What absorbs at 3550 cm⁻¹ in an FTIR spectrum?
A band near 3550 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 3550 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) | 29 | 25 | 1.0 |
| Water (H2O) | 4 | 4 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Siloxane (Si-O-Si) | 2 | 2 | 1.0 |
| Silanol (Si-OH) | 2 | 2 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| C#c | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Metal oxygen | 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 |
|---|---|---|---|
| PVA | 3550, 1660, 2930 | Hydroxyl (O-H) | 1 |
| quartz | 3550, 800, 3053 | Hydroxyl (O-H), Silicon (Si), Siloxane (Si-O-Si) | 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 3550 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 coefficient for cm-1 the fundamental OH-stretching vibration at 3550 is 63.9 ± 5.4 L/(mol·cm).”
Behrens 等 - 2009 - Solubility of H2O and CO2 in ultrapotassic melts a DOI: 10.2138/am.2009.2796 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Edgrewite Ca9(SiO4)4F2-hydroxyledgrewite Ca9(SiO4)4(OH)2, a new series of calcium humite-group minerals from altered xenoliths in the ignimbrite of Upper Chegem caldera, Northern Caucasus, Kabardino-Balkaria, Russia DOI: 10.2138/am.2012.4161 -
Water (H2O) confidence 1.0
“water, indeed, should show a band at 3550 The band at the spectra show shoulders that decrease in intensity going from cm-1 3473 was attributed to hydrogen bonded water molecules Synth1 to MF to Synth2 samples.”
Investigation of the hydrozincite structure by infrared and solid-state NMR spectroscopy DOI: 10.2138/am.2013.4158 -
Hydroxyl (O-H) confidence 1.0
“The radius (R) of the hemispherical droplet cm(cid:3)1 found that the OH stretching band at 3550 was easily satucanbemeasuredwiththemicroscope.Intheapertureareacovered rated because of the relatively high water concentrations in samby the d”
Xu 等 - 2022 - Mid-infrared spectroscopy of hemispherical water d DOI: 10.1016/j.saa.2021.120256 -
Hydroxyl (O-H) confidence 1.0
“745 797 and 3550cm-1 3750cm-1 914cm-1 four decreasing absorption peaks between and are attributed to the bending vibration of the hydroxyl”
Cao 和 Gu - 2023 - Mineralogical and spectral characteristics of Chan DOI: 10.3389/feart.2023.1183522 -
Silicon (Si) confidence 1.0
“The broadband around 3550 is related to the absorption of Si-OH group, Si-O-Si asymmetrical transversal stretching and surface hydroxyl groups, respectively (Ceballos-Mendivil et al.”
Elwan 等 - 2018 - DOI: 10.5028/jatm.v10.935 -
Hydroxyl (O-H) confidence 1.0
“cm-1 broad absorption peak between 3550 and 3350 observed in the spectrums of all t catalysts is attributed to OH-stretching vibrations of hydroxyl groups and water molecules cm-1 [48].”
Efficient transformation in characteristics of cations supported-reduced graphene oxide nanocomposites for the destruction of trichloroethane DOI: 10.1016/j.apcata.2017.07.007. -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Solid-state characterization of triamcinolone acetonide nanosuspensiones by X-ray spectroscopy, ATR Fourier transforms infrared spectroscopy and differential scanning calorimetry analysis DOI: 10.1016/j.ijpharm.2017.03.082
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