingvibrationofSi-O-Alat578cm-1 andin-plane cm-1 bending vibration of Si-O-Si and O-Si-O at 453 respectively as in”
Meng 等 - 2021 - Effects of load types and critical molar ratios on DOI: 10.1515/rams-2021-0019 -
Ring structure confidence 1.0
“on cm-1 cm-1, PORTUGAL band at 698 computations also provided a value of 1032 for a probably due to ring puckering, being the 2008 combination of the only exception.”
Low-Temperature FTIR Spectroscopic and Theoretical Study on an Energetic Nitroimine: Dinitroammeline (DNAM) DOI: 10.1021/jp711153g
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