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Cationic Polymerization quiz

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  • What type of alkenes typically undergo cationic polymerization?
    Alkenes with electron-donating groups typically undergo cationic polymerization.
  • What initiates the cationic polymerization reaction?
    An electrophile, such as H+ or a Lewis acid like boron trifluoride, initiates the reaction.
  • What are the three main steps in the cationic polymerization mechanism?
    The three main steps are initiation, propagation, and termination.
  • How is the H+ ion generated in the initiation step?
    A Lewis acid, typically boron trifluoride, reacts with water to form an adduct that donates an H+ ion.
  • What happens to the alkene during the initiation step?
    The alkene uses its pi bond to grab the H+ ion, forming a carbocation.
  • Why are electron-donating groups important in cationic polymerization?
    Electron-donating groups stabilize the carbocation intermediate formed during the reaction.
  • Describe the propagation step in cationic polymerization.
    The monomer cation reacts with another monomer molecule, forming a new cation through head-to-tail addition.
  • What is meant by 'head-to-tail' addition in propagation?
    It refers to the pi bond of a new monomer attacking the carbocation at the end of the growing chain.
  • What are the two possible ways termination can occur in cationic polymerization?
    Termination can occur by removal of H+ (similar to beta elimination) or by nucleophilic attack by a counter ion.
  • What is the result of termination by H+ removal?
    The result is the formation of an alkene and regeneration of boron trifluoride and water.
  • How does nucleophilic attack terminate the polymerization?
    A counter ion from the initiation step attacks the carbocation, neutralizing the charge and ending the chain.
  • What role does boron trifluoride play in the mechanism?
    Boron trifluoride acts as a Lewis acid, helping to generate the H+ ion needed for initiation.
  • What happens to boron trifluoride at the end of the reaction?
    Boron trifluoride is regenerated during the termination step.
  • What is the significance of the carbocation intermediate in this mechanism?
    The carbocation intermediate allows for chain growth and is stabilized by electron-donating groups.
  • How does the mechanism of cationic polymerization exemplify electrophilic addition?
    The mechanism involves an electrophile (H+) adding to an alkene, forming a carbocation that propagates the chain.