Electrophilic and nucleophilic aromatic substitution: Analogous and complementary processes

Analysis of many variants of nucleophilic aromatic substitution of hydrogen proceeding according to an addition-elimination pattern reveals that this is the major reaction pathway, whereas nucleophilic replacement of halogen or another nucleofugal group is the secondary process, i.e., ipso-substitution, In this respect electrophilic and nucleophilic aromatic substitution can be considered as analogous processes.