alkanes & alkenes

• free radical

  atom or group of atoms that has an unpaired electron
• homolytic fission

  when a bond breaks in a way such that each of the atoms involved in forming the bond acquired 1 of the 2 bonding electrons, forming free radicals
• why do alkanes generally lack reactivity?

  non-polar

  • lack high e- density regions, dont attract electrophiles
  • lack e- deficient regions, dont attract nucleophiles

  relatively strong C-C C-H bonds, dont break under normal conditions
• why does FRS not stop immediately after UV removed

  • UV results in homolytic cleavage of CL2 to give CL radicals which are highly reactive, reaction stars immediately
  • when initiation stops, free radicals are still being regenerated in propagation step, reaction continues
• alkenes reactant

  sym: 1 pdt

  unsym: more than 1
• why are alkenes highly reactive?

  1. e- rich C=C: attracts electrophile
  2. sigma bond stronger than pi bond, bond easily broken, undergoes addition reaxtions
• why alkene cant be red by lialh4

  As NaBH4 is a hydride source, the reduction involves the H− nucleophile. Since the carbon atom of the C=C group in alkenes do not have a partial positive charge/ is not electrophilic, it will be unable to attract the H− nucleophile, hence reduction will not occur