What absorbs at 3275 cm⁻¹ in an FTIR spectrum?
A band near 3275 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 3275 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) | 12 | 12 | 1.0 |
| N h | 5 | 5 | 1.0 |
| Amide | 5 | 5 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| Protein | 2 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Phenolic | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| pectin | 3275, 1746, 1150 | Hydroxyl (O-H), Amide | 1 |
| TiO2 | 3275, 1700, 1093 | Hydroxyl (O-H) | 1 |
| hydrogel | 3275, 1632, 1062 | Amide, Hydroxyl (O-H), N h | 1 |
| saliva | 3275, 1648, 1664 | Amide | 1 |
| TiO2 nanoparticles | 3275, 1700, 455 | 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 3275 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”
Bio-engineered TiO2 nanoparticles using Ledebouria revoluta extract: Larvicidal, histopathological, antibacterial and anticancer activity DOI: 10.1080/03067319.2020.1718668 -
confidence 1.0
“The two prominent peaks at 3275.13 and 1635.54 are typical of N-H bond of amines and C=C stretch of alkenes or C=O stretch of amides [42] respectively.”
Biomedical Applications of Cocoa Bean Extract-Mediated Silver Nanoparticles as Antimicrobial, Larvicidal and Anticoagulant Agents DOI: 10.1007/s10876-016-1055-2 -
Amide confidence 1.0
“is cross-linking with GA, the intensity of the OH stretching In addition, major amide absorption peaks associated with cm-1 vibration peaks between 3275 and 3300”
Manesa 等 - 2022 - Fabrication and Characterization of Sericin-PVA Co DOI: 10.1021/acsomega.2c00897 -
Carbohydrate confidence 1.0
“3000 and 3600 shifted slightly away from the first reference peak of WP (3275 tween 3000 and 3600 cm-1 shifted slightly away from the first reference peak of WP (3275 Peak shift within that region is attributed to pectin and protein interac”
Complexation of Anthocyanin-Bound Blackcurrant Pectin and Whey Protein: Effect of pH and Heat Treatment DOI: 10.3390/molecules27134202 -
Carbohydrate confidence 1.0
“Pectin spectra showed distinctive peaks at 3275 due to the stretching of -OH group and cm-1”
Abdullah 和 Lazim - 2014 - Study on Swelling Behaviour of Hydrogel Based on A DOI: 10.1063/1.4895246 -
confidence 1.0
“cm-1 ∼3736 stretching O-H cm-1 ∼3346 stretching N-H cm-1 ∼3275 stretching O-H symmetric”
The Role of the Preanalytical Step for Human Saliva Analysis via Vibrational Spectroscopy DOI: 10.3390/metabo13030393 -
Hydroxyl (O-H) confidence 1.0
“maximum at 686 and it is preceded by a shoulder at 900 The large absorption cm-1 band having the maximum at 3275 is due to OH stretching vibration along with”
Spectroscopic Investigations of Porphyrin-TiO2 Nanoparticles Complexes DOI: 10.3390/molecules28010318 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Hiddenocysta matsuokae gen. nov. et sp. nov. from the Holocene of Vancouver Island, British Columbia, Canada DOI: 10.1080/01916122.2020.1750500
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