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Carbon-13 NMR (A2 Only)

Chemistry: AQA A Level, topic 6.9.2

C13 NMR

The first type of NMR we shall look at is 13C NMR. This is slightly more simple than 1H NMR.

13C spectra

13C spectra

  • We can work out the different 13C environments from the 13C spectra.
  • In the spectra, different chemical shifts represent 13Cs in different environments.
  • Remember it is only the isotope 13C that this NMR works for, NOT the more common 12C.
  • 13C's abundance is only 1.1%.
Tetramethylsilane

Tetramethylsilane

  • Tetramethylsilane (TMS) is used during the 13C spectrum readings as a reference.
  • This is used because the chemical shifts along the x-axis are relative to the shift of TMS.
  • TMS is a good reference since it only produces one peak at 0ppm because each 13C is in the same environment.
    • For this reason, lots of spectra will have a single peak at 0ppm. Remember this is just your reference peak.
13C example

13C example

  • 13C NMR of ethanal. You need to look at a data table to determine the carbon environments represented by the peaks in the spectrum.
  • The peak at 200 ppm represents the carbon in the C=O bond.
  • The peak at 31 ppm represents the carbon in the C-C bond.
  • The peak at 0 ppm is the reference peak from TMS.

Test yourself on Carbon-13 NMR (A2 Only)

  • In a 13C spectrum, there are 4 peaks. How many 1H environments do the peaks represent?

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