FURTHER SUBSTITUTION

• HOW MAY AN ATOM OR GROUP ON THE BENZENE RING AFFECT A SUBSTITUTION REACTION?

  1. Make it more or less susceptible to further electrophilic substitution
  2. Direct further substitution to particular positions on the ring
• HOW CAN AN ATOM OR GROUP CHANGE THE BENZENE SUSCEPTIBILITY TO FURTHER ELECTROPHILIC SUBSTITUTION?

  ELECTRON-RELEASING: more susceptible

  ELECTRON-WITHDRAWING: less susceptible
• HOW CAN AN ATOM OR GROUP CHANGE POSITION OF FURTHER SUBSTITUTION?

  ELECTRON-RELEASING: 2,4,6

  ELECTRON-WITHDRAWING: 3,5
• EXAMPLES OF ELECTRON RELEASING GROUPS?

  • CH3
  • OCH3
  • OH
  • NH2
• EXAMPLES OF ELECTRON WITHDRAWING GROUPS?

  • NO2
  • COCl
• EXCEPTIONS TO FURHTER SUBSITUTIONS RULE?

  halogens

  -> withdraw electrons but direct further substitution to positions 2 and 4