Stereochemistry: \cip locants should not be printed in italics

[tstone-1]

The manual says:

I'm pretty sure™ that (2S,3S) and (2E,4Z) should be (2S,3S) and (2E,4Z) instead, respectively, so that the locant numbers are printed in roman. This resource seems to confirm my opinion, see page 17 and 19, for example.

[Sonja-K]

The 2013 version of the IUPAC Blue book, sepcifically "Chapter P-9 SPECIFICATION OF CONFIGURATION AND CONFORMATION" seems to agree on that (https://www.qmul.ac.uk/sbcs/iupac/BlueBook/PDF/P9.pdf)

chemmacros' nomenclature module offers several options to alter the format of entries inside of \cip. Among these, is also cip-number-format which you could use to get the expected behaviour: italic letters and upright numbers:

\documentclass{article}
\usepackage{chemmacros}
\chemsetup{modules=nomenclature}
\chemsetup{nomenclature/cip-number-format=\normalfont}
\begin{document}

\iupac{\cip{2S,3S}-Wein|s\"aure}\par
\iupac{\cip{2S,3R}-($-$)-2,3,4-Tri|hydroxy|butanal}\par
\iupac{\cip{2E,4Z}-Hexa|diene}

\end{document}

[cgnieder]

This should be the default behavior, changed for the next update.