The Carbon-13 NMR spectrum of propylamine (1-aminopropane)

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 C-13 NMR spectra of propylamine

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TMS is the acronym for tetramethylsilane, formula Si(CH₃)₄, whose ¹³C atoms are arbitrarily given a chemical shift of 0.0 ppm. This is the 'standard' in ¹³C NMR spectroscopy and all other ¹³C shifts, called chemical shifts, depend on the individual (electronic) chemical environment of the ¹³C atoms in an organic molecule - propylamine here.

Interpreting the C-13 NMR spectrum of propylamine

As you can see from the diagram above there are only 3 chemical shift lines in the C-13 NMR spectrum of propylamine indicating 3 different chemical environments of the carbon atoms.

CH₃CH₂CH₂NH₂

(Note the 3 colours indicating the 3 different chemical environment of the carbon atoms in propylamine).

Note the decreasing effect on the chemical shift as the carbon atom is further from the highly electronegative nitrogen atom of propylamine.

The C-13 NMR spectra a provides evidence of 3 different carbon atom environments in the propylamine molecule from 3 different chemical shifts (ppm).