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Blocking Groups - Sulfonic Acid quiz

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  • What is the only reversible electrophilic aromatic substitution (EAS) reaction?
    Sulfonation is the only reversible EAS reaction.
  • What reagent is used to carry out sulfonation of benzene?
    Concentrated sulfuric acid is used for sulfonation.
  • What group is formed on benzene during sulfonation?
    A sulfonic acid group is formed during sulfonation.
  • How can the sulfonic acid group be removed from benzene?
    It can be removed with heat, acid, or steam.
  • Why is sulfonic acid considered a blocking group in synthesis?
    Because it is not present in the final product and is used only to facilitate ortho substitution.
  • What position does sulfonation typically block on toluene?
    Sulfonation typically blocks the para position.
  • What is the typical yield of para sulfonation on toluene?
    Over 90% yield is achieved for para sulfonation.
  • What type of director is the CH3 group on toluene?
    The CH3 group is an ortho/para director.
  • What type of director is the sulfonic acid group?
    Sulfonic acid is a meta director and a strong deactivator.
  • Why is ortho substitution usually not highly favored in EAS reactions?
    Ortho substitution is not highly favored due to steric hindrance.
  • How does blocking the para position affect ortho substitution?
    Blocking the para position forces ortho substitution, increasing its yield.
  • What happens to the sulfonic acid group after the EAS reaction is complete?
    It is removed by desulfonation using dilute acid, leaving only a hydrogen.
  • What is the main purpose of using a blocking group in aromatic synthesis?
    The main purpose is to control the position of substitution, such as favoring ortho over para.
  • What is the sequence of steps in a typical blocking group strategy for ortho substitution?
    First, sulfonation to block para, then EAS for ortho substitution, and finally desulfonation to remove the blocking group.
  • Why is the sulfonic acid group not found in the final product after blocking group strategy?
    Because it is removed after the desired substitution, serving only as a temporary blocking group.