Organic Chemistry MCAT Practice Exam

Friedel-Crafts reactions typically follow an electrophilic substitution mechanism. In these reactions, an aromatic compound, such as benzene, reacts with an electrophile to form a substituted aromatic product.

The core of this mechanism involves the generation of a highly reactive electrophile, often created in situ from a metal halide and an alkyl or acyl halide. Once the electrophile is formed, it can then attack the π electrons of the aromatic ring. This attack disrupts the aromaticity temporarily, leading to the formation of a carbocation intermediate. Afterward, a proton is removed to restore aromaticity, resulting in the substituted aromatic product.

This electrophilic substitution mechanism is characteristic of aromatic compounds due to the stability offered by resonance, which stabilizes the intermediate formed during the reaction. As a result, the Friedel-Crafts reaction exemplifies the behavior of electrophiles in reacting with the electron-rich π system of the aromatic ring, making it an excellent illustration of electrophilic substitution in organic chemistry.