Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?

Explanation

Due to the presence of six delocalised t-electrons, benzene ring behaves as a source of electrons and invites electrophiles (which are electron-deficient) to attack on it. This is why benzene undergoes electrophilic substitution reactions easily. Since nucleophiles are electron-rich species, benzene ring repels them. On account of this benzene undergoes nucleophilic substitution reactions with difficulty.