What absorbs at 1615 cm⁻¹ in an FTIR spectrum?
A band near 1615 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 1615 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 |
|---|---|---|---|
| Amide | 10 | 10 | 1.0 |
| Carboxyl (COOH) | 7 | 7 | 1.0 |
| Methacrylate | 6 | 6 | 1.0 |
| Acetate | 6 | 6 | 1.0 |
| N h | 6 | 5 | 1.0 |
| Alkene (C=C) | 5 | 5 | 1.0 |
| C c single bond | 5 | 4 | 1.0 |
| Hydroxyl (O-H) | 4 | 4 | 1.0 |
| Ketone | 4 | 4 | 1.0 |
| Ester | 4 | 4 | 1.0 |
| Carbonyl (C=O) | 4 | 4 | 1.0 |
| Secondary amine | 3 | 3 | 1.0 |
| C n single bond | 3 | 3 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| C-O single bond | 3 | 3 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Water (H2O) | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Protein beta sheet | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Guanidine core | 1 | 1 | 0.9 |
| Thiocyanate | 1 | 0 | 1.0 |
| Lewis acid site | 1 | 0 | 0.7 |
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 |
|---|---|---|---|
| polyaniline | 1615, 1565, 1570 | Amide, Methacrylate, Acetate | 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 1615 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
-
C c single bond confidence 1.0
“In 4HBN, the C-C stretching vibrations are observed at 1615, 1249cm(cid:2)1 1587, 1510, 1449, 1326 and in IR and 1611, and 1591cm(cid:2)1 1510cm(cid:2)1 in Raman spectra.”
Arjunan 等 - 2012 - Quantum chemical studies and vibrational analysis DOI: 10.1016/j.saa.2012.08.053 -
Carboxyl (COOH) confidence 1.0
“In the region of the IR band could (1615cm-1) be assigned as the ionized asymmetric carboxylate 1547cm-1), 3+ and NH deformation vibration (1567 (shoulder) and 1350cm-1, these bands corresponded respectively.”
Hsu 和 Lin - 2009 - Rapid examination of the kinetic process of intram DOI: 10.1016/j.tca.2008.12.008 -
Amide confidence 1.0
“exchange caused only small shifts in the amide cm-1 I region, although again with a large effect on the 1615 peak, and much larger losses in the amide II region as cm-1, expected.”
Iwaki 等 - 2005 - Direct observation of redox-linked histidine proto DOI: 10.1021/bi047533v -
C c single bond confidence 1.0
“Raman band at 1615 cm-1 cm-1 is attributed to C-C stretching vibration of benzene ring, and Raman band at 1565 is”
Jin 等 - 2018 - Polymer anode used in hydrometallurgy Anodic beha DOI: 10.1016/j.hydromet.2018.01.020 -
N-O bond confidence 1.0
“to WT Mb has an absorption at 1615 however, its (24)Vibrational Stark spectroscopy can also be a good way to identify the NO stretch peaks in the ground state, and this is seen for V68E-NO in”
Park 等 - 2000 - Vibrational Stark spectroscopy of NO bound to heme DOI: 10.1021/ja0014741 -
Protein beta sheet confidence 1.0
“The 1615-1618 peaks β-sheet, observed in FTIR spectra of the proteins, which are assigned to intermolecular is due to the cm-1”
Sadat 和 Joye - 2020 - Peak Fitting Applied to Fourier Transform Infrared DOI: 10.3390/app10175918 -
Alkene (C=C) confidence 1.0
“LLM confirmed rule peak-group candidate”
Adam 等 - 2022 - Comparative Evaluation of Amlodipine Besylate Gene DOI: 10.14227/DT290422PGC2 -
Alkyl C-H confidence 1.0
“FT-IR 3075 (C-H, s, stretching), 1615 (C=N, m, bending), 1145”
A Comprehensive Approach to Derivatization: Elemental Composition, Biochemical, and In Silico Studies of Metformin Derivatives Containing Copper and Zinc Complexes DOI: 10.3390/molecules28031406
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