Question

To prepare \(3\)-ethylpentan-\(3\)-ol, the reagents needed are

• A. \(\mathrm{CH_3CH_2MgBr + CH_3COCH_2CH_3}\)
• B. \(\mathrm{CH_3MgBr + CH_3CH_2CH_2COCH_2CH_3}\)
• C. \(\mathrm{CH_3CH_2MgBr + CH_3CH_2COCH_2CH_3}\)
• D. \(\mathrm{CH_3CH_2CH_2MgBr + CH_3COCH_2CH_3}\)

Hint:

Ketone \(+\) Grignard reagent: \[ \Rightarrow \] tertiary alcohol after hydrolysis.

Answer 1

The Correct Option is C

Step 1: Identify the target alcohol.
Given alcohol: \[ \mathrm{3\text{-}ethylpentan\text{-}3\text{-}ol} \] Structure: \[ \mathrm{ CH_3CH_2-C(OH)(CH_2CH_3)-CH_2CH_3 } \] The carbon containing: \[ OH \] is attached to: \[ 3\ \text{ethyl groups} \] Hence it is a: \[ \text{tertiary alcohol} \]

Step 2: Recall Grignard reaction.
A ketone reacts with Grignard reagent: \[ \mathrm{RMgX} \] to form a tertiary alcohol. To obtain: \[ 3\text{-ethylpentan-}3\text{-ol} \] we require: \[ \mathrm{CH_3CH_2COCH_2CH_3} \] which is: \[ \mathrm{pentan\text{-}3\text{-}one} \] and: \[ \mathrm{CH_3CH_2MgBr} \]

Step 3: Write the reaction.
\[ \mathrm{ CH_3CH_2COCH_2CH_3 + CH_3CH_2MgBr } \] followed by hydrolysis gives: \[ \mathrm{ (CH_3CH_2)_3COH } \] which is: \[ \mathrm{3\text{-}ethylpentan\text{-}3\text{-}ol} \]

Step 4: Identify the correct option.
Therefore: \[ \boxed{ \mathrm{ (C)\ CH_3CH_2MgBr + CH_3CH_2COCH_2CH_3 } } \]