

$(I)$ $ CH_3 - NO_2$
$(II)$ $NO_2 - CH_2 - NO_2$
$(III)$ $ CH_3 - CH_2 - NO_2 $
$(IV)$ $\begin{array}{*{20}{c}}
{N{O_2} - CH - N{O_2}} \\
{|\,\,\,\,\,\,} \\
{\,N{O_2}}
\end{array}$
$1. \,{H_3}C - \mathop O\limits^ + {H_2} \to CH_3^ + + {H_2}O$
$2.\,{(C{H_3})_3}C - \mathop O\limits^ + {H_2} \to {(C{H_3})_3}{C^ + } + {H_2}O$
$3.\,{(C{H_3})_2}CH - \mathop O\limits^ + {H_2} \to {(C{H_3})_2}C{H^ + } + {H_2}O$

