Outline the reaction sequence for the conversion of methanal to ethanal (the number of steps should not be more than three).

Explanation

To convert methanal (formaldehyde) to ethanal (acetaldehyde), we can follow a simple three-step reaction sequence. Here’s how it can be done:

### Step 1: Formation of the Grignard Reagent
1. **React methanal with methyl magnesium bromide (CH3MgBr)** in dry ether.
- **Reaction**:
\[ \text{HCHO} + \text{CH}_3\text{MgBr} \rightarrow \text{CH}_3\text{CH}_2\text{OMgBr} \]
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