Modify part of an environment from a package: experimental environment of chemmacros

Question

General Question: How do I use an environment from a package and modify one or more commands but keep all the functionality of the the others? Sorry if I should know that this isn't possible or viable and it's just easier to make the environments yourself from scratch (which would be beyond my skills).

Specific question: How do I use the experimental environment from chemmacros but modify for example the \NMR, \pos and maybe \J commands? And is it possible to still make \\#{} work with a renewed \NMR command?

For our reports we need to present NMR data like shown in the picture.

Renewing the \NMR command works well for use in the experimental environment and outside. But renewing the other commands doesn't work. And just \newcommand for example for \J{}{}{} works but only outside the environment.

\documentclass[12pt,a4paper]{scrartcl}
\usepackage{textgreek}
\usepackage{siunitx}
\usepackage{chemmacros}
\chemsetup{modules={all},greek=textgreek}

\renewcommand{\NMR}[6]{\noindent\textbf{$\mathbf{^{#1}#2}$-NMR (#3)} (#4~MHz, #5~K, \ch{#6}, $\delta/\si{ppm}$):}   %\nmr{MZ}{Kern}{Nummer}{Frequenz}{Temperatur}{Lsm}
\renewcommand{\J}[3]{$^{{\textsl{##1}}}J_{\mathrm{##2}} = ##3~\mathrm{Hz}$} %\J{Bindungen}{koppelnde Kerne}{Frequenz}
\renewcommand{\pos}[1]{\textbf{##1}}    %Zuordnung

\begin{document}
\begin{experimental}
\NMR{1}{H}{prakt\_AC.999}{400}{298}{CDCl3} \val{1.11--2.22} (d, 4 H, \J{4}{HH}{6.66}, \pos{7})
\end{experimental}
\end{document}

And renewing the environment "deletes" all the other commands, like for example the \val{} command or the \J command.

\renewenvironment{experimental}{
\renewcommand{\NMR}[6]{\noindent\textbf{$\mathbf{^{##1}##2}$-NMR (##3)} (##4~MHz, ##5~K, \ch{##6}, $\delta/\si{ppm}$):} %\nmr{MZ}{Kern}{Nummer}{Frequenz}{Temperatur}{Lsm}
\renewcommand{\pos}[1]{\textbf{##1}}    %Zuordnung
\renewcommand{\#}[1]{\textbf{##1}}  %Anzahl Kerne
}{}

Answer 1

The macros \pos, \J, and \# are set up through the experimental environment. They don't have a meaning outside -- at least not from chemmacros. For each of them there exists an internal command which in case of pos can easily be redefined as the example below shows.

Here's a way to get the desired output (apart from the italic nuclei subscript – I suspect the example has this rather by chance than on purpose…)

\documentclass[12pt,a4paper]{scrartcl}
\usepackage{textgreek}
\usepackage{siunitx}
\usepackage{chemmacros}

\chemsetup{
  modules = spectroscopy ,
  greek   = textgreek ,
}

\ExplSyntaxOn
\chemmacros_define_keys:nn {spectroscopy}
  { atom-number-space .skip_set:N = \l__chemmacros_nmr_space_skip }
\cs_set_protected:Npn \chemmacros_nmr_position:n #1
  { \textbf {#1} }
\ExplSyntaxOff

\chemsetup{
  spectroscopy/format = \bfseries ,
  spectroscopy/coupling-pos = sub ,
  spectroscopy/atom-number-space = 0pt
}

\begin{document}

\begin{experimental}
  \data{\NMR*{1,H} (ac\_prakt 12345)}
  (\SI{250}{\mega\hertz}, \SI{298}{\kelvin}, \ch{CDCl3}, $\delta$/ppm):
    \val{8.71} (d, \#{1}, \J(3;HH){4.4}, \pos{2})
    \val{7.66} (d, \#{1}, \J(3;HH){7.7}, \pos{4})
    \val{7.38} (dd, \#{1}, \J(3;HH){4.5}, \J(3;HH){7.8}, \pos{3})
    \val{3.03} (t, \#{2}, \J(3;HH){5.99}, \pos{8})
    \val{2.81} (t, \#{2}, \J(3;HH){5.98}, \pos{10})
    \val{2.2} (p, \#{2}, \J(3;HH){6.11}, \pos{9})
\end{experimental}

\end{document}