So I'm making a table with chemfig figures in a particular row. I want these figures to be centered vertically. I tried the answers in this answer, which seemed to work fine. However, I wanted some cell padding as well. That's why I tried the command \renewcommand{\arraystretch}{2}
from this answer. However, unfortunately it doesn't seem like this extends to chemfig diagrams.
Then I tried manually adding spaces before and after the table rows and tried centering them that way. This was kind of strange (I had to use negative spaces because sometimes I needed a space before the horizontal line and sometimes afterwards). However, in the fifth row, there appears to be some sort of a space which carries on to other columns as well.
Is there any way I can fix this problem? My MWE is here:
\documentclass[a4paper]{article}
\usepackage{array}
\usepackage[margin=2cm]{geometry}
\usepackage{chemfig}
\begin{document}
\thispagestyle{empty}
\renewcommand{\arraystretch}{2}
\begin{tabular}{|m{4cm}|m{4cm}|}
\hline
\textbf{Name of homologous series} & \textbf{Structure} \\
\hline
alkene & \chemfig{R-C=C-R'} \\
\hline
alkyne & \chemfig{R-C~C-R'} \\
\hline
alcohol & \chemfig{R-O-[:-30]H} \\[1.5em]
\hline
\\[-2em] ether & \chemfig{R-[:30]O-[:-30]R'} \\
\hline
\end{tabular}
\end{document}