What absorbs at 3340 cm⁻¹ in an FTIR spectrum?
A band near 3340 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 3340 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) | 37 | 36 | 1.0 |
| N h | 18 | 18 | 1.0 |
| Carbohydrate | 6 | 6 | 1.0 |
| Hydrogen bond | 5 | 5 | 1.0 |
| Carboxyl (COOH) | 4 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Lignin | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Urethane | 1 | 1 | 1.0 |
| Carbon dioxide | 1 | 1 | 1.0 |
| Amine primary | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 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 |
|---|---|---|---|
| graphene oxide | 3340, 1150, 3400 | Hydroxyl (O-H) | 1 |
| polysaccharide | 3340, 1637, 1320 | Hydroxyl (O-H), N h | 1 |
| cellulose nanocrystals | 3340, 1110, 1640 | Carbohydrate, 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 3340 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
“In addition, the relatively broader peak at 3340 (hydroxyl group, H-bonded O-H stretching) in Fig.”
Surface modification of bacterial cellulose membrane by oxygen plasma treatment DOI: 10.1016/j.surfcoat.2016.06.035 -
Hydroxyl (O-H) confidence 1.0
“The peaks at 3340 in all of the spectra correspond correspond to O-H stretching and reflect the tendency of OPMF to be hydrophilic [7].”
Isolation and Characterization of Cellulose Nanocrystals from Oil Palm Mesocarp Fiber DOI: 10.3390/polym9080355 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Daud 等 - 2017 - Functionalizing Graphene Oxide with Alkylamine by DOI: 10.3390/nano7060135 -
confidence 1.0
“1.1(cid:3)1020 and H-Si-HSiN 2140 [15] Si-H H-Si-SiN2 4(cid:3)1020 2170 [15] Si-H H-Si-HN2 2(cid:3)1020 Si-H H-Si-N3 2220 [15] 1.2(cid:3)1020 N-H?N [15] N-H stretching 3340 9(cid:3)1019 [16] N-H N-H stretching 3400 3.2(cid:3)1020 [16] O-H H”
Effect of PECVD silicon oxynitride film composition on the surface passivation of silicon wafers DOI: 10.1016/j.solmat.2011.09.052 -
Hydroxyl (O-H) confidence 1.0
“(cm-1) infrared (FTIR) absorption bands used in this study according to γ(O-H) 3340 stretching Cellulose Artz et al.”
Molecular Fingerprints of Soil Organic Carbon in Wetlands Covered by Native and Non-native Plants in the Yellow River Delta DOI: 10.1007/s13157-020-01340-2 -
Hydroxyl (O-H) confidence 1.0
“cm-1 (which unusually shifted to lower frequency) 1602 O-H cm-1 and the stretching modes at 3340 and 3450 (not shown) show that water molecules around the thisassignmentisthatbyfurtherremovalofthesurfactant °C).35 headgroups are possibly in”
Nikoobakht 和 El-Sayed - 2001 - Evidence for bilayer assembly of cationic surfacta DOI: 10.1021/la010530o -
Hydroxyl (O-H) confidence 1.0
“cm-1, The characteristic vibrational peak at 3340 which The complex impedance plot for TSP containing different O-H corresponds to stretching, gets shifted from 3368 to concentrations of LiBr measured at ambient temperature is cm-1.”
Premalatha 等 - 2017 - Tamarind seed polysaccharide (TSP)-based Li-ion co DOI: 10.1007/s11581-017-1989-x -
Hydrogen bond confidence 1.0
“LLM confirmed rule peak-group candidate”
Walnut Oil Oleogels as Milk Fat Replacing System for Commercially Available Chocolate Butter DOI: 10.3390/gels8100613
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