Write the mechanism of the following reaction:
nBuBr + KCN `overset(EtOH-H_(2)O) rarr` nBuCN

Explanation

To write the mechanism of the reaction between n-butyl bromide (nBuBr) and potassium cyanide (KCN) in the presence of ethanol and water, we will follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are:
- n-butyl bromide (nBuBr), which is a primary alkyl halide.
- Potassium cyanide (KCN), which is an ambidentate nucleophile.

### Step 2: Understand the Nature of KCN
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