What absorbs at 3328 cm⁻¹ in an FTIR spectrum?
A band near 3328 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 3328 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) | 18 | 16 | 1.0 |
| N h | 13 | 11 | 1.0 |
| Carbohydrate | 6 | 5 | 1.0 |
| Hydrogen bond | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 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 |
|---|---|---|---|
| Chitosan | 3328, 1650, 1655 | Hydroxyl (O-H), N h | 2 |
| cellulose | 3328, 1735, 1650 | Hydroxyl (O-H), Carbohydrate | 1 |
| lignin | 3328, 1035, 1510 | Hydroxyl (O-H) | 1 |
| polymer | 3328, 1718, 1722 | 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 3328 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
“LLM confirmed rule peak-group candidate”
Hassan 和 Badri - 2014 - Lignin Recovery from Alkaline Hydrolysis and Glyce DOI: 10.1063/1.4895236 -
Hydroxyl (O-H) confidence 1.0
“A broad interpreted as the hydrolysis of the ester linkages in peak at around 3328 cm-' is due to the -OH roups the xylan." Xylans are closely associated with other”
Pan 等 - 2007 - Characterization of liquefied wood residues from d DOI: 10.1002/app.26435 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Synthesis and characterizations of o-nitrochitosan based biopolymer electrolyte for electrochemical devices DOI: 10.1371/journal.pone.0212066 -
confidence 1.0
“The PU prepolymer has shown some study of prepared polymers provides useful characteristic absorption peaks, were assigned information about their structural features as cm-1, cm-1 at 1535 1495 for (-N-H and -C-N, it gives the idea about th”
Salem 和 Salama - 2020 - Developing a New Class of UV-curable Polyurethane DOI: 10.21608/ejchem.2019.14853.1906 -
Hydrogen bond confidence 1.0
“The F2 and F3 formulated films were showed drug and polymer interacted with hydrogen bonding to broad peak at 3328 and 3365 cm -1 that was assigned to enable the drug to release quickly and may aim for rapid O-H stretching vibration for the”
AnjiReddy 和 Karpagam - 2020 - Micro and nanocrystalline cellulose based oral dis DOI: 10.1590/s2175-97902020000117797 -
Alkene (C=C) confidence 1.0
“The FTIR of cm-1, cm-1, NPs showed a typical primary N-H band at 3328 C=C vibration at 2118 N-H NPs showed a typical primary N-H band at 3328 cm-1, C=C vibration at 2118 cm-1, N-H cm-1, cm-1,”
Bharathi 等 - 2023 - Facile Synthesis and Characterization of Chitosan DOI: 10.3390/polym15122700 -
confidence 1.0
“In the specfoaming agent has partially elevated mechanical trum of AC foaming agent, the peaks at 3328 (N-H properties, and the thickness swelling rate of water stretch), 1727 (C =O stretch), 1631 (N-H bend), and cm-1 absorption significant”
Preparation, morphology, FTIR and performance properties of foaming particleboard DOI: 10.1186/s10086-021-01984-6 -
Acetate confidence 1.0
“The presence of the broad -OHstretching vibration peak at 3328 cm-1 and C-O stretching cm-1 The FTIR spectra of CaSt2-KF and raw-KF can be seen in Figure 4a and 4b, respectively.”
Blaquera 等 - 2023 - Oil Adsorption Kinetics of Calcium Stearate-Coated DOI: 10.3390/polym15020452
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