Which of the following will not undergo aldol condensation?

Options

A. Formaldehyde
B. 2-methyl pentanal
C. cyclohexanone
D. Acetone

Answer

To determine which compound will not undergo aldol condensation, we need to understand the requirements for this reaction. Aldol condensation typically requires:

1. The presence of a carbonyl group (aldehyde or ketone).
2. At least one alpha hydrogen (hydrogens attached to the carbon adjacent to the carbonyl carbon).

Let's analyze the options provided:

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Option 1: Formaldehyde (HCHO)
- Option 2: Pentanal (C5H10O)
- Option 3: Cyclohexanone (C6H10O)
- Option 4: Acetone (C3H6O)

2. **Check for Alpha Hydrogens**:
- **Formaldehyde (HCHO)**:
- Structure: H-C(=O)-H
- Alpha Hydrogens: None (there are no carbons adjacent to the carbonyl carbon).
- **Pentanal (C5H10O)**:
- Structure: CH3-CH2-CH2-CH2-CHO
- Alpha Hydrogens: Yes (the carbon adjacent to the carbonyl has 2 hydrogens).
- **Cyclohexanone (C6H10O)**:
- Structure: A six-membered ring with a carbonyl group.
- Alpha Hydrogens: Yes (the carbons adjacent to the carbonyl have hydrogens).
- **Acetone (C3H6O)**:
- Structure: CH3-CO-CH3
- Alpha Hydrogens: Yes (the methyl groups adjacent to the carbonyl each have 3 hydrogens).

3. **Conclusion**:
- The only compound that does not have any alpha hydrogens is **Formaldehyde**. Therefore, it will not undergo aldol condensation.

### Final Answer:
**Formaldehyde (Option 1) will not undergo aldol condensation.**

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