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Epoxide Reactions quiz

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  • Why are epoxides more reactive than ethers?
    Epoxides are more reactive because their three-membered ring structure is highly strained, making them eager to undergo ring-opening reactions.
  • What is the first step in an acid-catalyzed epoxide ring opening?
    The first step is protonation of the epoxide oxygen by the acid.
  • In acid-catalyzed ring opening, which carbon does the nucleophile attack?
    The nucleophile attacks the more substituted carbon of the epoxide ring.
  • What is the product arrangement in acid-catalyzed epoxide opening?
    The nucleophile ends up on the more substituted carbon, and an alcohol forms on the least substituted carbon.
  • What is the first step in a base-catalyzed epoxide ring opening?
    There is no protonation step; the nucleophile directly attacks the epoxide.
  • In base-catalyzed ring opening, which carbon does the nucleophile attack?
    The nucleophile attacks the least substituted carbon of the epoxide ring.
  • What is the typical product of base-catalyzed epoxide opening with NaOH?
    The typical product is an anti vicinal diol, where two alcohols are added to adjacent carbons in a trans (anti) fashion.
  • What does 'vicinal diol' mean in the context of epoxide reactions?
    A vicinal diol means two alcohol groups are added to adjacent carbons.
  • Why do both acid- and base-catalyzed epoxide openings give anti products?
    Because opening the three-membered ring forces the substituents to end up on opposite sides (anti) due to ring strain.
  • How can you distinguish between anti and syn vicinal diols?
    Anti vicinal diols have alcohols on opposite sides (trans), while syn vicinal diols have them on the same side (cis); the mechanism determines which forms.
  • What is unique about using NaOH in base-catalyzed epoxide opening?
    Using NaOH specifically leads to anti vicinal diols, which is important for distinguishing from syn diol formation.
  • What happens to the O- formed in base-catalyzed epoxide opening?
    The O- is typically protonated in a subsequent step, often by water, to form an alcohol.
  • What determines the regioselectivity in acid-catalyzed epoxide opening?
    Regioselectivity is determined by the nucleophile attacking the carbon that can best stabilize positive charge, usually the more substituted carbon.
  • What determines the regioselectivity in base-catalyzed epoxide opening?
    The nucleophile attacks the least substituted carbon because it is less hindered and more accessible.
  • What is the key difference between acid- and base-catalyzed epoxide ring opening?
    Acid-catalyzed opening favors attack at the more substituted carbon after protonation, while base-catalyzed opening favors attack at the least substituted carbon without protonation.