CHEM 109A CLAS Reactions of Alkenes Reagent(s) Groupsthat add Intermediate Regiochemistry Example of Regiochemistry Stereochemistry(Syn or Anti) Example of Stereochemistry H2 or D2 w/ Pt/C or Pd/C or Ni -H and -H Concerted N/A H2Pt/CHH Syn H2Pd/CHH H2O or ROH w/ H2SO4, HCl -H and –OH or –OR Carbocation* Markovnikov EtOHH2SO4OEtH Non-stereoselective (Syn and Anti) HOHOHHH2OH2SO4 1. Hg(OAc)2, H2O or ROH 2. NaBH4 -H and -OH or -OR Cyclic mercurinium ion -OH or -OR adds Markovnikov 1. Hg(OAc)2, MeOH2. NaBH4OMeH Anti 1. Hg(OAc)2, H2O2. NaBH4OHH 1. BH3, THF 2. NaOH, H2O2, H2O -H and –OH None, 1st step concerted Anti-Markovnikov 1) BH3, THF2) H2O2, H2O, NaOHHOH Syn 1) BH3, THF2) H2O2, H2O, NaOHHOHHOH Hydrogen Halide (HCl, HBr, HI) -H and –X Carbocation* Markovnikov HBrBrH Non-stereoselective (Syn and Anti) HClHClClH * Watch for carbocation rearrangement Page 1 of 2CHEM 109A CLAS Reactions of Alkenes Reagent(s) Groups that add Intermediate Regiochemistry Example of Regiochemistry Stereochemistry (Syn or Anti) Example of Stereochemistry Hydrogen Halide (HCl, HBr, HI) w/ peroxide (H2O2) -H and -X Carbon radical Anti-Markovnikov HBrHBrH2O2 Non-stereoselective (Syn and Anti) HClHHClHClHClCl Cl2 or Br2w/ CH2Cl2, benzene (nonpolar aprotic solvent) -X and –X Cyclic halonium ion N/A Cl2CH2Cl2ClCl Anti Br2CH2Cl2BrBrBrBr Cl2 or Br2w/H2O or ROH (protic solvent) -X and –OH or –OR Cyclic halonium ion -OH or -OR adds Markovnikov Br2H2OHOBr Anti Cl2MeOHClOMeOMeCl * Watch for carbocation rearrangement Page 2 of
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