What absorbs at 3300 cm⁻¹ in an FTIR spectrum?
A band near 3300 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 3300 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) | 173 | 165 | 1.0 |
| N h | 72 | 65 | 1.0 |
| Amide | 48 | 44 | 1.0 |
| Water (H2O) | 31 | 29 | 1.0 |
| Alkyl C-H | 30 | 28 | 1.0 |
| Secondary amine | 22 | 20 | 1.0 |
| Hydrogen bond | 16 | 16 | 1.0 |
| Methacrylate | 15 | 15 | 1.0 |
| Acetate | 14 | 14 | 1.0 |
| C-O single bond | 12 | 12 | 1.0 |
| Methoxy (OCH3) | 11 | 11 | 1.0 |
| Carboxyl (COOH) | 9 | 9 | 1.0 |
| Ester | 7 | 6 | 1.0 |
| Carbohydrate | 6 | 6 | 1.0 |
| Protein | 6 | 5 | 1.0 |
| C n single bond | 5 | 5 | 1.0 |
| N-O bond | 5 | 5 | 1.0 |
| Silanol (Si-OH) | 4 | 4 | 1.0 |
| Amine primary | 4 | 3 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| Ketone | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Methyl | 3 | 2 | 1.0 |
| Urea | 2 | 2 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 2 | 2 | 1.0 |
| Amino acid | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Phosphate (PO4) | 2 | 2 | 1.0 |
| Phenolic | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Azide | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| C#c | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| Lipid | 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 |
|---|---|---|---|
| STARCH | 3300, 1650, 1540 | Hydroxyl (O-H), Amide | 1 |
| biodiesel | 3300, 858, 3470 | Hydroxyl (O-H) | 1 |
| alumina | 3300, 460, 1000 | 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 3300 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
“nNH gelatin granules, after time exposure (30 and 60 min) to UV irradisplayed relevant peaks ascribed to amide A stretching cm(cid:1)1) diation.Inthesecondregionfrom1700to1500cm(cid:1)1,ashiftoccurs nOH and stretching (around 3300 coupled w”
Spectroscopic analyses of the influence of electron beam irradiation doses on mechanical, transport properties and microstructure of chitosan-fish gelatin blend films DOI: 10.1016/j.foodhyd.2014.09.038 -
Phosphate (PO4) confidence 1.0
“The intensity and waverelative population of the P=O, O-P-O and O=P-O bending units due 3300cm-1”
Chowdhury 等 - 2019 - Structural properties of Er3+ doped lead zinc phos DOI: 10.1016/j.mseb.2019.01.014 -
N-O bond confidence 1.0
“Before immersion, a broad band between 3300 shows that there was no detachment or decohesion of cm(cid:2)1 was assigned to fundamental stretching and 3500 the coatings from the substrate.”
Devi 等 - 2011 - Synthesis and characterization of nanoporous sodiu DOI: 10.1007/s11998-011-9344-z -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Effect of alumina on the performance and characterization of cross-linked PVA / PEG 600 blended membranes for CO2/N2 separation DOI: 10.1016/j.seppur.2018.08.026 -
N h confidence 1.0
“cm-1, C=O Peaks of interest were, NH stretching vibration of amid A at 3300 stretching vibration of”
Elgamouz 等 - 2019 - The Effects of Storage on Quality and Nutritional DOI: 10.3390/biom9090442 -
Acetyl confidence 1.0
“It is possible (NS, LAS, and HAS), which can be confirmed by the that HAS sample has a more electronegative surface cm-1 peak at 3300 which is commonly attributed to than LAS sample, as more acetyl groups were incorstretching of -OH groups”
Felipe Tirado 等 - 2017 - EVALUATION OF THE COAGULANT CAPACITY OF STARCH OBT DOI: 10.20937/RICA.2017.33.esp01.11 -
Water (H2O) confidence 1.0
“versicolor the band at 3300 indicates the presence of higher moisture in the cell structure of compared”
Gupta 等 - 2022 - In vitro cell composition identification of wood d DOI: 10.1098/rsos.201935 -
Alkyl C-H confidence 1.0
“absence of residual The peak between 3300 and 3600 -O-H was attributed to the axial and present in the cases of MOTechnical grade MO contains oleate methyl esters as the major constituent along with laurate, myristate, stearate, palmitate,”
Evaluation of the performance and emission and spectroscopic analysis of an improved soy methyl ester DOI: 10.1039/c9ra04342j
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