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Carbene quiz

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  • What is the product when a double bond reacts with a carbene or carbenoid in a cyclopropanation reaction?
    The product is a cyclopropane, a three-membered ring structure.
  • Why are carbenes considered highly reactive intermediates?
    Carbenes are highly reactive because they violate the octet rule, having only six electrons around the carbon atom.
  • What is the formal charge on a typical carbene?
    A typical carbene has a formal charge of zero.
  • What happens to the stereochemistry of the cyclopropane ring formed in cyclopropanation?
    The cyclopropane ring is always formed as a cis product due to ring strain and the mechanism of addition.
  • How can the hydrogens on a carbene be substituted in cyclopropanation reactions?
    The hydrogens can be replaced with other atoms like halogens, such as bromine or chlorine.
  • What is the role of tert-butoxide in generating a carbene from a trihalogenated compound?
    Tert-butoxide acts as a strong base, abstracting a hydrogen and facilitating alpha elimination to generate the carbene.
  • What is alpha elimination in the context of carbene generation?
    Alpha elimination involves removing a hydrogen and a halogen from the same carbon to form a carbene.
  • What is diazomethane and how does it generate a carbene?
    Diazomethane is a compound with a diazo group that, upon exposure to light or heat, releases nitrogen gas and forms a carbene.
  • Why is nitrogen gas so stable when released from diazomethane?
    Nitrogen gas is stable due to its strong triple bond and inert nature, making it unlikely to react further.
  • What is the Simmons-Smith reaction used for?
    The Simmons-Smith reaction is used to add a cyclopropane ring to a double bond using diiodomethane and a zinc-copper couple.
  • What is the key reagent formed in the Simmons-Smith reaction?
    The key reagent is iodozincmethyl iodide, also known as the Simmons-Smith reagent.
  • Does the final cyclopropane product from the Simmons-Smith reaction contain iodine atoms?
    No, the final cyclopropane product does not contain iodine atoms; the iodines are removed during the reaction.
  • What is the difference between a carbene and a carbenoid?
    A carbene is a neutral carbon species with two nonbonded electrons, while a carbenoid is a compound that behaves like a carbene but is not a true carbene.
  • How many main methods for cyclopropanation were discussed in the lesson?
    Four main methods for cyclopropanation were discussed: direct carbene addition, alpha elimination, diazomethane, and the Simmons-Smith reaction.
  • What is the general mechanism shared by all cyclopropanation reactions discussed?
    All cyclopropanation reactions involve the addition of a CH2 group to a double bond, forming a three-membered cyclopropane ring.