Free radicals

• Free radical substitution pt1

  First stage is the initiation forming a free radical

  • An equation to show this Cl2 → 2Cl•
  • It must occur until UV light
• Free radical substitution pt2

  The second stage is the propagation

  • Always in two steps
  • e.g. formula CH4 + Cl• → •CH3 + HCl
  • And then •CH3 + Cl2 → CH3Cl + Cl•
  • The halogens remove the hydrogens
• Free radical substitution pt3

  The last stage is termination where 2 free radicals cancel each other out

  • E.g. Cl• + Cl• → Cl2
  • And Cl• + •CH3 → CH3Cl
• The initiation step is breaking the Cl-Cl bond to form chlorine atoms using UV light.

  • The chlorine molecule absorbs the energy from the UV light causing the bond to break
  • Since the atoms are the same , the Cl-Cl bond break homolytically so one electron goes to each chlorine atom
  • This forms 2 highly reactive free radicals