HaloAlkanes - AS Chemistry

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  • Created by: Tom94
  • Created on: 01-03-11 13:45


a nucleophile is an electron pair donor and have at least 1 lone pair of electrons. they have a partial or full negative charge and are attracted to the slightly positive electron deffiecient atoms. Examples of these are:OH- , CN- , NH3 and H2O. Remember to always drAw them there lone pair!







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The Mechanism

the nucleophile uses its lone pair to provide the electrons for a new bond.

the halogen is displaced. carbon can only have 8 electrons in its outer shell.

the nucleophile replaces the halogen.

the mechanism is there for known as:





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the steps in the mechanism

  • nucleophiles have lone pair of electrons
  • the carbon-hydrogen bond is polar
  • a curly arrow is drawn from the lone pair to the slightly positive carbon atom
  • a curly arrow is used to shown the movement of a pair of electrons
  • carbon is restricted to only 8 electrons in its outer shell, so a bond must be broken.
  • the polar carbon-hydrogen bond breaks.
  • the second curly arrow shows the shared pair moving onto the halogen
  • the halogen now has its own electron pair back plus the pair from the carbon atom
  • it is now a negativly charged halide ion
  • a halide ion (leaving the group) is displaced.


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thankyou this helped

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