\documentclass[a4paper,12pt]{report}
\usepackage{german,ochem}
\begin{document}

Als Beispiel f"ur ein gleitendes Reaktionsschema soll die Synthese
der Chrysanthemums"aure in Schema~\ref{chrysanth} dienen.

\begin{schema}
\begin{chemistry}[darv1]
set("rArrowExtend",18)
joinv(2,B)
{ joinv(2,B)
  { formula(T,B)
    { bond(30,=; -30; 30)
      branch { bond(150);  bond(30) atom("OH",L); } bond(-30)
    }
    arrow(-90){ text(T,L){formula(C,C){atom("HBr")}}}
    formula(T,B)
    { atom("Br") bond(30; -30; 30,=)
      branch { bond(90); } bond(-30)
    };

    formula(T,B,"Tosylchlorid",V,24)
    { ring(){ 2: bond(r); 5: bond(r) atom("SO$_2$Cl",L); }
    }
    arrow(-90)
    {  text(T,L){formula(C,C){atom("NaOH")}}
       text(B,L){formula(C,C){atom("Zn")}}
    }
    formula(T,B)
    { ring(){ 2: bond(r); 5: bond(r) atom("SO$_2$Na",L); }
    };
  }
  arrow(-90){} % 80%

  formula(T,B)
  { ring(){ 2: bond(r);
            5: bond(r) atom("SO$_2$",L,R) bond(30; -30; 30,=)
               branch{bond(90);} bond(-30); }
  };

  formula(T,B,"3-Methylbutens""aure",V,24)
  { bond(30) branch{ bond(90); } bond(-30,=; 30) atom("COOH",L)
  }
  arrow(-90){ text(T,L){formula(C,C){atom("CH$_3$OH")}}}
  formula(T,B)
  { bond(30) branch{ bond(90); } bond(-30,=; 30) atom("CO$_2$CH$_3$",L)
  };
}

arrow(-90){ text(T,L){formula(C,C){atom("NaOCH$_3$")}}}

formula(T,B)
{ ring()
  { 3: bond(r);
    0: bond(r) atom("S")
       branch { bond(180,=C) atom("O");
                bond(0,=C) atom("O"); }
       bond(-90)
       saveXY(#1)
       bond(-150) bond(150,=)
         branch { bond(-150); bond(90); }
       restoreXY(#1)
       bond(-30) branch { bond(-150);
                          bond(-30); }
       bond(30)
       branch{ bond(90,s,S) atom("$\ominus$"); }
       bond(-30) atom("CO$_2$CH$_3$",L);
  }
}
bracket()

arrow(-90,10){}
arrow(-90,10){ text(T,L){formula(C,C){atom("KOH")}}}

formula(T,B,"\textit{trans}-Chrysanthemums""aure",V,24)
{ ring(,,H,,3,90)
  { 1: bond(r,<.) atom("COOH",L);
    2: bond(150,<<) bond(-150,=) branch{ bond(-90); bond(150); };
    0: bond(t);
    0: bond(b);
  }
}
\end{chemistry}
\caption{Chemie mit \LaTeX: Die Synthese der Chrysanthemums"aure als 
Beispiel f"ur die Anwendung von \texttt{ochem.sty}.\label{chrysanth}}
\end{schema}

\end{document}