Name and draw the mechanism by which benzene reacts with ethanoyl chloride in the presence of a catalyst. Also explain why benzene undergoes a substitution reaction, rather than an addition reaction.
Electrophilic substitution. (drawn) AlCl3 + CH3COCl --> AlCl4- + CH3CO+ (drawn) Then the electrophile CH3CO+ attracts electrons from benzene's delocalised ring to form an intermediate, that the AlCl4- reacts with to remove the hydrogen, producing HCl, AlCl3, and phenylethanone. Benzene undergoes substitution rather than addition because this maintains the stable delocalised ring in benzene.
