What absorbs at 699 cm⁻¹ in an FTIR spectrum?
A band near 699 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 699 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 |
|---|---|---|---|
| Alkyl C-H | 8 | 8 | 1.0 |
| Aromatic ring | 6 | 6 | 1.0 |
| Ring structure | 4 | 4 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 2 | 2 | 1.0 |
| Anhydride | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Chlorine | 1 | 1 | 1.0 |
| Oxygen heterocycle | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Styrene | 1 | 1 | 0.9 |
| Metal oxygen | 1 | 1 | 0.8 |
| C c single bond | 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 |
|---|---|---|---|
| Polystyrene | 699, 1020, 1600 | Aromatic ring, Alkyl C-H | 1 |
| TiO2 | 699, 1700, 1093 | Alkyl C-H | 1 |
| SiO2 | 699, 1739, 695 | Alkyl C-H | 1 |
| MgO | 699, 874, 467 | Alkyl C-H | 1 |
| TiO | 699, 1730, 1699 | Alkyl C-H | 1 |
| asphalt binder | 699, 1700, 1242 | Alkyl C-H, Aromatic ring, Alkene (C=C) | 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 699 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
-
Silicon (Si) confidence 1.0
“699cm-1, centhydrocarbonchainsandthesplitismorepronouncedatlower the Due to the strong peak of Si-O-Al bending at 730cm-1 temperature with an orthorhombic subcell [28].”
Li 等 - 2008 - An FTIR investigation of hexadecyltrimethylammoniu DOI: 10.1016/j.saa.2008.05.015 -
Acetate confidence 1.0
“The bands at 1254 is assigned to asymmetric vibration of C-O-C while cm-1 are indicating the presence of C-O-C (epoxy ring) vibration and C-Cl of the absorption peaks at 874 and 699 cm-1 PVC, respectively [6].”
Nor 等 - 2013 - Gas Permeability of ENRPVC Membrane with the Addi DOI: 10.1063/1.4858770 -
Alkyl C-H confidence 1.0
“The peak at 699 cm-1 performed with high resolution (R = 5000, 10 % corresponds to the C-H out-of-plane deformation valley), in the peak matching mode, with PFK ions for specific to an aromatic ring [15].”
Tosa 等 - 2012 - Simultaneous Determination Of Some Artificial Swee DOI: 10.1063/1.3681976 -
Aromatic ring confidence 1.0
“cm-1 Additionally, the FTIR spectra are similar except for some bands, such as the one at 699 Additionally, the FTIR spectra are similar except for some bands, such as the one at 699 cm-1 which is characteristic of the out-of-plane skeleton”
Sulfonated Polystyrene Nanoparticles as Oleic Acid Diethanolamide Surfactant Nanocarriers for Enhanced Oil Recovery Processes DOI: 10.3390/polym11091513 -
S eq o confidence 1.0
“and 699 The stretching vibration of sulfoxide S=O functional group appeared at”
Research on the Interaction Capability and Microscopic Interfacial Mechanism between Asphalt-Binder and Steel Slag Aggregate-Filler DOI: 10.3390/coatings12121871 -
Alkyl C-H confidence 1.0
“Lastly, the band that appears at 699 is associated with the out-of-plane bending of the C-H group in monosubstituted aromatic rings [52].”
Lima 等 - 2022 - Asphalt Binder Skincare Aging Evaluation of an DOI: 10.3390/nano12101678 -
Aromatic ring confidence 1.0
“The peaks that appear between 910 cm-1 and 699 cm-1 can be analyzed carefully to show ortho-, metaand paradisubstituted rings presented in aromatic compounds and are associated with out-of-plane C-H bending vibrations in this structure.”
Physicochemical and Rheological Properties of a Transparent Asphalt Binder Modified with Nano-TiO2 DOI: 10.3390/nano10112152 -
Alkene (C=C) confidence 1.0
“It can also be seen that the increased from 0.25 L/min to 1 L/min, newly-formed characteristic absorption bands appeared at characteristic band of C=C at 967 and 699 cm-1 became weak, which indicates that the increasing cm-1, nearly 3446, 1”
Investigation of Molecular Structure and Thermal Properties of Thermo-Oxidative Aged SBS in Blends and Their Relations DOI: 10.3390/ma10070768
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