MnO2 has an α-polymorph that can incorporate a variety of atoms (as well as water molecules) in the "tunnels" or "channels" between the manganese oxide octahedra.

The complicated solid-state chemistry of this material is relevant to the lore of "freshly prepared" MnO2 in organic synthesis.

[7] The α-polymorph of MnO2 has a very open structure with "channels", which can accommodate metal ions such as silver or barium.

At temperatures of 400 °C, the salt decomposes, releasing N2O4 and leaving a residue of purified manganese dioxide.

To complete the process, a suspension of this material in sulfuric acid is treated with sodium chlorate.

[8] Lastly, the action of potassium permanganate over manganese sulfate crystals produces the desired oxide.

EMD is commonly used in zinc manganese dioxide rechargeable alkaline (Zn RAM) cells also.

In a classical laboratory demonstration, heating a mixture of potassium chlorate and manganese dioxide produces oxygen gas.

[4] The reaction would not be expected to proceed, based on the standard electrode potentials, but is favoured by the extremely high acidity and the evolution (and removal) of gaseous chlorine.

[13] Excavations at the Pech-de-l'Azé cave site in southwestern France have yielded blocks of manganese dioxide writing tools, which date back 50,000 years and have been attributed to Neanderthals .

Usually, however, the reagent is generated in situ by treatment of an aqueous solution KMnO4 with a Mn(II) salt, typically the sulfate.

MnO2 oxidizes allylic alcohols to the corresponding aldehydes or ketones:[16] The configuration of the double bond is conserved in the reaction.