Which of the following compounds can be synthesized by intramolecular aldol condensation in very good yield ?

Options

A.
B.
C.
D.

Answer

To determine which compounds can be synthesized by intramolecular aldol condensation in very good yield, we need to analyze the given options based on the characteristics of intramolecular aldol reactions.

### Step-by-Step Solution:

1. **Understanding Intramolecular Aldol Condensation**:
- Intramolecular aldol condensation occurs when a molecule contains both an aldehyde or ketone functional group and an active hydrogen atom in the same molecule, allowing it to react with itself to form a cyclic compound.
- The reaction typically leads to the formation of a β-hydroxy carbonyl compound, which can then dehydrate to form an α,β-unsaturated carbonyl compound.

2. **Identifying the Functional Groups**:
- For a successful intramolecular aldol condensation, the compound must contain a ketone or aldehyde group and a suitable number of carbon atoms to form a stable ring (preferably 5 or 6 members).
- Compounds with aldehyde groups are generally less favorable for intramolecular aldol reactions compared to those with ketone groups.

3. **Analyzing Each Option**:
- **Option 1**: Contains an aldehyde group. Aldehydes are not suitable for intramolecular aldol condensation, so this option is not viable.
- **Option 2**: Contains a ketone group and can form a 5 or 6-membered ring. This is likely to yield a stable product.
- **Option 3**: Contains a ketone group but would form an 8-membered ring. Larger rings are generally less stable, making this option less favorable for good yield.
- **Option 4**: Contains a ketone group and can form a 5 or 6-membered ring. This is also likely to yield a stable product.

4. **Conclusion**:
- Based on the analysis, the compounds that can be synthesized by intramolecular aldol condensation in very good yield are **Option 2 and Option 4**.

### Final Answer:
The compounds that can be synthesized by intramolecular aldol condensation in very good yield are **Option 2 and Option 4**.