# Aligning labels of chemical reaction

how do I do this:

so far I have:

\begin{center}
\schemestart
\chemfig{CH_3Cl}
\chemsign{+}
\chembelow[.25ex]{\chemfig{Si(Cu)}}{Silicon/CopperAlloy}
\chemrel{->}
\chembelow[.25ex]{\chemfig{(CH3)_2SiCl2}}{Dimethyldichlorosilane}
\chemsign{+}
\chemfig{Cu}
\schemestop
\end{center}


and I got this:

• You might want to consider using \chemname instead of \chembelow (it has essentially the same syntax)... you can add line breaks to the name given there with \: Silicon/\\copper alloy. The reason the Cu and CH3 look bad is because () are used for branches in the chemfig syntax. You should look in the polymers section of the manual for an idea of how to add parens, but I'm not sure if that's the easiest way. Hope it helps! – darthbith Sep 25 '14 at 13:42

Here I use stacks to accomplish the underset. The \useanchorwidth{T} option means that the width of the underset text does not affect the equation spacing.

\documentclass{beamer}
\usepackage{chemfig}
\usepackage[usestackEOL]{stackengine}
\renewcommand\useanchorwidth{T}
\renewcommand\stacktype{L}
\begin{document}
\begin{center}
\schemestart
\chemfig{CH_3Cl}
\chemsign{+}
\stackunder[18pt]{\chemfig{Si{(}Cu{)}}}{\Longunderstack{Silicon/\\Copper Alloy}}
\chemrel{->}
\stackunder[18pt]{\chemfig{{(}CH3{)}_2SiCl2}}{Dimethyldichlorosilane}
\chemsign{+}
\chemfig{Cu}
\schemestop
\end{center}
\end{document}


If you want the "Silicon/Copper Alloy" to be left-aligned, then change that input to \Longunderstack[l]{Silicon/\\Copper Alloy} by adding the [l] option.

No need an extra package, \chemname does the job:

\documentclass{article}
\usepackage{chemfig}
\begin{document}
\begin{center}
\schemestart
\chemfig{CH_3Cl}
\+
\chemname{\chemfig{Si{(Cu)}}}{Silicon\\/CopperAlloy}
\arrow(.mid east--.mid west)
\chemname{\chemfig{{(CH3)}_2SiCl2}}{Dimethyldichlorosilane}
\+
\chemfig{Cu}
\schemestop
\end{center}
\end{document}