$\begin{array}{*{20}{c}}
{Ph - CH - CH - CHO\xrightarrow[\Delta ]{{{K_2}C{O_3}}}} \\
{\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{\,\,\,\,\,\,Br\,\,\,\,\,\,\,\,\,\,Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}
\end{array}$

$I.$ $DDT$ $II.$ Gammerane
$III.$ Carbon tetrachloride $IV.$ Chlorobenzene