AROMATIC ELECTROPHILIC SUBSTITUTION REACTIONS
The electrophilic substitution reactions of aromatic ring are very common. The electron rich aromatic ring easily reacts with an electrophile to yield a substituted ring. On the other hand nucleophilic substitution on aromatic ring demands the ring to be sufficiently electron deficient to make it convenient for the nucleophile to react.
Two of the common electrophilic aromatic substitution reactions are nitration and sulfonation of benzene.
NITRATION OF BENZENE
The nitration of benzene takes place in the presence of a nitrating mixture (nitric acid + sulfuric acid). The mixture reacts first to yield an electrophile that is the nitronium ion in this case, which is attacked by the pi electrons of benzene ring to produce nitrobenzene.
A detailed stepwise mechanism and reaction conditions are discussed in the above video.
SULFONATION OF BENZENE
Sulfonation is the second type of electrophilic aromatic substitution reaction. This reaction is carried out in the presence of oleum (H2SO4 + SO3), yielding benzene sulfonic acid as the final product. The electrophile in this reaction is the sulfonium ion formed by the reaction of sulfur trioxide with sulfuric acid.
A detailed stepwise mechanism and reaction conditions are discussed in the above video.
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