What absorbs at 3325 cm⁻¹ in an FTIR spectrum?
A band near 3325 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 3325 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) | 13 | 11 | 1.0 |
| N h | 10 | 9 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Amine primary | 2 | 2 | 1.0 |
| Silicate | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Carbohydrate | 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 |
|---|---|---|---|
| Silver nanoparticles | 3325, 1636, 1631 | Hydroxyl (O-H), Alkyl C-H, N h | 1 |
| proteins | 3325, 1735, 1270 | Alkyl C-H, Hydroxyl (O-H), Methoxy (OCH3) | 1 |
| wood | 3325, 1740, 1730 | Alkyl C-H, Methoxy (OCH3) | 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 3325 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
“Peak at 3325 2930 1710 and cm-1 within OS polymer, the 2θ value of P-BNT moved to a lower 1385 were attributed to O-H of OS, C-H of OS, C = O”
Modification of Oxidized Starch Polymer with Nanoclay for Enhanced Adhesion and Free Formaldehyde Emission of Plywood DOI: 10.1007/s10924-021-02101-w -
confidence 1.0
“Figure showed that the stretching mode of N-H group generated Therefore, the current research work was designed to 3325cm-1.”
Ahmad 等 - 2022 - Synthesis and characterization of poly(o-chloroani DOI: 10.30955/gnj.004205 -
confidence 1.0
“for the stabilization of the silver nanoparticles formed due to the broad peak at wavelength 3324.52 and The EDX analysis revealedcarbon,nitrogen,oxygen,aluminum,potassium,copper,andsilverastheelementspresentinthenanoparticles.Resultsobtain”
Akintelu 等 - 2020 - Characterization and Pharmacological Efficacy of S DOI: 10.1155/2020/2876019 -
N h confidence 1.0
“CHD displayed peaks at 3325 and 3119cm(cid:3)1 The cumulative CHD release from both groups of tablets was (asymmetric and symmetric NH stretching vibrations), cm(cid:3)1 affectedbytheratioofP407.IncreasingP407contentelevatesdrug 2938 and 28”
Al-Ani 等 - 2019 - The effect of the source and the concentration of DOI: 10.1016/j.jsps.2019.04.012 -
Hydroxyl (O-H) confidence 1.0
“Observed peak cm-1 intensity at 3324.6 was assigned to the -O-H structuring vibrations modes, 2971.6, cm-1, 2926.4, and 2881.2 which are attributed to the presence of asymmetric and symmetric structuring vibration modes of C-H aliphatic car”
Alamier 等 - 2022 - Thermodynamic and Spectroscopic Studies of SDS in DOI: 10.3390/app122312020 -
Amide confidence 1.0
“cm-1 peak in the region of 3324.7 corresponds to amide A, cm-1 and the peak in the region of 1640.0 corresponds to”
Application of SPRA Technology for Delivery of Erythropoietin: Stability Evaluation of Conjugated Erythropoietin with Adamantane and in SPRA Inclusion Complex DOI: 10.5812/ijpr-134282. -
Amine primary confidence 1.0
“LLM confirmed rule peak-group candidate”
Baloyi 和 Marx - 2021 - Preparation of bio-oil from Scenedesmus acutus usi DOI: 10.17159/2413-3051/2021/v32i2a8903 -
Hydroxyl (O-H) confidence 1.0
“(b) peak (1508 Hydroxyl peak (3325 relative to lignin peak (1508 cm-1) relative to lignin citric acid and 39% sorbitol citric acid modified samples.”
Leachability and Decay Resistance of Wood Polyesterified with Sorbitol and Citric Acid DOI: 10.3390/f11060650
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