\(\mathop {C{H_3} - \mathop {CH}\limits_{\mathop {|\,\,\,\,\,}\limits_{Br\,\,} } - C{H_2} - C{H_3}}\limits_{\scriptstyle{\rm{2}} - {\rm{Bromo}}\,{\rm{butane}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{ }}\atop \scriptstyle\,\,\,{\rm{(Main}}\,{\rm{product)}}} + \mathop {C{H_3} - C{H_2} - C{H_2} - C{H_2} - Br}\limits_{\scriptstyle{\rm{1}} - {\rm{Bromo}}\,{\rm{butane}}\atop \scriptstyle\,\,\,\,\,\,\,\,\,\,\,{\rm{(Minor)}}} \)
\(2-\) Bromobutane is the main product because
\({2^o}\) carbonium ion is more stable than \({1^o}\).
(figure) $\xrightarrow[{(2)\,Zn}]{{(1)\,{O_3}}}\mathop {\begin{array}{*{20}{c}}
{\,\,\,\,O\,\,\,\,\,\,\,O\,\,} \\
{\,||\,\,\,\,\,\,\,\,\,||} \\
{H - C - C - H}
\end{array}}\limits_{Glyoxal} + $ $\mathop {\begin{array}{*{20}{c}}
{\,\,\,O\,\,\,\,\,O\,\,} \\
{\,||\,\,\,\,\,\,\,\,||} \\
{C{H_3} - C - C - C{H_3}}
\end{array}}\limits_{2,3 - Bu\tan edione} + \mathop {\begin{array}{*{20}{c}}
{\,\,\,\,\,\,O\,\,\,\,\,O} \\
{\,\,\,\,\,\,||\,\,\,\,\,\,||} \\
{C{H_3} - C - C - H}
\end{array}}\limits_{Pyrualdehyde} $
