-H + Formation of electrophile HNO 3 + H 2 SO 4 + HSO 4 - + H 2 O NO 2 + Reaction of electrophile with aromatic compound NO 2 + + H nitronium ion NITRATION – ELECTROPHILIC SUBSTITUTION H + + HSO 4 - → H 2 SO 4
Reactions with halogens React in the presence of a catalyst called a halogen carrier Benzene + Chlorine Chlorobenzene + Hydrochloric acid Common halogen carriers are FeCl 3, AlCl 3 and AlBr 3
Reactions with halogens –mechanism of reaction Electrophilic substitution Br 2 + FeBr 3 → Br + + FeBr 4 - The halogen carrier reacts with the halogen molecule to produce the halide ion which then goes on to react with the benzene
Comparing benzene with alkenes o benzene is more stable (1) o benzene π electrons are delocalised (1) o benzene has lower electron density (1) o so bromine is less polarised /attracted to it / benzene is less susceptible to electrophiles (1)
Finishing off Draw the complete mechanism for the nitration of benzene. Include the reaction conditions and catalyst Draw the complete reaction for the chlorination of benzene
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