Write the mechanism of the following reaction:

nBuBr + KCN nBuCN

The given reaction is a nucleophillic reaction:

nBuBr + KCN nBuCN

The given reaction is an SN2 reaction. In this reaction, CN acts as the stronger nucleophile and attacks the carbon atom to which Br is attached in nBuBr.

And, CN^- ion is an ambident nucleophile and can attack through both C and N. In this case, it attacks through the C-atom.

The mechanism is shown below: