What absorbs at 3315 cm⁻¹ in an FTIR spectrum?
A band near 3315 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 3315 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) | 9 | 9 | 1.0 |
| N h | 9 | 7 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Amide | 3 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Methyl | 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 |
|---|---|---|---|
| starch | 3315, 1650, 1540 | Hydroxyl (O-H), Alkyl C-H, Amide | 1 |
| polyurethane | 3315, 2270, 1700 | Alkyl C-H, N h, Amide | 1 |
| PANI | 3315, 2930, 1300 | Alkyl C-H, N h, Amide | 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 3315 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
“LLM confirmed rule peak-group candidate”
Ternary Natural Deep Eutectic Solvent (NADES) Infused Phthaloyl Starch as Cost Efficient Quasi-Solid Gel Polymer Electrolyte DOI: 10.1016/j.carbpol.2017.03.023 -
confidence 1.0
“- 3200-3400 N-H Stretching 3315 - - 3324 3324 3324 3324 and CH3 Stretching 2985, 2936 2900 2870-2950 2850, 2870, 2850, 2870, 2850, 2870, 3000-2800 CH2”
El-Shekeil 等 - 2012 - Effect of pMDI isocyanate additive on mechanical a DOI: 10.1177/0021998310385030) -
Amide confidence 1.0
“Conversely, the analysis of the back side of the films yielded only signals corresponding to gelatin (e.g., Amide A at 3315 cm-1, Amide I at 1659 cm-1 and Amide II at 1555 cm-1), as previously observed for ATR.”
Advantages of External Reflection and Transflection over ATR in the Rapid Material Characterization of Negatives and Films via FTIR Spectroscopy DOI: 10.3390/polym14040808 -
Hydroxyl (O-H) confidence 1.0
“The ATR-FTIR spectra of the extracts obtained from cm-1, carob kibbles (trace a in all panels) displayed a major broad band at 3315 attributed unroasted carob kibbles (trace a in all panels) displayed a major broad band at 3315 cm-1, primar”
Linking the Dynamic Changes in the In Vitro Antioxidant Activity of Carob Kibbles upon Roasting to the Chemical and Structural Changes Revealed by FTIR Spectroscopy DOI: 10.3390/antiox10122025 -
N h confidence 1.0
“for NH-bending 3315cm-1 .”
Istanbullu 等 - 2013 - Development and Characterization of Novel Polyuret DOI: 10.1155/2013/178973 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Kamarudin 等 - 2018 - Adsorption of Copper Ion using Acrylic Acid-g-Poly DOI: 10.1088/1755-1315/140/1/012022 -
confidence 1.0
“(cm-1) Assignments * Wavelength 3315, 3326 stretching vibrations of N-H in urethane groups (as for II amides), P-O-Ca stretch the strongest polarized stretching vibrations of asymmetric and symmetric CH2 groups”
The Influence of Calcium Glycerophosphate (GPCa) Modifier on Physicochemical, Mechanical, and Biological Performance of Polyurethanes Applicable as Biomaterials for Bone Tissue Scaffolds Fabrication DOI: 10.3390/polym9080329 -
Hydroxyl (O-H) confidence 1.0
“Peapollencompositionunderheatstress (= cm-1),oxidative cm-1),lipids cm-1),amide | Table 1 Integrated absorption peaks of O-H stretching-amideA (3315 stress CH,3015 (3000-2800 = cm-1),phosphate cm-1),carbohydrates cm-1),nucleotides cm-1),and”
ATR–FTIR spectroscopy reveals involvement of lipids and proteins of intact pea pollen grains to heat stress tolerance DOI: 10.3389/fpls.2014.00747
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