\documentclass{ppex}
\nonstopmode
\usepackage {m-chemic}
\pagestyle{empty}
\setlength\textwidth{207.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage {m-chemic}
\definechemical[sixring]
   {\chemical[SIX,B,R,RZ]}
\startchemical[size=small]
 \chemical[sixring]
\qquad\qquad\qquad\qquad\qquad
 \chemical[sixring]
   [R_1,R_2,R_3,R_4,R_5,R_6]
\stopchemical
\end{document}