Electrophilic substitution of benzeneEdexcel A-Level Chemistry: Mind map

Exam questions on Electrophilic substitution of benzene

1. Nitrobenzene is manufactured by reacting benzene with a mixture of concentrated nitric acid and concentrated sulfuric acid. The reaction is an electrophilic substitution and the reaction mixture is kept at about 50 °C.
   Write an equation for the formation of the electrophile in this reaction, and explain why the temperature is kept at about 50 °C rather than being allowed to rise much higher.2 marks
2. Phenol, C₆H₅OH, decolourises aqueous bromine at room temperature and forms a precipitate, whereas benzene does not react with aqueous bromine. In an experiment, 0.940 g of phenol was added to an excess of bromine water. Relative atomic masses: H = 1.0, C = 12.0, O = 16.0, Br = 79.9.
   Calculate the maximum mass of 2,4,6-tribromophenol, C₆H₂Br₃OH, formed in this experiment. Give your answer to three significant figures.2 marks
3. Phenylethanone, C₆H₅COCH₃, is made by reacting benzene with ethanoyl chloride, CH₃COCl, in the presence of anhydrous aluminium chloride, AlCl₃. This is a Friedel-Crafts reaction.
   Write an equation for the formation of the electrophile in this reaction. Explain the role of aluminium chloride and why it is classed as a catalyst.3 marks