What absorbs at 3656 cm⁻¹ in an FTIR spectrum?
A band near 3656 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 3 cited sources
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Literature behind these assignments
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Ammonium confidence 1.0
“Additionally, the band at 3656 that we recently associated to ]+ sites28 is also eroded, indicating that ammonia could be adsorbed even on these particular sites.”
Giordanino 等 - 2014 - Interaction of NH3 with Cu-SSZ-13 Catalyst A Comp DOI: 10.1021/jz500241m -
Water (H2O) confidence 1.0
“cm(cid:1)1 For all these reasons, we propose here a model for an resulted in a negative band at 3656 assigned to the ordered water adsorption in the pores of AFI type vibrations of the terminal P-OH and/or terminal Memolecular sieves, gener”
Muller 等 - 2004 - Interactions of water and methanol with MeAPO-5. F DOI: 10.1016/j.micromeso.2003.12.025 -
Hydroxyl (O-H) confidence 1.0
“The peak cm-1 at 3656 is attributed to an OH group on an extra-framework Al species.”
Relationship between Acidity and Activity on Propane Conversion over Metal-Modified HZSM-5 Catalysts DOI: 10.3390/catal11101138
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