The Carbon-13 NMR spectrum of propanamide (propionamide)

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 propanamide

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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 - propanamide here.

propanamide (propionamide), C₃H₇NO, , ,

Interpreting the C-13 NMR spectrum of Propanamide

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

CH₃CH₂CONH₂

Note the 3 colours indicating the 3 different chemical environment of the carbon atoms in propanamide.

Note the decreasing effect on the chemical shift as the carbon atom is further from the highly electronegative oxygen and nitrogen atoms of propanamide.

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