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!
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:
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.