Skip to main content
Back

chapter 8

Control buttons has been changed to "navigation" mode.
1/20
  • What is an addition reaction in alkenes?
    An addition reaction converts a pi bond into a sigma bond, opposite of elimination.
  • Why are pi bonds more reactive than sigma bonds in addition reactions?
    Pi bonds act as Lewis bases (nucleophiles or Brønsted-Lowry bases) because their electrons are more exposed and reactive.
  • What is the relationship between addition and elimination reactions?
    Addition is the reverse of elimination, and often these processes exist in equilibrium.
  • What determines the regiochemistry in electrophilic addition to asymmetrical alkenes?
    Markovnikov's Rule: The electrophile adds to the less substituted carbon, and the proton adds to the carbon with more hydrogens.
  • What is the rate-determining step in hydrohalogenation?
    The formation of the carbocation intermediate is the rate-determining step.
  • What causes carbocation rearrangements during addition reactions?
    Hydride or methyl shifts occur to form a more stable carbocation intermediate.
  • What is Anti-Markovnikov addition and when does it occur?
    Anti-Markovnikov addition occurs in the presence of peroxides (ROOR), leading to the electrophile adding to the more substituted carbon.
  • Describe the acid-catalyzed hydration of alkenes.
    Water adds across the double bond with acid catalysis, forming an oxonium ion intermediate followed by nucleophilic attack by water.
  • What is hydroboration-oxidation and its regioselectivity?
    Hydroboration-oxidation adds water anti-Markovnikov, with OH adding to the less substituted carbon.
  • What is the stereochemistry of catalytic hydrogenation of alkenes?
    Catalytic hydrogenation adds H2 syn across the double bond, often using metal catalysts like Pt.
  • What is the mechanism of halogenation of alkenes?
    Halogenation proceeds via a bromonium ion intermediate and results in anti addition of halogens.
  • How are halohydrins formed from alkenes?
    Halohydrins form when halogens add to alkenes in water solvent, with water attacking the bromonium ion to add OH.
  • What determines the regioselectivity in halohydrin formation?
    The OH group adds to the more substituted carbon due to nucleophilic attack on the bromonium ion.
  • What is anti dihydroxylation and how is it achieved?
    Anti dihydroxylation adds two OH groups anti via an epoxide intermediate followed by acid-catalyzed ring opening.
  • What is syn dihydroxylation and common reagents?
    Syn dihydroxylation adds two OH groups syn in one step using reagents like OsO4 or cold KMnO4.
  • What is ozonolysis in alkene chemistry?
    Ozonolysis cleaves C=C bonds oxidatively using ozone, producing carbonyl compounds.
  • What are common reducing agents used after ozonolysis?
    Dimethyl sulfide and Zn/H2O are common reducing agents to convert ozonides to carbonyl products.
  • What is the role of the bromonium ion in halogenation?
    The bromonium ion is a three-membered ring intermediate that prevents carbocation formation and leads to anti stereochemistry.
  • Why does water attack the bromonium ion instead of Br- in halohydrin formation?
    Water is a better nucleophile under these conditions and attacks the more substituted carbon of the bromonium ion.
  • What is the stereochemical outcome of halogen addition to alkenes?
    Halogen addition occurs with anti stereochemistry, adding to opposite faces of the double bond.