What absorbs at 664 cm⁻¹ in an FTIR spectrum?
A band near 664 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 664 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 |
|---|---|---|---|
| Siloxane (Si-O-Si) | 3 | 3 | 1.0 |
| Silicon-oxygen (Si-O) | 3 | 3 | 1.0 |
| C-S single bond | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Metal oxygen | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Carbohydrate | 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 |
|---|---|---|---|
| chitosan | 664, 1650, 1655 | Methoxy (OCH3) | 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 664 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
-
C-S single bond confidence 1.0
“cm-1 cm-1 Band at 1226 is due to CH wagging, C-S stretching vibration at 664 2 cm-1 confirmed the presence of S-S group.”
Crystal Growth, Spectral, Optical, Laser damage, Photoconductivity and Dielectric Properties of Semiorganic L-cystine hydrochloride Single Crystal DOI: 10.1016/j.saa.2015.06.113 -
Acetate confidence 1.0
“The totally symmetric C assigned these bands as the A Mn H and Mn C O bending, and 1 664cm-1 planarC Ostretchingmodeisexpectedtobeoflowestintensity assignMn C Ooutofplanebendingvibrations)and 455cm-1.”
Mahmood 等 - 2006 - Comparative vapour phase FTIR spectra and vibratio DOI: 10.1016/j.saa.2005.11.024 -
confidence 1.0
“The bands cm-1 cm-1 bands at 664 and 1250 in sample D are due to titanium oxide;”
Effect of Microstructural and Tribological Behaviors of Sputtered Titanium Carbide Thin Film on Copper Substrate DOI: 10.3390/ma16010174 -
Carboxyl (COOH) confidence 1.0
“COOH bending peaks (664cm(cid:2)1) 12h in air and then cured in a convection oven for 5h.”
Sgriccia 等 - 2008 - Characterization of natural fiber surfaces and nat DOI: 10.1016/j.compositesa.2008.07.007 -
Carbohydrate confidence 1.0
“Heavy and strong woods are 664 peak showed some modifications in cellulose cm-1 more resistant to weathering factors than softwoods [43].”
Tomak - 2014 - Changes in chemical composition of decayed Scots p DOI: 10.1515/secm-2013-0180 -
Metal oxygen confidence 1.0
“4 1,8 (4,000-400cm-1), gated region all obtained spectra have 555cm-1 664Cm-1 ʋ ʋ two absorption bands 1, at and 2 1,6 band metal-oxygen assigned from stretching vibration of the [3-21].”
Abdelhak 等 - 2019 - Characterization of Mn-Doped Co3O4 Thin Films Prep DOI: 10.1515/htmp-2017-0185 -
Metal oxygen confidence 1.0
“One band is due to Ni-O bond stretching around 567 which represents cm-1, tetrahedral sites, whereas the second is attributed to Fe-O bond stretching at 664”
Synthesis, Characterization, and Solar Photo-Activation of Chitosan-Modified Nickel Magnetite Bio-Composite for Degradation of Recalcitrant Organic Pollutants in Water DOI: 10.3390/catal12090983 -
Silicon (Si) confidence 1.0
“cm-1 band at around 460 The band at 664 can be attributed to the Si-O-Si symmetric -1 to the out-of-plane bending vibration of SiO [15, 16].”
Colovic 等 - 2013 - Creating of Highly Active Calcium-Silicate Phases DOI: 10.2298/SOS1303341C
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