Question

What will be compound $A$ in the following reaction?

A.)

B.)

C.)

D.)

Answer 1

Hint: In this question, this reaction happens by the mechanism of oxymercuration-demercuration mechanism in which the hydroxyl group that is $OH$ attaches to the most substituted carbon and $H$ attaches to the least substituted carbon.

Complete step by step solution:
In this given reaction the regents given that are $Hg(OAc)/THF$ and $NaB{H_4}/NaOH$ are the reagents of oxymercuration-demercuration reaction. Here, in these reagents $Ac$ represents acetone. This oxymercuration- demercuration reaction is a two step pathway that is used to produce corresponding alcohol by the hydration of the alkene. That is by reacting alkene with reagents of oxymercuration- demercuration reaction we can get corresponding alcohol. The oxymercuration- demercuration reaction follows the Markovnikov regioselectivity rule. According to Markovnikov regioselectivity rule, the $OH$ group will attach to the most substituted carbon and the $H$ (Hydrogen) will attach to the least substituted carbon.
In the given alkene,

The carbon number $1$ of alkene functional group is least substituted so the hydrogen ($H$) will attach with the carbon number $1$ and the carbon number $2$ of alkene group is more substituted so hydroxyl group ($OH$) will attach with carbon number $2$. Hence the final reaction can be represented as:
$
  {\text{ }}C{H_3}{\text{ }} \\
  {\text{ |}} \\
  {H_3}C - C - CH = C{H_2}{\text{ }}\xrightarrow[{(ii)NaB{H_4},NaOH}]{{(i)Hg{{(OOCC{H_3})}_2}/THF}} \\
  {\text{ |}} \\
  {\text{ }}C{H_3} \\
 $$
  {\text{ }}C{H_3}{\text{ }} \\
  {\text{ |}} \\
  {H_3}C - C - CH(OH)C{H_3} \\
  {\text{ |}} \\
  {\text{ }}C{H_3} \\
 $

Hence, option (A) is the correct answer.

Note: Always remember that the oxymercuration- demercuration reaction mechanism follows the Markovnikov regioselectivity rule and when alkene reacts with these reagents of oxymercuration demercuration mechanism then the product formed is a corresponding alcohol.