Free radical substitution

• What is a free radical?


  Atoms/molecules with unpaired electron.

  Free radicals are very reactive.
• CH4(g) + Cl2(g) > CH3Cl(g) + HCl(g)


  Initiation: Cl2 > 2.Cl

  Propagation: .Cl + CH4 > .CH3 + HCl

  .CH3 + Cl2 > CH3Cl + .Cl

  Termination: .Cl + .Cl > Cl2

  .Cl + .CH3 > CH3Cl

  .CH3 + .CH3 > C2H6
• What does free radical substitution require?


  UV light. Gaseous states.
• What does ozone do?


  Protect earth from UV rays that cause skin cancer.
• Depletion of ozone (O3) layer?


  Caused by chlorofluorocarbons (CFCs)

  CF2CL2 > .CF2CL + .Cl (making free radical)

  .Cl + O3 > O2 + ClO.

  ClO. + O3 > 2O2 + Cl.

  Overall= 2O3 > 3O2
• Characteristics of homologous series?


  Chemically similar, gradual change in physical properties, differ by CH2 .
• Whatre CFCs used as?

  Solvents and refrigerants. They rise up to the ozone layer.