Reactions of Alkenes

Attachments:

• Reactions of Alkenes - created from Mind Map

1. Free Radical Addition of HBr: Anti-Markovnikov Addition
   1. Does NOT include HCl or HI
   2. Peroxides give rise to free radicals that initiate addition

      Annotations:

      • The oxygen-oxygen bonds are relatively weak so it can break to give any two alkoxy radicals
      • Alkoxy radicals (R - O) initiate the anti-Markovnikov addition of HBr

Annotations:

• Adding excess H2O to drive the equilibrium toward the alcohol
• Follows Markovnikov's rule
• May take place with rearrangement

1. Hydration by Oxymercuration-Demercuration

   Annotations:

   • Makes alcohols
   • Follows Markovnikov's orientation
   • No free carbocation is formed so no rearrangements or polymerization can occur
   • Reagent used is mercuric acetate, Hg(OCOCH3), which is abbreviated as Hg(OAc)2

Annotations:

• Alcohol solvent Alcohol is the nucleophile that attacks the mercurinium ion
• Makes ethers
• Follows Markovnikov's orientation

Annotations:

• Anti-Markovnikov's orientation
• BH3 adds to the double bond of an alkene to give an alkyborane

1. Oxidation

   Annotations:

   • H2O2 (peroxide) oxidizes the alkylborane to an alchol

Annotations:

• Solvents must be inert to halogens CH2Cl2-methylene chloride CHCl3-chloroform CCl4-carbon tetrachloride
• Anti-addition because the nucleophilic halide must do a back-side attack

1. Halohydrins

   Annotations:

   • Forms alcohols with a halogen on adjacent carbons
   • Water is the solvent and nucleophile
   • Back-side attack by the nucleophile ensures anti-addition
   • Follows Markovnikov's orientation

Annotations:

• Syn-addition
• A reduction with H2 gas adding across a double bond to produce an alkane
• Catalyst required is usually Pt, Pd, or Ni.
• Alkene is usually dissolved in alcohol, an alkane, or acetic acid

Annotations:

• Carbenes - uncharged, reactive intermediates that have a carbon atom with two bonds and two non-bonding electrons
• Forms cyclopropanes

1. Simmons-Smith Reaction

   Annotations:

   • Reagent is methylene iodide added to a zinc-copper couple (zinc dust). Also called a carbenoid.
   • The cis or trans stereochemistry of the products is retained from the reactants

Annotations:

• Converts alkenes into different functional groups
• Uses peroxyacids which are carboxylic acids with an extra oxygen atom 
• cis or trans stereochemistry is retained from the reactant

1. Acid-Catalyzed Opening of Epoxides

   Annotations:

   • An acid protonates the epoxide and water, the nucleophile, attacks the protonated epoxide to open the ring and form the 1,2 diol (glycol)
   • Anti-stereochemistry of hydroxyl groups

Annotations:

• Both reactions will produce syn stereochemistry in the products

1. Osmium Tetroxide
2. Permanganate Dihydroxylation

Annotations:

• Break the C-C double bond to form carbonyl groups
• Aldehydes further oxidize to carboxylic acids

Annotations:

• Break C-C double bonds to generate carbonyl groups
• Aldehydes are not further oxidized