# Latex on chemical reaction

There is some problem with my code. It don't show Mg(OH)X correctly and arrow passes to reactant sites also

\documentclass[11pt]{article}

\usepackage{chemfig}

\begin{document}
\schemestart
\chemname{\chemfig{HC~CH}}{Acetylene}
\arrow{->[Red Hot \chemfig{Cu} tube][400C]}
\chemname{\chemfig{**6(------)}}{Benzene}
\+ \chemfig{Mg (OH) Cl}
\schemestop
\end{document}


It gives me output like these :(

Clearly they are not aligned and the arrow length is very short and how to show degree at 400 degree celcius below arrow and how to display Mg(OH)X correctly .

Thank YOU :)

Like this?

The code:

\documentclass[11pt]{article}
\usepackage{chemfig}
\usepackage{siunitx}

\begin{document}
\schemestart
\chemname{\chemfig{HC~CH}}{Acetylene}
\arrow(.{15.5}--){->[Red Hot \chemfig{Cu} tube][\SI{400}{\celsius}]}[0,2,]
\chemname{\chemfig{**6(------)}}{Benzene}
\arrow{0}[,0] \+ \chemfig{Mg {(OH)} Cl}
\schemestop
\end{document}


## Remarks

• For units,such as degree Celsius, use the siunitx package. In your concrete case I used \SI{400}{\degreeCelsius}.

• \arrow admits an optional argument with three values: angle, length coefficient and style, so I used [0,2,,] (i.e., angle=0, double the length and no style modification).

• I used an extra pair or braces arround (OH), as in \chemfig{Mg {(OH)} Cl} (I am not sure if this is the desired result, though).

• An invisible arrow \arrow{0}[,0] was used so that "+ Mg(OH)Cl" is vertically aligned with the arrow to the left.

• To improve the vertical alignment with the acetylene, the anchor specification (.{15.5}--) was used for the \arrow (thanks to clemens for his comment).

• Thanks , This is what exactly i want :) And your explanation is very good i understand every thing now :) – aftershock Jun 22 '15 at 16:59
• Would it be possible to adjust the vertical alignment of the last bit? – egreg Jun 22 '15 at 17:34
• @egreg I guess so; you mean align the elements in such a way that "+ Mg(OH)Cl" vertically aligns with the middle of the Benzene, right? When I return home I'll do it. – Gonzalo Medina Jun 22 '15 at 17:39
• At least aligned with the arrow at the left side. – egreg Jun 22 '15 at 17:41
• A better alignment with the acetylene can be achieved by giving an anchor to \arrows(<name1>.<anchor1>--<name2>.<anchor2>) (where all <name>s and <anchor>s are optional). Here 15.5 seems about right: \arrow(.{15.5}--){->[Red Hot \chemfig{Cu} tube][\SI{400}{\celsius}]}[,2] – cgnieder Jun 22 '15 at 19:45