# Chemfig and tikz: shaded arrow

How can I make these arrow shades, for example to blue from white?

\documentclass{article}
\usepackage{chemfig}
\usepackage[version=3]{mhchem}

\begin{document}
\begin{figure}[!htb]
\centering
\scalebox{2}{
\schemestart
\chemfig{@{O1-2}\textcolor{gray}{O}=@{C1-2}\textbf{C}=@{O2-2}\textcolor{gray}{O}}
\schemestop
\chemmove{
\draw[blue][shorten <=3pt, shorten >=3pt](O1-2).. controls +(north:1cm) and +(120:1cm).. (C1-2);
\draw[blue][shorten <=3pt, shorten >=3pt](O2-2).. controls +(north:1cm) and +(60:1cm).. (C1-2);
}
}
\end{figure}
\end{document}


• Here are some ways to accomplish that. – user121799 Apr 19 '18 at 20:09

Building upon Sebastiano's answer, one can also apply the path fading option directly to chemfig arrows as shown in the following example:

\documentclass{article}
\usepackage{chemfig}
\usepackage[version=3]{mhchem}

\begin{document}

\begin{figure}[!htb]
\centering
\scalebox{2}{
\schemestart
\chemfig{@{O1-2}\textcolor{gray}{O}=@{C1-2}\textbf{C}=@{O2-2}\textcolor{gray}{O}}
\schemestop
\chemmove{
\draw[blue, path fading = west][shorten <=3pt, shorten >=3pt](O1-2).. controls +(north:1cm) and +(120:1cm).. (C1-2);
\draw[blue, path fading = east][shorten <=3pt, shorten >=3pt](O2-2).. controls +(north:1cm) and +(60:1cm).. (C1-2);
}
}
\end{figure}

\end{document}


A possible solution with tikz-cd it is very simple to have the arrows shades to blue from white.

\documentclass[a4paper,12pt]{article}
\usepackage{tikz-cd,amsmath}

• +1. Maybe you want to add, that path fading can also be applied to chemfig arrows. Using \draw[blue, path fading = west][shorten <=3pt, shorten >=3pt](O1-2).. controls +(north:1cm) and +(120:1cm).. (C1-2); ... will result in the following output: i.stack.imgur.com/YMnc8.png – leandriis Mar 12 '19 at 22:35