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Write the mechanism of the following reaction:
\(n-\mathrm{BuBr}+\mathrm{KCN} \stackrel{\mathrm{EtOH}-\mathrm{H}_2 \mathrm{O}}{\longrightarrow} n-\mathrm{BuCN}\)
\(n-\mathrm{BuBr}+\mathrm{KCN} \stackrel{\mathrm{EtOH}-\mathrm{H}_2 \mathrm{O}}{\longrightarrow} n-\mathrm{BuCN}\)
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Verified Answer
KCN is a resonance hybrid of the following two contributing structures:
Thus, \(\mathrm{CN}^{-}\)ion is an ambident nucleophile. Therefore, it can attack the carbon atom of \(\mathrm{C}-\mathrm{Br}\) bond in \(\mathrm{n}-\mathrm{BuBr}\) either through \(\mathrm{C}\) or \(\mathrm{N}\). Since \(\mathrm{C}-\mathrm{C}\) bond is stronger than \(\mathrm{C}-\mathrm{N}\) bond, therefore, attack occurs through \(\mathrm{C}\) to form n-butyl cyanide.
Thus, \(\mathrm{CN}^{-}\)ion is an ambident nucleophile. Therefore, it can attack the carbon atom of \(\mathrm{C}-\mathrm{Br}\) bond in \(\mathrm{n}-\mathrm{BuBr}\) either through \(\mathrm{C}\) or \(\mathrm{N}\). Since \(\mathrm{C}-\mathrm{C}\) bond is stronger than \(\mathrm{C}-\mathrm{N}\) bond, therefore, attack occurs through \(\mathrm{C}\) to form n-butyl cyanide.
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