alcohols

• What is an environmental concern of the use of organohalogen compounds?

  Ultraviolet (UV) radiation in the upper atmosphere can cause CFCs to produce halogen radicals.

  These radicals catalyse the breakdown of the Earth's protective ozone layer.

  CFCs are chlorofluorocarbons (haloalkanes containing chlorine, fluorine & carbon atoms only)
• What is the radical mechanism for the breakdown of ozone (O3)?

  Initiation: CF3Cl -> CF3. + Cl.

  Propagation: 1) Cl. + O3 -> ClO. + O2

  2) ClO. + O3 ->Cl. + 2O2

  Overall equation for the breakdown of ozone: 2O3 -> 3O2
• What is the benefit of ozone for living organisms?

  Ozone traps/reflects UV light  which can penetrate organisms' protective layers, like skin, so  it protects living things from ultraviolet radiation from the sun
• What is a dehydration reaction?

  a reaction where water is lost to form an organic compound
• What are the products of dehydration reaction of alcohol?

  alkene and water
• What are the conditions required for dehydration of alcohol?

  concentrated H2SO4 or H3PO4

  170oC
• electronegativity of the halogens decreases down the group

  a carbon-fluorine bond is more polar than a carbon-iodine bond

  the carbon-fluorine bond is shorter and stronger
• the greater the Mr of the halogen in the polar bond, the lower the bond enthalpy, meaning the bond can be broken more easily

  thus, rate of reaction increases down the group