$C{H_3}C{H_2}OH\xrightarrow{{P + {I_2}}}A\xrightarrow[{ether}]{{Mg}} $ $B\xrightarrow{{HCHO}}C\xrightarrow{{{H_2}O}}D$
$\begin{array}{*{20}{c}}
{OH\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{C{H_3} - CH - C{H_2} - C{H_2} - OH}
\end{array}\,$ ${\xrightarrow[{Pyridine{\kern 1pt} cold}]{{Cr{O_3}}}}$ નીપજ
$\begin{matrix}
O\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \,\, \\
||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
N\equiv C-C{{H}_{2}}-C-C{{H}_{2}}-CH=C{{H}_{2}}\to \\
\end{matrix}$ $\begin{matrix}
OH\,\,\,\,\,\,\,\,\, \\
|\,\,\,\,\,\,\,\,\, \,\,\,\, \\
N\equiv C-C{{H}_{2}}-\underset{H}{\mathop{C}}\,-C{{H}_{2}}-CH=C{{H}_{2}} \\
\end{matrix}$