Page 162 - Pharm.Org.Chem-I 02-06-05-101
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A noteworthy example of electrophilic aromatic substitution in nature is biosynthesis
of the thyroid hormone thyroxine, where iodine is incorporated into benzene rings
that are derived from tyrosine.
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Nitration of benzene occurs with a mixture of concentrated nitric and sulfuric acids (catalyst).
Mechanism:
• Nitric acid accepts a proton from sulfuric acid, then the protonated nitric acid dissociates to
form a nitronium cation.
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