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18.11: Electrophilic Aromatic Substitution: Nitration of Benzene

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JoVE Core
Organic Chemistry

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Electrophilic Aromatic Substitution: Nitration of Benzene
 
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18.11: Electrophilic Aromatic Substitution: Nitration of Benzene

The nitration of benzene is an example of an electrophilic aromatic substitution reaction. It involves the formation of a very powerful electrophile, the nitronium ion, which is linear in shape. The reaction occurs through the interaction of two strong acids, sulfuric and nitric acid.

Figure1

Sulfuric acid is stronger and protonates the nitric acid on the hydroxyl group, followed by loss of water molecule, generating the nitronium ion.

Figure2

The nitronium ion acts as an electrophile that reacts with benzene to form a resonance-stabilized arenium ion. The arenium ion then loses its proton to a Lewis base forming nitrobenzene.

Figure3

The resulting nitro group can be reduced to a primary amino group. Reduction is achieved either by hydrogenation with a transition metal catalyst such as nickel, palladium, or platinum under mild conditions or upon treatment with metals in aqueous acid. Iron, zinc, and tin in dilute HCl are widely used reducing agents. However, ammonium ion is obtained as a salt under acidic conditions, which is then treated with a base such as sodium hydroxide to liberate the free amine.

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Electrophilic Aromatic Substitution Nitration Of Benzene Nitronium Ion Sulfuric Acid Nitric Acid Arenium Ion Nitrobenzene Reduction Hydrogenation Transition Metal Catalyst Iron Zinc Tin Ammonium Ion Primary Amino Group

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