\documentclass{article}
\usepackage{xymtex}
\usepackage{chemist}
\pagestyle{empty}
\begin{document}

\tetrahedral{0==C;1==\utrigonal{0==C;1==(yl);3D==O;2==O$^-$};2==$^+$H$_3$N;3==\dtrigonal{0==CH;1==(yl);2==CH$_3$;3==H$_3$C};4==H}

\end{document}
