What absorbs at 909 cm⁻¹ in an FTIR spectrum?
A band near 909 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 5 cited sources
Quick answer
A band near 909 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 |
|---|---|---|---|
| Silicon (Si) | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
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 |
|---|---|---|---|
| chitosan | 909, 1650, 1655 | Hydroxyl (O-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 909 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
-
Alkyl C-H confidence 1.0
“Moreover, peaks at 909 and C-H out-of-plane C-H ascribed to bending modes and The conducted research is not related Ethical approval:”
Ahmad 等 - 2020 - Synthesis and characterization of a novel chitosan DOI: 10.1515/chem-2020-0137 -
Alkene (C=C) confidence 1.0
“As expected, crosslinking was induced in the polymer: radicals formed by radiations move rapidly along polyethylene chains in the amorphous phase and react easily with terminal double bonds cm-1 (absorption at 909 decreases), creating the s”
Barus 等 - 2009 - Preparation of polymeric hybrid nanocomposites bas DOI: 10.1016/j.polymer.2009.04.012 -
Siloxane (Si-O-Si) confidence 1.0
“H-OH bending of adsorbed water 1104 Si-O stretching 1104 Si-O stretching 1036 Si-O-Si stretching 1036 Si-O-Si stretching 909”
SO42-/Sn-MMT Solid Acid Catalyst for Xylose and Xylan Conversion into Furfural in the Biphasic System DOI: 10.3390/catal7040118 -
confidence 1.0
“cm-1, cm-1 cm-1 The telescopic vibration adsorption peaks at 909 837 and 779 correspond to Al-O-H, Si-O and Mg-O-H in the SB chemical structure, respectively, and they were clearly abated, as evident in the spectra cm-1 of TLSB.”
Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent DOI: 10.1038/s41598-020-73570-7 -
confidence 0.9
“Explicit assignment: IR band at 909 cm-1 characteristic of 31 helical conformation of stereocomplex PLA.”
Crystallization and Stereocomplexation of PLA-mb-PBS Multi-Block Copolymers DOI: 10.3390/polym10010008
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