Math & Science ⇒ chemfig | Custom Arrows in Reaction Schemes

[niteshs]

Hi,

I am trying to produce a reaction scheme with curved arrows as shown in this example (the structures are purely for example):

react1.png (8.41 KiB) Viewed 13895 times

I have been able to create the basic scheme with the following code:

Code: Select all

\documentclass{article}
\usepackage{chemfig}
\begin{document}
%\schemedebug{true}
\schemestart
\tiny\chemname{\chemfig{*6(-=-(-R2)=-*6(-(-R1)=-(-*5(-----))--)=)}}{\small Some structure}
\arrow(.-10--){->[Text]}[,3]
\tiny\chemname{\chemfig{*6(=-*6(-=-=-)=-=-)}}{\small Another structure}
\arrow{0}[,0.5]
+\arrow{0}[,0.5]
\tiny\chemname{\chemfig{[:20]*5(-----)}}{\small And another}
\schemestop
\end{document}

which produces the following result:

react2.png (3.79 KiB) Viewed 13895 times

I don't know how to add the curved arrows.
Can someone help me with this please?

[niteshs]

I guess I could have made the MWE much more simpler as follows:

Code: Select all

\documentclass{article}
\usepackage{chemfig}
\begin{document}
\schemestart
A\arrow{->[Text]}[,3]
B\arrow{0}[,0.5]+\arrow{0}[,0.5]
C
\schemestop
\end{document}

[cgnieder]

The following is a quick solution so I guess there are probably better ones. ChemFig provides the command \definearrow and some others (see section 10 of part V in the manual). The code below adapts the definition of the -U> arrow made by ChemFig:

Code: Select all

\documentclass{article}
\usepackage{chemfig}

\makeatletter
\definearrow5{-n>}{% #4=coeff du rayon de l'arc de cercle  #5=1/2 angle
	\CF@arrow@shift@nodes{#3}%
	\expandafter\draw\expandafter[\CF@arrow@current@style,-CF@full](\CF@arrow@start@node)--(\CF@arrow@end@node)node[pos=.2](narrow@arctangent@i){} node[pos=.5](narrow@arctangent@ii){};%
	\edef\CF@tmp@str{[\ifx\@empty#1\@empty draw=none,\fi-CF@full]}%
	\expandafter\draw\CF@tmp@str (narrow@arctangent@i)%
		arc[radius=\CF@compound@sep*\CF@current@arrow@length*\ifx\@empty#4\@empty0.333\else#4\fi,start angle=\CF@arrow@current@angle+90,%
		delta angle=-\ifx\@empty#5\@empty60\else#5\fi]node(narrow@start){};
	\edef\CF@tmp@str{[\ifx\@empty#2\@empty draw=none,\fi-CF@full]}%
	\expandafter\draw\CF@tmp@str (narrow@arctangent@ii)%
		arc[radius=\CF@compound@sep*\CF@current@arrow@length*\ifx\@empty#4\@empty0.333\else#4\fi,start angle=\CF@arrow@current@angle+90,%
		delta angle=-\ifx\@empty#5\@empty60\else#5\fi]node(narrow@end){};
	\edef\CF@tmp@str{\if\string-\expandafter\@car\detokenize{#4.}\@nil+\else-\fi}%
	\CF@arrow@display@label{#1}{0}\CF@tmp@str{narrow@start}{#2}{1}\CF@tmp@str{narrow@end}%
}
\makeatother

\begin{document}

\schemestart
A \arrow{-n>[1][2]}[,2] B
\schemestop

\schemestart
\subscheme{A \arrow{-n>[1][2]}[,2] B}
\arrow{0}[90,0]text
\schemestop

\schemestart
A \arrow{-n>[*01][*02]}[-90,2] B
\schemestop

\end{document}

customarrow.png (7.88 KiB) Viewed 13885 times

Regards

[niteshs]

Excellent! Thank you cgnieder!