Second symbol on arrows in the package mhchem

Question

Why does the following formula have problem?

$\ce{A ->[k''] B}$

It doesn't have any problem with prime symbol but with second symbol it won't be compiled.

Any idea about how to use second symbol in this package?

Answer 1

Grouping the argument seems to solve the issue.

\documentclass{article}
\usepackage{mhchem}
\begin{document}
$\ce{A ->[{k''}] B}$
\end{document}

If one needed the k in math mode, then $\ce{A ->[{$k''$}] B}$ would do.

\documentclass{article}
\usepackage{mhchem}
\begin{document}
$\ce{A ->[{$k''$}] B}$
\end{document}