A Nucleophilic Aromatic Displacement Reactions of Aryl Halides

The carbon-halogen bonds of aryl halides are like those of alkenyl halides in being much stronger than those of alkyl halides. The simple aryl halides generally are resistant to attack by nucleophiles in either SN1 or Sn2 reactions. However, this low reactivity can be changed dramatically by changes in the reaction conditions and the structure of the aryl halide. In fact, nucleophilic displacement becomes quite rapid

1. when the aryl halide is activated by substitution with strongly electron-attracting groups such as NO₂, and
2. when very strongly basic nucleophilic reagents are used.