Q12 / 150 · MHT CET 2026 (19 April Shift 1) · Chemistry
Identify the compound obtained when ethyl methyl ketone is treated with $\text{CH}_3\text{MgBr}$ and hydrolyzed.
- A$(\text{CH}_3)_3\text{C}-\text{OH}$
- Correct answerB$\text{C}_2\text{H}_5 - \overset{\overset{\text{CH}_3}{|}}{\underset{\underset{\text{CH}_3}{|}}{\text{C}}} - \text{OH}$
- C$(\text{C}_2\text{H}_5)_3\,\text{C}-\text{OH}$
- D$\text{CH}_3 - \overset{\overset{\text{C}_2\text{H}_5}{|}}{\underset{\underset{\text{C}_2\text{H}_5}{|}}{\text{C}}} - \text{OH}$
Solution
Ethyl methyl ketone is $\text{CH}_3-\text{CO}-\text{C}_2\text{H}_5$.
When it reacts with the Grignard reagent $\text{CH}_3\text{MgBr}$, the nucleophilic methyl group attacks the electrophilic carbonyl carbon to form an intermediate alkoxide.
$\text{CH}_3-\text{CO}-\text{C}_2\text{H}_5 + \text{CH}_3\text{MgBr} \rightarrow \text{CH}_3-\text{C}(\text{OMgBr})(\text{CH}_3)-\text{C}_2\text{H}_5$
Upon hydrolysis, the alkoxide is protonated to yield a tertiary alcohol.
$\text{CH}_3-\text{C}(\text{OMgBr})(\text{CH}_3)-\text{C}_2\text{H}_5 \xrightarrow{\text{H}_2\text{O}} \text{C}_2\text{H}_5-\text{C}(\text{CH}_3)_2-\text{OH} + \text{Mg}(\text{OH})\text{Br}$
The final product is 2-methylbutan-2-ol, which matches the structure $\text{C}_2\text{H}_5 - \overset{\overset{\text{CH}_3}{|}}{\underset{\underset{\text{CH}_3}{|}}{\text{C}}} - \text{OH}$.
Answer: $\text{C}_2\text{H}_5 - \overset{\overset{\text{CH}_3}{|}}{\underset{\underset{\text{CH}_3}{|}}{\text{C}}} - \text{OH}$
When it reacts with the Grignard reagent $\text{CH}_3\text{MgBr}$, the nucleophilic methyl group attacks the electrophilic carbonyl carbon to form an intermediate alkoxide.
$\text{CH}_3-\text{CO}-\text{C}_2\text{H}_5 + \text{CH}_3\text{MgBr} \rightarrow \text{CH}_3-\text{C}(\text{OMgBr})(\text{CH}_3)-\text{C}_2\text{H}_5$
Upon hydrolysis, the alkoxide is protonated to yield a tertiary alcohol.
$\text{CH}_3-\text{C}(\text{OMgBr})(\text{CH}_3)-\text{C}_2\text{H}_5 \xrightarrow{\text{H}_2\text{O}} \text{C}_2\text{H}_5-\text{C}(\text{CH}_3)_2-\text{OH} + \text{Mg}(\text{OH})\text{Br}$
The final product is 2-methylbutan-2-ol, which matches the structure $\text{C}_2\text{H}_5 - \overset{\overset{\text{CH}_3}{|}}{\underset{\underset{\text{CH}_3}{|}}{\text{C}}} - \text{OH}$.
Answer: $\text{C}_2\text{H}_5 - \overset{\overset{\text{CH}_3}{|}}{\underset{\underset{\text{CH}_3}{|}}{\text{C}}} - \text{OH}$
Hence, the correct answer is option: 'B'.