What absorbs at 1515 cm⁻¹ in an FTIR spectrum?
A band near 1515 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 1515 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 |
|---|---|---|---|
| Aromatic ring | 18 | 16 | 1.0 |
| Amide | 13 | 13 | 1.0 |
| Lignin | 7 | 7 | 1.0 |
| Alkyl C-H | 6 | 6 | 1.0 |
| Ring structure | 6 | 5 | 1.0 |
| C c single bond | 6 | 5 | 1.0 |
| N h | 5 | 5 | 1.0 |
| Hydroxyl (O-H) | 4 | 4 | 1.0 |
| Amino acid | 4 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonate | 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 |
|---|---|---|---|
| ZnS | 1515, 1650, 1116 | Alkyl C-H | 1 |
| protein | 1515, 1650, 1640 | Amide, Alkyl C-H | 1 |
| proteins | 1515, 1735, 1270 | Amide, 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 1515 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
-
N-O bond confidence 1.0
“The asymmetric stretch mode of the N-O group is perceived cm-1 from the narrow peak near 1515 which shows the presence of capping agent EDTA.”
In-doped ZnS nanoparticles: structural, morphological, optical and antibacterial properties DOI: 10.1007/s00339-021-04425-9 -
confidence 1.0
“cm-1 The peak at 1515 in Figure 2(b) is ascribed to the vibrating N-H of the amine group [18, 25,”
Indarti 等 - 2020 - Effect of temperature on the silylation of nanocry DOI: 10.1088/1755-1315/425/1/012065 -
Aromatic ring confidence 1.0
“LLM confirmed rule peak-group candidate”
Synchrotron based phase contrast X-ray imaging combined with FTIR spectroscopy reveals structural and biomolecular differences in spikelets play a significant role in resistance to Fusarium in wheat DOI: 10.1186/s12870-014-0357-5 -
Ketone confidence 1.0
“This peak usually appears at 1515is related with O cm(cid:2)1 1500 (conjugated aryl ketones), unconjugated C depending on the ring substituents.”
Temiz 等 - 2007 - Effect of accelerated weathering on surface chemis DOI: 10.1016/j.apsusc.2006.12.005 -
Amide confidence 1.0
“cm(cid:1)1), cm(cid:1)1 during and four negative cross-peaks at (1716, 1500 which the amide II band shifted to 1515 cm(cid:1)1), cm(cid:1)1), (1550, 1500”
Investigation on thermallyinduced conformation transition of soy protein film with variabletemperature FTIR spectroscopy DOI: 10.1002/app.35309 -
Acetate confidence 1.0
“The photomicrograph of the (stretching vibration of carbonyl C O), 1515 (aromatic tissue, however, is not informative with respect to molecular”
Rapid characterization of molecular chemistry, nutrient make-up and microlocation of internal seed tissue DOI: 10.1107/S0909049507014264 -
Carbonyl (C=O) confidence 1.0
“15dC f bond is the strong band at tyrosinate in the Pr Pfr transformation should result in shifts ization model around the C 16 19dO cm-1, cm-1 respectively.41,42 1704 of the strong bands around 1515 or 1495 which belongs to the C carbonyl”
van Thor 等 - 2005 - Assignments of the Pfr-Pr FTIR difference spectrum DOI: 10.1021/jp052323t -
Amide confidence 1.0
“C=O 1592 stretching +C-N N-H 1532* 1539 1532 1549 1562 bending stretching (Amide II) C=C 1515 1515 stretching of tyrosine C-O-C 1469 1469* bending vibration COO(cid:0)”
Organic biopolymers of venus clams: Collagen-related matrix in the bivalve shells with crossed-lamellar ultrastructure DOI: 10.1016/j.bbrep.2021.100939
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a literature-backed analysis — in seconds.