Chemical Structures

I have trouble in entering the following chemical reaction in LaTeX. I will be very grateful for every help.

• You're welcome to TeX.SE. Could you add a minimal working example, please? You can visit the link wiki.contextgarden.net/Chemistry. – Sebastiano Jan 23 '17 at 15:35
• Thank you Sebastiano. I used \chemfig as below but it does not exactly what I need: \chemfig{n(CH_2(=[:0]CHCOOH))} – Reza Jan 23 '17 at 15:52
• @Reza search the chemfig manual for polymers – clemens Jan 23 '17 at 16:06
• Reza, yet I have not undestood your picture because I have not your source. Add your source and a figure with your hand. I'm not an expert of chemical structures, sorry. – Sebastiano Jan 23 '17 at 16:06

As I mentioned already in the comments: the chemfig manual has a section about those kind of schemes. In an example in the manual there are the macro \makebraces and \setpolymerdelims defined which can be used here. A remark for the first formula: parentheses have a special meaning inside chemfig's formulas (branching). In order to have them printed they have to be enclosed with braces.

\documentclass{article}
\usepackage{chemfig}

\newcommand*\delimleft{}
\newcommand*\delimright{}
\newcommand*\makebraces{}
\newcommand*\delimhalfdim{}
\newcommand*\delimvshift{}
\newcommand*\setpolymerdelim[2]{\def\delimleft{#1}\def\delimright{#2}}
\def\makebraces[#1,#2]#3#4#5{%
\edef\delimhalfdim{\the\dimexpr(#1+#2)/2}%
\edef\delimvshift{\the\dimexpr(#1-#2)/2}%
\chemmove{
\node[at=(#4),yshift=(\delimvshift)]
{$\left\delimleft\vrule height\delimhalfdim depth\delimhalfdim width0pt \right.$};
\node[at=(#5),yshift=(\delimvshift)]
{$\left.\vrule height\delimhalfdim depth\delimhalfdim width0pt \right\delimright_{\rlap{$\scriptstyle#3$}}$};}
}
\setpolymerdelim()

\begin{document}

\schemestart
$n$ \chemfig{{(}CH_2=CHCOOH{)}}
\arrow(--.-165)
\chemfig{-[@{b1}]CH_2-CH(-[2]COOH)-[@{b2}]}
\schemestop
\makebraces[5pt,5pt]{n}{b1}{b2}

\end{document}


Remarks:

The chemmacros package has a module polymers which defines a \makepolymerdelims. Using it one doesn't need to add definitions to the preamble. However, using it may only make sense if chemmacros is used anyway. The code then becomes:

\documentclass{article}
\usepackage{chemfig,chemmacros}

\chemsetup{
modules = {polymers} ,
polymers/delimiters = ()
}

\begin{document}

\schemestart
$n$ \chemfig{{(}CH_2=CHCOOH{)}}
\arrow(--.-165)
\chemfig{-[@{b1}]CH_2-CH(-[2]COOH)-[@{b2}]}
\schemestop
\makepolymerdelims{5pt}{b1}{b2}

\end{document}