What absorbs at 398 cm⁻¹ in an FTIR spectrum?
A band near 398 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
Quick answer
A band near 398 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 |
|---|---|---|---|
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Lignin | 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 |
|---|---|---|---|
| lignin | 398, 1035, 1510 | Methacrylate, Acetate, C-O single bond | 1 |
| polyaniline | 398, 1565, 1570 | Methacrylate, Acetate | 1 |
| nanocomposites | 398, 1717, 1630 | C-O single bond, Methacrylate, Acetate | 1 |
| titanium dioxide | 398, 1716, 1724 | Methacrylate, Acetate | 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 398 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
-
Lignin confidence 1.0
“Another peak at 398.1 eV should be attributed to the N in the -NHfor F-lignin@APP [35].”
Liang 等 - 2020 - Thermal Kinetics of a Lignin-Based Flame Retardant DOI: 10.3390/polym12092123 -
N h confidence 1.0
“The first peak at 398.39 eV corresponded to neutral amines, the second peak at in Table 1.”
Bekhoukh 等 - 2021 - Development, Investigation, and Comparative Study DOI: 10.3390/polym13193344 -
Acetate confidence 1.0
“397 the powder cellulose and the gel, which can be assigned to C-O stretching in 398 amorphous cellulose.”
Lefroy 等 - 2021 - A natural, cellulose-based microgel for water-in-o DOI: 10.1016/j.foodhyd.2020.106408
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