Manganese (VII) oxide

Structural formula
General
Surname	Manganese (VII) oxide
other names	Dimanganese heptoxide
Molecular formula	Mn 2 O 7
Brief description	oily, greenish-brown liquid
External identifiers / databases
CAS number 12057-92-0 EC number 235-025-8 ECHA InfoCard 100,031,829 PubChem 13879826 Wikidata Q27506
properties
Molar mass	221.87 g mol −1
Physical state	liquid
density	2.40 g cm −3
Melting point	6 ° C
boiling point	Slow decomposition from −10 ° C, from 40 ° C deflagration
solubility	Decomposes on contact with water in permanganic acid
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Manganese (VII) oxide is a chemical compound with the empirical formula Mn ₂ O ₇ . The oily liquid is highly reactive as it is a strong oxidizing agent . The first description was made in 1860.

Extraction and presentation

Manganese (VII) oxide is obtained from the reaction of sulfuric acid with potassium permanganate .

${\displaystyle \mathrm {2\ KMnO_{4}+2\ H_{2}SO_{4}\longrightarrow } }$ ${\displaystyle \mathrm {Mn_{2}O_{7}+H_{2}O+2\ KHSO_{4}} }$

properties

At low temperatures, the compound is a crystalline solid that reflects green light and looks red in transmitted light. The compound consists of a pair of tetrahedra connected by an oxygen atom, which can be described by the structural formula O ₃ Mn – O – MnO ₃ . The outer Mn – O bonds are 158.5 pm in length  , the central bond is 177 pm. The central Mn – O – Mn bond has an angle of 120.7 °. These properties are similar to pyrosulfates , pyrophosphates , dichromates and other R ₂ O ₇ compounds (where R stands for chlorine or metals such as technetium or rhenium ).

safety instructions

Manganese (VII) oxide is a highly reactive compound. It decomposes slowly from −10 ° C and explosively from 95 ° C, whereby the explosion can also be triggered by shock or contamination. Deflagration is observed between these temperatures. Emerge with manganese (IV) oxide (manganese dioxide), oxygen and small amounts of ozone , which gives a strong odor of the compound.

${\displaystyle \mathrm {2\ Mn_{2}O_{7}\longrightarrow 4\ MnO_{2}+3\ O_{2}} }$

It carbonizes most organic substances, such as wood, in a sometimes explosive reaction and is therefore extremely corrosive. Self-ignition occurs with acetone or other solvents. It is relatively stable in carbon tetrachloride .

Individual evidence

1. ↑ ^{a b c d e f} Entry on manganese (VII) oxide in the GESTIS substance database of the IFA , accessed on February 28, 2017(JavaScript required) .
2. ^ AF Holleman, E. Wiberg, N. Wiberg: Inorganische Chemie . 103rd edition. tape 2 : Subgroup elements, lanthanoids, actinides, transactinides . Walter de Gruyter & Co KG, Berlin / Boston 2017, ISBN 978-3-11-049590-4 , p. 1913 ( limited preview in Google Book Search).
3. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
4. ↑ H. Aschoff: About the composition and the properties of overmanganic acid . In: Annals of Physics . tape 187 , no. 10 , 1860, p. 217-229 , doi : 10.1002 / andp.18601871003 .
5. ↑ Georg Brauer (ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1583.
6. ↑ A. Simon, R. Dronskowski, B. Krebs, B. Hettich: The crystal structure of Mn ₂ O ₇ . In: Angewandte Chemie . tape 99 , no. 2 , 1987, pp. 160-161 , doi : 10.1002 / anie.19870990225 .
7. ↑ B. Krebs, A. Mueller, HH Beyer: Crystal structure of rhenium (VII) oxide . In: Inorganic Chemistry . tape 8 , no. 3 , 1969, p. 436-443 , doi : 10.1021 / ic50073a006 .
8. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 1490.
9. ^ ^{A b} Erwin Riedel and Christoph Janiak: Inorganic Chemistry . 2007, ISBN 978-3-11-018168-5 ( page 809 in the Google book search).