Aldol condensation will not take place in

Options

A. `HCHO`
B. `CH_(3)CHO`
C. `CH_(3)COCH_(3)`
D. `CH_(3)CH_(2)CHO`

Explanation

To determine where aldol condensation will not take place, we need to look for compounds that do not have alpha-hydrogens. Aldol condensation requires the presence of alpha-hydrogens on the carbon adjacent to the carbonyl group (aldehyde or ketone) for the reaction to proceed.

### Step-by-Step Solution:

1. **Understanding Aldol Condensation**:
- Aldol condensation is a reaction between aldehydes or ketones that contain at least one alpha-hydrogen. The alpha-hydrogen is crucial for the formation of the enolate ion, which is necessary for the condensation reaction.

2. **Identifying Alpha-Hydrogens**:
- An alpha-hydrogen is a hydrogen atom attached to the carbon atom adjacent to the carbonyl group. If a compound lacks alpha-hydrogens, it cannot participate in aldol condensation.

3. **Analyzing Each Option**:
- **Option A**: HCHO (Formaldehyde)
- Structure: H-C(=O)-H
- **Alpha-Hydrogens**: None (No carbon adjacent to the carbonyl)
- **Conclusion**: Aldol condensation will NOT take place.

- **Option B**: CH3CHO (Acetaldehyde)
- Structure: CH3-C(=O)-H
- **Alpha-Hydrogens**: Yes (The methyl group has three alpha-hydrogens)
- **Conclusion**: Aldol condensation will take place.

- **Option C**: CH3COCH3 (Acetone)
- Structure: CH3-C(=O)-CH3
- **Alpha-Hydrogens**: Yes (Both methyl groups have three alpha-hydrogens each)
- **Conclusion**: Aldol condensation will take place.

- **Option D**: CH3CH2CHO (Propionaldehyde)
- Structure: CH3-CH2-C(=O)-H
- **Alpha-Hydrogens**: Yes (The ethyl group has two alpha-hydrogens)
- **Conclusion**: Aldol condensation will take place.

4. **Final Conclusion**:
- The only compound that does not undergo aldol condensation due to the absence of alpha-hydrogens is **Option A: HCHO (Formaldehyde)**.

### Summary:
Aldol condensation will not take place in **HCHO (Formaldehyde)** since it lacks alpha-hydrogens.

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