Potassium permanganate

Potassium permanganate

Names
IUPAC name Potassium manganate(VII)
Systematic IUPAC name Potassium permanganate
Other names Chameleon mineral Condy's crystals Permanganate of potash Hypermangan Purple potion powder
Identifiers
CAS Number	7722-64-7 Y
3D model ( JSmol )	Interactive image
ChEMBL	ChEMBL3833305
ChemSpider	22810
DrugBank	DB13831
ECHA InfoCard	100.028.874
EC Number	231-760-3
KEGG	D02053 Y
PubChem CID	516875
RTECS number	SD6475000
UNII	00OT1QX5U4
UN number	1490
CompTox Dashboard (EPA)	DTXSID2034839
InChI InChI=1S/K.Mn.4O/q+1;;;;;-1 Y Key: VZJVWSHVAAUDKD-UHFFFAOYSA-N Y
SMILES [K+].[O-] [Mn](=O)(=O)=O
Properties
Chemical formula	KMnO4
Molar mass	158.034 g/mol
Appearance	Purplish-bronze-gray needles purple in solution[1]
Odor	odorless
Density	2.7 g/cm3[2]: 4.83
Melting point	240 °C (464 °F; 513 K) (decomposes)
Solubility in water	76 g/L (25 °C)[2] 250 g/L (65 °C)
Solubility	decomposes in organic solvents
Magnetic susceptibility (χ)	+20.0·10−6 cm3/mol[2]: 4.134
Refractive index (nD)	1.59
Structure[3]
Crystal structure	Orthorhombic, oP24
Space group	Pnma, No. 62
Lattice constant	a = 0.909 nm, b = 0.572 nm, c = 0.741 nm
Formula units (Z)	4
Thermochemistry
Heat capacity (C)	119.2 J/mol K
Std molar entropy (S⦵298)	171.7 J K−1 mol−1
Std enthalpy of formation (ΔfH⦵298)	−813.4 kJ/mol
Gibbs free energy (ΔfG⦵)	-713.8 kJ/mol
Pharmacology
ATC code	D08AX06 (WHO) V03AB18 (WHO)
Hazards
GHS labelling:
Pictograms
NFPA 704 (fire diamond)	2 0 2 OX
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1090 mg/kg (oral, rat)[4]
Related compounds
Other anions	Potassium pertechnetate Potassium perrhenate
Other cations	Sodium permanganate Ammonium permanganate Calcium permanganate Silver permanganate
Related manganates	Potassium hypomanganate Potassium manganate
Related compounds	Manganese heptoxide
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

Potassium permanganate

Clinical data
License data	US DailyMed: Potassium_permanganate
Identifiers
ECHA InfoCard	100.028.874

Potassium permanganate is an

Potassium permanganate is the potassium salt of the tetrahedral transition metal oxo complex permanganate, in which four O²⁻ ligands are bound to a manganese(VII) center.^{[citation needed]}

Structure

KMnO₄ forms

The purplish-black color of solid potassium permanganate, and the intensely pink to purple color of its solutions, is caused by its permanganate anion, which gets its color from a strong charge-transfer absorption band caused by excitation of electrons from oxo ligand orbitals to empty orbitals of the manganese(VII) center.^[8]

Medical uses

Mechanism of action

Potassium permanganate functions as a strong

It can be used in children and adults.[12] It can be applied as a soaked dressing or a bath.^[13] Petroleum jelly may be used on the nails before soaking to prevent their discoloration.^[14] For treating eczema, it is recommended using for a few days at a time due to the possibility of it irritating the skin.^[15]

The

Side effects from topical use may include irritation of the skin and discoloration of clothing.^[23] A harsh burn on a child from an undissolved tablet has been reported.^[24] Higher concentration solutions can result in chemical burns.^[25] Therefore, the British National Formulary recommends 100 mg be dissolved in a liter of water before use to form a 1:10,000 (0.01%) solution.^{[26] [27][28]} Wrapping the dressings soaked with potassium permanganate is not recommended.^{[citation needed]}

Potassium permanganate is toxic if taken by mouth.^[29] Side effects may include nausea, vomiting, and shortness of breath may occur.^[30] If a sufficiently large amount (about 10 grams) is eaten death may occur.^[30]

Concentrated solutions when drunk have resulted in

In the United States the FDA requires tablets of the medication to be sold by prescription.^[32] Potassium permanganate, however, does not have FDA approved uses and therefore non medical grade potassium permanganate is sometimes used for medical purposes.^{[citation needed]}

It is available under a number of

Potassium permanganate may be used to prevent the spread of glanders among horses.^[35]

Industrial and other uses

Almost all applications of potassium permanganate exploit its oxidizing properties.^[36] As a strong oxidant that does not generate toxic byproducts, KMnO₄ has many niche uses.^{[citation needed]}

Water treatment

Potassium permanganate is used extensively in the water treatment industry. It is used as a regeneration chemical to remove

A major application of KMnO₄ is as a reagent for the synthesis of organic compounds.

KMnO₄ solution is a common

Aqueous, acidic solutions of KMnO₄ are used to collect gaseous mercury in flue gas during stationary source emissions testing.^[49]

In histology, potassium permanganate was used as a bleaching agent.^[50][51]

Fruit preservation

Ethylene absorbents extend storage time of bananas even at high temperatures. This effect can be exploited by packing bananas in polyethylene together with potassium permanganate. By removing ethylene by oxidation, the permanganate delays the ripening, increasing the fruit's shelf life up to 4 weeks without the need for refrigeration.^[52][53][54]

Survival kits

Potassium permanganate is sometimes included in survival kits: as a

Potassium permanganate is added to "plastic sphere dispensers" to create backfires, burnouts, and controlled burns. Polymer spheres resembling ping-pong balls containing small amounts of permanganate are injected with ethylene glycol and projected towards the area where ignition is desired, where they spontaneously ignite seconds later.^[59][60] Both handheld^[60] helicopter-^[59] unmanned aircraft systems (UAS) or boat-mounted^[60] plastic sphere dispensers are used.

Other uses

Potassium permanganate is one of the principal chemicals used in the film and television industries to "age" props and set dressings. Its ready conversion to brown MnO₂ creates "hundred-year-old" or "ancient" looks on

Potassium permanganate can be used to oxidize cocaine paste to purify it and increase its stability. This led to the Drug Enforcement Administration launching Operation Purple in 2000, with the goal of monitoring the world supply of potassium permanganate; however, potassium permanganate derivatives and substitutes were soon used thereafter to avoid the operation.^[62]

Potassium permanganate is used as an oxidizing agent in the synthesis of cocaine and methcathinone.^[63]

Potassium permanganate is one of a number of possible treatments for Ichthyophthirius multifiliis (commonly known as "ich"), a parasite that infects and usually kills freshwater aquarium fish.

History

In 1659, Johann Rudolf Glauber fused a mixture of the mineral pyrolusite (manganese dioxide, MnO₂) and potassium carbonate to obtain a material that, when dissolved in water, gave a green solution (potassium manganate) which slowly shifted to violet and then finally red.^[64] The reaction that produced the color changes that Glauber observed in his solution of potassium permanganate and potassium manganate (K₂MnO₄) is now known as the "chemical chameleon". This report represents the first description of the production of potassium permanganate.^[65] Just under 200 years later, London chemist Henry Bollmann Condy had an interest in disinfectants; he found that fusing pyrolusite with sodium hydroxide (NaOH) and dissolving it in water produced a solution with disinfectant properties. He patented this solution, and marketed it as 'Condy's Fluid'. Although effective, the solution was not very stable. This was overcome by using potassium hydroxide (KOH) rather than NaOH. This was more stable, and had the advantage of easy conversion to the equally effective potassium permanganate crystals. This crystalline material was known as 'Condy's crystals' or 'Condy's powder'. Potassium permanganate was comparatively easy to manufacture, so Condy was subsequently forced to spend considerable time in litigation to stop competitors from marketing similar products.^[66]

Early photographers used it as a component of flash powder. It is now replaced with other oxidizers, due to the instability of permanganate mixtures.^{[citation needed]}

Preparation

Potassium permanganate is produced industrially from

(With sodium hydroxide, the end product is not sodium manganate but an Mn(V) compound, which is one reason why the potassium permanganate is more commonly used than sodium permanganate. Furthermore, the potassium salt crystallizes better.^[36])

The potassium manganate is then converted into permanganate by electrolytic oxidation in alkaline media:

${\displaystyle {\ce {2 K2MnO4 + 2 H2O -> 2 KMnO4 + 2 KOH + H2}}}$

Other methods

Although of no commercial importance, potassium manganate can be oxidized by chlorine or by disproportionation under acidic conditions.^[67] The chlorine oxidation reaction is

${\displaystyle {\ce {2 K2MnO4 + Cl2 -> 2 KMnO4 + 2 KCl}}}$

and the acid-induced

${\displaystyle {\ce {3 K2MnO4 + 4 HCl -> 2 KMnO4 + MnO2 + 2 H2O + 4 KCl}}}$

A weak acid such as carbonic acid is sufficient for this reaction:

${\displaystyle {\ce {3 K2MnO4 + 2 CO2 -> 2 KMnO4 + 2 K2CO3 + MnO2}}}$

Permanganate salts may also be generated by treating a solution of Mn²⁺ ions with strong oxidants such as lead dioxide (PbO₂), sodium bismuthate (NaBiO₃), or peroxydisulfate. Tests for the presence of manganese exploit the vivid violet color of permanganate produced by these reagents.

Reactions

Organic chemistry

Dilute solutions of KMnO₄ convert

Under acidic conditions, the alkene double bond is cleaved to give the appropriate carboxylic acid:^[68]

${\displaystyle {\ce {CH3(CH2)17CH=CH2 + 2 KMnO4 + 3 H2SO4 -> CH3(CH2)17COOH + CO2 + 4 H2O + K2SO4 + 2 MnSO4}}}$

Potassium permanganate oxidizes aldehydes to carboxylic acids, illustrated by the conversion of n-heptanal to heptanoic acid:^[69]

${\displaystyle {\ce {5 C6H13CHO + 2 KMnO4 + 3 H2SO4 -> 5 C6H13COOH + 3 H2O + K2SO4 + 2 MnSO4}}}$

Even an alkyl group (with a benzylic hydrogen) on an

Glycols and polyols are highly reactive toward KMnO₄. For example, addition of potassium permanganate to an aqueous solution of sugar and sodium hydroxide produces the chemical chameleon reaction, which involves dramatic color changes associated with the various oxidation states of manganese. A related vigorous reaction is exploited as a fire starter in survival kits. For example, a mixture of potassium permanganate and glycerol or pulverized glucose ignites readily.^[55] Its sterilizing properties are another reason for inclusion of KMnO₄ in a survival kit.^{[citation needed]}

Ion exchange

Treating a mixture of aqueous potassium permanganate with a

Similarly, addition of a crown ether also gives a lipophilic salt.^[72]

Reaction with acids and bases

Permanganate reacts with concentrated hydrochloric acid to give chlorine and manganese(II):

${\displaystyle {\ce {2 KMnO4 + 16 HCl -> 2 MnCl2 + 5 Cl2 + 2 KCl + 8 H2O}}}$

In neutral solution, permanganate slowly reduces to manganese dioxide (MnO₂). This is the material that stains one's skin when handling KMnO₄.

KMnO₄ reduces in

Solid potassium permanganate decomposes when heated:

${\displaystyle {\ce {2 KMnO4 -> K2MnO4 + MnO2 + O2}}}$

It is a redox reaction.

Safety and handling

Potassium permanganate poses risks as an