Latex on chemical reaction

Question

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 :)

Answer 1

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).