What absorbs at 3428 cm⁻¹ in an FTIR spectrum?
A band near 3428 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 3428 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) | 20 | 19 | 1.0 |
| N h | 5 | 3 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Chitosan | 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 |
| Amide | 1 | 1 | 1.0 |
| N-O 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 |
|---|---|---|---|
| chitosan | 3428, 1650, 1655 | Acetate, Methacrylate, Hydroxyl (O-H) | 2 |
| copper oxide | 3428, 624, 1686 | Hydroxyl (O-H), Methacrylate, Acetate | 1 |
| cellulose | 3428, 1735, 1650 | Acetate, Methacrylate, Hydroxyl (O-H) | 1 |
| chitin | 3428, 1650, 1655 | Methacrylate, Acetate, N h | 1 |
| quercetin | 3428, 1745, 1612 | Methacrylate, Acetate, 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 3428 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
-
confidence 1.0
“The deuteration method revealed that the new band at cm-1 OH3428 could be assigned to the dislocated ions by substituting Ti(IV) ions.”
FTIR studies on photocatalytic activity of Ti(IV)-doped calcium hydroxyapatite particles DOI: 10.1016/j.molcata.2012.04.009 -
Hydroxyl (O-H) confidence 1.0
“Peslier 2002) neither cm(cid:2)1 cm(cid:2)1 cm(cid:2)1 and the one at 3360 between the band at 3428 nor the Na-associated OH-absorption band at 3428 Fe3þ cm(cid:2)1 indicates the presence of two different OH-defects.”
Purwin 等 - 2009 - Hydrogen incorporation in Feand Na-doped diopsid DOI: 10.1127/0935-1221/2009/0021-1938 -
Hydroxyl (O-H) confidence 1.0
“at 1731 FTIR spectrum of the physical mixture showed O-H cm-1 stretching at 3428 and C=O stretching of carboxylic cm-1.”
Setyawan 等 - 2018 - Improvement in vitro Dissolution Rate of Quercetin DOI: 10.22146/ijc.28511 -
Chitosan confidence 1.0
“FTIR spectra of chitin exhibited prominent peaks at cm-1 3447, 2918, 1655, 1379, 1073 (black colour) and chitosan revealed that the peaks at 3428, cm-1 cm-1 2921, 1636, 1420, 1096 (red colour).”
Chitin and Chitosan preparation from shrimp shells Penaeus monodon and its human Ovarian Cancer Cell Line, PA-1 DOI: 10.1016/j.ijbiomac.2017.09.035 -
Hydroxyl (O-H) confidence 1.0
“The broad absorption band at 3427.99 assigned to O-H stretching of cm-1, as seen 1621.50, 1424.16, 1325.22, 1224.67, 1178.22, 1067.69, 861.22, 752.97 and 574.11 free hydroxyl groups could be assigned to the polyphenolic compounds of pomegra”
Facile Green Synthesis of Zinc Oxide Nanoparticles with Potential Synergistic Activity with Common Antifungal Agents against Multidrug-Resistant Candidal Strains DOI: 10.3390/cryst12060774 -
Hydroxyl (O-H) confidence 1.0
“The FT-IR analysis of plant extract displayed 46 47 48 different peaks at 3428 (O-H stretch of phenols), 2918 (N-H bond of ammonium ions), 2853 (O-”
Yugandhar 等 - 2019 - Biofabrication, characterization and evaluation of DOI: 10.1088/2053-1591/ab0db9 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Zhao 等 - 2021 - Evaluation of a strawberry fermented beverage with DOI: 10.7717/peerj.11974 -
Hydroxyl (O-H) confidence 1.0
“Absorption band at wave number 3427.51 indicates stretching vibrations of -OH functional group which overlap with the -NH vibration (amine group) [21].”
Az-Zahra 等 - 2019 - Reinforcement of chitosan film using cellulose iso DOI: 10.1088/1742-6596/1402/5/055039
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