Which of the following will not give aldol condensation ?

Options

A. Phenyl acetaldehyde
B. 2 - Methylpentanal
C. Benzaldehyde
D. 1 - Phenylpropanone

Explanation

To determine which of the given compounds will not undergo aldol condensation, we need to analyze the presence of alpha hydrogens in each compound. Aldol condensation requires at least two alpha hydrogens adjacent to the carbonyl group.

### Step-by-Step Solution:

1. **Understanding Aldol Condensation**:
- Aldol condensation is a reaction between two carbonyl compounds (aldehydes or ketones) that have at least two alpha hydrogens.
- The reaction typically occurs in the presence of a base (like sodium hydroxide or potassium hydroxide) and leads to the formation of a beta-hydroxy carbonyl compound, which can further dehydrate to form an alpha, beta-unsaturated carbonyl compound.

2. **Analyzing Each Compound**:
- **Option 1: Phenyl Acetaldehyde (C6H5CH2CHO)**:
- Structure: Contains a carbonyl group (CHO) and two alpha hydrogens (from CH2).
- Conclusion: Can undergo aldol condensation.

- **Option 2: 2-Methylpentanal (C6H12O)**:
- Structure: Contains a carbonyl group (CHO) but only one alpha hydrogen (from CH).
- Conclusion: Cannot undergo aldol condensation because it lacks the required two alpha hydrogens.

- **Option 3: Benzaldehyde (C6H5CHO)**:
- Structure: Contains a carbonyl group (CHO) but has no alpha hydrogens (the carbon adjacent to the carbonyl is part of the benzene ring).
- Conclusion: Cannot undergo aldol condensation due to the absence of alpha hydrogens.

- **Option 4: Another compound with two alpha hydrogens**:
- Assuming this compound has a carbonyl group and two alpha hydrogens.
- Conclusion: Can undergo aldol condensation.

3. **Final Conclusion**:
- The compounds that will **not** undergo aldol condensation are **2-Methylpentanal** and **Benzaldehyde**. However, since the question asks for only one option, we can conclude that **2-Methylpentanal** is the primary compound that does not undergo aldol condensation due to having only one alpha hydrogen.

### Answer:
**2-Methylpentanal** will not give aldol condensation.