Permanganic acid

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Permanganic acid
Permanganic-acid-3D-balls.png
Names
IUPAC name
Permanganic acid
Other names
Manganic(VII) acid
Hydroxy(trioxo)manganese
Hydrogen permanganate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.346 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 236-695-4
PubChem CID
  • InChI=1S/Mn.H2O.3O/h;1H2;;;/q+1;;;;/p-1
    Key: ZJBYBXHCMWGGRR-UHFFFAOYSA-M
  • O=[Mn](=O)(=O)O
Properties
HMnO4
Molar mass 119.94 g mol−1
AppearanceViolet
Acidity (pKa)about -4.6 to -2.3 [1] [2]
Conjugate base Permanganate
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Oxidant, Corrosive
Related compounds
Other cations
Potassium permanganate
Sodium permanganate
Calcium permanganate
Related compounds
Pertechnetic acid
Perrhenic acid
Perchloric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

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 characterization as well as its uses are very limited.

Contents

Preparation and structure

Permanganic acid is most often prepared by the reaction of dilute sulfuric acid with a solution of barium permanganate, the insoluble barium sulfate byproduct being removed by filtering: [3]

Ba(MnO4)2 + H2SO4 → 2 HMnO4 + BaSO4

The sulfuric acid used must be dilute; reactions of permanganates with concentrated sulfuric acid yield the anhydride, manganese heptoxide.

Permanganic acid has also been prepared through the reaction of hydrofluorosilicic acid with potassium permanganate, [4] through electrolysis, and through hydrolysis of manganese heptoxide, though the last route often results in explosions. [5]

Crystalline permanganic acid has been prepared at low temperatures as the dihydrate, HMnO4·2H2O. [3]

Although its structure has not been verified spectroscopically or crystallographically, HMnO4 is assumed to be adopt a tetrahedral structure akin to that for perchloric acid.

Reactions

As a strong acid, HMnO4 is deprotonated to form the intensely purple coloured permanganates. Potassium permanganate, KMnO4, is a widely used, versatile and powerful oxidising agent.

Permanganic acid solutions are unstable, and gradually decompose into manganese dioxide, oxygen, and water, with initially formed manganese dioxide catalyzing further decomposition. [6] Decomposition is accelerated by heat, light, and acids. Concentrated solutions decompose more rapidly than dilute. [6]

Related Research Articles

<span class="mw-page-title-main">Manganese dioxide</span> Chemical compound

Manganese dioxide is the inorganic compound with the formula MnO
2
. This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for MnO
2
is for dry-cell batteries, such as the alkaline battery and the zinc–carbon battery. MnO
2
is also used as a pigment and as a precursor to other manganese compounds, such as KMnO
4
. It is used as a reagent in organic synthesis, for example, for the oxidation of allylic alcohols. MnO
2
has an α-polymorph that can incorporate a variety of atoms in the "tunnels" or "channels" between the manganese oxide octahedra. There is considerable interest in α-MnO
2
as a possible cathode for lithium-ion batteries.

<span class="mw-page-title-main">Potassium permanganate</span> Chemical compound

Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and MnO
4
, an intensely pink to purple solution.

<span class="mw-page-title-main">Potassium ferrate</span> Chemical compound

Potassium ferrate is the chemical compound with the formula K2FeO4. This purple salt is paramagnetic, and is a rare example of an iron(VI) compound. In most of its compounds, iron has the oxidation state +2 or +3 (Fe2+ or Fe3+). Reflecting its high oxidation state, FeO2−4 is a powerful oxidizing agent.

<span class="mw-page-title-main">Permanganate</span> Chemical compound

A permanganate is a chemical compound with the manganate(VII) ion, MnO
4
, the conjugate base of permanganic acid. Because the manganese atom has a +7 oxidation state, the permanganate(VII) ion is a strong oxidising agent. The ion is a transition metal ion with a tetrahedral structure. Permanganate solutions are purple in colour and are stable in neutral or slightly alkaline media. The exact chemical reaction depends on the carbon-containing reactants present and the oxidant used. For example, trichloroethane (C2H3Cl3) is oxidised by permanganate ions to form carbon dioxide (CO2), manganese dioxide (MnO2), hydrogen ions (H+), and chloride ions (Cl).

<span class="mw-page-title-main">Manganate</span> Chemical compound

In inorganic nomenclature, a manganate is any negatively charged molecular entity with manganese as the central atom. However, the name is usually used to refer to the tetraoxidomanganate(2−) anion, MnO2−
4
, also known as manganate(VI) because it contains manganese in the +6 oxidation state. Manganates are the only known manganese(VI) compounds.

Selenic acid is the inorganic compound with the formula H2SeO4. It is an oxoacid of selenium, and its structure is more accurately described as O2Se(OH)2. It is a colorless compound. Although it has few uses, one of its salts, sodium selenate is used in the production of glass and animal feeds.

<span class="mw-page-title-main">Sodium oxalate</span> Chemical compound

Sodium oxalate, or disodium oxalate, is the sodium salt of oxalic acid with the formula Na2C2O4. It is a white, crystalline, odorless solid, that decomposes above 290 °C.

<span class="mw-page-title-main">Potassium manganate</span> Chemical compound

Potassium manganate is the inorganic compound with the formula K2MnO4. This green-colored salt is an intermediate in the industrial synthesis of potassium permanganate, a common chemical. Occasionally, potassium manganate and potassium permanganate are confused, but these compounds's properties are distinct.

<span class="mw-page-title-main">Kipp's apparatus</span> Laboratory device for preparing gases

Kipp's apparatus, also called a Kipp generator, is an apparatus designed for preparation of small volumes of gases. It was invented around 1844 by the Dutch pharmacist Petrus Jacobus Kipp and widely used in chemical laboratories and for demonstrations in schools into the second half of the 20th century.

In chemistry, hypomanganate, also called manganate(V) or tetraoxidomanganate(3−), is a trivalent anion (negative ion) composed of manganese and oxygen, with formula MnO3−
4
.

Potassium hypomanganate is the inorganic compound with the formula K3MnO4. Also known as potassium manganate(V), this bright blue solid is a rare example of a salt with the hypomanganate or manganate(V) anion, where the manganese atom is in the +5 oxidation state. It is an intermediate in the production of potassium permanganate and the industrially most important Mn(V) compound.

<span class="mw-page-title-main">Manganese heptoxide</span> Chemical compound

Manganese(VII) oxide (manganese heptoxide) is an inorganic compound with the formula Mn2O7. This volatile liquid is highly reactive. It is a dangerous oxidizer and was first described in 1860. It is the acid anhydride of permanganic acid.

Technetium compounds are chemical compounds containing the chemical element technetium. Technetium can form multiple oxidation states, but often forms in the +4 and +7 oxidation states. Because technetium is radioactive, technetium compounds are extremely rare on Earth.

<span class="mw-page-title-main">Barium chlorate</span> Chemical compound

Barium chlorate, Ba(ClO3)2, is the barium salt of chloric acid. It is a white crystalline solid, and like all soluble barium compounds, irritant and toxic. It is sometimes used in pyrotechnics to produce a green color. It also finds use in the production of chloric acid.

<span class="mw-page-title-main">Ammonium permanganate</span> Chemical compound

Ammonium permanganate is the chemical compound NH4MnO4, or NH3·HMnO4. It is a water soluble, violet-brown or dark purple salt.

<span class="mw-page-title-main">Calcium permanganate</span> Chemical compound

Calcium permanganate is an oxidizing agent and chemical compound with the chemical formula Ca(MnO4)2. This salt consists of the metal calcium and two permanganate ions.

<span class="mw-page-title-main">Barium manganate</span> Chemical compound

Barium manganate is an inorganic compound with the formula BaMnO4. It is used as an oxidant in organic chemistry. It belongs to a class of compounds known as manganates in which the manganese resides in a +6 oxidation state. Manganate should not be confused with permanganate which contains manganese(VII). Barium manganate is a powerful oxidant, popular in organic synthesis and can be used in a wide variety of oxidation reactions.

Barium permanganate is a chemical compound, with the formula Ba(MnO4)2. It forms violet to brown crystals that are sparingly soluble in water.

Rhenium compounds are compounds formed by the transition metal rhenium (Re). Rhenium can form in many oxidation states, and compounds are known for every oxidation state from -3 to +7 except -2, although the oxidation states +7, +6, +4, and +2 are the most common. Rhenium is most available commercially as salts of perrhenate, including sodium and ammonium perrhenates. These are white, water-soluble compounds. Tetrathioperrhenate anion [ReS4] is possible.

Magnesium permanganate is an inorganic compound with the chemical formula Mg(MnO4)2. It can be used as an oxidant.

References

  1. Stewart, R.; Mocek, M.M. (1963). "The Mechanisms of Permanganate Oxidation VII: The Oxidation of Fluoral Hydrate". Canadian Journal of Chemistry. 41 (5): 1160–9. doi:10.1139/v63-164.
  2. Bailey, N.; Carrington, A.; Lott, K.A.K.; Symons, M.C.R (1960). "Structure and Reactivity of the Oxyanions of Transition Metals Part VII: Acidities and Spectra of Protonated Oxyanions". Journal of the Chemical Society (Resumed): 290–7. doi:10.1039/JR9600000290.
  3. 1 2 Frigerio, Norman A. (1969). "Preparation and properties of crystalline permanganic acid". Journal of the American Chemical Society. 91 (22): 6200–1. doi:10.1021/ja01050a058. PMID   5823192.
  4. Black, Homer Van Valkenburg (1900). The permanganates of barium, strontium, and calcium. Easton, PA. p. 6.{{cite book}}: CS1 maint: location missing publisher (link)
  5. Olsen, J. C. (1900). Permanganic Acid by Electrolysys. Easton, PA: The Chemical Publishing Company.
  6. 1 2 Byers, Horace Greeley (1899). A Study of the Reduction of Permanganic acid by Manganese Dioxide. Chemical Publishing Company.