Can some please explain to me the mechanism of nitration of acetanilide. The explanation in words is better for me. Thank you
The Correct Answer and Explanation is:
The nitration of acetanilide is an example of an electrophilic aromatic substitution reaction. In this process, a nitro group (NO₂) is introduced onto the benzene ring of acetanilide. The overall reaction typically involves the use of a mixture of concentrated nitric acid and concentrated sulfuric acid, which together generate the nitronium ion (NO₂⁺), the key electrophile in this reaction.
The mechanism begins when nitric acid reacts with sulfuric acid. Sulfuric acid acts as a stronger acid and protonates the nitric acid, leading to the formation of water and the nitronium ion. The nitronium ion is highly reactive and seeks out electron-rich areas such as the aromatic ring of acetanilide.
Acetanilide has an acylated amino group (NHCOCH₃) attached to the benzene ring. This group is an activating group that donates electron density to the ring through resonance, particularly directing substitution to the ortho and para positions. Due to steric hindrance, the nitration tends to occur predominantly at the para position.
Once the nitronium ion approaches the benzene ring, it reacts with the electrons in the π system of the aromatic ring at the para position, forming a resonance-stabilized sigma complex (also called an arenium ion). This intermediate is not aromatic and therefore not very stable. To restore aromaticity, a proton is removed from the carbon that was attacked, usually by a base such as the bisulfate ion.
The result of the reaction is para-nitroacetanilide as the major product. A small amount of ortho-nitroacetanilide may also form but is less favored due to steric effects.
In summary, nitration of acetanilide involves generating a nitronium ion, electrophilic attack at the para position of the benzene ring, formation of a resonance-stabilized intermediate, and restoration of aromaticity through deprotonation.
