Stephen Reduction.

Explanation

### Step-by-Step Solution for Stephen Reduction

**Step 1: Understanding Stephen Reduction**
Stephen Reduction is a specific type of reduction reaction that primarily involves the conversion of nitriles (R-C≡N) to aldehydes (R-CHO) using tin(II) chloride (SnCl2) in the presence of hydrochloric acid (HCl).

**Step 2: Reaction Mechanism**
1. **Starting Material**: Begin with a nitrile compound (R-C≡N).
2. **Reagents**: Add SnCl2 and HCl to the nitrile.
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