What absorbs at 1805 cm⁻¹ in an FTIR spectrum?
A band near 1805 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 1805 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 |
|---|---|---|---|
| N-O bond | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 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 |
|---|---|---|---|
| polyethylene | 1805, 1737, 1720 | Hydroxyl (O-H) | 1 |
| HDPE | 1805, 1369, 1216 | 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 1805 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
-
confidence 1.0
“In particular, addition of 14 cm-1 O to NO slightly increases the amount of Pd(II)-NO complex with ν at ~1865 whereas 15 2 NO 16 cm-1, the low frequency ν band at 1805 assigned to Pd(I)-NO, decreases in intensity.”
Molecular Level Understanding of How Oxygen and Carbon Monoxide Improve NOx Storage in Palladium/SSZ-13 Passive NOx Adsorbers: The Role of NO+ and Pd(II)(CO)(NO) Species DOI: 10.1021/acs.jpcc.8b01007 -
Carbonyl (C=O) confidence 1.0
“a consistent amount of ethylene carbonate (EC) is obtained, as cm-1 testified by the presence of a doublet of bands at 1805 and cm-1 1774 that can be easily ascribed to the combined carbonyl stretching modes of the ethylene carbonate.”
Dani 等 - 2015 - Design of high surface area poly(ionic liquid)s to DOI: 10.1039/c5ta00272a -
N-O bond confidence 1.0
“In this case a cm(cid:2)1 new band appears at 1805 corresponds to gas phase NO.”
Diaz Consul 等 - 2008 - NO reduction with CO on alumina-modified silica-su DOI: 10.1016/j.apcata.2008.01.022 -
Hydroxyl (O-H) confidence 1.0
“1409-1460 C = O (Asymetric stretching) O-H (Bending) 1805 Vibrations of carbonate ions 2512 C = O from calcite”
da Silva 和 Wiebeck - 2022 - ATR-FTIR Spectroscopy Combined with Chemometric Me DOI: 10.21203/rs.3.rs-905784/v1 -
confidence 0.9
“band around ~1805 cm-1 for Pd/SSZ-13 belonged to Pd(I)-NO”
The superior hydrothermal stability of Pd/SSZ-39 in low temperature passive NOx adsorption (PNA) and methane combustion DOI: 10.1016/j.jcat.2010.07.031.
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