Base catalysed aldol condensation occurs with:

Options

A. Propanaldehyde
B. Benzaldehyde
C. 2-Methyl propanaldehyde
D. 2,2-Dimethyl propanaldehyde

Explanation

To determine which compound undergoes base-catalyzed aldol condensation, we need to analyze the given compounds based on the presence of alpha hydrogens. Aldol condensation requires at least two alpha hydrogens on the carbon adjacent to the carbonyl group. Here’s a step-by-step solution:

### Step 1: Identify the Compounds
We have four compounds to analyze:
1. Propanal (propanaldehyde)
2. Benzaldehyde
3. 2-Methylpropanal
4. 2,2-Dimethylpropanal

### Step 2: Analyze Each Compound for Alpha Hydrogens
- **Propanal (Propanaldehyde)**:
- Structure: CH3-CH2-CHO
- Alpha Carbon: The carbon next to the carbonyl (CHO) is CH2.
- Alpha Hydrogens: There are 2 alpha hydrogens (from CH2).

- **Benzaldehyde**:
- Structure: C6H5-CHO
- Alpha Carbon: The carbon next to the carbonyl is part of the phenyl ring.
- Alpha Hydrogens: There are 0 alpha hydrogens (no hydrogen on the carbon adjacent to the carbonyl).

- **2-Methylpropanal**:
- Structure: (CH3)2CH-CHO
- Alpha Carbon: The carbon next to the carbonyl is CH.
- Alpha Hydrogens: There is 1 alpha hydrogen (from CH).

- **2,2-Dimethylpropanal**:
- Structure: (CH3)3C-CHO
- Alpha Carbon: The carbon next to the carbonyl is a tertiary carbon.
- Alpha Hydrogens: There are 0 alpha hydrogens (no hydrogen on the carbon adjacent to the carbonyl).

### Step 3: Determine Which Compounds Can Undergo Aldol Condensation
- **Propanal**: Has 2 alpha hydrogens, can undergo aldol condensation.
- **Benzaldehyde**: Has 0 alpha hydrogens, cannot undergo aldol condensation.
- **2-Methylpropanal**: Has 1 alpha hydrogen, cannot undergo aldol condensation.
- **2,2-Dimethylpropanal**: Has 0 alpha hydrogens, cannot undergo aldol condensation.

### Conclusion
The only compound that can undergo base-catalyzed aldol condensation is **Propanal** (option A).

### Final Answer
**Propanal (option A)** is the compound that can undergo base-catalyzed aldol condensation.

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