\nocaret\pagecolor{silver}\small
%\def\Horiz{\vrule width 11pt height 4pt depth -3pt}
\def\Horiz{\mbox{-----}}
\def\Vertical{|}
\def\Br{\mbox{Br}}
\def\C{\mbox{C}}
\def\CH{\mbox{CH}}
\def\H{\mbox{H}}
\def\NH{\mbox{NH}}
$$
\begin{array}{rcccl}
&&\hphantom{\H_3}\CH_3 \\
&&\Vertical\\
\CH_3&\Horiz&\C&\Horiz& \CH_3 \\
&&\Vertical\\
&& \Br
\end{array}
\quad\stackrel{{\tiny \NH_3}}{-\!\!\!-\!\!\!-\!\!\!\longrightarrow}\quad
\begin{array}{rcccl}
&&\hphantom{\H_3}\CH_3 \\
&&\Vertical\\
\CH_3&\Horiz&\C&\mbox{===}& \CH_2\, +\, \NH_4 \Br \\
&&\vphantom{\Vertical}\\
&&\vphantom{\Br}
\end{array}
$$