Which of the following will not undergo aldol condensation-

Options

A. Acetaldehyde
B. Propanaldehyde
C. Benzaldehyde
D. Trideuteroacetaldehyde

Answer

To determine which of the following compounds will not undergo aldol condensation, we need to analyze the presence of alpha hydrogens in each compound. Aldol condensation requires at least one alpha hydrogen on the carbon adjacent to the carbonyl group (C=O).

### Step-by-Step Solution:

1. **Identify the Compounds:**
The compounds given are:
- Acetaldehyde (CH3CHO)
- Propanaldehyde (CH3CH2CHO)
- Benzaldehyde (C6H5CHO)
- Deuteroacetaldehyde (CD3CHO)

2. **Check for Alpha Hydrogens:**
- **Acetaldehyde (CH3CHO):**
- The structure shows that the carbon adjacent to the carbonyl group (C=O) has three hydrogen atoms attached (CH3 group).
- **Alpha Hydrogens Present:** Yes (3 alpha hydrogens).

- **Propanaldehyde (CH3CH2CHO):**
- The structure shows that the carbon adjacent to the carbonyl group has two hydrogen atoms attached (CH2 group).
- **Alpha Hydrogens Present:** Yes (2 alpha hydrogens).

- **Benzaldehyde (C6H5CHO):**
- The structure shows that the carbon adjacent to the carbonyl group is part of a phenyl ring (C6H5) and does not have any hydrogen atoms attached to it.
- **Alpha Hydrogens Present:** No (0 alpha hydrogens).

- **Deuteroacetaldehyde (CD3CHO):**
- The structure shows that the carbon adjacent to the carbonyl group has three deuterium atoms attached (CD3 group).
- **Alpha Hydrogens Present:** Yes (3 alpha deuteriums).

3. **Conclusion:**
Since benzaldehyde does not have any alpha hydrogens, it will not undergo aldol condensation. Therefore, the answer to the question is **Benzaldehyde**.

### Final Answer:
**Benzaldehyde will not undergo aldol condensation.**