Electrophilic substitution of benzeneAQA A-Level Chemistry: Mind map

Exam questions on Electrophilic substitution of benzene

1. In a laboratory preparation of nitrobenzene, a technician adds benzene slowly to a mixture of concentrated nitric acid and concentrated sulfuric acid. The flask is kept in a water bath at about 50 °C and stirred, and the nitrobenzene is later separated from the acids.
   Write an equation for the formation of the electrophile in this reaction and state the role of sulfuric acid overall.2 marks
2. A chemist wants to make phenylethanone, C₆H₅COCH₃, from benzene. The chemist adds ethanoyl chloride, CH₃COCl, to benzene in the presence of anhydrous aluminium chloride, AlCl₃, and warms the mixture. Hydrogen chloride gas is given off.
   Write an equation for the formation of the electrophile in this reaction and explain why the reagents and apparatus must be anhydrous.2 marks
3. A student prepares nitrobenzene, C₆H₅NO₂, from benzene using a mixture of concentrated nitric acid and concentrated sulfuric acid at 50 °C. The student uses 15.6 g of benzene (Mr = 78.0) and obtains 19.7 g of pure nitrobenzene (Mr = 123.0). The reaction is a monosubstitution of the ring.
   Calculate the percentage yield of nitrobenzene.3 marks