What absorbs at 3323 cm⁻¹ in an FTIR spectrum?
A band near 3323 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 3323 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 h | 7 | 6 | 1.0 |
| Hydroxyl (O-H) | 5 | 5 | 1.0 |
| Secondary amine | 3 | 3 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Amine primary | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Carbon bromine | 1 | 1 | 1.0 |
| C-O single bond | 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 |
|---|---|---|---|
| polyurethane | 3323, 2270, 1700 | Alkyl C-H, N h | 2 |
| CS | 3323, 1645, 1720 | Hydroxyl (O-H), Alkyl C-H | 1 |
| CA | 3323, 1045, 1650 | Hydroxyl (O-H), Alkyl C-H | 1 |
| composite | 3323, 1703, 1295 | Alkyl C-H, 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 3323 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
-
Amide confidence 1.0
“The amide A absorption peak of PSC at cm-1 cm-1, 3323.20 is slightly higher than ASC at the wavenumber of 3327.06 indicating that more N-H groups in the ASC are hydrogen-bonded, which suggested that the PSC is slightly weaker than Mar.”
Song 等 - 2019 - Physicochemical and Biocompatibility Properties of DOI: 10.3390/md17030137 -
Alkyl C-H confidence 1.0
“In PVA, the stretching vibration of characteristic cm-1, peaks of -OH in PVA molecules was located at 3323 and the characteristic bands of C-H and cm-1, different C-O bonds were at 2942, 1435 and 1090 respectively (Figure 6a).”
Novel Polyvinyl Alcohol (PVA)/Cellulose Nanocrystal (CNC) Supramolecular Composite Hydrogels: Preparation and Application as Soil Conditioners DOI: 10.3390/nano9101397 -
Amide confidence 1.0
“irradiation with Co gamma rays and the spectrum changed cm-1) cmBoth amide A (3323 and amide B band (3057 notably as a function of doses.”
Bessalah 等 - 2023 - Effect of Gamma Radiation on Novel Gelatin Extract DOI: 10.17582/journal.pjz/20220218020207 -
confidence 1.0
“C-H 2943 Alkane Medium stretching N-H 3323 Aliphatic primary amine Medium stretching Without Berry Seeds C-Br 677 Halo compound”
Development and characterization of natural sourced bioplastic for food packaging applications DOI: 10.1016/j.heliyon.2023.e13538 -
Alkyl C-H confidence 1.0
“of the methyl (-CH3) group from N-acetyl-glucosamine related to the deacetylation degree cm-1 The FTIR spectrum of CS exhibits typical bands at 3323 (stretching vibration of [31]: H2 of the glucosamine unit, H3, H4, H5, and H6 of the glucop”
Cojocaru 等 - 2022 - Electrospun Nanofibrous Membranes Based on Citric DOI: 10.3390/polym14020294 -
Carbonyl (C=O) confidence 1.0
“After storage for 36 month a decrease in intensity of bands at 1738 (HS), 1708 cm-1, following bands are identified: low-intense peak of carbonyl stretching at 1729 wide (HS-SS) cm-1 and growth of intensity of band at 1721 (SS-SS) cm-1 with”
The Influence of Long-Time Storage on the Structure and Properties of Multi-Block Thermoplastic Polyurethanes Based on Poly(butylene adipate) Diol and Polycaprolactone Diol DOI: 10.3390/ma16020818 -
N h confidence 1.0
“cm-1, cm-1 assay was carried out by following the protocol 2939 and 2854 peaks observed at 3323 cm-1 cm-1 cm-1 , 1730 and 1703 were attributes to NH as discussed earlier.”
Jaganathan 等 - 2019 - Blood compatibility assessments of electrospun pol DOI: 10.1590/0001-3765201920190018 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Manufacturing and Characterization of Novel Electrospun Composite Comprising Polyurethane and Mustard Oil Scaffold with Enhanced Blood Compatibility DOI: 10.3390/polym9050163
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