CIE A Level Chemistry (9701) exams from 2022

Revision Notes

8.1.6 Use of Tetramethylsilane (TMS)

Use of Tetramethylsilane (TMS)

  • In NMR spectroscopy, Tetrametylsilane (TMS) is used as a reference compound
  • The organic compound is dissolved in TMS before being introduced to the magnetic field of the spectrometer
  • It is an ideal chemical to use as a reference
    • TMS is inert and volatile
    • This reduces undesirable chemical reactions with the compound to be analysed
    • It also mixes well with most organic compounds
  • TMS gives a single sharp peak on the NMR spectrum and is given a value of zero
  • The molecular formula of TMS is Si(CH3)4
    • There are 12 hydrogens in this molecule
    • All of the protons are in the same molecular environment. Therefore gives rise to just one peak
    • This peak has a very high intensity as it is accounting for the absorption of energy from 12 1H nuclei

Tetramethylsilane (TMS) – Si(CH3)4

  • When peaks are recorded from the sample compound, they are measured and recorded by their shift away from the sharp TMS peak
  • This gives rise to the chemical shift values for different 1H environments in a molecule

 

Analytical Techniques - TMS 1H NMR, downloadable AS & A Level Chemistry revision notes

 1H NMR spectrum for TMS showing it’s signal at 0 ppm

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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