Benzene formed nitrobenzene at temperature of 600 0 C when it reacts with mixture of concentrated trioxonitrate(V) acid and concentrated

Assessment: JAMB UTME - Chemistry - 2024 Subject: Chemistry

Question 1 Report

Benzene formed nitrobenzene at temperature of 600 0 C when it reacts with mixture of concentrated trioxonitrate(V) acid and concentrated 
Answer Details

The reaction described is the nitration of benzene to form nitrobenzene. This is an example of an electrophilic aromatic substitution reaction. **Nitration** involves replacing a hydrogen atom on a benzene ring with a nitro group (NO2). This reaction requires a nitrating mixture composed of concentrated nitric acid (trioxonitrate(V) acid) and concentrated sulfuric acid (tetraoxosulphate(VI) acid). Let me explain why:


Nitration is typically carried out using a mixture of **concentrated nitric acid and concentrated sulfuric acid** at a temperature of around **60°C**. The role of sulfuric acid in this mixture is to act as a catalyst and a dehydrating agent. It helps generate the nitronium ion (NO2+), which is the active electrophile that attacks the benzene ring.


Here's a simplified mechanism for this reaction:


  • The concentrated sulfuric acid protonates the nitric acid, forming nitronium ion (NO2+).
  • This powerful electrophile (NO2+) then attacks the electron-rich benzene ring, leading to the formation of an arenium ion.
  • Lastly, the arenium ion loses a proton to regenerate the aromatic character of the benzene ring, resulting in the formation of nitrobenzene.

None of the other options listed (hydrochloric acid, phosphoric acid, and hydrogen iodide) contain the necessary combination of properties to generate the nitronium ion and facilitate the nitration of benzene.


Therefore, the correct mixture to carry out the nitration of benzene, forming nitrobenzene at a temperature of 60°C, is a combination of **concentrated nitric acid and concentrated sulfuric acid (tetraoxosulphate(VI) acid)**.

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