In alkaline medium, the reduction of permanganate anion involves a gain of 3 electrons.

The balanced chemical equation for the reduction of permanganate anion in alkaline medium is:

$ \begin{equation} \ce{MnO4^{-}(aq) + 3 e^{-} + 2 H2O(l) -> MnO2(s) + 4 OH^{-}(aq)} \end{equation}$

In this reaction, the permanganate anion (MnO₄^-) is reduced to manganese dioxide (MnO₂) by gaining 3 electrons. The water molecules (H₂O) are oxidized by losing 2 electrons. The hydroxide ions (OH^-) are spectator ions that do not participate in the redox reaction.

The reduction of permanganate anion in alkaline medium is a useful reaction for a variety of analytical and synthetic purposes. For example, it can be used to quantitatively determine the concentration of an analyte in a solution, or to synthesize a variety of organic compounds.