What absorbs at 3664 cm⁻¹ in an FTIR spectrum?
A band near 3664 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 320,000+ reference spectra and knowledge graph.
Backed by 3 cited sources
Quick answer
A band near 3664 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 |
|---|---|---|---|
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
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 3664 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
-
Hydroxyl (O-H) confidence 1.0
“Furthermore, an additional band appeared at 3664 whose attribution was hard from the literature data since it could correspond either to bridging OH groups [62,63] or to hydrogen bonded OH groups [62,63b] or to Ti VI-OH located on the 2”
Unravelling water effects on solid acid catalysts: Case study of TiO 2 /SiO 2 as a catalyst for the dehydration of isobutanol DOI: 10.1016/j.jcat.2016.12.007 -
Hydroxyl (O-H) confidence 1.0
“A A h o spectrum hydrated with H 2O (red line) has peaks at 3664 (+), 3657 (-), 3622 (-), 3587 (-) and r cm-1.”
Iwata 等 - 2009 - Identification of FTIR Bands Due to Internal Water DOI: 10.1021/bi801990s. -
Hydroxyl (O-H) confidence 0.9
“The text states: 'two shoulders at ~3664 and ~3615 that were assigned to arrangements having ... OH stretching'.”
Tobelite and NH4+-rich muscovite single crystals from Ordovician Armorican sandstones (Brittany, France): Structure and crystal chemistry DOI: 10.2138/am.2012.4023
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