Curved arrows for denoting chemical reactions (as a commutative diagram)

Question

The following code generates the sequence of reactions for formation of specific products.

\begin{tikzpicture}[
start chain = going below,
block/.style = {text width=2em,
    font=\linespread{1.5}\selectfont, align=center,
    on chain, join=by line},
line/.style = {-Stealth, semithick}
]
\begin{scope}[every node/.style = {block}]
\node (start) {CaCl$_{2}$} ; 
\node (c1) [below=of start, suspend join] {CaOHCl} ;
\node (c2) [left=of start, suspend join] {H$_{2}$O} ;
\node (c3) [below =of c2, suspend join] {CaO} ; 
\node (c4) [right=of start, suspend join] {CaCl$_2$.2H$_2$O} ; 
\node (c5) [below=of c4, suspend join] {Ca(OH)$_2$} ; 
\node (c6) [below =of c5, suspend join] {HCl} ; 
\end{scope} 
\draw[line] (start) -- (c1) ; 
\draw[line] (start) -- (c2) ; 
\draw[line] (c2) -- (c3) ; 
\draw[line] (c2) -- (c5) ; 
\draw[line] (c5) -- (start) ; 
\draw[line] (c5) -- (c4) ; 
\draw[line] (c4) -- (c1) ; 
\draw[line] (c5) -- (c6) ; 
\draw[line] (c6) -- (c1) ;  
\end{tikzpicture}

I would like to use tikzcd package to re-draw the sequence as a commutative diagram using curved arrows as shown in the attached image. Itried modifying the code available at http://ctan.math.washington.edu/tex-archive/graphics/pgf/contrib/tikz-cd/tikz-cd-doc.pdf

I am not sure how does the command \arrow[bend left] works, and how to modify it accordingly to the image requirements. Is there a possible solution?

Answer 1

You can use tikz-cd here. Whether it is worthwhile I do not know, nor whether the content makes sense. As suggested by daleif, you may want to use some tool that allows you to typeset the molecules. As for what seems to be the main question, you can use bend left and bend right, and add a bending angle where needed, e.g. bend left=20. You can also redefine the arrow head.

\documentclass{article}
\usepackage{chemformula}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}[/tikz/>=stealth,/tikz/column 1/.style={column sep=2em}]
 & & &  \ch{H2O} \arrow[dr,->,bend left] \arrow[dddr,->,bend left=20] & \\
 & & &   & \ch{CaO}\\
 & & \ch{CaCl2} \arrow[uur,->,bend left] \arrow[dll,->,bend right] &   & \\
 \ch{CaOHCl} & & & & \ch{Ca(OH)2} \arrow[ddll,->,bend left] \arrow[dll,->] 
 \arrow[ull,->]\\
 & &  \ch{CaCl2. 2 H2O}\arrow[ull,->,bend right]  & &\\ 
 & &  \ch{HCl} \arrow[uull,->,bend left] & &\\ 
\end{tikzcd}
\end{document}