Nucleophiles and leaving groups in substitution reactions
Substitution reactions at saturated carbon involve displacement of a group bonded to that carbon by a nucleophile.
The group that is displaced is referred to as the leaving group.
Substitution reactions are faster if the leaving group is better .
When comparing two leaving groups, the better leaving group
The group that is displaced is referred to as the leaving group.
CH3Br + –OH 
CH3OH + Br–
The nucleophile in this reaction is hydroxide ion; the leaving group is bromide ion.
The atom in the leaving group that was originally bonded to carbon is one unit more negative in the product.
The atom in the nucleophile that becomes bonded to carbon is one unit more positive in the product.
CH3OH + Br–The nucleophile in this reaction is hydroxide ion; the leaving group is bromide ion.
The atom in the leaving group that was originally bonded to carbon is one unit more negative in the product.
The atom in the nucleophile that becomes bonded to carbon is one unit more positive in the product.
Substitution reactions are faster if the leaving group is better .
When comparing two leaving groups, the better leaving group
is the weaker base (X– > H2O > –OH where X = Br or Cl or I).
has a larger atom to stabilise the negative charge. (I– > Br– > Cl–).
has a larger atom to stabilise the negative charge. (I– > Br– > Cl–).