Reactions of Aromatic Compounds

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Reactions of Aromatic Compounds
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Electrophilic Aromatic Substitution

• Electrophile substitutes for a hydrogen on the
  benzene ring.

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Mechanism
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Bromination of Benzene

• Requires a stronger electrophile than Br2.
• Use a strong Lewis acid catalyst, FeBr3.

Animation
Animation
Animation
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Energy Diagramfor Bromination
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Chlorination and Iodination

• Chlorination is similar to bromination. Use
  AlCl3 as the Lewis acid catalyst.
• Iodination requires an acidic oxidizing agent,
  like nitric acid, which oxidizes the iodine to an
  iodonium ion.

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Nitration of Benzene

• Use sulfuric acid with nitric acid to form the
  nitronium ion electrophile.

NO2 then forms a sigma complex with benzene,
loses H to form nitrobenzene. gt
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Sulfonation

• Sulfur trioxide, SO3, in fuming sulfuric acid is
  the electrophile.

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Desulfonation

• All steps are reversible, so sulfonic acid group
  can be removed by heating in dilute sulfuric
  acid.
• This process is used to place deuterium in place
  of hydrogen on benzene ring.

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Nitration of Toluene

• Toluene reacts 25 times faster than benzene. The
  methyl group is an activator.
• The product mix contains mostly ortho and para
  substituted molecules.