\pgfmathsetmacro{\a}{2.5}
\pgfmathsetmacro{\b}{0.9}
\tikzset{ apply style/.code     = {\tikzset{#1}}, triangle_edges/.style = {thick,draw=black} }
\foreach \theta/\facestyle in {%
    0/{triangle_edges, fill = gray!50},
  120/{triangle_edges, fill = gray!25},
  240/{triangle_edges, fill = gray!90}%
}{
  \begin {scope}[rotate=\theta]
   \draw[apply style/.expand once=\facestyle]
      ({-sqrt(3)/2*\a},{-0.5*\a})                     --
      ++(-\b,0)                                       --
        ({0.5*\b},{\a+3*sqrt(3)/2*\b})                -- % higher point    
        ({sqrt(3)/2*\a+2.5*\b},{-.5*\a-sqrt(3)/2*\b}) -- % rightmost point
      ++({-.5*\b},-{sqrt(3)/2*\b})                    -- % lower point
        ({0.5*\b},{\a+sqrt(3)/2*\b})                  --
      cycle;
    \end{scope}
}    

\usepackage{chemfig}
\begin {document}
\chemfig{*6(=-=(-[::-60] (=[::-60]O)(-[::+60]OH))-(-OH)=-)}
\quad+\quad\chemfig{(CH_3-[::+30] (=[::+60]O)(-[::-60]O-[::+60] (=[::+60]O)(-[::-60]CH_3)))} 
\quad $\longrightarrow$ \quad
\chemfig{*6(=-=(-[::-60] (=[::-60]O)(-[::+60]OH))-(-O-[::+60] (=[::+60]O)(-[::-60]CH_3))=-)}
\quad+\quad\chemfig{(HO-[::+30] (=[::+60]O)(-[::-60]CH_3))} 
\end{document}

\usepackage{circuitikz}
\begin {document}
  \begin {circuitikz}[american, voltage shift=0.5]
    \draw (0,0)
    to[isource, l=$I_0$, v=$V_0$] (0,3)
    to[short, -*, i=$I_0$] (2,3)
    to[R=$R_1$, i>_=$i_1$] (2,0) -- (0,0);
    \draw (2,3) -- (4,3)
    to[R=$R_2$, i>_=$i_2$]
    (4,0) to[short, -*] (2,0);
  \end{circuitikz}
\end{document}