Halogenoalkanes

• Nucleophillic substitution: rates of reaction with halogenoalkanes

  The lower the bond enthalpy of the halogen-carbon bond, the faster the reaction will be. 

  This is because lower bond enthalpies result in lower activation energies: 
• how do you measure reactivity of nucleophilic substitution with halogenoalkanes ?

  1. Dissolve halogenoalkanes in ethanol. 
  2. Add silver nitrate and water in the form of aqueous silver nitrate.
  3. The water reacts with the halogenoalkane to produce an alcohol and a halide ion
  4. The halide ion that’s produced reacts with the silver nitrate to form a precipitate
  5. Measure how long it takes for the silver-halide precipitates to form.

   

  The quicker the precipitate forms, the faster the reaction.
• What is the reaction mechanisms for the decomposition of ozone

  Initiation - C2F4Cl2 —> C2F4Cl. + Cl.

  Propagation -

  Cl.+ O3 —> ClO.+ O2

  ClO. + O3 —> 2O2 + Cl.

  overall - 2O3 —> 3O2