Question

For each of the following alcohols, which method of synthesis, (a) hydroboration?oxidation or (b) oxymercuration?reduction, can produce the alcohol relatively free of constitutional isomers and diastereomers? (Drag an alcohol to the appropriate bin if it can be made by that method.)

Answer 1

Concepts and reason

The structures of some alcohols are given. Their synthesis path needs to be identified whether they are prepared through hydroboration-oxidation or oxymercuration-demercuration.

Distinguish the alcohols by drawing the corresponding alkene of the alcohol and then determining whether the alcohol is formed via Markovnikov’s or anti-Markovnikov’s rule.

Fundamentals

Hydroboration reaction of alkenes: The hydroboration of alkenes takes place in the presence of borane $\left( {{\rm{B}}{{\rm{H}}_3}} \right)$ and hydrogen peroxide in alkaline medium $\left( {{{\rm{H}}_2}{{\rm{O}}_2}/{\rm{O}}{{\rm{H}}^ - }} \right)$ to form alcohols. The reaction occurs in anti-Markovnikov’s fashion where the addition of hydroxyl group takes place on the carbon having more number of protons.

Oxymercuration-demercuration reaction: As the name suggests, it is a double reaction as described below:

• Oxymercuration: It involves the formation of hydroxymercurial compound via the reaction of alkenes with mercuric acetate and water in presence of tetrahydrofuran.

• Demercuration: It involves the formation of alcohol via the reduction of the hydroxymercurial compound with sodium borohydride.

The reaction occurs in Markovnikov’s fashion where the addition of hydroxyl group takes place on the carbon having less number of protons.

The following alcohols are formed via hydroboration oxidation reaction:

The following alcohols are formed via oxymercuration-demercuration reaction:

Ans: