2

Why \colordoesn't work? I need to color the -OH oxydrilic function:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[italian]{babel}
\usepackage[
  a4paper,
  margin=15mm,
  bindingoffset=2mm,
  heightrounded,
]{geometry}

\usepackage{amsmath}
\usepackage{chemfig}
\usepackage[version=3]{mhchem}

\begin{document}
\schemestart
\chemfig{CH_3CH_2-[:-60,,3]C(-[:-120]H)=C(-[:-60]H)-[:60]H}
\arrow(.-1--){->[\chemfig{H_2O}][\chemfig{H^+}]}[,1.5]
\chemfig{CH_3CH_2-[:-0]C(-[:90]{\color{red}OH})(-[:-90]H)-C(-[:-90]H)(-[:90]H)(-[:0]H)}
\schemestop
\end{document}

enter image description here

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2
  • 1
    Have a look at the manual section 12.1 How to write a colored atom (p. 42 of the manual to v1.2e 2017-05-20)
    – cgnieder
    Jun 21, 2017 at 20:10
  • Unrelated to the question, but: version 4 of mhchem was released about two years ago so \usepackage[version=4]{mhchem} seems more appropriate (unless you have an outdated TeX distribution…)
    – cgnieder
    Jun 21, 2017 at 20:23

1 Answer 1

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4

Using \textcolor seems to make it work.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[italian]{babel}
\usepackage[
  a4paper,
  margin=15mm,
  bindingoffset=2mm,
  heightrounded,
]{geometry}

\usepackage{amsmath}
\usepackage{chemfig}
\usepackage[version=3]{mhchem}
\usepackage{xcolor}
\begin{document}
\schemestart
\chemfig{CH_3CH_2-[:-60,,3]C(-[:-120]H)=C(-[:-60]H)-[:60]H}
\arrow(.-1--){->[\chemfig{H_2O}][\chemfig{H^+}]}[,1.5]
\chemfig{CH_3CH_2-[:-0]C(-[:90]{\textcolor{red}{OH}})(-[:-90]H)-C(-[:-90]H)(-[:90]H)(-[:0]H)}
\schemestop
\end{document}

enter image description here

Apparently, using {\color{red}{OH}} also makes it work, just by bracing the "OH". Alternately, so does {{\color{red}OH}}, with the double brace.

However, as noted by the OP, it would be desirable to get just the oxygen linked to the bond, and so (after consulting the manual against my better judgment :^) I came up with this, in which I use a | to separate the atom specification, and apply color to each, respectively, as in {\color{red}{O}|\color{red}{H}}.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[italian]{babel}
\usepackage[
  a4paper,
  margin=15mm,
  bindingoffset=2mm,
  heightrounded,
]{geometry}

\usepackage{amsmath}
\usepackage{chemfig}
\usepackage[version=3]{mhchem}
\usepackage{xcolor}
\begin{document}
\schemestart
\chemfig{CH_3CH_2-[:-60,,3]C(-[:-120]H)=C(-[:-60]H)-[:60]H}
\arrow(.-1--){->[\chemfig{H_2O}][\chemfig{H^+}]}[,1.5]
\chemfig{CH_3CH_2-[:-0]C(-[:90]{\color{red}{O}|\color{red}{H}})(-[:-90]H)-C(-[:-90]H)(-[:90]H)(-[:0]H)}
\schemestop
\end{document}

enter image description here

Improve this answer
8
  • 2
    This behaviour is actually documented: section 12.1 How to write a colored atom p. 42 of the manual to v1.2e 2017-05-20 :)
    – cgnieder
    Jun 21, 2017 at 20:10
  • I noticed that adding the color effect, it changes the bind offset. How would I do if I wanted carbon directly bound to oxygen?
    – Salvo Matteini
    Jun 21, 2017 at 21:26
  • @SalvoMatteini I am not a user of the package to know the proper way, but this will, I think, give what you want: {\textcolor{red}{O\rlap{H}}}
    – Steven B. Segletes
    Jun 22, 2017 at 0:10
  • 1
    @SalvoMatteini -{\color{red}O}|{\color{red}H} should work
    – cgnieder
    Jun 22, 2017 at 7:00
  • @StevenB.Segletes using \llap/\rlap with chemfig should rarely if ever be necessary…
    – cgnieder
    Jun 22, 2017 at 7:22

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