c
$(c)$
$\begin{array}{*{20}{c}}
{C{H_3} - CH - C{H_2} - \boxed{Mg - Br + {C_2}{H_5}O}H} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{H_{3\,\,\,\,\,\,}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}
\end{array} \to $
$\mathop {\begin{array}{*{20}{c}}
{C{H_3} - CH - C{H_3}} \\
| \\
{C{H_3}}
\end{array}}\limits_{Isobu\tan e} $ $+$ $\underset{\begin{smallmatrix}
Ethoxy\,magnesium \\
bromide
\end{smallmatrix}}{\mathop{{{C}_{2}}{{H}_{5}}OMgBr}}\,$