Manganese(VII) oxide (manganese heptoxide) is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistr ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a '' chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betw ...

Mn₂O₇. This volatile liquid is highly reactive. It is a dangerous

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...

and was first described in 1860. It is the

acid anhydride An acid anhydride is a type of chemical compound derived by the removal of water molecules from an acid. In organic chemistry, organic acid anhydrides contain the functional group R(CO)O(CO)R'. Organic acid anhydrides often form when one equivalen ...

permanganic acid Permanganic acid (or manganic(VII) acid) is the inorganic compound with the formula H MnO4. This strong oxoacid has been isolated as its dihydrate. It is the conjugate acid of permanganate salts. It is the subject of few publications and its ...

Properties

The

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

form of this chemical compound is dark green. The liquid is green by reflected light and red by transmitted light. It is soluble in

carbon tetrachloride Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVACR) is an organic compound with the chemic ...

, and decomposes when in contact with water.

Structure

Its solubility properties indicate a

nonpolar In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end. Polar molecules must contain one or more polar ...

molecular species, which is confirmed by its structure. The molecules consist of a pair of

tetrahedra In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the ...

that share a common vertex. The vertices are occupied by oxygen atoms and at the centers of the tetrahedra are the Mn(VII) centers. The connectivity is indicated by the formula O₃Mn−O−MnO₃. The terminal Mn−O distances are 1.585 Å and the bridging oxygen is 1.77 Å distant from the two Mn atoms. The Mn−O−Mn angle is 120.7°.

Pyrosulfate In chemistry, disulfate or pyrosulfate is the anion with the molecular formula . Disulfate is the IUPAC name. It has a dichromate-like structure and can be visualised as two corner-sharing SO4 tetrahedra, with a bridging oxygen atom. In this a ...

pyrophosphate In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P–O–P linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate (Na2H2P2O7) and tetrasodium pyrophosphate (Na4P2O7), among ot ...

, and dichromate adopt structures similar to that of Mn₂O₇. Probably the most similar main group species is Cl₂O₇. Focusing on comparisons within the transition metal series, Tc₂O₇ and Mn₂O₇ are structurally similar but the Tc−O−Tc angle is 180°. Solid Re₂O₇ is not molecular but consists of crosslinked Re centers with both tetrahedral and octahedral sites; in the vapour phase it is molecular with a similar structure to Tc₂O₇.

Synthesis and reactions

Mn₂O₇ arises as a dark green oil by the addition of concentrated H₂SO₄ to KMnO₄. The reaction initially produces permanganic acid, HMnO₄ (structurally, HOMnO₃), which is dehydrated by cold sulfuric acid to form its

anhydride An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the p ...

, Mn₂O₇. :2 KMnO₄ + 2 H₂SO₄ → Mn₂O₇ + H₂O + 2 KHSO₄ Mn₂O₇ can react further with sulfuric acid to give the remarkable manganyl(VII) cation , which is

isoelectronic Isoelectronicity is a phenomenon observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electronic configurations, but differ by what specific elements are at certain locations in the ...

with CrO₃ :Mn₂O₇ + 2 H₂SO₄ → 2 + H₂O Mn₂O₇ decomposes near room temperature, explosively so above 55 °C. The explosion can be initiated by striking the sample or by its exposure to oxidizable organic compounds. The products are MnO₂ and O₂.Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. .

Ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lowe ...

is also produced, giving a strong smell to the substance. The ozone can spontaneously ignite a piece of paper impregnated with an alcohol solution. Manganese heptoxide reacts with

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3 ...

in presence of

sulfuric acid Sulfuric acid ( American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...

, liberating

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

and

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lowe ...

: : 2 Mn₂O₇ + 2 H₂O₂ + 4 H₂SO₄ → 4 MnSO₄ + 6 H₂O + 2 O₃ + 3 O₂

References

{{Oxides Explosive chemicals Manganese(VII) compounds Acid anhydrides Acidic oxides