What absorbs at 672 cm⁻¹ in an FTIR spectrum?
A band near 672 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 6 cited sources
Quick answer
A band near 672 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 |
|---|---|---|---|
| Carbon dioxide | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 0.7 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| calcite | 672, 2850, 2864 | Alkyl C-H | 1 |
| hydroxyapatite | 672, 1620, 1639 | 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 672 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
-
Phosphate (PO4) confidence 1.0
“The peak at 672 cm-1 belongs to symmetric P-O”
Novel synthesis of bioactive hydroxyapatite/f-multiwalled carbon nanotube composite coating on 316L SS implant for substantial corrosion resistance and antibacterial activity DOI: 10.1016/j.jallcom.2018.10.341 -
Borate confidence 1.0
“Especially, the Raman peak located at 672 is ascribed to the vibration of the B-O-P bond, which is the connector between the PO and BO tetrahedron.”
Zhang 等 - 2013 - Vibrational spectra and first principles calculati DOI: 10.7498/aps.62.037802 -
Metal oxygen confidence 1.0
“The cm-1 peak at 672 was ascribed to O-Sn-O stretching vibration of tin-oxide.”
A facile hydrothermal approach for catalytic and optical behavior of tin oxide- graphene (SnO2/G) nanocomposite DOI: 10.1371/journal.pone.0202694 -
Alkyl C-H confidence 1.0
“Additionally, the new peak at 672 represents the stretching vibration of H-C-H in SAF.”
Application of a Superplasticizer in Scheelite Selective Flotation from Calcite DOI: 10.3390/min12040483 -
Carbon dioxide confidence 1.0
“can observe the obvious strong absorption bands of CO 2 (2233-2420cm-1, 672cm-1),”
Zhao 等 - 2021 - Five Dinuclear Lanthanide Complexes Based on 2,4-d DOI: 10.3389/fchem.2021.726813 -
Siloxane (Si-O-Si) confidence 0.7
“FTIR transmittance bands at 672 cm-1 attributed to Si-O-Si stretching present in clay minerals”
Goonetilleke 等 - 2021 - Acid-assisted leaching of iron and manganese from DOI: 10.4038/jnsfsr.v49i2.10177
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 confidence-rated evidence chain — in seconds.