haloalkanes and the environment

• Chlorofluorocarbons

  CFC are class of organic compounds that contain chlorine + fluorine atoms

  • gases at room temperature so after use they disperse into air

  → as they diffuse through the layers of the atmosphere , they’re exposed to UV radiation

  therefore homolytic fission occurs

  C2F2Cl2

  initiation:

  C2F2Cl2 →C2F2Cl ‘ + Cl’

  1st propagation:

  Cl’ + O3 → ‘ClO + O2

  2nd propagation:

  ‘ClO + O3 → Cl’ + 2O2

  Overall:

  2O2 → 3O2
• • ozone layer is full of O3
  • ozone is toxic to humans in troposphere + key contributor to photochemical smog

  →absorbs UV-C radiation and most of UV-B radiation it can cause genetic damage; skin cancer + cataracts

  • UV-A has low energy + doesn’t pose any health concerns; also not absorbed by ozone layer

  stratosphere is decomposed naturally by UV radiation + so more ozone is made in the process
• other radicals formed

  • ozone layers is shrinking + no ozone layers in the troposphere in some areas due

  →scientists have researched through satellite ~+ ground stations that the ozone layer is reduced by 4% , CFC have been in atmosphere for 50 + years from satellites since 1970s

  other radicals :

  • ‘NO + O3 → ‘NO2 + O2
  • ‘NO2 + O3 → ‘NO3 + O2
  • O3 + O → O2