Question
Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?
Solution
Benzene is a rich source of an electron because of the presence of electron cloud containing 
-electrons above and below the plane of the ring. As a result, it attracts the electrophiles (electron-deficient species) towards it and repels nucleophiles (electron-rich species). Hence benzene undergoes electrophilic substitution reactions easily.
