The reaction scheme shown below is to long to fit in one line. I would like to place the two left compounds atop one another, so the +
is in the middle between them, vertically centered with the arrow.
MWE:
\documentclass[10pt,a4paper]{article}
\usepackage[left=32.5mm, right=25mm, showframe]{geometry}
\usepackage[version=4]{mhchem}
\usepackage{chemfig}
\setchemfig{fixed length=true, atom sep=1.5em, arrow offset=6pt}
\def\x{\vphantom{C}}
\begin{document}
\setchemfig{arrow coeff=1.65}
\centering\small
\schemestart
\chemfig{\x-[@{li}]N(-[2]H)-\x|{(}CH_2{)}_{11}|\x-C(=[6]O)-[@{re}]}
\polymerdelim[delimiters={[]},height=25pt,depth=29pt]{li}{re}
\+
\chemfig{\x-[@{li}]N(-[2]H)-\x|{(}CH_2{)}_{11}|\x-C(=[6]O)-[@{re}]}
\polymerdelim[delimiters={[]},height=25pt,depth=29pt,indice=m]{li}{re}
\arrow{<->>[$T$, $t$, $\Delta p_{\ce{H2O}}$][]}
\chemfig{\x-[@{li}]N(-[2]H)-\x|{(}CH_2{)}_{11}|\x-C(=[6]O)-[@{re}]}
\polymerdelim[delimiters={[]},height=25pt,depth=29pt,indice=n+m]{li}{re}
\+
\chemfig{H_2O} \
\schemestop
\end{document}
EDIT: As @leandriis pointed out, simply putting the arrow text in a \parbox
, such as in this question, solves the issue.
EDIT 2: I forgot to add a H and a OH group at the sides on all molecules, making them even longer. Thus, the original issue still exists and is even worse.
MWE 2:
\setchemfig{arrow label sep=5pt}
\centering\small
\schemestart
\chemfig{\x H-[@{li}]N(-[2]H)-\x|{(}CH_2{)}_{11}|\x-C(=[6]O)-[@{re}]OH}
\polymerdelim[delimiters={[]},height=25pt,depth=29pt]{li}{re}
\+
\chemfig{\x H-[@{li}]N(-[2]H)-\x|{(}CH_2{)}_{11}|\x-C(=[6]O)-[@{re}]OH}
\polymerdelim[delimiters={[]},height=25pt,depth=29pt,indice=m]{li}{re}
\arrow{<->>[\parbox{5cm}{\centering $T$, $t$,\\$\Delta p_{\ce{H2O}}$}][]}
\chemfig{\x H-[@{li}]N(-[2]H)-\x|{(}CH_2{)}_{11}|\x-C(=[6]O)-[@{re}]OH}
\polymerdelim[delimiters={[]},height=25pt,depth=29pt,indice=n+m]{li}{re}
\+
\chemfig{H_2O}
\schemestop