Numbers in \cip should be upright about chemmacros HOT 4 CLOSED

As far as I can see the document you have linked makes no typographical suggestion at all?! Nowhere in the text it is said the numbers should be upright… I am not convinced that a mere usage in a draft document can be counted as recommendation.

However, if you insist then just put the numbers in math mode:

\documentclass{article}
\usepackage{chemmacros}
\begin{document}
\cip{$2$R,$3$S}
\end{document}

from chemmacros.

Although no explicit typographical suggestion is made, always the numbers are typeset upright. I referred to the draft document because I couldn't find a freely accessible PDF of the latest release of the IUPAC Blue Book. There is one behind a paywall, but if you don't have access I cannot show you that this document also shows preferred IUPAC names with upright numbers. It just feels weird to me that I should resort to putting the numbers in math mode to get the same result as there.

As another source not behind a paywall, in the IUPAC Red Book, again the numbers are typeset upright, for example on page 40 (52 in the PDF). In that section (IR-2.14.2), it is mentioned that these locants should be Arabic numerals. Granted, still nothing is explicitly said about whether these should be italic or not, but also in other cases the locant is not italicised in combination with an italic letter (e.g. 1H-1,2,3-disilagermirene on page 39 (51 in the PDF)), and in other cases it is explicitly stated when something should be italic.

from chemmacros.

I'll check other sources and in any way will add an interface for setting the appearance of numbers and letters differently. I'm not sure if I'll change the default appearance, yet.

from chemmacros.

This is now implemented and can be customized with the three options cip-inner-format, cip-outer-format and cip-number-format.

from chemmacros.