What absorbs at 1602 cm⁻¹ in an FTIR spectrum?
A band near 1602 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 1602 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 | 10 | 1.0 |
| Carboxyl (COOH) | 8 | 6 | 1.0 |
| Alkene (C=C) | 6 | 6 | 1.0 |
| Ring structure | 6 | 5 | 1.0 |
| Carbonyl (C=O) | 6 | 5 | 1.0 |
| Methacrylate | 5 | 4 | 1.0 |
| Acetate | 5 | 4 | 1.0 |
| C=n | 4 | 3 | 1.0 |
| Hydroxyl (O-H) | 4 | 3 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Ketone | 3 | 2 | 1.0 |
| Ester | 3 | 2 | 1.0 |
| Amide | 3 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Water (H2O) | 2 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 0.8 |
| Lignin | 1 | 1 | 0.8 |
| Adsorbed carbon monoxide | 1 | 0 | 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 |
|---|---|---|---|
| polyimide | 1602, 1720, 1778 | Carboxyl (COOH) | 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 1602 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
“The where from it was concluded that IR radiation induced a fast 2 3 1602cm-1 loading at is the typical C C stretching.”
Fernandez-Varela 等 - 2006 - Monitoring photooxidation of the Prestige's oil sp DOI: 10.1016/j.talanta.2005.10.006 -
C=n confidence 1.0
“cm-1 cm-1 1086 C-N stretching in amines, 1530 C=C Authors' contributions cm-1 stretching, 1602 C=N stretching (in ring),”
Hanif 和 Zaman - 2017 - Thiolation of arabinoxylan and its application in DOI: 10.1186/s40199-017-0172-2 -
Aromatic ring confidence 1.0
“2 cm-1, 1493cm-1 and 2851 the aromatic ring vibrations at 1602 and cm-1 and the lines due to the CH deformation vibrations at 1452 2 (Kondyurin et al., 2008;”
60MeV Ni ion induced modifications in nano-CdS/polystyrene composite films DOI: 10.1016/j.radphyschem.2013.06.022 -
confidence 1.0
“Text: 'The peaks at 3486 and 1602 represent N-H ODA.'”
Surface and structural changes in polyimide by 100 MeV Ag7+ ion irradiation DOI: 10.1016/j.surfcoat.2009.02.078 -
Hydroxyl (O-H) confidence 1.0
“cm-1 (which unusually shifted to lower frequency) 1602 O-H cm-1 and the stretching modes at 3340 and 3450 (not shown) show that water molecules around the thisassignmentisthatbyfurtherremovalofthesurfactant °C).35 headgroups are possibly in”
Nikoobakht 和 El-Sayed - 2001 - Evidence for bilayer assembly of cationic surfacta DOI: 10.1021/la010530o -
Water (H2O) confidence 1.0
“It was also worth pointing out that a peak near cm-1 1602 may rise from in-plane deformations of water molecules hydrogen-bonded to the cm-1 polysaccharide molecule [40].”
Rafe 和 Razavi - 2015 - Effect of Thermal Treatment on Chemical Structure DOI: 10.1080/10942912.2014.999864 -
Ring structure confidence 1.0
“NH+ ± Lysine asymmetric bending 1629 1 ± Tyrosine Ring vibration 1602 2 a Dataadoptedfromrefs[6,51].”
Sadat 和 Joye - 2020 - Peak Fitting Applied to Fourier Transform Infrared DOI: 10.3390/app10175918 -
Aromatic ring confidence 1.0
“In addition, bands at 1602 and cm-' (aromatic skeletal vibrations) either disappeared or decreased drastically.”
ZAVARIN 等 - 1990 - ANALYSIS OF SOLID WOOD SURFACES BY DIFFUSE REFLECT DOI: 10.1080/02773819008050253
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