What absorbs at 670 cm⁻¹ in an FTIR spectrum?
A band near 670 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 670 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 | 9 | 9 | 1.0 |
| Metal oxygen | 9 | 6 | 1.0 |
| Aromatic ring | 4 | 4 | 1.0 |
| Hydroxyl (O-H) | 4 | 3 | 1.0 |
| Methoxy (OCH3) | 3 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| C-O single bond | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Sulfate (SO4) | 3 | 3 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Metal sulfur | 2 | 2 | 1.0 |
| Thiol | 2 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 2 | 1 | 1.0 |
| Silicon hydride | 2 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| C-S single bond | 1 | 0 | 1.0 |
| Water (H2O) | 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 |
|---|---|---|---|
| ZnO | 670, 1400, 3430 | Metal oxygen, Hydroxyl (O-H), Alkyl C-H | 1 |
| TiO2 | 670, 1700, 1093 | Metal oxygen, 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 670 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
-
Metal oxygen confidence 1.0
“cm21, Waser,8 which may corresample the peaks at 670 and 725 an earlier report by in which no solubility was found spond to the Nb-O stretching modes, disappeared or signifiin donor-doped SrTiO by the hot water vapor method, as 3 decreased.”
Dai 等 - 2003 - Ambient-temperature incorporated hydrogen in Nb S DOI: 10.1063/1.1574842 -
C c single bond confidence 1.0
“was found that the pure and manganese-doped ZnO present (cid:19) (cid:18)c -c film bulk σ = -233×109 Pa, (4) characteristic bulk vibration modes of ZnO, which are located c 670cm-1, bulk at about 332, 410, 437, 581 and as indicated E”
Kharroubi 等 - 2012 - Mn doping effect on the structural properties of Z DOI: 10.1088/0031-8949/86/01/015805 -
Aromatic ring confidence 1.0
“The absorption peaks including aromatic C-H deformation at 670 cm-1, C-O stretching at 1052 cm-1, phenolic C-OH stretching at 1200 cm-1, C-OH at 1361 cm-1, hydroxyl groups of molecular water and C=C at 1625 cm-1,”
Influence of Sputtering Temperature of TiO2 Deposited onto Reduced Graphene Oxide Nanosheet as Efficient Photoanodes in Dye-Sensitized Solar Cells DOI: 10.3390/molecules25204852 -
Alkyl C-H confidence 1.0
“to a peak displacement at 3041 However, in the reaction with formic acid, the cm-1 absorption peak at 3009 of the C=C bond is verified, indicating that the difference in events is related to the unsaturation conversion into an oxirane ring,”
Montenegro 等 - 2023 - Enzymatic and Synthetic Routes of Castor Oil Epoxi DOI: 10.3390/polym15112477 -
Thiol confidence 1.0
“In FT-IR experiments, a prominent peak at 670 corresponding to for -SH Cd2+ stretching vibrations, indicates strong ground-state interactions between the of GSH and ions.”
Probing How Various Metal Ions Interact with the Surface of QDs: Implication of the Interaction Event on the Photophysics of QDs DOI: 10.1021/acs.langmuir.1c00548 -
Metal sulfur confidence 1.0
“of CdS thin films prepared by spin coating technique cm-1 Another peak detected around 670 is due to the Cd-S at 2000 rpm and annealed at 300 °C for 5 min from CdS vibrational mode which agrees well with reported value solution with and wit”
Effect of Triton X-100 surfactant on thiol-amine cosolvents assisted facile synthesized CdS thin films on glass substrate by spin coating method DOI: 10.1007/s42452-020-2423-y -
Hydroxyl (O-H) confidence 1.0
“1378.13 1384.4 1384.47 1385 O-H asymmetric stretching 670.00 664.89 662.89 660”
Investigation on structural, optical and electrical nature of pure and Cr-incorporated cobalt oxide nanoparticles prepared via co-precipitation method for photocatalytic activity of methylene blue dye DOI: 10.1007/s10854-020-04708-6 -
Acetate confidence 1.0
“C-O dio etera koji je supstituiran benzilom cm-1gives weight loss curve can be used to tell the point at which The peak at 670 information on C-OH weight loss is most apparent (Figure 8).”
Uner 等 - 2016 - Wood Waste Turned Into Value Added Products Therm DOI: 10.5552/drind.2016.1534
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