Give the mechanism to generate nitronium ion and explain the role of sulfuric – [Free] B100
Give the mechanism to generate nitronium ion and explain the role of sulfuric acid.
Question:
1. Give the mechanism to generate nitronium ion and explain the role of sulfuric acid.
Answer:
🔷 Step 1: Protonation of Nitric Acid
Sulfuric acid (H2SO4), being a much stronger acid than nitric acid (HNO3), donates a proton to nitric acid. This protonation occurs typically at one of the oxygen atoms, forming protonated nitric acid.
HNO3 + H2SO4 → [H2NO3]+ + HSO4−
🔶 Step 2: Formation of the Nitronium Ion
The protonated nitric acid is unstable and loses a molecule of water, thereby generating the nitronium ion (NO2+), which is a powerful electrophile.
[H2NO3]+ → NO2+ + H2O
Overall: HNO3 + H2SO4 → NO2+ + HSO4− + H2O
🟠 Role of Sulfuric Acid:
- Proton Donor: It efficiently protonates nitric acid, increasing its reactivity.
- Dehydrating Agent: Removes water formed during the reaction, driving the equilibrium forward and enhancing the yield of NO2+.
- Maintains Electrophile Concentration: Prevents the reverse reaction by absorbing water, ensuring a high concentration of the nitronium ion for effective electrophilic substitution.
🔍 This mechanism is fundamental in nitration reactions, especially for aromatic systems such as benzene where the nitronium ion serves as the key electrophile.