(a) $C{H_3}\, - \,\,\mathop C\limits_{\mathop |\limits_{C{H_3}} } \, = \,\,C{H_2}\,\xrightarrow{{HBr}}\,\,C{H_3}\, - \,\,\mathop {\mathop C\limits_{\mathop |\limits_{C{H_3}} } }\limits^{\mathop |\limits^{Br} } \,\, - \,\,C{H_3}$
(b) $C{H_3}\, - \,\,CH\,\, = \,\,C{H_2}\,\mathop {\xrightarrow{{HBr}}}\limits_{Peroxide} \,\,C{H_3}\,C{H_2}\,C{H_2}\,Br$
(c) $C{H_4}\, + \,\,C{l_2}\,\xrightarrow{{hv}}\,\,C{H_3}Cl\,\, + \,\,HCl$
$\begin{array}{*{20}{c}}
{C{H_3}\,\,\,\,\,\,\,\,\,} \\
{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{C{H_3} - CH - C = CH}
\end{array}\xrightarrow[{{H_2}O}]{{HgS{O_4},{H_2}S{O_4}}}X$ $\xrightarrow[{(ii)\,conc.{H_2}S{O_4}/\Delta }]{{(i)\,{C_2}{H_5}MgBr,{H_2}O}}Y$