Which of the following expected to have `100%` enolic form?

Options

A.
B.
C.
D.

Answer

To determine which of the given compounds is expected to have 100% enolic form, we need to analyze the stability of the enol form compared to the keto form for each compound. The stability of the enolic form is influenced by factors such as hydrogen bonding and resonance stabilization.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four compounds to analyze. We need to look at their structures and functional groups to assess their ability to form enols.

2. **Understand Enol and Keto Forms**: Enols are the tautomeric forms of ketones, characterized by a hydroxyl group (-OH) and a double bond (C=C). The keto form has a carbonyl group (C=O). The stability of the enol form can be enhanced by hydrogen bonding and resonance.

3. **Analyze Each Compound**:
- **Compound 1**: This compound has potential for hydrogen bonding but lacks resonance stabilization. Therefore, it is unlikely to have a significant enolic form.
- **Compound 2**: This compound exhibits resonance stabilization, which can help stabilize the enolic form. However, the hydrogen bonding is weaker compared to other compounds.
- **Compound 3**: This compound has both strong hydrogen bonding and resonance stabilization due to the presence of a benzene ring. The enolic form can be significantly stabilized through resonance, making it likely to exist in a high percentage as an enol.
- **Compound 4**: While this compound may have some stability, it lacks the resonance stabilization provided by a benzene ring, making its enolic form less favorable.

4. **Conclusion**: Based on the analysis, Compound 3 is expected to have 100% enolic form due to the combination of strong hydrogen bonding and resonance stabilization.

### Final Answer:
**The compound expected to have 100% enolic form is Compound 3.**