Which one of the following compounds will not give aldol:

Options

A. Acetaldehyde
B. Formaldehyde
C. Pivaldehyde
D. Crotonaldehyde

Answer

To determine which compound will not undergo aldol condensation, we need to analyze the presence of alpha-hydrogens in the given compounds. Aldol condensation occurs in carbonyl compounds that have at least one alpha-hydrogen. Let's evaluate each option one by one.

### Step-by-Step Solution:

1. **Understanding Aldol Condensation**:
- Aldol condensation is a reaction between two carbonyl compounds (aldehydes or ketones) that have alpha-hydrogens. The reaction can occur in both acidic and basic conditions, but the presence of alpha-hydrogens is crucial for the formation of enolate ions.

2. **Analyzing Acetaldehyde (CH3CHO)**:
- Structure: Acetaldehyde has the formula CH3CHO.
- Alpha-hydrogens: The carbon adjacent to the carbonyl carbon (C=O) has three hydrogen atoms (from the methyl group).
- Conclusion: Since acetaldehyde has alpha-hydrogens, it can undergo aldol condensation.

3. **Analyzing Formaldehyde (HCHO)**:
- Structure: Formaldehyde has the formula HCHO.
- Alpha-hydrogens: There are no carbons adjacent to the carbonyl carbon (only one carbon in the structure).
- Conclusion: Since formaldehyde lacks alpha-hydrogens, it cannot undergo aldol condensation.

4. **Analyzing 2,2-Dimethylpropanal (C5H10O)**:
- Structure: 2,2-Dimethylpropanal has the formula (CH3)2C(CH2CHO).
- Alpha-hydrogens: The carbon adjacent to the carbonyl carbon does not have any hydrogen atoms (due to the two methyl groups).
- Conclusion: Since there are no alpha-hydrogens, this compound cannot undergo aldol condensation.

5. **Analyzing Crotonaldehyde (CH3CH=CHCHO)**:
- Structure: Crotonaldehyde has the formula CH3CH=CHCHO.
- Alpha-hydrogens: The carbon adjacent to the carbonyl carbon has two hydrogen atoms.
- Conclusion: Since crotonaldehyde has alpha-hydrogens, it can undergo aldol condensation.

### Final Conclusion:
The compounds that will **not** give aldol are:
- **Formaldehyde (HCHO)**
- **2,2-Dimethylpropanal**

Thus, the correct answer to the question is **Formaldehyde** and **2,2-Dimethylpropanal**.