Manganese heptoxide

Manganese(VII) oxide

Manganese(VII) oxide
Ball-and-stick model of manganese heptoxide
Manganese(VII) oxide
Names
IUPAC name Manganese(VII) oxide
Other names Manganic oxide dimanganese heptoxide Permanganic anhydride Permanganic oxide
Identifiers
CAS Number	12057-92-0  Y
3D model (JSmol)	Interactive image
ChemSpider	9944714
ECHA InfoCard	100.031.829
EC Number	235-025-8
PubChem CID	13879826
CompTox Dashboard (EPA)	DTXSID10894891
InChI InChI=1S/2Mn.7O/q;;7*-2 Key: ZEFXULJEOUCCOQ-UHFFFAOYSA-N
SMILES O=[Mn](=O)(=O)O[Mn](=O)(=O)=O
Properties
Chemical formula	Mn2O7
Molar mass	221.87 g/mol
Appearance	dark red oil (room temp.), green if in contact with sulfuric acid
Density	2.79 g/cm3
Melting point	5.9 °C (42.6 °F; 279.0 K)
Boiling point	explodes on heating
Solubility in water	decomposes to permanganic acid, HMnO4
Structure
Crystal structure	monoclinic
Coordination geometry	bitetrahedral
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	explosive, strong oxidizer, very corrosive
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H201, H271, H314, H300+H310+H330
Precautionary statements	P260, P284, P283, P221
NFPA 704 (fire diamond)	4 4 4 OX
Related compounds
Related compounds	Re2O7 KMnO4 Tc2O7 Cl2O7
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N  verify  (what is  YN ?) Infobox references

Manganese(VII) oxide (manganese heptoxide) is an inorganic compound with the formula Mn ₂ O ₇. Manganese heptoxide is a volatile liquid with an oily consistency. It is a highly reactive and powerful oxidizer that reacts explosively with nearly any organic compound. It was first described in 1860. ^[1] It is the acid anhydride of permanganic acid.

Properties

The crystalline form of this chemical compound is dark green. The liquid is green by reflected light and red by transmitted light. ^[2] It is soluble in carbon tetrachloride, and decomposes when in contact with water.

Structure

Its solubility 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°. ^[3]

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; ^[4] in the vapour phase it is molecular with a similar structure to Tc₂O₇. ^[5]

Synthesis and reactions

Mn₂O₇ arises as a dark green oil by the addition of cold concentrated H₂SO₄ to solid KMnO₄ . ^[2] The reaction initially produces permanganic acid, HMnO₄ (structurally, HOMnO₃), which is dehydrated by cold sulfuric acid to form its anhydride, Mn₂O₇:

2 KMnO₄ + 2 H₂SO₄ → Mn₂O₇ + H₂O + 2 KHSO₄

Mn₂O₇ can react further with sulfuric acid to give the remarkable manganyl(VII) cation MnO+3, which is isoelectronic with CrO₃ :

Mn₂O₇ + 2 H₂SO₄ → 2 [MnO₃]⁺[HSO₄]⁻ + H₂O

Mn₂O₇ decomposes near room temperature, explosively so above 55 °C (131 °F). The explosion can be initiated by striking the sample or by its exposure to oxidizable organic compounds. The products are MnO₂ and O₂ . ^[6] 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.^{[ citation needed ]}

Manganese heptoxide reacts with hydrogen peroxide in presence of sulfuric acid, liberating oxygen and ozone:

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

References

1. Aschoff, H. Ann. Phys. Chem. Ser. 2 volume 111 (1860) page 217 and page 224.
2. H. Lux (1963). "Manganese(VII) Oxide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. pp. 1459–1460.
3. Simon, A.; Dronskowski, R.; Krebs, B.; Hettich, B. (1987). "The Crystal Structure of Mn₂O₇". Angew. Chem. Int. Ed. Engl. 26 (2): 139–140. doi:10.1002/anie.198701391.
4. Krebs, B.; Mueller, A.; Beyer, H. H. (1969). "The Crystal Structure of Rhenium(VII) Oxide". Inorganic Chemistry . 8 (3): 436–443. doi:10.1021/ic50073a006.
5. Wells A.F. (1962) Structural Inorganic Chemistry 3d edition Oxford University Press
6. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN   0-12-352651-5.

External links

Demonstration of manganese heptoxide's properties on YouTube