${C_2}{H_5}I\xrightarrow{{Alco.\,\,KOH}}X\xrightarrow{{B{r_2}}}Y\xrightarrow{{KCN}}Z$
$\begin{array}{*{20}{c}}
{C{H_3}} \\
|\,\,\,\,\,\, \\
{C{H_{_3}} - C - C{H_2}Br} \\
|\,\,\,\,\,\, \\
H\,\,\,\,
\end{array}\,\xrightarrow[{C{H_3}OH}]{{C{H_3}{O^ - }}}$