Manganese(VII) oxide
Encyclopedia
Manganese oxide is an inorganic compound
with the formula
Mn2O7. This volatile liquid is highly reactive and more often discussed than intentionally prepared. It is a dangerous oxidizer and was first described in 1860.
, and decomposes when in contact with water. It melts at only 5.9 °C, and sublimes at −10 °C. These properties indicate a nonpolar molecular species, which is confirmed by its structure. The molecules consist of a pair of tetrahedra 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°.
It contains manganese in its highest oxidation state. This oxidation state, +7, is shared by permanganate
s, which are more stable compounds.
Pyrosulfate, pyrophosphate, 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.
to KMnO4
. The reaction initially produces permanganic acid, HMnO4 (structurally, HOMnO3), which is dehydrated by sulfuric acid to form its anhydride, Mn2O7.
Mn2O7 can react further with sulfuric acid to give the remarkable cation MnO3+, which is isoelectronic
with CrO3
:
Mn2O7 decomposes near room temperature, explosively so at > 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
. Ozone
is also produced, giving a strong smell to the substance. The ozone can spontaneously ignite a piece of paper impregnated with an alcohol solution. The production of manganese heptoxide is an undesirable byproduct in many situations.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
Mn2O7. This volatile liquid is highly reactive and more often discussed than intentionally prepared. It is a dangerous oxidizer and was first described in 1860.
Properties
The crystalline form of this chemical compound is dark green. It is soluble in carbon tetrachlorideCarbon tetrachloride
Carbon tetrachloride, also known by many other names is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent...
, and decomposes when in contact with water. It melts at only 5.9 °C, and sublimes at −10 °C. These properties indicate a nonpolar molecular species, which is confirmed by its structure. The molecules consist of a pair of tetrahedra 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°.
It contains manganese in its highest oxidation state. This oxidation state, +7, is shared by permanganate
Permanganate
A permanganate is the general name for a chemical compound containing the manganate ion, . Because manganese is in the +7 oxidation state, the permanganate ion is a strong oxidizing agent. The ion has tetrahedral geometry...
s, which are more stable compounds.
Pyrosulfate, pyrophosphate, and dichromate adopt structures similar to that of Mn2O7. Probably the most similar main group species is Cl2O7
Dichlorine heptoxide
Dichlorine heptoxide is the chemical compound with the formula Cl2O7. This chlorine oxide is the anhydride of perchloric acid. It is produced by the careful distillation of perchloric acid in the presence of the dehydrating agent phosphorus pentoxide:...
. Focusing on comparisons within the transition metal series, Tc2O7 and Mn2O7 are structurally similar but the Tc-O-Tc angle is 180°. Solid Re2O7
Rhenium(VII) oxide
Rhenium oxide is the chemical compound with the formula Re2O7. It is the anhydride of the hypothetical acid . Perrhenic acid, Re2O7·2H2O, however is closely related structurally to Re2O7. Solid Re2O7 is polymeric consisting, unusually, of the metal centers in two coordination environments...
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 H2SO4Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
to KMnO4
Potassium permanganate
Potassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...
. The reaction initially produces permanganic acid, HMnO4 (structurally, HOMnO3), which is dehydrated by sulfuric acid to form its anhydride, Mn2O7.
- 2 KMnO4 +(cold) 2 H2SO4 → Mn2O7 + H2O + 2 KHSO4
Mn2O7 can react further with sulfuric acid to give the remarkable cation MnO3+, which is isoelectronic
Isoelectronicity
Two or more molecular entities are described as being isoelectronic with each other if they have the same number of electrons or a similar electron configuration and the same structure , regardless of the nature of the elements involved.The term valence isoelectronic is used when these molecular...
with CrO3
Chromium trioxide
Chromium trioxide is the inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name.This compound is a dark-red/orange brown solid, which dissolves in water concomitant with hydrolysis...
:
- Mn2O7 + 2 H2SO4 → 2 + H2O
Mn2O7 decomposes near room temperature, explosively so at > 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
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
. Ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
is also produced, giving a strong smell to the substance. The ozone can spontaneously ignite a piece of paper impregnated with an alcohol solution. The production of manganese heptoxide is an undesirable byproduct in many situations.