What absorbs at 3332 cm⁻¹ in an FTIR spectrum?
A band near 3332 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 3332 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) | 4 | 4 | 1.0 |
| Amine primary | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 0.9 |
| Protein | 1 | 1 | 0.9 |
| Ammonium | 1 | 0 | 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 | 3332, 1650, 1655 | Hydroxyl (O-H), N 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 3332 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
“Peaks at 3332 cm-1 3356 showed the N-H stretching peak assigned to monopeptides or dipeptides [9].”
Wei 等 - 2014 - An Optimization Study on the Inclusion of Aluminiu DOI: 10.4028/www.scientific.net/AMR.844.399 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Chemometric analysis of cow dung ash as an adsorbent for purifying biodiesel from waste cooking oil DOI: 10.1038/s41598-017-09881-z -
confidence 1.0
“The hardness data for Acron are observed at 979 Again, a broad band at approxicm-1 MC showed significant differences between groups of mately 3332 was assigned to N-H stretchings.”
Ayaz 等 - 2013 - The effect of acrylamide incorporation on the ther DOI: 10.4047/jap.2013.5.2.110 -
Silicon (Si) confidence 1.0
“The strong bands at 992 cm-1and 453 cm-1 were caused by -XO4 and O-X-O groups, respectively (X means Si/Al), and the band at 3332 cm-1 corresponded to the Si-OH group and Al-OH group on the surface of zeolite molecular sieve framework [46].”
Chitosan Modified Zeolite Molecular Sieve Particles as a Filter for Ammonium Nitrogen Removal from Water DOI: 10.3390/ijms21072383 -
Carboxyl (COOH) confidence 1.0
“The band, with its maximum at ~3332 represents carboxylic acids, whose”
Quality Assessment of Honey Powders Obtained by High- and Low-Temperature Spray Drying DOI: 10.3390/app11010224 -
confidence 1.0
“It is groups in the temperature range of 202 to C effect evident that the of heat treatment led to the formawere the emergence of additional contributions to N-H peak different (3332cm-1), (2620-3035cm-1), tion/evolution of functional group”
Masite 等 - 2022 - Trace Metals, Crude Protein, and TGA-FTIR Analysis DOI: 10.1155/2022/1509569 -
confidence 1.0
“The peak visible cm-1 at 3332 in this band indicated the stretching of the N-H bond (amide A) of biomass at 3332 cm-1 in this band indicated the stretching of the N-H bond (amide A) of biomass proteins [26].”
The Effect of Modifying Canadian Goldenrod (Solidago canadensis) Biomass with Ammonia and Epichlorohydrin on the Sorption Efficiency of Anionic Dyes from Water Solutions DOI: 10.3390/ma16134586 -
confidence 1.0
“In CI presented as a shoulder at 3336, 3376, and 3378 cm-1 cm-1 and 3332 and CA, this peak is less notorious and is found as an inflection at 3402 respectively.[33] This indicates that CB, CP, and CE contain moisture from the environmental”
Pavon 等 - 2022 - Comparative characterization of gum rosins for the DOI: 10.1002/app.51734
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