# Misunderstanding reactions environment of chemmacros v. 5.10

I wanted to give my answer to this question

with the environment reactions into the manual of chemmacros. I think always that my low level to understand English language is my Achilles' heel.

My apologies to the author of the package Clemens Niederberger of chemmacros v5.10 2020/02/03 for this question. I have seen your guide to the pag. 43:

But how does the reactions environment operate? I don't understand it. For this MWE I have an error:

! LaTeX3 Error: The key 'chemmacros/reactions/before-tag' is unknown and is (LaTeX3) being ignored. For immediate help type H . ...

l.10 }

?

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath}
\usepackage{chemmacros} %%%%% <---- or chemformula?
\chemsetup[reactions]{
before-tag =  , %%%%<----automatic number without bold characther
tag-open = ( ,
tag-close = )
}
\begin{document}
\begin{reactions}
A + 2 B &-> 3 C + D "\label{rxn:test}"
\intertext{Some text in between aligned reactions}
E + F &<=> G + 1/2 H
\end{reactions}
\end{document}

• You need to load chemmacros with the reactions module. – cgnieder Feb 15 at 22:58
• @cgnieder Hi, I have put after \begin{document} the macro \chemsetup[reactions]{ before-tag = , %%%%<----automatic number without bold characther tag-open = ( , tag-close = ) } but I have an error: The key chemmacros/reactions/before-tag' is unknown and is [ }]. Please, can I have an answer? Thank you very much. – Sebastiano Feb 16 at 10:40
• I see that. But what you do not do is load the module reactions which defines the environment and the options. – cgnieder Feb 16 at 14:42

Addendum: I leave this post to remember my mistake for the next time.

After the comment of the very good user @cgnieder, excuse me again with the author of the package. I have not read to the begin of the manual that needed to be loaded \usechemmodule{all} or the specific module \usechemmodule{reactions}. I'm very happy to compile himself the code. Thank you very much @cgnieder.

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath}
\usepackage{chemmacros}
\usechemmodule{reactions}
\chemsetup[reactions]{
before-tag =  ,
tag-open = ( ,
tag-close = )
}
\begin{document}

\begin{reactions}
A + 2 B &-> 3 C + D "\label{rxn:test}"
\intertext{After many attempts I was been able to compile it :-)}
E + F &<=> G + 1/2 H
\end{reactions}
\end{document}