Representing movement of a single electron

Question

I would like to represent the movement of a single electron in a reaction mechanism (grignard-reaction)

Is there a predefined arrow (something like a harpoon) for that in chemfig? Or does anyone have an idea?

Answer 1

You can load the TikZ-library arrows and use the arrow tips left to and right to. Here's a quick example:

\documentclass{article}
\usepackage{chemfig}
\setatomsep{1.8em}
\usetikzlibrary{arrows}
\begin{document}

\schemestart
  \chemfig{Cl|@{Cl}\Lewis{0.,\strut}}
  % a long invisible bond should suffice but this demonstrates
  % that also scheme nodes can be referenced in \chemmove{}:
  \arrow(--nb){0}[,.2]
  \mbox{}
  \arrow{0}[,.2]
  \chemfig{H-[@{bd}]@{C}C|H_3}
\schemestop
\chemmove{
  \draw[red,-right to,shorten >=3pt]
    (Cl) ..controls +(90:7mm) and +(100:7mm) .. (nb) ;
  \draw[red,-left to,shorten >=3pt]
    (bd) ..controls +(100:7mm) and +(80:7mm) .. (nb) ;
  \draw[red,-right to,shorten >=3pt]
    (bd) ..controls +(80:7mm) and +(100:7mm) .. (C) ;
}

\end{document}