Which of the following will undergo aldol condensation ?

Options

A. Acetaldehyde
B. Propanaldehyde
C. Benzaldehyde
D. Trideutereo acetaldehyde

Explanation

To determine which of the given compounds will undergo aldol condensation, we need to identify if they contain alpha hydrogens. Aldol condensation occurs in aldehydes and ketones that have at least one alpha hydrogen. Let's analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Aldol Condensation**:
Aldol condensation is a reaction between aldehydes or ketones that contain alpha hydrogens. In this reaction, an alpha hydrogen is removed by a base to form a carbanion, which then attacks the carbonyl carbon of another molecule, leading to the formation of a β-hydroxy aldehyde or ketone.

2. **Analyzing Acetaldehyde (Option A)**:
- Structure: CH₃CHO
- Acetaldehyde has one alpha hydrogen on the methyl group (CH₃).
- Therefore, it can undergo aldol condensation.

3. **Analyzing Propanaldehyde (Option B)**:
- Structure: CH₃CH₂CHO
- Propanaldehyde has two alpha hydrogens on the ethyl group (CH₃CH₂).
- Therefore, it can also undergo aldol condensation.

4. **Analyzing Benzaldehyde (Option C)**:
- Structure: C₆H₅CHO
- Benzaldehyde has no alpha hydrogen because its carbonyl carbon is directly attached to a phenyl group (C₆H₅).
- Therefore, it cannot undergo aldol condensation.

5. **Analyzing Tri-deuteroacetaldehyde (Option D)**:
- Structure: CD₃CHO (where D is deuterium, an isotope of hydrogen)
- Tri-deuteroacetaldehyde has three alpha hydrogens (deuterium atoms).
- Since deuterium behaves similarly to hydrogen in chemical reactions, it can undergo aldol condensation.

### Conclusion:
Based on the analysis, the compounds that can undergo aldol condensation are:
- Option A: Acetaldehyde
- Option B: Propanaldehyde
- Option D: Tri-deuteroacetaldehyde

**Final Answer**: Options A, B, and D will undergo aldol condensation. Option C (Benzaldehyde) will not.