# Benzene undergoes nitration when heated with a mixture of concentrated nitric acid and concentrated sulfuric acid. Explain the mechanism by which nitrobenzene is formed, including the role of concentrated sulfuric acid and the type of reaction involved.

> Edexcel A-Level Chemistry (9CH0) — 18.1 Aromatic chemistry · Explain · 5 marks

> Nitrobenzene, C₆H₅NO₂, is an important industrial chemical used in the manufacture of dyes and pharmaceuticals. It is produced by reacting benzene with a nitrating mixture at approximately 55 °C.

## Mark scheme (5 marks)

1. Concentrated sulfuric acid acts as a catalyst / protonates concentrated nitric acid to generate the nitronium ion (NO₂⁺)
2. The nitronium ion (NO₂⁺) is the electrophile that attacks the benzene ring
3. The electrophile is attracted to / attacks the delocalised π electron system of benzene, forming a positively charged intermediate
4. A proton (H⁺) is lost from the intermediate / the ring re-aromatises by loss of H⁺
5. The overall reaction is electrophilic substitution (not addition)

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