$\begin{array}{*{20}{c}}
{C{H_3}} \\
|\,\,\,\,\, \\
{H - C - OH} \\
|\,\,\,\,\,\,\, \\
{HO - C - H\,\,\,\,\,\,\,\,\,} \\
|\,\,\,\,\,\,\, \\
{\,\,\,\,C{H_3}}
\end{array}\,\,\,\,\,\,\,\begin{array}{*{20}{c}}
\vdots \\
\vdots \\
\vdots \\
\vdots \\
\vdots \\
\vdots \\
\vdots
\end{array}\,\,\,\,\,\begin{array}{*{20}{c}}
{\,\,\,\,\,\,\,\,\,\,\,C{H_3}} \\
\,\,\,\,\,\,| \\
{HO - C - H} \\
\,\,\,\, \,\,|\\
{\,\,\,\,\,\,\,\,H - C - OH} \\
\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\\
{\,\,\,\,\,\,\,\,\,\,\,\,C{H_3}}
\end{array}$
$(I)$ $C{H_2} = CH - C{H_3} + {H_2}O\xrightarrow{{{H^ + }}}$
$(II)$ $C{H_3}CHO\xrightarrow[{(ii)\,{H_2}O}]{{(i)\,\,C{H_3}MgI}}$
$(III)$ $CH_2O\xrightarrow[{(ii)\,{H_2}O}]{{(i)\,\,C{_2}H_5MgI}}$
$(IV)$ $C{H_2} = CH - C{H_3}\xrightarrow{{nutral \,KMn{O_4}}}$