3.15 NMR

• why is NMR used?

  to help determine the structure of a molecule
• what are the two main types of NMR?

  1. Carbon-13 NMR - tells us information on how carbon atoms are arranged

  2. Proton NMR - tells us information on how hydrogen atoms are arranged
• when does an atomic nucleus have a nuclear spin?

  when there are an odd number of protons and neutrons
• what is tetramethylsilane (TMS)?


  - a reference compound

  - TMS shows a single sharp peak on NMR spectra, at a value of zero

  - sample peaks are then plotted as a 'shift' away from this reference peak
• why is TMS a suitable solvent for NMR analysis?

  - non toxic

  - does not react with the sample

  - easily separated from the sample molecule due to its low boiling point

  - produces one strong, sharp absorption peak on the spectrum
• how many adjacent protons are in a singlet splitting pattern?

  zero
• how many adjacent protons are in a double-splitting pattern?

  one
• how many adjacent protons are in a triplet-splitting pattern?

  two
• how many adjacent protons are in a quartet-splitting pattern?

  three