Question

Reaction of butanone with methyl magnesium bromide following by hydrolysis gives

• A. $2$-methyl-$2$-butanol
• B. $2$-butanol
• C. $3$-methyl-$2$-butanol
• D. $2, 2$-dimethyl-$1$-butanol

Answer 1

Answer: (A)

$2$-methyl-$2$-butanol

Answer 2

The reaction of butanone with methyl magnesium bromide takes place in two steps. The first step involves the nucleophilic attack of the Grignard reagent to the carbonyl group to form an adduct and the second step involves hydrolysis of adduct preferably with diL $HCl$ or ${{H}_{2}}S{{O}_{4}}$ to for tertiary alcohol.
$\underset{addition\text{ }product}{\mathop{\left[ {{H}_{3}}C-\underset{\begin{smallmatrix} | \\\ C{{H}_{2}}C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix} C{{H}_{3}} \\\ | \end{smallmatrix}}{\mathop{C}}}\,-OMgBr \right]}}\,\xrightarrow[(ii){{H}^{+}}(hydrolysis)]{{}}$ $\underset{2-methyl-2-butanol}{\mathop{{{H}_{3}}C-\underset{\begin{smallmatrix} | \\\ C{{H}_{2}}C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix} C{{H}_{3}} \\\ | \end{smallmatrix}}{\mathop{C}}}\,-OH}}\,$