What absorbs at 3633 cm⁻¹ in an FTIR spectrum?
A band near 3633 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 4 cited sources
Quick answer
A band near 3633 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) | 4 | 4 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single authoritative 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 3633 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
“The double peaks at 3680 cm-1 and 3633 cm-1 were observed due to the stretching vibration of the hydroxyl group at the surface of HNTs.”
Synthesis and Optimization of Superhydrophilic-Superoleophobic Chitosan–Silica/HNT Nanocomposite Coating for Oil–Water Separation Using Response Surface Methodology DOI: 10.3390/nano12203673 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Growth, structure, Hirshfeld surface and spectroscopic properties of 2-amino-4-hydroxy-6-methylpyrimidinium-2,3-pyrazinedicorboxylate single crystal DOI: 10.1016/j.molstruc.2017.11.019 -
Hydroxyl (O-H) confidence 1.0
“Most of the SM samcm-1, which are due obvious peaks at 3633, 3525 and 3323 ples are in the form of amorphous carbon, while semi-coke to -OH stretching vibration in alcohols and stretching vibrashows a tendency to graphitize.”
Huang 等 - 2021 - Experimental research on semi-coke for blast furna DOI: 10.1007/s42243-020-00480-3 -
confidence 1.0
“In the control CTAC-MMT, the absorption peak observed at 3633 was attributed to the stretching vibration of Al-Al-OH groups in the octahedral layer.”
Mushtaq 等 - 2020 - Composite of PLA Nanofiber and Hexadecyl Trimethyl DOI: 10.3390/coatings10050484
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