What absorbs at 1616 cm⁻¹ in an FTIR spectrum?
A band near 1616 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 1616 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 | 12 | 10 | 1.0 |
| Aromatic ring | 9 | 8 | 1.0 |
| Alkene (C=C) | 8 | 7 | 1.0 |
| Carbonyl (C=O) | 8 | 7 | 1.0 |
| Methacrylate | 6 | 5 | 1.0 |
| Ketone | 6 | 5 | 1.0 |
| Ester | 6 | 5 | 1.0 |
| Carboxyl (COOH) | 6 | 5 | 1.0 |
| Acetate | 6 | 5 | 1.0 |
| Protein beta sheet | 5 | 4 | 1.0 |
| N h | 4 | 4 | 1.0 |
| Water (H2O) | 3 | 3 | 1.0 |
| C=n | 3 | 3 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Ring structure | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Chlorine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Nitrate | 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 |
|---|---|---|---|
| silk fibroin | 1616, 1050, 1511 | Amide | 1 |
| lignin | 1616, 1035, 1510 | 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 1616 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
-
Alkene (C=C) confidence 1.0
“New peaks appeared at 1616 and 1710 344 1 cm-1) that related to C=C stretching of newly formed polyaromatic, and, C=O stretching (1710 345”
Balan 等 - 2021 - Esterification of residual palm oil using solid ac DOI: 10.1016/j.jtice.2012.07.001. -
Alkene (C=C) confidence 1.0
“Both absorption peaks at cm-1 1616 and 1633 represented the C=C stretching vibration belonged to the aromatic ring in lignin [24].”
Hassan 和 Badri - 2014 - Lignin Recovery from Alkaline Hydrolysis and Glyce DOI: 10.1063/1.4895236 -
N-O bond confidence 1.0
“Loss of DNF and NPM was followed cm-1 using the 1616 and 1244 peaks (assigned to the -NO respectively).46,54 asymmetric and symmetric stretches,”
Probing Matrix Effects on the Heterogeneous Photochemistry of Neonicotinoid Pesticides, Dinotefuran and Nitenpyram DOI: 10.1021/acsearthspacechem.1c00059 -
confidence 1.0
“while the 1712 and 1616 cm-1 peaks are associated with amine stretching and C=C [47].”
Green Energy Generated in Single-Chamber Microbial Fuel Cells Using Tomato Waste DOI: 10.3390/su151310461 -
Amide confidence 1.0
“The intermolecular structure showed two signature peaks at 1616 cm-1 and 1623 [49], corresponding to 36% of the total amide I band.”
Sadat 和 Joye - 2020 - Peak Fitting Applied to Fourier Transform Infrared DOI: 10.3390/app10175918 -
Protein beta sheet confidence 1.0
“LLM confirmed rule peak-group candidate”
Wu 和 Zuo - 2011 - Research on Structure and Property of Silk Fibroin DOI: 10.4028/www.scientific.net/AMR.175-176.176 -
C c single bond confidence 1.0
“cm-1), H stretching (around 3431 C O group due to O cm-1), cm-1), (1616 C C and C N stretching (1381 O H cm-1) cm-1).”
Evaluation of different extracts and synthesised silver nanoparticles from leaves of Euphorbia prostrata against Haemaphysalis bispinosa and Hippobosca maculata DOI: 10.1016/j.vetpar.2012.02.001 -
Amide confidence 1.0
“There is also absorption at 1616 THERMOGRAVIMETRY ANALYSIS cm-1 wavenumber which indicates (-C-N) stretching The thermogravimetric analysis was performed by using (Rangel-Vazquez et al.”
Zainuddin 等 - 2018 - Synthesis and Thermal Properties of Poly(ethylene DOI: 10.17576/jsm-2018-4706-06
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