NMR-C13

• what is nuclear spin different?

  Have different energy levels depending on whether their spin is aligned with or against the applied magnetic field
• what do you need to consider to determine the peaks?


  symmetry
• what is chemical shift dependent on?

  • if an carbon is attached to an electronegative, pulls electron density away from the carbon atoms (deshielded)
  • hybridisation: saturated carbon nuclei are more shielded. Electrons in a pi bond less effective at shielding the nucleus because electron distribution around nucleus (more deshielded)
  • carbon nuclei that are unsaturated and bonded to oxygen are even more deshielded
• Peak c=o

  200-150
• c=c

  150-100
• o-c

  100-50
• saturated c

  50-0
• what does peak height tell us?

  in c13 nmr

  tells us the amount of carbons in an environment

  Quaternary carbon atoms (fully substituted)
• how does delocalization affect c nmr?

  can lead to partial positive or negative character

  more positive = more deshielded

  more negative = more shielded
• which electrons push into the aromatic ring?

  oh

  ome

  nh2
• which are electron withdrawing group?

  Co2Me

  CN

  NO2