Answer
🧪 Grignard Reaction with Ethyl Butyrate
Reaction Overview
Reaction Type: Nucleophilic addition of a Grignard reagent to an ester
Reactants: Ethyl butyrate + 2 equivalents of CH3CH2CH2MgBr + H3O+
Step-by-Step Explanation
Step 1: First Nucleophilic Attack
The Grignard reagent (propylmagnesium bromide) attacks the electrophilic carbonyl carbon in ethyl butyrate, forming a tetrahedral intermediate. The ethoxy group is eliminated, forming a ketone intermediate (heptan-4-one).
Step 2: Second Nucleophilic Attack
A second equivalent of Grignard reagent attacks the ketone to form a tertiary alkoxide intermediate.
Step 3: Acidic Workup
Acidic hydrolysis (H3O+) protonates the alkoxide to yield the final alcohol.
Final Product
4-Propylheptan-4-ol — a tertiary alcohol.
Structure: CH3CH2CH2–C(CH2CH2CH3)2–OH
Summary Table
| Step | Reactant | Intermediate/Product | Description |
|---|---|---|---|
| 1 | Ethyl butyrate + 1 equiv. Grignard | Heptan-4-one | Ester converted to ketone |
| 2 | Heptan-4-one + 1 equiv. Grignard | Tertiary alkoxide | Ketone converted to alkoxide |
| 3 | Acidic workup (H3O+) | 4-Propylheptan-4-ol | Alkoxide protonated to alcohol |
Key Concepts
- Grignard reagents react with esters to give tertiary alcohols when used in excess.
- The reaction requires two equivalents of the Grignard reagent.
- Intermediate steps include formation of a ketone followed by a tertiary alkoxide.