Alkenes

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Alkenes

• Addition Reactions
• Synthesis

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Addition of HBr or HClMarkovnikov Addition
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HBr Addition with RO-ORAnti-Markovnikov
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Free-Radical Mechanism
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Addition of Br2
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A Similar Mechanism to the Addition of HBr?
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Trans is formed exclusively(No cis is formed)
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Carbocation can be Stabilized by Neighboring Br
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Bromonium Ion is Opened Equally from Both Sides
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Definitions

• Stereospecific only one stereoisomer is formed
  at the expense of the other (e.g. trans vs. cis)
• Stereoselective one stereoisomer is formed
  preferentially over the other.

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Bromonium Ion Intermediate
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Halohydrins
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Bromohydrin FormationAddition of Br
OHStereospecific Regiospecific
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Unsymmetrical Bromonium ionH2O opens ring at
more hindered site
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Br and OH are trans in anti addition
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Catalytic Hydrogenationsyn addition
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Mechanism Syn Addition
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Syn Addition of H2
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Hydrogenationall alkene p bonds are reduced
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Hydrogenated Vegetable Oil
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HydrationAddition of H2O
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Oxymercuration HydrationMarkovnikov
additionRegiospecific Reaction
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Oxymercuration Mechanism
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Predict the Oxymercuration Hydration Products
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What Alkene would you use to Make These Alcohols?
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Hydroboration Hydration Anti-Markovnikov Syn
addition
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BH3 adds to Alkene
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Hydroboration
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Regiochemistry is Anti-Markovnikov
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Syn Addition of H2O
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Draw the Major Products
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2 Complementary Hydration Reactions
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Oxymercuration the more highly substituted
alcohol formsHydroboration the less highly
substituted alcohol forms
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Predict Both Oxymercuration and Hydroboration
Products
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Epoxide PreparationFrom Halohydrins
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Mechanism
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Epoxide groups are Common in Biologically Active
Molecules
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A New Class of Anti-tumor Agents
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Ozonolysis Forms 2 Carbonyl Compounds
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OzonolysisAlkene Cleavage
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Mechanism of Ozonolysis
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What Alkene will Undergo Ozonolysis to Give the
Products Shown?
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Problem

• A symmetrical unknown compound A, C8H16,
  reacts with H2 on a 1 Pt/C catalyst to form B
  (C8H18). Treatment of A with O3 followed by
  Zn/HOAc affords butanone only. Identify A and B.

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