Question

How is the following conversion carried out?

\[\ce{Methyl magnesium bromide -> 2-Methylpropan-2-ol}\]

Answer 1

When methyl magnesium bromide is treated with propane, an adduct forms that gives 2-methylpropane-2-ol on hydrolysis.

\[\begin{array}{cc}
\ce{H3C}\phantom{..................................}\\
\backslash\phantom{.............................}\\
\ce{C = O + CH3 - MgBr ->}\phantom{.}\\
/\phantom{............................}\\
\ce{H3C}\phantom{..................................}
\end{array}\]\[\begin{bmatrix} 
\ce{CH3}\phantom{.}\\
|\phantom{.....}\\
\ce{CH3 - C - \overset{-}{O}\overset{+}{Mg}Br}\\
|\phantom{.....}\\
\ce{\underset{Adduct}{CH3}}\phantom{.}\\
\end{bmatrix}\]\[\begin{array}{cc}
\ce{OH}\phantom{.........}\\
|\phantom{............}\\
\ce{->[H2O]CH3 - C - CH3 + Mg(OH)Br}\\
|\phantom{.............}\\
\ce{\underset{2-Methylpropan-2-ol}{CH3}}\phantom{..........}\\
\end{array}\]

Answer 2

\[\begin{array}{cc}
\phantom{....................}\ce{O}\phantom{............................}\ce{CH3}\\
\phantom{................}||\phantom{..............................}|\\
\ce{\underset{bromide}{\underset{Methyl magnesium}{H3C - MgBr}} + C ->[(i) Dry ether][(ii) H3O+] CH3 - C - OH}\\
\phantom{..............}/\phantom{.}\backslash\phantom{.............................}|\\
\phantom{....................}\ce{\ce{H3C}\phantom{....}\ce{CH3}\phantom{..............}\underset{2-Methylpropan-2-ol}{CH3}}
\end{array}\]