Alkene Reactions-III

For each of the reactions on the left, predict the major organic product. Pay particular attention to the regiochemistry of the reaction and the possibility of carbocation rearrangement.

Click the mouse on the reactant molecule to view the answer;

click on the reagent to review the mechanism and regiochemistry of the reaction.

The reaction of an alkene with BH3 in THF proceeds through the formation of an organo-borane intermediate with the boron bonded adjacent to the alkene carbon which would form the most stable carbocation (anti-Markovnikov addition). Work-up with alkaline peroxide results in the formation of an anti-Markovnikov alcohol with overall cis stereochemistry for the addition of H-OH.
































The reaction of an alkene with H2 in the presence of a catalyst such as Pt or Pd, results in the reduction of the alkene to give the corresponding alkane.
 















































The reaction of an alkene with OsO4 proceeds through the formation of a osmium diester intermediate in which two of the osmium oxygens are bonded to the carbons of the alkene.  Work-up with bisulfite results in the formation of a glycol (a 1,2-diol) with cis stereochemistry.  The same products are obtained from reaction with alkaline KMnO4;  this latter reaction does not require bisulfite work-up and proceeds through the formation of a permanganate diester, as above.
 






































The reaction of an alkene with BH3 in THF proceeds through the formation of an organo-borane intermediate with the boron bonded adjacent to the alkene carbon which would form the most stable carbocation (anti-Markovnikov addition).  Work-up with alkaline peroxide results in the formation of an anti-Markovnikov alcohol with overall cis stereochemistry for the addition of H-OH.
 




































The reaction of an alkene with BH3 in THF proceeds through the formation of an organo-borane intermediate with the boron bonded adjacent to the alkene carbon which would form the most stable carbocation (anti-Markovnikov addition).  Work-up with alkaline peroxide results in the formation of an anti-Markovnikov alcohol with overall cis stereochemistry for the addition of H-OH.
 




































The reaction of an alkene with H2 in the presence of a catalyst such as Pt or Pd, results in the reduction of the alkene to give the corresponding alkane.
 













































The reaction of an alkene with OsO4 proceeds through the formation of a osmium diester intermediate in which two of the osmium oxygens are bonded to the carbons of the alkene.  Work-up with bisulfite results in the formation of a glycol (a 1,2-diol) with cis stereochemistry.  The same products are obtained from reaction with alkaline KMnO4;  this latter reaction does not require bisulfite work-up and proceeds through the formation of a permanganate diester, as above.
 




































The reaction of an alkene with BH3 in THF proceeds through the formation of an organo-borane intermediate with the boron bonded adjacent to the alkene carbon which would form the most stable carbocation (anti-Markovnikov addition).  Work-up with alkaline peroxide results in the formation of an anti-Markovnikov alcohol with overall cis stereochemistry for the addition of H-OH.