What absorbs at 1511 cm⁻¹ in an FTIR spectrum?
A band near 1511 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 1511 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 | 12 | 12 | 1.0 |
| Alkene (C=C) | 6 | 6 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Amide | 4 | 4 | 1.0 |
| Lignin | 3 | 3 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| C=n | 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 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Urethane | 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 |
|---|---|---|---|
| lignin | 1511, 1035, 1510 | Alkyl C-H, Aromatic ring | 2 |
| cellulose | 1511, 1735, 1650 | Alkyl C-H, Amide | 1 |
| hemicelluloses | 1511, 1735, 1270 | Alkyl C-H, Aromatic ring | 1 |
| polyurethane | 1511, 2270, 1700 | Alkyl C-H, Amide | 1 |
| wood | 1511, 1740, 1730 | Alkyl C-H, Aromatic ring | 1 |
| activated carbon | 1511, 1575, 1210 | Alkyl C-H, Aromatic ring | 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 1511 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
“hydroxy group in eugenol can react with NaOH to form a is attributed to =C-H The absorption band at 1511 cm-1 eugenolate salt.”
Djunaidi 等 - 2018 - Synthesis of A Novel Carrier Compound Thiazoethyl DOI: 10.22146/ijc.25075 -
Urethane confidence 1.0
“cm-1 cm-1 and remaining OH groups at 3316 The C-H stretches was observed at 2926 and 2854 cm-1, cm-1 cm-1 followed by peaks at 1511 1213 and 1068 which indicates the urethane linkages of N-”
Norshahli 等 - 2018 - Mechanical Properties of Palm Oil Polyol based Pol DOI: 10.1088/1742-6596/1082/1/012041 -
Carbohydrate confidence 1.0
“Lignin reference peaks at 1511, 1462, 1269, and 1225 cm(cid:1)1 were ratioed against carbohydrate peaks at cm(cid:1)1.”
Examination of the lignin content in a softwood and a hardwood decayed by a brown-rot fungus with the acetyl bromide method and Fourier transform infrared spectroscopy DOI: 10.1002/pola.20071 -
Carbohydrate confidence 1.0
“versicolor, lignin and carbobands at 1511, 1268 and xylan bands at 1734 hydrate reduction occurred at a similar rate, with a slight decrease in decayed wood.”
Pandey 和 Pitman - 2003 - FTIR studies of the changes in wood chemistry foll DOI: 10.1016/S0964-8305(03)00052-0 -
Aromatic ring confidence 1.0
“1602 Aromatic skeletal stretching (lignin) 1511 1509 Aromatic skeletal stretching (lignin) 1463”
Rapid identification of Pterocarpus santalinus and Dalbergia louvelii by FTIR and 2D correlation IR spectroscopy DOI: 10.1016/j.molstruc.2014.01.085 -
Aromatic ring confidence 1.0
“cm-1, cm-1, The red grape sample showed higher absorbance intensities at 1606 1511 The red grape sample showed higher absorbance intensities at 1606 cm-1, 1511 cm-1, cm-1 and 1421 assigned to aromatic skeletal vibration of lignin [44-46].”
Cabalova 等 - 2023 - Valorization of Wood-Based Waste from Grapevine DOI: 10.3390/f14030442 -
Acetate confidence 1.0
“1729 Asymmetric stretch of carboxylate (C=O)O 1631 Aromatic C=O stretch 1511, 1426 Ring modes of the aromatic ring 102”
Conversion of Eragrostis plana Nees leaves to activated carbon by microwave-assisted pyrolysis for the removal of organic emerging contaminants from aqueous solutions DOI: 10.1007/s11356-018-2439-7 -
Aromatic ring confidence 1.0
“(b) Another characteristic aromatic band is cm-1, located at 1511 due to the aromatic C=C stretching of lignin residues.”
Polarity-Based Sequential Extraction as a Simple Tool to Reveal the Structural Complexity of Humic Acids DOI: 10.3390/agronomy11030587
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