The most stabl enol tautomer of `MeCOCH_(2)CO_(2)Et` is

Options

A. `CH_(2)=C (OH)CH_(2)CO_(2)Et`
B. `MeC(OH)=CHCO_(2)Et`
C. `MeCOCH=C(OH)OEt`
D. `CH_(2)=C(OH)CH=C(OH)Et`

Explanation

To determine the most stable enol tautomer of the compound `MeCOCH2CO2Et` (ethyl acetoacetate), we will follow these steps:

### Step 1: Identify the Keto Form
The given compound is ethyl acetoacetate, which can be represented as:
\[ \text{CH}_3\text{C(=O)CH}_2\text{CO}_2\text{Et} \]
This is the keto form of the compound.

### Step 2: Draw the Enol Form
The enol form is obtained by the deprotonation of the alpha hydrogen (the hydrogen on the carbon adjacent to the carbonyl group) and the formation of a double bond between the alpha carbon and the carbonyl carbon. The enol form can be represented as:
\[ \text{CH}_3\text{C(=C(OH))CH}_2\text{CO}_2\text{Et} \]

### Step 3: Analyze the Stability of the Enol Form
The stability of the enol form can be influenced by several factors:
- **Hydrogen Bonding**: The enol can form intramolecular hydrogen bonds, which can stabilize the structure.
- **Resonance**: The enol can exhibit resonance stabilization due to the presence of the hydroxyl group.

### Step 4: Compare the Stability of Keto and Enol Forms
In general, keto forms are more stable than enol forms due to the presence of a carbonyl group. However, in some cases, the enol form can be stabilized by hydrogen bonding or resonance.

### Step 5: Conclusion
For ethyl acetoacetate, the enol tautomer is stabilized by intramolecular hydrogen bonding and resonance. Thus, the most stable enol tautomer of `MeCOCH2CO2Et` is:
\[ \text{CH}_3\text{C(=C(OH))CH}_2\text{CO}_2\text{Et} \]