What absorbs at 708 cm⁻¹ in an FTIR spectrum?
A band near 708 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 7 cited sources
Quick answer
A band near 708 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 |
|---|---|---|---|
| C-O single bond | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 2 | 2 | 1.0 |
| Metal oxygen | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Ring 6m | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 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 |
|---|---|---|---|
| polyethylene | 708, 1737, 1720 | C-O single bond, Aromatic ring | 1 |
| HDPE | 708, 1369, 1216 | Aromatic ring | 1 |
| calcite | 708, 2850, 2864 | C-O single bond | 1 |
| quartz | 708, 800, 3053 | Silicon-oxygen (Si-O), Metal oxygen | 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 708 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 carbon confidence 1.0
“According to Sawpan et al., peaks cm-1 cm-1 for Si-C symmetric stretching, at 708 for Si-O-Si symmetric at 780”
Hajiha 等 - 2014 - Modification and Characterization of Hemp and Sisa DOI: 10.1080/15440478.2013.861779 -
confidence 1.0
“The peak value at 707.74 was due to the presence of Fe 2O in RIPT”
Sakthisharmila 等 - 2017 - A characteristic study on generation and interacti DOI: 10.1016/j.molliq.2017.01.106 -
confidence 1.0
“The major peak at 708 shows the cm-1 presence of Mg-O vibrations.”
Abuhimd 等 - 2020 - Influence of Magnesium Aluminate Nanoparticles on DOI: 10.3390/coatings10100968 -
confidence 1.0
“Si-O-Al stretching vibrations at 707.58 and”
A Novel Open-System Method for Synthesizing Muscovite from a Biotite-Rich Coal Tailing DOI: 10.3390/min11030269 -
C-O single bond confidence 1.0
“At 154 mainly caused by glycosidic bond, six-membered ring ◦C, decomposition and decarbonylation, the maximum heat release peak also occurs at 708 which 3.1.3.”
Synthesis of Phosphated K-Carrageenan and Its Application for Flame-Retardant Waterborne Epoxy DOI: 10.3390/polym10111268 -
Aromatic ring confidence 1.0
“3054 CH aromatic rings (Symmetric stretching) CaCO 708 CO (Stretching) 3 3”
da Silva 和 Wiebeck - 2022 - ATR-FTIR Spectroscopy Combined with Chemometric Me DOI: 10.21203/rs.3.rs-905784/v1 -
Metal oxygen confidence 0.9
“Explicit assignment in text”
Thakur 等 - 2022 - SUPERCRITICAL ANTISOLVENT METHOD FOR RECRYSTALLIZA DOI: 10.24425/cpe.2022.140819
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 literature-backed analysis — in seconds.