b
$\mathop {C{H_3} - C \equiv N}\limits_{ethane\,\,nitrile} $ $+$ $RMgX$ $\to $ ${\begin{array}{*{20}{c}}
{C{H_3} - C = N - RMgX} \\
{|{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} \,\,\,\,\,\,\,\,\,\,\,\,\,{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} } \\
{R\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} }
\end{array}}$ $\xrightarrow {H_2O}$ $\mathop {\begin{array}{*{20}{c}}
{\,\,\,\,\,\,\,\,\,O} \\
{\,\,\,\,\,\,\,\,\,||} \\
{RC{H_3} - C - R}
\end{array}}\limits_{(ketone)} $ $+$ $NH_3$ $+$ $Mg(OH)X$