# Can I annotate the links in chemfig?

chemfig is really great chemical picture editor, but just one problem doesn't allow me to continue the work.

In the picture below, you see the chemical picture from the book with numbered links and framed CH_3 radicals. Is these feature available in the chemfig package?

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You may want to have a look at How to number atoms using chemfig? and How to modify just some nodes' styles in chemfig – clemens Jun 28 '13 at 18:30

This may not be the best way... The code below sets marks in the molecule using chemfig's @{<nodename>} syntax and then uses these marks with \chemmove (which basically is a {tikzpicture} with options remember picture, overlay) to add dashed rectangles. The main chain is numbered using a submol, similar to unbonpetit's answer to How to number atoms using chemfig?

\documentclass{article}
\usepackage{chemfig}
\definesubmol{\nr}{-[:120,.3,,,draw=none]\scriptstyle}
\begin{document}
\chemfig{
CH_3-[@{me3,.1}]CH(-[2]C_2H_5(!\nr{7, 8}))(!\nr6)
-CH([6]-[@{iPr}]CH(-[0]CH_3)-CH_3)(!\nr5)
-CH([2]-[@{tBu}]C(-[:30]CH_3)(-[:150]H_3C)-CH_3)(!\nr4)
-CH_2(!\nr3)-C(-[@{me2,.9}2]CH_3)(-[@{me1,.9}6]CH_3)(!\nr2)
-CH_3!\nr1
}
\chemmove{
\draw[dashed]
([xshift=-8pt,yshift=-8pt]iPr) rectangle ++(2.3,-1.6)
([xshift=-1.6cm]tBu) rectangle ++(3.2cm,2cm)
([xshift=-5pt]me1) rectangle ++(.75,-.5)
([xshift=-5pt]me2) rectangle ++(.75,.5)
([xshift=-3pt,yshift=-7pt]me3) rectangle ++(-.75,.5) ;
}
\end{document}


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