Question

The enol form in which ethyl-3-oxobutanoate exists is

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The Correct Option is C

To determine the correct enol form of ethyl-3-oxobutanoate, we analyze the compound's tendency to undergo keto-enol tautomerism.

Step-by-step Analysis: 

1. Structure of Ethyl-3-oxobutanoate: This is a β-keto ester with a ketone at the 3-position and an ester at the 1-position. Such compounds readily exhibit keto-enol tautomerism. 

2. Enol Formation: The hydrogen at the alpha carbon (between the ester and ketone groups) is acidic and can be removed to form a double bond with the carbon adjacent to the ketone. The carbonyl oxygen of the ketone becomes an OH group. 

3. Stability of Enol: The most stable enol is typically the one where the OH group is hydrogen bonded to the ester oxygen, forming a six-membered ring. Additionally, conjugation between the C=C bond and the ester group enhances stability. 

4. Evaluating the Options: Among the given images, the correct enol form is the one where:
 - A C=C bond is formed between the alpha and carbonyl carbon 
- The ketone oxygen is converted into an OH group 
- Intramolecular hydrogen bonding and conjugation are possible 

Conclusion: The correct enol form is shown in the third image.