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Addition Reactions of Furan quiz

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  • What is the relationship between aromaticity and the electronegativity of the heteroatom in five-membered heterocycles?
    There is an inverse relationship; as the electronegativity of the heteroatom increases, aromaticity decreases.
  • Which heteroatom in five-membered heterocycles is the most electronegative?
    Oxygen is the most electronegative heteroatom among sulfur, nitrogen, and oxygen.
  • How does the aromaticity of furan compare to thiophene and pyrrole?
    Furan has the lowest aromaticity, while thiophene has the highest and pyrrole is intermediate.
  • Why does furan act most like a diene among five-membered heterocycles?
    Because it is the least aromatic, furan behaves more like a diene in addition reactions.
  • What type of reaction can furan undergo due to its diene-like behavior?
    Furan can undergo Diels-Alder reactions similar to cyclopentadiene.
  • What is a dienophile in the context of Diels-Alder reactions?
    A dienophile is an alkene or alkyne that reacts with a diene, often enhanced by electron-withdrawing groups.
  • What happens to the pi bonds during the Diels-Alder reaction of furan?
    The pi bonds rearrange to form a new six-membered ring with specific stereochemistry.
  • Which product is favored in the Diels-Alder reaction of furan?
    The endo product is favored, resulting in a specific arrangement of substituents.
  • How does the stereochemistry of the endo product manifest in the Diels-Alder reaction?
    Substituents such as carboxylic acids are cis and point down, while hydrogens point up.
  • What structural change occurs to the oxygen atom in furan during the Diels-Alder reaction?
    The oxygen bends up out of the way in the three-dimensional structure of the product.
  • How does the Diels-Alder reaction of furan compare to that of cyclopentadiene?
    The process is similar, but furan's heteroatom (oxygen) affects the product's structure and reactivity.
  • What is the effect of increasing electronegativity of the heteroatom on the reactivity of five-membered heterocycles?
    Increasing electronegativity decreases aromaticity, making the compound more reactive in addition reactions.
  • Why does thiophene react differently from furan in addition reactions?
    Thiophene is more aromatic due to sulfur's lower electronegativity, making it less reactive than furan.
  • What is the role of resonance stability in the reactivity of heterocyclic compounds?
    Lower resonance stability (less aromaticity) increases the compound's tendency to undergo addition reactions.
  • What is the general structure of furan and how does it relate to butadiene?
    Furan is a five-membered ring with two double bonds and an oxygen atom, resembling butadiene bridged by a heteroatom.