Interpreting the infrared spectrum of 1,1,2-trichloroethane

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 1,1,2-trichloroethane

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Spectra obtained from a liquid film of 1,1,2-trichloroethane. The right-hand part of the of the infrared spectrum of 1,1,2-trichloroethane, wavenumbers ~1500 to 400 cm^-1 is considered the fingerprint region for the identification of 1,1,2-trichloroethane and most organic compounds. It is due to a unique set of complex overlapping vibrations of the atoms of the molecule of 1,1,2-trichloroethane.

Interpretation of the infrared spectrum of 1,1,2-trichloroethane

The most prominent infrared absorption lines of 1,1,2-trichloroethane

As with any molecule with an alkyl group in the molecule, C-H stretching vibrations occur at wavenumbers 2975 to 2845 cm^-1 and 1470 to 1340 cm^-1.

For 1,1,1-trichloroethane, there are series of C-Cl vibrations bands of various modes at wavenumbers 800 to 580 cm^-1.

The absence of other specific functional group bands will show that a particular functional group is absent from the 1,1,2-trichloroethane molecular structure.