How to insert a big brace, arrows crossing etc

Question

As english is not my primary language, I don't know how describe my problem the right way. But I have a picture of what I want to type.

This is how far I have made it:

\documentclass[a4paper]{article}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}
    Cr & 3\downarrow \arrow[rd] & 2Cr: & 6\downarrow \\
    C & 2\uparrow \arrow[ru]& 3C: & 6\uparrow
\end{tikzcd}
\end{document}
\

Background: At my school we use this to show how to align(?) a redox-reaction.

This won't help your problem, but it's usually best if you include everything we need to copy and paste to get a working example. In this case, I think that would mean just adding a handful of lines: \documentclass{article} / \usepackage{tikz} / \tikzlibrary{tikzcd} / \begin{document}, and then \end{article}. — Teepeemm, Oct 28 '16 at 11:53

score 3 · Answer 1 · answered Oct 29 '16 at 15:13

Try with \tikzmark:

\documentclass[a4paper]{article}
\usepackage{tikz}
\usepackage{tikz-cd}
\usetikzlibrary{decorations.pathreplacing}
\usetikzlibrary{calc,tikzmark}

\begin{document}
  \begin{tikzcd}
      Cr: & 3\downarrow  \tikzmark{bracebegin} \hspace{4pt} \arrow[rd] & \hspace{4pt} 2Cr: & 6\downarrow \\
      C: & 2\uparrow  \tikzmark{braceend} \hspace{4pt} \arrow[ru]   & \hspace{4pt} 3C: & 6\uparrow
  \end{tikzcd}
  \begin{tikzpicture}[overlay,remember picture]
  \draw[decorate,decoration={brace}] ( $ (pic cs:bracebegin) +(0, 9pt)  $ ) -- ( $ (pic cs:braceend) -(0, 4pt) $ );
  \end{tikzpicture}%
\end{document}

score 2 · Answer 2 · edited Oct 30 '16 at 06:58

\documentclass[a4paper]{article}
\usepackage{tikz}
    \usetikzlibrary{decorations.pathreplacing}
\begin{document}
    \begin{tikzpicture}[node distance = 3cm]
        \node at (-1,1){Cr: 3};
        \draw[->](-0.5,1.1)--(-0.5,0.8);
        \node at (-1,-1){C: 2};
        \draw[->](-0.5,-1.1)--(-0.5,-0.8);
        \draw [->] (0,1) --(1,-1);
        \draw [->]  (0,-1) -- (1,1);
        \draw[decorate,decoration={brace}]  (-0.3,1.2) -- (-0.3,-1.2);
        \node at (1.7, 1.0){2 Cr: 6};
        \node at (1.7, -1.0){3Cr: 6};
        \draw[->](2.4,-1.1)--(2.4,-0.9);
        \draw[->](2.4,1.1)--(2.4,0.9);
    \end{tikzpicture}
\end{document}

I have edited your minimal working example to make it compilable and I've used your \draw[decorate,decoration={brace}] in my answer :) — CarLaTeX, Oct 30 '16 at 07:02

Emma · Accepted Answer · 2016-10-30T13:24:57.780

If you would like to think of the reaction as an equation rather than a diagram, you can also use tikz marks to do that:

\documentclass{article}
\usepackage{amsmath, tikz}
\usetikzlibrary{decorations.pathreplacing, calc}
\newcommand{\tikzmathnode}[2]{\tikz[remember picture, baseline]{\node[inner sep=1pt, outer sep=0pt, anchor=base, minimum height=1em] (#1) {$\displaystyle #2$};}}
\newcommand{\redoxdraw}{
  \begin{tikzpicture}[overlay, remember picture]
    \draw[decoration = {brace, amplitude=.3em, raise=.1em}, decorate] (redox1.north east) -- (redox2.south east);
    \draw[-to, out=0, in=180] ([xshift=.8em] redox1.east) to ([xshift=2.5em] redox2.east);
    \draw[-to, out=0, in=180] ([xshift=.8em] redox2.east) to ([xshift=2.5em] redox1.east);
  \end{tikzpicture}
}
\newcommand{\redoxfirst}[1]{\tikzmathnode{redox1}{#1}\qquad}
\newcommand{\redoxsecond}[1]{\tikzmathnode{redox2}{#1}\qquad\redoxdraw}


\begin{document}
\begin{equation*}
  \begin{array}{rrrr}
    Cr: & \redoxfirst{3\downarrow} & 2Cr: & 6\downarrow\\[.3em]
     C: & \redoxsecond{2\uparrow}   & 3C: & 6\uparrow
  \end{array}
\end{equation*}
\end{document}

You can of course play around with the spacing or hard-code less of the format. You could also make \redoxfirst and \redoxsecond take an optional argument to name the reaction, so as to allow multiple reactions in the same line.

How to insert a big brace, arrows crossing etc

3 Answers3

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