Step 1: Understanding the Concept:
The synthesis of alcohols from carbonyl compounds using Grignard reagents (\( RMgX \)) is a fundamental organic reaction.
A Grignard reagent acts as a nucleophile and attacks the electrophilic carbonyl carbon.
- Reaction with Formaldehyde yields a Primary alcohol.
- Reaction with other Aldehydes yields a Secondary alcohol.
- Reaction with Ketones yields a Tertiary alcohol.
The target alcohol, 3-ethylpentan-3-ol, is a tertiary alcohol because the carbon with the \( -OH \) group is attached to three other carbon atoms.
Step 2: Key Formula or Approach:
Let's analyze the structure of 3-ethylpentan-3-ol:
Pentan-3-ol has a 5-carbon chain with the hydroxyl group on the 3rd carbon.
Adding an "ethyl" group to that same 3rd carbon means the central carbon is bonded to:
1. One Ethyl group (\( -CH_2CH_3 \)) from the main chain (left side).
2. One Ethyl group (\( -CH_2CH_3 \)) from the main chain (right side).
3. One Ethyl group (\( -CH_2CH_3 \)) added as a substituent.
The structure is effectively \( (CH_3CH_2)_3C-OH \).
To make this tertiary alcohol \( R_3C-OH \), we need a ketone \( R_2C=O \) and a Grignard reagent \( R-MgX \).
In this specific case, all three groups attached to the central carbon are ethyl groups.
Step 3: Detailed Explanation:
We need to combine a ketone with two ethyl groups and a Grignard reagent with one ethyl group.
- Ketone: Diethyl ketone, also known as pentan-3-one. Formula: \( CH_3CH_2COCH_2CH_3 \).
- Grignard Reagent: Ethyl magnesium bromide. Formula: \( CH_3CH_2MgBr \).
Let's check the options:
- (A) Ethyl magnesium bromide + Butanone (\( CH_3COCH_2CH_3 \)): The carbon already has a methyl and an ethyl group. Adding another ethyl group would give 3-methylpentan-3-ol. Incorrect.
- (B) Methyl magnesium bromide + Pentan-3-one (\( CH_3CH_2COCH_2CH_3 \)): This would also yield 3-methylpentan-3-ol. Incorrect.
- (C) Ethyl magnesium bromide + Pentan-3-one (\( CH_3CH_2COCH_2CH_3 \)): The ketone has two ethyl groups. The Grignard reagent adds the third ethyl group. This yields 3-ethylpentan-3-ol. Correct.
- (D) Propyl magnesium bromide + Acetone: This would give a completely different alcohol. Incorrect.
Step 4: Final Answer:
The reaction of Ethyl magnesium bromide with Pentan-3-one, followed by acidic hydrolysis, provides the specific spatial arrangement of three ethyl groups around a single hydroxylated carbon atom.
Therefore, the correct reagents are given in option (C).