We have discussed in chemical properties of haloarenes that electrophilic substitution reactions are common in haloarenes and that haloarenes are o,p-directing groups.
We have already studied some electrophilic substitution reactions of benzene such as halogenation, sulphonation, nitration, friedel-crafts reactions in reactions of arenes . Let us see how haloarenes undergo these reactions :
In halogenation of haloarenes, ortho and para substitution occurs when dihalogen reacts with haloarenes in the presence of lewis acids such as Fe, FeCl3, AlCl3. The following reaction is an example of chlorination :
Nitration of haloarenes requires a mixture of conc. HNO3 and conc. H2SO4. The mixture is used to generate nitronium ion (NO2+), which acts as electrophile.
In sulphonation, sulphur trioxide (SO3) acts as electrophile. SO3 electrophile can be prepared as shown below :
Sulphonation reaction :
Friedel-Crafts reactions are the reactions of the benzene derivatives with alkyl halides or acyl halides in the presence of lewis acid catalysts (anhydrous AlCl3 for example).
Haloarenes and suitable alkyl halides in the presence of a Lewis acid catalyst form alkyl derivatives of benzene.
In Friedel-Crafts acylation, benzene derivatives are treated with acid chlorides(−COCl) or acid anhydrides ((−CO2)O) to produce aromatic ketones.
You should be able to solve the following conversions provided you have studied the previous tutorials.