Carbonyl (C=O) — FTIR absorption peaks and assignments

Quick answer

Carbonyl (C=O) 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 Carbonyl (C=O)

Showing the 30 best-supported peaks of 1083 total for Carbonyl (C=O).

Possible materials

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

• 1735 cm⁻¹ confidence 1.0

  “The new peak appears cm-1 at 1735 which indicates the presence of a C=O bond from carboxylic acid.”

  Synthesis and Physical Properties Characterization of Montmorillonite-modified Carbon Nanotubes Filler DOI: 10.1088/1757-899X/546/4/042004
• 1731 cm⁻¹ confidence 1.0

  “LLM confirmed rule peak-group candidate”

  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
• 1672 cm⁻¹ confidence 1.0

  “The most intense bands were the carbonyl peak at 1672 cm-1 and the benzene ring stretching at 1514, 1477, and 1392 cm-1.”

  FTIR Approaches for Diuron Determination in Commercial Pesticide Formulations DOI: 10.1021/jf050268f
• 747 cm⁻¹ confidence 1.0

  “Therefore, the ging band appears between 850 and regions, even though only one carbonyl group is present, prob746cm-1 747cm-1 in the infrared and in Raman is band at ably due to Fermi resonance.”

  Fourier transform infrared and Raman spectral assignments and analysis of 7-amino-4-trifluoromethylcoumarin DOI: 10.1016/j.saa.2006.09.044
• 2137 cm⁻¹ confidence 1.0

  “The peak value at 2137, and 3391 The presence of alkyl, benzyl, methyl, 500 nm showed a characteristic wavelength for the synthesis and carbonyl groups in the molecule and the polar groups like -OH -NH of gold nanoparticles to increase in a”

  Biogenic Synthesis of Gold Nanoparticle from Enicostema axillare and Their In Vitro Cytotoxicity Study Against MCF-7 Cell Line DOI: 10.1007/s12668-019-00656-6
• 1723 cm⁻¹ confidence 1.0

  “The characteristics sharp peak at 1723 is attributed to stretching vibration of carbonyl (-C=O) group from GMSG/VMSG [46, 47], the intensity of which increases with the increase of GMSG/VMSG contents in the membrane”

  Novel Silica Functionalized Monosodium Glutamate/PVA Cross-linked Membranes for Alkali Recovery by Diffusion Dialysis DOI: 10.21203/rs.3.rs-283846/v1
• 1695 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
• 1746 cm⁻¹ confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Quantitative Investigations of Biodiesel Fuel Using Infrared Spectroscopy: An Instrumental Analysis Experiment for Undergraduate Chemistry Students DOI: 10.1021/ed101097n