Interpreting the infrared spectrum of iodoethane (ethyl iodide)

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 iodoethane

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

Interpretation of the infrared spectrum of iodoethane

The most prominent infrared absorption lines of iodoethane

C-H stretching vibrations at wavenumbers ~2880 to 3080 cm^-1.

C-H bending/deformation vibrations at wavenumbers ~1300 to 1500 cm^-1.

C-C stretching vibrations peaking at wavenumbers ~1200 cm^-1.

Characteristic groups of C-I vibrations at wavenumbers ~500 to 600 cm^-1.

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