Interpreting the infrared spectrum of N,N-dimethylmethanamine (N,N-dimethylmethylamine, trimethylamine)

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 N,N-dimethylmethanamine (trimethylamine)

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

Interpretation of the infrared spectrum of N,N-dimethylmethanamine (trimethylamine)

The most prominent infrared absorption lines of N,N-dimethylmethanamine (trimethylamine)

Around 3000 to 2800 cm^-1 are absorptions due to C-H stretching vibrations.

N-CH₃ vibrations occur at wavenumbers 2820 to 2760 cm^-1 and overlap with the C-H vibration absorptions quoted above.

Absorption due to C-N vibrations, characteristic of C-N bonds in aliphatic amines like trimethylamine occur at 1220 to 1020 cm^-1.

There are no N-H vibration absorptions because tertiary amines do NOT have a N-H bond, which, in terms of infrared spectra, distinguishes them from primary and secondary aliphatic amines.,

The absence of other specific functional group bands will show that a particular functional group is absent from the N,N-dimethylmethanamine (trimethylamine) molecular structure.