# Overlong line even with suggestions for hyphenation

I have a paragraph which starts with

\documentclass[a4paper,11pt,twoside]{book}
\setlength{\textwidth}{14.6cm}
\hyphenation{MnTPPCl  CoTPP}
\begin{document}

We studied surface doping with the following molecules:
2,3,5,6-tetrafluoro-7,7,8,8-tetra\-cyano\-quino\-dimethane
(F$_4$TCNQ), manganese(III)-tetra\-phenyl\-porphyrin-chloride
(MnTPPCl), cobalt(II)-tetra\-phenyl\-porphyrin (CoTPP), and
fullerene (C$_{60}$).
\end{document}


which ends up to give an overlong line at "(MnTPPCl)"

Even giving possibilities for hyphenation, it gives me the overlong line with "(MnTPPCl)" sticking out. Why doesn't it just make a line break before "(MnTPPCl)"? How can I prevent it?

Without a full example, it is impossible to test but presumably breaking the line (MnTPPCl) would require stretching the white space more than the specified values.

You can use \sloppy to tell LaTeX to allow white space to stretch more than its usual limits.

or as egreg suggested set \emergencystretch which is a less aggressive change to teh typesetting quality:

\documentclass[a4paper,11pt,twoside]{book}
\setlength{\textwidth}{14.6cm}
\hyphenation{MnTPPCl  CoTPP}
\begin{document}
\setlength\emergencystretch{2em}

We studied surface doping with the following molecules:
2,3,5,6-tetrafluoro-7,7,8,8-tetra\-cyano\-quino\-dimethane
(F$_4$TCNQ), manganese(III)-tetra\-phenyl\-porphyrin-chloride
(MnTPPCl), cobalt(II)-tetra\-phenyl\-porphyrin (CoTPP), and
fullerene (C$_{60}$).
\end{document}


• I updated it with a minimal example producing the mentioned overlong line. – Tanja Sep 8 '13 at 13:48
• Rather than \sloppy, something like \setlength{\emergencystretch}{.3\textwidth} might give better results, reserving \sloppy or (better) the sloppypar environment to very tough cases. – egreg Sep 8 '13 at 14:01
• @egreg true but I was thinking chemical names with hyphenation patterns designed for natural language probably is a "tough case" so reached straight for the sledgehammer. – David Carlisle Sep 8 '13 at 14:39
• @user2758804 see update – David Carlisle Sep 8 '13 at 14:47
• @user2758804 -- the line you would like broken has only two spaces in it. tex can distribute the stretch needed for breaking a line only at the existing spaces, so there is almost no flexibility in this example. applying \emergencystratch as suggested by egreg really requires some attention to the particular circumstance. sloppypar is probably the most appropriate action here, as its effect is more "surgical" than global. – barbara beeton Sep 8 '13 at 17:06