nmr

• in carbon NMR, each set of equivalent C atoms is represented by one peak
• in hydrogen NMR, each set of equivalent H atoms is represented by one peak
• TMS (tetramethylsilane) is used to calibrate the NMR spectrum
• TMS is used because

  • only gives one signal
  • signal is far away from the H signals
  • non toxic
  • inert
  • low boiling point so can be removed easily
• NMR spectra are recorded on a scale called the chemical shift, measured in ppm
• in hydrogen NMR each signal is split into separate peaks to represent hydrogen atoms on neighbouring carbon atoms
• peak split = number of Hydrogens on neighbouring carbons + 1

  e.g. 3 split (triplet) means there are 2 hydrogens on neighbouring carbons
• solvents for NMR do not interfere with the results

  • CCl4
  • CDCl3
• CCl4 and CDCl3 are good solvents in NMR because they don't create any signals as they don't have hydrogens