How will you convert acetaldehyde into the following compounds ?
But-2-enal

Explanation

To convert acetaldehyde (CH3CHO) into but-2-enal (CH3CH=CHCHO), we can follow these steps:

### Step 1: Aldol Condensation Reaction
1. **Starting Material**: Begin with acetaldehyde (CH3CHO).
2. **Reaction Conditions**: Add dilute sodium hydroxide (NaOH) as a catalyst.
3. **Formation of Aldol**: Under these conditions, two molecules of acetaldehyde will undergo aldol condensation. The first step involves the nucleophilic addition of one acetaldehyde molecule to the carbonyl carbon of another acetaldehyde molecule. This results in the formation of 3-hydroxybutanal (CH3CHOHCH2CHO).

### Step 2: Dehydration
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