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\documentclass{scrartcl}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage[ngerman]{babel}
\usepackage{mychemistry}

\setatomsep{1.8em}
\setcrambond{3pt}{0.5pt}{1pt}
\setarrowlength{3em}
\setarrowline{thin}

\begin{document}
\mCsetup{bondlength=1.7em,rcndist=.9em}
\begin{rxn}
   \reactant{\chemfig{R-[:-90]NH_2}}
   \chemand
   \reactant{\chemfig{N(=[:90]O)-[:-30]O(-[:-30,.4,,,draw=none]+)(-[:30]H)-[:-90]H}}
   \arrow[,<=>,,,]{}{}
   \reactant{\chemfig{R-[:-90]N(-[:45,.5,,,draw=none]+)(-[:180]H)(-[:-90]H)-[:0]\lewis{1,N}=[:-60]O}}
   \chemand
   \reactant{\ce{H2O}}
   \arrow[,<=>,,,]{}{}
   \reactant{\chemfig{R-[:-90]\lewis{6,N}(-[:-150]H)-[:-30]\lewis{6,N}=[:30]O}}
   \chemand[,plus]
   \reactant{\ce{H3O+}}
   \branch[plus.-90,glgw,,yshift=-1em]{
     \arrow[-90,<=>,,,]{}{}
   }
   \mesomeric[glgw.-90,,xshift=-5.5em]{
     \reactant{\chemfig{R-[:-90]N(-[:45,.5,,,draw=none]+)(-[:-150]H)=[:-30]\lewis{6,N}-[:30]O-[:-30]H}}
     \marrow
     \reactant{\chemfig{R-[:-90]\lewis{6,N}(-[:-150]H)-[:-30]\lewis{6,N}=[:30]\chemabove{O}{+}-[:-30]H}}
   }
\end{rxn}
\mCsetup{reset,arrowlength=3em,arrowline=thin}
\end{document}

\documentclass{scrartcl}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage[ngerman]{babel}
\usepackage{mychemistry}

\setatomsep{1.8em}
\setcrambond{3pt}{0.5pt}{1pt}
\setarrowlength{3em}
\setarrowline{thin}

\begin{document}
\begin{rxn}
	\reactand{\chemfig{R-[:-90]NH_2}}
	\chemand
	\reactand{\chemfig{N(=[:90]O)-[:-30]O(-[:-30,.4,,,draw=none]+)(-[:30]H)-[:-90]H}}
		\arrow[,<=>,,,]{}{}
	\reactand{\chemfig{R-[:-90]N(-[:45,.5,,,draw=none]+)(-[:180]H)(-[:-90]H)-[:0]\lewis{1,N}=[:-60]O}}
	\chemand
	\reactand{\ce{H2O}}
		\arrow[,<=>,,,]{}{}
	\reactand{\chemfig{R-[:-90]\lewis{6,N}(-[:-150]H)-[:-30]\lewis{6,N}=[:30]O}}
	\chemand
	\reactand{\ce{H3O+}}
	  \arrow[below,<=>,,,]{}{}
	\mesomeric{
	\reactand[below]{\chemfig{R-[:-90]\lewis{6,N}(-[:-150]H)-[:-30]\lewis{6,N}=[:30]\chemabove{O}{+}-[:-30]H}}
	\marrow[below]
	\reactand[below]{\chemfig{R-[:-90]N(-[:45,.5,,,draw=none]+)(-[:-150]H)=[:-30]\lewis{6,N}-[:30]O-[:-30]H}}
	}
\end{rxn}
\end{document}