Interpreting the infrared spectrum of propanone (acetone)

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses involving molecular spectroscopy analysing infrared spectra of propanone

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Spectra obtained from a liquid film of propanone. The right-hand part of the of the infrared spectrum of propanone, wavenumbers ~1500 to 400 cm^-1 is considered the fingerprint region for the identification of propanone and most organic compounds. It is due to a unique set of complex overlapping vibrations of the atoms of the molecule of propanone.

Interpretation of the infrared spectrum of propanone  (acetone)

The most prominent infrared absorption lines of propanone

The strongest and most characteristic absorption band of propanone is at wavenumbers ~1700 to 1725 cm^-1 for the stretching vibrations of the carbonyl group bond C=O.

There are multiple C-H absorptions at wavenumbers ~1215 to 1435 cm^-1 and ~3000 cm^-1, but non particularly characteristic of ketones.

The absence of other specific functional group bands will show that particular functional group is absent from the propanone molecular structure.