Manganese heptoxide
{{Short description|Chemical compound}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 450876772
| Name = Manganese(VII) oxide
| ImageFile = Mn2O7.svg
| ImageClass = skin-invert-image
| ImageSize =
| ImageName = Manganese(VII) oxide
| ImageFile1 = Manganese-heptoxide-3D-balls.png
| ImageClass1 = bg-transparent
| ImageSize1 =
| ImageName1 = Ball-and-stick model of manganese heptoxide
| ImageFile2 = Manganese-heptoxide-3D-vdW.png
| ImageClass2 = bg-transparent
| ImageName2 = Manganese(VII) oxide
| ImageFile3 = Manganese_heptoxide.jpg
| ImageName3 =
| IUPACName = Manganese(VII) oxide
| OtherNames = Manganic oxide
dimanganese heptoxide
Permanganic anhydride
Permanganic oxide
| SystematicName =
| Section1 = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 12057-92-0
| ChemSpiderID = 9944714
| EINECS = 235-025-8
| PubChem = 13879826
| StdInChI=1S/2Mn.7O/q;;7*-2
| StdInChIKey = ZEFXULJEOUCCOQ-UHFFFAOYSA-N
| SMILES = O=[Mn](=O)(=O)O[Mn](=O)(=O)=O
}}
| Section2 = {{Chembox Properties
| Formula = Mn2O7
| MolarMass = 221.87 g/mol
| Appearance = dark red oil (room temp.), green if in contact with sulfuric acid
| Density = 2.79 g/cm3
| Solubility = decomposes to permanganic acid, HMnO4
| MeltingPtC = 5.9
| MeltingPt_notes =
| BoilingPt = explodes on heating
}}
| Section3 = {{Chembox Structure
| Coordination = bitetrahedral
| CrystalStruct = monoclinic
}}
| Section4 =
| Section5 =
| Section6 =
| Section7 = {{Chembox Hazards
| ExternalSDS =
| MainHazards = explosive, strong oxidizer, very corrosive
| GHSPictograms = {{GHS01}}{{GHS03}}{{GHS05}}{{GHS06}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|201}}, {{H-phrases|271}}, {{H-phrases|314}}, {{H-phrases|300+310+330}}
| PPhrases = {{P-phrases|260}}, {{P-phrases|284}}, {{P-phrases|283}}, {{P-phrases|221}}
| NFPA-H = 4
| NFPA-F = 4
| NFPA-R = 4
| NFPA-S = OX
}}
| Section8 = {{Chembox Related
| OtherCompounds = Re2O7
KMnO4
Tc2O7
Cl2O7
}}
}}
Manganese(VII) oxide (manganese heptoxide) is an inorganic compound with the formula {{chem2|Mn2O7}}. 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.Aschoff, H. Ann. Phys. Chem. Ser. 2 volume 111 (1860) page 217 and page 224. 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.{{cite book|author=H. Lux|chapter=Manganese(VII) Oxide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=1459–1460}} 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°.{{cite journal |author1=Simon, A. |author2=Dronskowski, R. |author3=Krebs, B. |author4=Hettich, B. | title = The Crystal Structure of Mn2O7 | journal = Angew. Chem. Int. Ed. Engl. | year = 1987 | volume = 26 |issue=2 | pages = 139–140 | doi = 10.1002/anie.198701391}}
Pyrosulfate, pyrophosphate, and dichromate adopt structures similar to that of {{chem2|Mn2O7}}. Probably the most similar main group species is {{chem2|Cl2O7}}. Focusing on comparisons within the transition metal series, {{chem2|Tc2O7}} and {{chem2|Mn2O7}} are structurally similar but the Tc−O−Tc angle is 180°. Solid {{chem2|Re2O7}} is not molecular but consists of crosslinked Re centers with both tetrahedral and octahedral sites;{{cite journal |author1=Krebs, B. |author2=Mueller, A. |author3=Beyer, H. H. | title = The Crystal Structure of Rhenium(VII) Oxide | journal = Inorganic Chemistry | year = 1969 | volume = 8 |issue=3 | pages = 436–443 | doi = 10.1021/ic50073a006}} in the vapour phase it is molecular with a similar structure to Tc2O7.Wells A.F. (1962) Structural Inorganic Chemistry 3d edition Oxford University Press
Synthesis and reactions
{{chem2|Mn2O7}} arises as a dark green oil by the addition of cold concentrated {{chem2|H2SO4}} to solid {{chem2|KMnO4}}. The reaction initially produces permanganic acid, {{chem2|HMnO4}} (structurally, {{chem2|HOMnO3}}), which is dehydrated by cold sulfuric acid to form its anhydride, {{chem2|Mn2O7}}:
:{{chem2|2 KMnO4 + 2 H2SO4 -> Mn2O7 + H2O + 2 KHSO4}}
{{chem2|Mn2O7}} can react further with sulfuric acid to give the remarkable manganyl(VII) cation {{chem2|MnO3+}}, which is isoelectronic with {{chem2|CrO3}}:
:{{chem2|Mn2O7 + 2 H2SO4 -> 2 [MnO3]+[HSO4]- + H2O}}
{{chem2|Mn2O7}} decomposes near room temperature, explosively so above {{convert|55|C}}. The explosion can be initiated by striking the sample or by its exposure to oxidizable organic compounds. The products are {{chem2|MnO2}} and {{chem2|O2}}.Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}. 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|date=June 2024}}
Manganese heptoxide reacts with hydrogen peroxide in presence of sulfuric acid, liberating oxygen and ozone:
:{{chem2|2 Mn2O7 + 2 H2O2 + 4 H2SO4 -> 4 MnSO4 + 6 H2O + 2 O3 + 3 O2}}
References
{{Reflist}}
External links
[https://www.youtube.com/watch?v=2BZGjycR7YM Demonstration of manganese heptoxide's properties] on YouTube{{Manganese compounds}}
{{Oxides}}