Interpreting the infrared spectrum of 1-iodopropane (n-propyl 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 1-iodopropane

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See also comparison of the infrared, mass, 1H NMR and 13C NMR spectra of the four isomers of C₄H₉I

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

Interpretation of the infrared spectrum of 1-iodopropane

The most prominent infrared absorption lines of 1-iodopropane

C-H stretching vibration absorptions. peaking at wavenumbers ~2845 to 2975 cm^-1.

C-H bending/deformation vibrations absorption bands peaking at wavenumbers ~1370 to 1470 cm^-1.

C-C-C skeletal vibrations from the CH₃-C-CH₃ grouping occur at wavenumbers ~1140 to 1175 cm^-1. and 840 to 790 cm^-1.

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

The absence of other specific functional group bands will show that a particular functional group is absent from the 1-iodopropane molecular structure.