What absorbs at 3390 cm⁻¹ in an FTIR spectrum?
A band near 3390 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 3390 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) | 22 | 22 | 1.0 |
| N h | 7 | 7 | 1.0 |
| Alkyl C-H | 5 | 5 | 1.0 |
| Water (H2O) | 3 | 3 | 1.0 |
| Hydrogen bond | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
| Phenolic | 1 | 1 | 0.8 |
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 |
|---|---|---|---|
| silica | 3390, 1100, 1080 | Hydroxyl (O-H), Alkyl C-H | 1 |
| SiO2 | 3390, 1739, 699 | Alkyl C-H, 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 3390 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
-
Water (H2O) confidence 1.0
“LLM confirmed rule peak-group candidate”
Ashraf 等 - 2021 - Identification and properties of ion-pairs in the DOI: 10.1016/j.molliq.2020.114891 -
Metal hydroxyl confidence 1.0
“LLM confirmed rule peak-group candidate”
Dahham 等 - 2018 - Studies of ENR-25TiO2 Composites for Electronic M DOI: 10.1088/1742-6596/1019/1/012054 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Lueder 等 - 2023 - A framework for quantitative in situ evaluation of DOI: 10.5194/ejm-35-243-2023 -
Silanol (Si-OH) confidence 1.0
“Part of range 3350-3390 cm-1 assigned to Si-OH”
High purity and amorphous silica (SiO2) prepared from oil palm frond (OPF) through sol⠍gel method DOI: 10.1016/j.matpr.2020.05.299 -
Alkyl C-H confidence 1.0
“The FTIR spectrum of IRP-P showed the presence of cm-1 which characteristic peaks at 3390, 2939, 1738, 1634, 1402, 1295, 1105, 1051, and 955 C-H could be assigned to the stretching frequency of -OH group, stretching of the methyl”
Bio-therapeutic Potential and Cytotoxicity Assessment of Pectin-Mediated Synthesized Nanostructured Cerium Oxide DOI: 10.1007/s12010-016-2121-9) -
confidence 1.0
“These two vibrations are affected little bit by other 3480cm-1 vibrations of N-H stretching assigned to the bands at vibrations and theoretically computed frequencies for C-NH 3390cm-1, and respectively.”
Vibrational spectroscopy [FTIR and FTRaman] investigation, computed vibrational frequency analysis and IR intensity and Raman activity peak resemblance analysis on 4-chloro 2-methylaniline using HF and DFT [LSDA, B3LYP and B3PW91] calculations DOI: 10.1016/j.saa.2010.12.068 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Retnoningtyas 等 - 2022 - Synthesis and Characterization of Methionine-Funct DOI: 10.33263/BRIAC125.58455859 -
Hydroxyl (O-H) 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
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