C$\,\begin{array}{*{20}{c}}
{O\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{Ph - C - NH - C{H_3}}
\end{array} ,$ $\begin{array}{*{20}{c}}
{O\,\,\,\,\,\,\,\,\,\,\,\,} \\
{||\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{C{H_3} - C - NH - Ph}
\end{array}$
c
It's Beckmann rearrangement only antigroup will migrate