Table without thin vertical lines in Tabularx (Table in style of ACS Macro Letter journal)

Question

In this Thread (https://tex.stackexchange.com/a/301036/229635) it was explained how to make the small vertical lines between two cells disappear by using tabularx and \columncolor and changing the overhang parameters within a multicolumn.

Now I am looking for a way how to create a Table like shown in the picture attached to this post.

The reason why I am asking for your help is that the code updated on August 7th 2020 by Bernard (see link above) doesn't create a table fitting to the text width of my document.

In other words: Is there a way to get rid of all the absolute values and the multicolumn used in the m{} parameters so that the table fits still the textwidth no matter how many columns the table has while still implementing the overhang parameter for color fill to avoid the thin white lines between the cells? I Want to create a Table having no gridlines and a light gray head row without the small vertical lines between color filled cells while using \cellcolor.

Thanks a lot in advance, Benson_G

Picture Reference: Worm, M.; Leibig, D.; Dingels, C.; Frey, H. Cleavable Polyethylene Glycol: 3,4-Epoxy-1-butene as a Comonomer to Establish Degradability at Physiologically Relevant pH.ACS Macro Letters2016,5(12), 1357–1363

\documentclass[a4paper,10pt, enabledeprecatedfontcommands]{scrartcl} %Art des Dokuments, Schriftgröße etc.
\usepackage[utf8]{inputenc}%Direkte Angabe von Umlauten möglich 
\usepackage[left=3cm,right=2cm,top=2cm,bottom=2cm,includehead]{geometry}%Maße für die wissenschaftliche Arbeit
\usepackage[parfill]{parskip} %Bessere Seitenumbrüche
\usepackage[onehalfspacing]{setspace} %Zeilenabstand
\usepackage[T1]{fontenc} %Silbentrennung
\usepackage[english]{babel} %Sprachanpassungen
\usepackage{graphicx} %Einfügen von Bildern
\usepackage{tabularx} %Tabellen
\usepackage{booktabs} %Weitere Möglichkeiten für Tabellen
\usepackage{here} %Lage von Tabellen und Bildern 
\usepackage{units}
\usepackage{physics}
\usepackage{amsmath}
\usepackage{textgreek}
\usepackage{textcomp}
\usepackage{amssymb}
\usepackage[labelformat=simple]{subcaption}
\usepackage{float}
\usepackage{pdfpages}
\usepackage{lmodern} 
\usepackage{enumitem}
\usepackage[hyphens]{url}  %% be sure to specify the option 'hyphens'
% \usepackage[pdftex,bookmarksnumbered,hidelinks,breaklinks]{hyperref}
\usepackage[superscript]{cite}
\usepackage[scaled]{helvet}
\renewcommand\familydefault{\sfdefault} 
\usepackage[version=3]{mhchem} %Summenformeln angeben
\usepackage[labelsep=period]{caption}
\usepackage[per-mode = reciprocal, output-decimal-marker={,}, exponent-product = {\cdot}]{siunitx} %Si-Einheiten
% \usepackage[colorlinks,
% pdfpagelabels,
% pdfstartview = FitH,
% bookmarksopen = true,
% bookmarksnumbered = true,
% linkcolor = black,
% plainpages = false,
% hypertexnames = false,
% citecolor = black]{hyperref}
\usepackage{color}
\usepackage{colortbl}
\definecolor{hellgrau}{rgb}{0.90,0.90,0.90}
\newcommand{\RM}[1]{\MakeUppercase{\romannumeral #1{.}}}
\renewcommand\thesubfigure{\thefigure.\arabic{subfigure}}
\addtokomafont{captionlabel}{\bfseries}
\DeclareNewTOC[
  type=scheme,                         % Name der Umgebung
  types=schemes,                       % Erweiterung (\listofschemes)
  float,                               % soll gleiten
  floatpos=tbp,                        % voreingestellte Gleitparameter
  name=Scheme,                         % Name in Überschriften
  listname={Verzeichnis der Schemata}, % Listenname
                                       % counterwithin=chapter
]{los}
\begin{document}
\begin{table}[H]
\vspace{-1.8 \baselineskip}
  \centering
  \setlength\belowcaptionskip{5 pt}
  \caption{\textbf{Reaction mixture used for the synthesis of cyclohexanone 4-nitrophenylhydrazone.}}
    \begin{tabular}{cccccc}

     \cellcolor{hellgrau} chemicals   &\cellcolor{hellgrau} \textit{M} $^a$ (g mol$^{\text{-1}}$)  &\cellcolor{hellgrau} \textit{n} $^a$(mol 10$^{\text{-4}}$)  &\cellcolor{hellgrau} \textit{V} $^a$ (mL) &\cellcolor{hellgrau}  \textit{m} $^a$ (g) &\cellcolor{hellgrau} $\varrho$ $^a$ (g mL$^{\text{-1}}$)\
    Cyclohexanone               & 98.14   &  \multicolumn{4}{c}{0.5 mL of the destillate}    \
    4-Nitrophenyl hydrazine     & 153.14  &  26    &   -  & 0.4   & -     \
    Sulfuric acid               & 98.08   &  372   &   2  & 3.68  & 1.84 \
    Water                       & 18.02   & 1664   &   3  & 3     & 1.00 \
    Ethanol                     & 47.07   & 1678   &   10 & 7.9   & 0.79    \
    \end{tabular} 
    \vspace{0.6 \baselineskip} \
    \raggedright
    $^a$Molecular mass \textit{M}, amount of substance \textit{n}, volume \textit{V}, mass \textit{m},  density $\varrho$.
  \label{tab:ReactionMixtureCyclohexanone4-nitrophenylhydrazone}%
  \vspace{-1.8 \baselineskip}
\end{table}
\end{document}

Answer 1

With {NiceTabular*} of nicematrix.

\documentclass{article}
\usepackage{nicematrix}
\usepackage{enumitem}
\begin{document}
\newcolumntype{-}{@{\extracolsep{\fill}}}
\begin{table}
\caption{Caption of my table\tabularnote{A tabular note.}}
\begin{NiceTabular}{\textwidth}{c-c-c-c-c}
\CodeBefore
  \rowcolor{lightgray}{1}
\Body
  Col 1 & Col 2 & Col 3 & Col 4 & Col 5 \
  text & text & text & text & text \
  text & text & text & text & text \
  text & text & text & text & text \
  text & text & text & text & text \
\end{NiceTabular}
\end{table}
\end{document}

You need several compilations (because nicematrix uses PGF/Tikz nodes).

Answer 2

Like this?

(red lines indicate page layout)

• from your document example I try to make MWE (Minimal Working Example),therefore from your example are removed all packages and settings not related to your problem
• to old version of packages or even deprecated are indicated and replaced with recent one
• for table is used tabularx environment, its width is set to \textwidth, so using them is solved your problem that table width should be equal to \textwidth
• for columns with numbers are used S columns, defined in siunitx package, which enable align numbers at their decimal points
• since I suspect, that you in table headers indicate "footnotes", I suggest that for this is better use tnotes defined in the threeparttable and for descriptions of their meaning use table notes

MWE:

\documentclass[a4paper,10pt, 
               enabledeprecatedfontcommands]{scrartcl} %Art des Dokuments, Schriftgröße etc.
\usepackage[hmargin={3cm,2cm},vmargin=2cm,
            includehead]{geometry}%Maße für die wissenschaftliche Arbeit
%\usepackage[utf8]{inputenc}% now is default encoding 
\usepackage{lmodern}
\usepackage[T1]{fontenc} %Silbentrennung
\usepackage[english]{babel} %Sprachanpassungen
\usepackage[column=O]{cellspace}                % <-- new
\setlength\cellspacetoplimit{2pt}
\setlength\cellspacebottomlimit{2pt}
\addparagraphcolumntypes{X}
\usepackage{booktabs, tabularx, % Tabellen
            threeparttable}     % new 
\newcommand\mcx[1]{\multicolumn{1}{>{\centering\arraybackslash}OX}{#1}}
\renewcommand\TPTtagStyle{\bfseries}%for formating tags (in table, in items)
\usepackage[version=4]{mhchem}  % newest version
\usepackage{siunitx}% instead of units, which is deprecate
\usepackage[skip=1ex, format=plain, font=small, labelfont=bf]{caption}     % new
%\usepackage[labelformat=simple]{subcaption}
\usepackage[table]{xcolor}  % changed, instead of "color" and "colortbl"
\definecolor{hellgrau}{rgb}{0.90,0.90,0.90}
%---------------- show page layout. don't use in a real document!
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%
\begin{document}
    \begin{table}[ht]
    \centering
    \renewcommand\tabularxcolumn[1]{m{#1}}
\begin{threeparttable}
\caption{Reaction mixture used for the synthesis of cyclohexanone 4-nitrophenylhydrazone.}
\label{tab:ReactionMixtureCyclohexanone4-nitrophenylhydrazone}
    \begin{tabularx}{0.8\linewidth}{l 
                                    S[table-format=3.2]
                                    S[table-format=4.0]
                                    S[table-format=2.0]
                                    S[table-format=1.1]
                                    S[table-format=1.2]
                                    }
    \rowcolor{hellgrau} 
chemicals   & \mcx{$M$\tnote{a} (\si{\gram\per\mole})}

                & \mcx{$n$\tnote{b} (\si{\gram\per\mole})}

                    & \mcx{$V$\tnote{c}\par     (\si{\milli\liter})} 
                        & \mcx{$m$\tnote{d}\par     (\si{\gram})}
                            & \mcx{$\varrho$\tnote{e}\par (\si{\gram\per\mole})}          \
% table body
Cyclohexanone           & 98.14   & \multicolumn{4}{c}{\SI{0.5}{\milli\liter} of the distillate} \
4-Nitrophenyl hydrazine & 153.14  &  26    & {--} & 0.4   & {--}     \
Sulfuric acid           & 98.08   &  372   &   2  & 3.68  & 1.84    \
Water                   & 18.02   & 1664   &   3  & 3     & 1.00    \
Ethanol                 & 47.07   & 1678   &   10 & 7.9   & 0.79    \
    \bottomrule
    \end{tabularx}
    \begin{tablenotes}[flushleft, para]\footnotesize
\item[a]    $M$: Molecular mass
\item[b]    $n$: amount of substance , 
\item[c]    $V$: volume, 
\item[d]    $m$: mass,

\item[e]    $\varrho$: density .
    \end{tablenotes}
\end{threeparttable}
    \end{table}
\end{document}

Edit:

• Suggested table design has width of the \texwidth, however number of columns cannot be any, if you you like avoid overlaping of cells contents. With other words, it is limited by size column contents.

• In the case that you not have numbers in table, than you can in above MWE use X column specifiers and omit use of \mcx for use in column headers (but this is not a case in your code example)

IN