Alkene (C=C) — FTIR absorption peaks and assignments

Quick answer

Alkene (C=C) is usually assigned by looking for a recurring cluster of characteristic peaks rather than one exact textbook number. The table below shows where the literature most often places this group in FTIR, ranked by accumulated evidence.

Characteristic FTIR peaks for Alkene (C=C)

Showing the 30 best-supported peaks of 801 total for Alkene (C=C).

Spectrum logic

A functional-group assignment becomes more confident when several expected bands appear together. Use this page to find the strongest-supported peaks, then confirm that the same sample exhibits a coherent pattern rather than a single isolated hit.

Real-world usage

These pages are useful for unknown material analysis, peak explanation in reports, polymer troubleshooting, and verifying whether a candidate material family is chemically plausible.

Common mistakes

• Using one functional-group page as a complete material verdict without checking the rest of the spectrum.
• Assuming the strongest band is always the most diagnostic one.
• Forgetting that processing, additives, aging, and mixtures can shift or broaden expected peaks.

Verification advice

Use DSC, GC-MS, or TGA when several material families share similar bands or when mixture effects make the FTIR assignment uncertain.

Literature behind these assignments

• 968 cm⁻¹ confidence 1.0

  “and quantified by using Fourier-transform infrared (FTIR) spectroscopy, in the mid-region of 400-4000 cm-1, The FTIR analysis shows that two oil extracts (with and without heat) present a well-defined peak at 968 which represents the double”

  Analysis of trans fatty acids production and squalene variation during amaranth oil extraction DOI: 10.2478/s11532-012-0104-4
• 1535 cm⁻¹ confidence 1.0

  “As observed in the MWCNTs sample, a typical signal at 1535 shows the cm-1 C=C vibration of structural aromatic.”

  Synthesis and Physical Properties Characterization of Montmorillonite-modified Carbon Nanotubes Filler DOI: 10.1088/1757-899X/546/4/042004
• 1643 cm⁻¹ confidence 1.0

  “cm-1 peak at 1705.1 means that there is a bond of cm-1 -C=O, and also absorption at 1643.4 and medium intensity which shows the presence of C=C.”

  Grafting of Oleic Acid On Cyclic Natural Rubber Resiprene-35 Using Dicumyl Peroxide Initiator and Divinylbenzene Compatibilizers For Paint Binder In Polyamide Thermoplastics DOI: 10.13005/ojc/350119
• 1645 cm⁻¹ confidence 1.0

  “The small peak at 1645 is attributed to the stretching vibration of C=C [48], which becomes gradually stronger by increasing content of VMSG.”

  Novel Silica Functionalized Monosodium Glutamate/PVA Cross-linked Membranes for Alkali Recovery by Diffusion Dialysis DOI: 10.21203/rs.3.rs-283846/v1
• 1634 cm⁻¹ confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Modified Dioscorea hispida starch-based hydrogels and their in-vitro cytotoxicity study on small intestine cell line (FHS-74 Int) DOI: 10.1016/j.ijbiomac.2017.10.125
• 1634 cm⁻¹ confidence 1.0

  “35 36 cm-1 The twin weak absorption bands at 1634 and 1613 are from C=C stretching vibration while the 37 cm-1 38 absorbances at 2847 and 2940 are attributed to the stretching vibration of aliphatic C-H groups.”

  Electrosprayed PMMA microcapsules containing green soybean oil-based acrylated epoxy and a thiol: a novel resin for smart self-healing coatings DOI: 10.1088/1361-665X/ab9754
• 1578 cm⁻¹ confidence 1.0

  “2 (bottom) cm-1, bands were located at 1578 that the highest signal-to-noise ratio was found for a resulting from the cm-1, nominal resolution of 4 C=C stretching in chloroalkenes, at 1541, 1394, 1273 which also provided the cm-1,”

  Determination of iprodione in agrochemicals by infrared and Raman spectrometry DOI: 10.1007/s00216-007-1152-z
• 3275 cm⁻¹ confidence 1.0

  “The two prominent peaks at 3275.13 and 1635.54 are typical of N-H bond of amines and C=C stretch of alkenes or C=O stretch of amides [42] respectively.”

  Biomedical Applications of Cocoa Bean Extract-Mediated Silver Nanoparticles as Antimicrobial, Larvicidal and Anticoagulant Agents DOI: 10.1007/s10876-016-1055-2