Chapter 20, Problem 20.75P

Reaction of butanenitrile ( ${\text{CH}}_3{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{CN}$) with methyl magnesium bromide

( ${\text{CH}}_3\text{MgBr}$), followed by treatment with aqueous acid, forms compound G. G has a molecular ion in its mass spectrum at $\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$z$}\right.=86$ and a base peak at $\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$z$}\right.=43$. G exhibits a strong absorption in its IR spectrum at ${\text{1721 cm}}^{-1}$ and has the ${}^1\text{H}$ NMR spectrum given below. What is the structure of G? We will learn about the details of this reaction in Chapter 22.