Alkene Reaction Mechanisms

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Author:
brownianmover
ID:
47497
Filename:
Alkene Reaction Mechanisms
Updated:
2010-11-10 09:59:12
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Alkene mechanisms
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Description:
Review on step-by-step process for alkene reactions.
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  1. Addition of Hydrogen Halide to Alkene
    • 1. Protonation to form Carbocation Intermediate
    • 2. Halide (EN element) attack protonated Carbon
  2. Reaction: Addition of Hydrogen Halide to Alkene

    RCH = CH2 + HX -->
    • RCHCH
    • --X
  3. Acid-Catalyzed Addition of Water Mechanism
    • 1. Protonation with H+ from H3O+ to least substituted carbon
    • 2. Nucleophile (H2O)adds to carbocation creating protonated alcohol
    • 3. Excess H2O removes proton from protonated alcohol, regenerating H3O+
  4. Reaction: Acid-Catalyzed Addition of Water

    RCH = CH2 + H2O H2SO4>
    • RCHCH3
    • --OH
  5. Mechanism: Acid-Catalyzed Addition of An Alcohol
    • 1. Protonation with H+ from alcohol
    • 2. Nucleophile (R-O) adds to carbocation creating protonated ether
    • 3. Excess alcohol removes proton
  6. Reaction: Acid Catalyzed Addition of Alcohol
    RCH = CH2 + CH3OH H2SO4>
    • RCHCH3
    • -OCH3
  7. Acid catalyzed reaction of an alkene with water creates an:
    Alcohol
  8. Acid catalyzed reaction of alkene with alcohol creates an:
    Ether
  9. Mechanism: Addition of Hydrogen Halide to Alkyne
    • 1. Relatively weak pi bond breaks because pi electrons are attracted to electrophilic proton.
    • - electrophile add to sp2 carbon bonded to greater number of hydrogens
    • 2. Positively charged carbocation intermediate reacts rapidly with negatively charged halide ion.
  10. Give major product of the following reaction:
    HC= CCH3 HBr >
    • CH2=CCH3
    • --------Br
  11. Product of addition of electrophilic reagent to an alkyne is an _________, meaning __________ can occur if in the presence of excess hydrogen halide.
    alkene

    second electrophilic addition reaction
  12. Give the major product of the following reaction:
    CH3C= CCH3 excess HBr>
    • -----Br
    • CH3CCH2CH3
    • -----Br
  13. The initial product of acid-catalyzed addition of water to an alkyne is:
    enol
  14. An enol immediately rearranges into:
    ketone
  15. A ketone and an enol only differ in the location of a _______ and a ________
    • double bond
    • hydrogen
  16. ___________ are isomers that are in rapid equilibrium
    Tautometers

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