What absorbs at 3431 cm⁻¹ in an FTIR spectrum?
A band near 3431 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 3431 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 | 7 | 6 | 1.0 |
| Alkyl C-H | 5 | 5 | 1.0 |
| Carbonyl (C=O) | 3 | 2 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| N eq o | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Hydrogen 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 |
|---|---|---|---|
| polyaniline | 3431, 1565, 1570 | Alkyl C-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 3431 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
-
Hydrogen bond confidence 1.0
“A cm-1 In this tautomer, the N1-H11 bond has intense stretching at 3431 and 3708 attributed to their symmetric and asymmetric vibrations which involved in intramolecular hydrogen bonding.”
Karimzadeh 等 - 2018 - FT-IR study and solvent-implicit and explicit effe DOI: 10.1016/j.saa.2018.03.009 -
Hydroxyl (O-H) confidence 1.0
“ascribed to metal-oxygen bonding, and in the fourth This analysis can be considered as confirmation of cm(cid:2)1 region, the broad absorption peak about 3431 the successful filling of strontium into the voids of group.35 is assigned to the”
Structural and Optical Studies on Strontium-Filled CoSb3 Nanoparticles Via a Solvo-/Hydrothermal Method DOI: 10.1007/s11664-020-08629-2 -
C c single bond confidence 1.0
“The Figure (1c) shows the FTIR spectra of polyaniline/NiZnO 3 cm-1 is due to the N H stretching, characteristic absorption peaks are found to be at3431 04 cm-1 cm-1 is corresponds to C C stretching vibration of quiniod ring, 1481 is 1564 14”
Patil 等 - 2011 - Electrical Conductivity of PolyanilineNiZnO3 Comp DOI: 10.1080/00150193.2011.620836 -
Hydroxyl (O-H) confidence 1.0
“This spectra exhibited a cm‾1 strong and broad peak at 3431 which is attributed to the O-H stretch of alcohols and phenols cm‾1 and another medium peak at 2852 which is attributed to the C-H stretch of alkanes.”
Siraj 等 - 2020 - Synthesis, characterization and electrochemical in DOI: 10.1016/j.mee.2020.111400 -
Hydroxyl (O-H) confidence 1.0
“Two species were studied, and it was observed that cm(cid:1)1at there was a strong absorption band at 3431 and 3435 stations 1and 2 respecively, these bands show the presence of hydroxy groups and H-bonded OH stretching.”
Sreenivasulu 等 - 2017 - Organic matter from benthic foraminifera (Ammonia DOI: 10.1016/j.mex.2017.01.001 -
Water (H2O) confidence 1.0
“The honey powder fortified with maltodextrin and gum arabic dominated the water bands at 3431 cm-1 and cm-1 fortified with maltodextrin and gum arabic dominated the water bands at 3431 and (O-H stretching), respectively, and may be associat”
Development and Characterization of a Nutritionally Rich Spray-Dried Honey Powder DOI: 10.3390/foods10010162 -
Hydroxyl (O-H) confidence 1.0
“Peak at 3431 might also 3 originate from bonded -NH and -OH vibrations of -COOH groups found in the P.”
Cytotoxicity and antibacterial activities of plant-mediated synthesized zinc oxide (ZnO) nanoparticles using Punica granatum (pomegranate) fruit peels extract DOI: 10.1016/j.molstruc.2019.04.026 -
Hydroxyl (O-H) confidence 1.0
“cm-1 1635.3 The bands centered around 3431.1 (a) (b) cm-1 and 1384.3 are, respectively, assigned to the O-H Figure 2.”
Wang 等 - 2020 - Evaluation of Different Blood Circulating miRNAs f DOI: 10.1166/jnn.2020.17160
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