$C{{H}_{3}}CON{{H}_{2}}\xrightarrow{B{{r}_{2}}/KOH}C{{H}_{3}}N{{H}_{2}}$
The unknown compounds $A$ and $B$ in the above reaction are :
$C{H_3}N{H_2} + X + KOH \to C{H_3}NC$ (highly offensive odour)