What absorbs at 3425 cm⁻¹ in an FTIR spectrum?
A band near 3425 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 3425 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) | 36 | 33 | 1.0 |
| N h | 6 | 6 | 1.0 |
| Alkyl C-H | 5 | 4 | 1.0 |
| Metal oxygen | 3 | 3 | 1.0 |
| Water (H2O) | 3 | 3 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Methyl | 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 |
|---|---|---|---|
| lignin | 3425, 1035, 1510 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| Copper | 3425, 1636, 1202 | 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 3425 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
“Page 7 of 8 519 Optical properties of graphene oxide thin film reduced by low-cost diode laser cm-1, correspondgroups, strong bands of 2860 and 2926 ing to symmetrical and anti-symmetrical stretching vibracm-1 tions of CH and 3425 bands cor”
Optical properties of graphene oxide thin film reduced by low-cost diode laser DOI: 10.1007/s00339-020-03710-3 -
Hydroxyl (O-H) confidence 1.0
“3 2 cm-1 Consent for publication respectively..Bands near 3425 (O-H stretching vibraAll authors are willing to submit the article in the journal and they have no cm-1 tion) and peak at 2892 was due to the C-H stretching conflict of interest”
Hanif 和 Zaman - 2017 - Thiolation of arabinoxylan and its application in DOI: 10.1186/s40199-017-0172-2 -
Water (H2O) confidence 1.0
“4, all peaks at 3425, 1628, 1108, 636, 596, 552, and 498 cm¡1 are attributed to the stretching modes of adsorbed water, at 3425, 1628 and 1108 by Downloaded”
Synthesized and magnetic and ferroelectric phase transitions of single phase multiferroic YMn2O5 nanoparticles through microwave assisted polyacrylamide gel method DOI: 10.1080/00150193.2017.1375302 -
Hydroxyl (O-H) confidence 1.0
“3/g, The spectra showed the similarity of vibrations at (cm (a) cm-1 3425 and 1627 which indicates the -OH from Adsorbed”
Mohadi 等 - 2022 - Low-Cost Yet High-Performance Hydrochar Derived fr DOI: 10.22146/ijc.73353 -
Hydroxyl (O-H) confidence 1.0
“cm-1 a broad peak at the 3425 region assigned to hydroxyl funcThe effect of monomer concentration on grafting percentage and”
Functionalization of lignin: Fundamental studies on aqueous graft copolymerization with vinyl acetate DOI: 10.1016/j.indcrop.2012.12.031 -
confidence 1.0
“However, it can be assumed An additional band at 3425 Cr-containing diopside was assigned to some type of a Crand was even desired that all CaO had reacted to Ca(OH) 2 et al., before the capsule was loaded.”
Purwin 等 - 2009 - Hydrogen incorporation in Feand Na-doped diopsid DOI: 10.1127/0935-1221/2009/0021-1938 -
Water (H2O) confidence 1.0
“The absorption bands cm-1 about 3425 and 1605 correspond to water absorption of”
Shoba 等 - 2022 - Copper nanoparticles incorporated manganese dioxid DOI: 10.14447/jnmes.v25i3.a05 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Proton conducting polymer electrolyte based on plasticized chitosan–PEO blend and application in electrochemical devices DOI: 10.1016/j.optmat.2013.03.004
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