Chapter 17, Problem 17.25P

Interpretation Introduction

Interpretation:

Whether the given reaction will take place via direct addition or conjugate addition is to be predicted, and the major product of the reaction is to be drawn.

Concept introduction:

In an $\text{α,β-unsaturated}$ nitrile, nucleophiles in general can attack at two positions – at the nitrile carbon itself or at the $\text{β}$-carbon. The attack by the nucleophile at the nitrile carbon is called $\text{1, 2-}$ or direct addition because after protonation, the species get added to adjacent atoms. The attack at the $\text{β}$-carbon, on the other hand, is called $\text{1, 4-}$ or conjugate addition. After protonation, the species get added to the atoms separated by three bonds. Whether direct or conjugate addition takes place depends in large part on whether the nucleophile adds to the nitrile carbon reversibly or irreversibly. This, in turn, depends on the type of the nucleophile.