پرمنگنات الپوتاسيوم

پرمنگنات الپوتاسيوم
Potassium permanganate

الأسماء
اسم أيوپاك Potassium manganate(VII)
أسماء أخرى پرمنگنات الپوتاسيوم منگنات الپوتاسيوم السباعية معدن الحرباء بلورات كوندي پرمنگنات البوتاش
المُعرِّفات
رقم CAS
ECHA InfoCard	100.028.874
رقم EC	231-760-3
KEGG	D02053
PubChem CID	24400
رقم RTECS	SD6475000
UN number	1490
CompTox Dashboard (EPA)	DTXSID2034839
الخصائص
الصيغة الجزيئية	KMnO4
كتلة مولية	158.034 g/mol
المظهر	إبر قرمزية-برونزية-رمادية ماجنتا–وردية في المحلول
الرائحة	عديم الرائحة
الكثافة	2.703 g/cm3
نقطة الانصهار
قابلية الذوبان في الماء	6.38 g/100 ml (20 °C) 25 g/100 mL (65 °C)
قابلية الذوبان	ينحل في الكحول و المذيبات العضوية
البنية
البنية البلورية	Orthorhombic
الكيمياء الحرارية
الإنتالپية المعيارية للتشكل ΔfHo298	−813.4 kJ/mol
Standard molar entropy So298	171.7 J K−1 mol−1
المخاطر
تبويب الاتحاد الاوروپي (DSD)	مؤكسد (O) ضار (Xn) خطر على البيئة (N)
توصيف المخاطر	R8, R22, R50/53
تحذيرات وقائية	(S2), S60, S61
NFPA 704 (معيـَّن النار)	3 3 0 OX
مركبات ذا علاقة
أنيونات أخرى	منگنيت الپوتاسيوم منگنات الپوتاسيوم
كاتيونات أخرى	پرمنگنات الصوديوم پرمنگنات الأمونيوم
ما لم يُذكر غير ذلك، البيانات المعطاة للمواد في حالاتهم العيارية (عند 25 °س [77 °ف]، 100 kPa).
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مراجع الجدول

پرمنگنات الپوتاسيوم أو برمنجنات البوتاسيوم هو مركب كيميائي صيغته الكيميائية KMnO₄ وفى هذا الملح يكون المنجنيز في حاله الأكسدة +7 وهو يسمى أيضا برمنجنات ملح القلي.

يعتبر أيون البرمنجنات عامل مؤكسد قوي وهو له القدرة على الذوبان في الماء ليعطى محلول ذو لون قرمزي غامق. وتبخيره يعطى بلورات سوداء ناعمة

بلورات پرمنگنات البوتاسيوم لها بنية بلورية من النمط orthorhombic (معينة من النمط أورثو).

 الخواص

 الخواص العامة

• بلورات پرمنگنات الپوتاسيوم لها بنية بلورية من النمط المعيني المستقيم، وتكون ثوابت الشبكة البلورية كالتالي: a = 910.5 pm و b = 572.0 pm و c = 742.5 pm ، في حين أن طول الرابطة Mn-O تبلغ 162.9 بيكومتر.
• ينحل فوق منغنات البوتاسيوم بشكل جيد في الماء، وتكون محاليله ذات لون لون قرمزي غامق. يستخدم حمض الأكساليك من أجل تقييس تلك المحاليل وذلك في الكيمياء التحليلية.

• عند تسخين بلورات فوق منغنات البوتاسيوم إلى درجات حرارة تصل إلى 240°س يتفكك المركب إلى كل من منغنات البوتاسيوم وأكسيد المنغنيز الرباعي (ثنائي أكسيد المنغنيز) وأكسيد البوتاسيوم، ويطلق غاز الأكسجين حسب المعادلة التالية:

10KMnO₄ –^Δ→ 3K₂MnO₄ + 7MnO₂ + 2K₂O + 6O₂

ويؤدي التسخين إلى درجات حرارة أعلى إلى تفكك المنغنات أيضاً:

2K₂MnO₄ –^Δ→ 2MnO₂ + K₂O + O₂

 الخواص المؤكسدة

محلول مائي من KMnO₄ في دورق حجمي

يتميز پرمنگنات الپوتاسيوم بخواصه المؤكسدة القوية، وذلك لأن المنغنيز يكون بأعلى حالة أكسدة له. لذلك فإن أغلب تفاعلاته الكيميائية مع المركبات المختلفة تتأثر بتلك الخاصية، وذلك عند التفاعل مع كل من:

 الأحماض

يتأكسد حمض هيدروكلوريك ليعطي غاز الكلور، وبشكل مشابه يتفاعل پرمنگنات الپوتاسيوم مع حمض الكبريتيك المركز بتفاعل أكسدة ليعطي أكسيد المنغنيز السباعي (سباعي أكسيد المنغنيز) Mn₂O₇، ويمكن أن يكون هذا التفاعل انفجارياً. يمكن لتفاعل فوق المنغنات مع حمض الكبريتيك أن يعطي غاز الأوزون حسب المعادلة:

6 KMnO₄ (aq) + 9 H₂SO₄ (aq) → 6 MnSO₄ (aq) + 3 K₂SO₄ (aq) + 9 H₂O (l) + 5 O₃ (g)

إلا أنه يجب أخذ الحيطة والحذر عند إجرائه.

 المركبات اللاعضوية

يؤكسد پرمنگنات الپوتاسيوم أيونات الحديد الثنائي إلى الثلاثي، كما يؤكسد أيونات الكبريتيت إلى أيونات الكبريتات، ويكون مخطط الأكسدة-اختزال للمثال الأخير كالتالي:

${\displaystyle{\displaystyle\mathrm{{\overset{\underset{+IV}{}}{\ S}}O_{3}^{2-}+3\ H_{2}O}}}$	${\displaystyle{\displaystyle\mathrm{\longrightarrow}}}$	${\displaystyle{\displaystyle\mathrm{{\overset{\underset{+VI}{}}{\ S}}O_{4}^{2-}+2\ e^{-}+2\ H_{3}O^{+}}}}$	${\displaystyle{\displaystyle\mathrm{|\cdot 5}}}$
${\displaystyle{\displaystyle\mathrm{{\overset{\underset{+VII}{}}{Mn}}O_{4}^{-}+5\ e^{-}+8\ H_{3}O^{+}}}}$	${\displaystyle{\displaystyle\mathrm{\longrightarrow}}}$	${\displaystyle{\displaystyle\mathrm{\ {\overset{\underset{+II}{}}{Mn}}{}^{2+}+12\ H_{2}O}}}$	${\displaystyle{\displaystyle\mathrm{|\cdot 2}}}$
${\displaystyle{\displaystyle\mathrm{5\ SO_{3}^{2-}+2\ MnO_{4}^{-}+6\ H_{3}O^{+}}}}$	${\displaystyle{\displaystyle\mathrm{\longrightarrow}}}$	${\displaystyle{\displaystyle\mathrm{5\ SO_{4}^{2-}+2\ Mn^{2+}+9\ H_{2}O}}}$

 المركبات العضوية

بالنسبة للمركبات العضوية فإن فوق منغنات البوتاسيوم يؤكسد الرابطة المضاعفة في الألكينات ليعطي الحمض الكربوكسيلي الموافق.

CH₃(CH₂)₁₇CH=CH₂ + [O] → CH₃(CH₂)₁₇COOH

كما يؤكسد الألدهيدات أيضاً إلى الأحماض الكربوكسيلية الموافقة، فعلى سبيل المثال فهو يؤكسد الهيبتانال إلى حمض الهيبتانويك.

C₆H₁₃CHO + [O] → C₆H₁₃COOH

كما أنه يؤكسد التولوين إلى حمض البنزويك

 التحضير

يحضر مركب پرمنگنات الپوتاسيوم من أكسيد المنغنيز الرباعي (ثنائي أكسيد المنغنيز) MnO₂ والذي يتفاعل مع هيدروكسيد البوتاسيوم بوجود أكسجين الهواء ليعطي مركب منغنات البوتاسيوم K₂MnO₄، والذي يؤكسد إلى فوق منغنات كهربائياً (أكسدة مصعدية).

أما مخبرياً فيمكن تحضير المركب بأكسدة ثنائي أكسيد المنغنيز باستعمال مركب كلورات البوتاسيوم في وسط قلوي ومن ثم بتمرير غاز ثنائي أكسيد الكربون في المحلول.

 الاستخدامات

 التعقيم ومعالجة المياه

استخدم مركب پرمنگنات الپوتاسيوم في السابق من أجل معالجة مياه الشرب مياه المسابح والخزانات. كما يمكن أن تستخدم محاليله المائية من أجل معالجة حالات متوسطة من مرض الفاقوع pompholyx، والتهاب الجلد Dermatitis (طفح). وفي حالات إصابة الأطراف بالفطريات.

Potassium permanganate is used extensively in the water treatment industry. It is used as a regeneration chemical to remove iron and hydrogen sulfide (rotten egg smell) from well water via a "manganese greensand" filter. "Pot-Perm" is also obtainable at pool supply stores and is used additionally to treat wastewater. Historically it was used to disinfect drinking water and can turn the water pink. Modern hiking and survivalist guides advise against using potassium permanganate in the field because it is difficult to dose correctly. It currently finds application in the control of nuisance organisms such as zebra mussels in fresh water collection and treatment systems.

وتستخدم في علاج ماء المسابح والخزانات.

 استخدامات طبية حيوية

• استعملت محاليل البرمنغنات فيما مضى من أجل علاج مرض السيلان، ويستعمل للآن من أجل علاج مرض داء المبيضات.
• يؤدي حضن أنسجة مثبتة بپرمنگنات الپوتاسيوم إلى منع أميلويد amyloid AA من تلطيخ صباغ أحمر الكونغو، في حين أن الأنواع الأخرى من الأميلويد لا تتأثر بذلك.

A major application of KMnO₄ is as a reagent for the synthesis of organic compounds. Significant amounts are required for the synthesis of ascorbic acid, chloramphenicol, saccharin, isonicotinic acid, and pyrazinoic acid.

KMnO₄ is used in qualitative organic analysis to test for the presence of unsaturation. It is sometimes referred to as Baeyer's reagent after the German organic chemist Adolf von Baeyer. The reagent is an alkaline solution of potassium permanganate. Reaction with double or triple bonds (R
2C=CR
2 or R−C≡C−R) causes the color to fade from purplish-pink to brown. Aldehydes and formic acid (and formates) also give a positive test. The test is antiquated.

Baeyer's reagent reaction

KMnO₄ solution is a common thin layer chromatography (TLC) stain for the detection of oxidizable functional groups, such as alcohols, aldehydes, alkenes, and ketones. Such compounds result in a white to orange spot on TLC plates.

 تخليق المركبات العضوية

يستعمل پرمنگنات الپوتاسيوم من أجل الاصطناع العضوي للعديد من المركبات العضوية. فعلى سبيل المثال تستهلك كميات كبيرة منه لتحضير حمض الأسكوربيك وكلورامفينيكول والسكارين وحمض إيزو النيكوتينيك وحمض البيرازينويك.

A solution of KMnO₄ in water, in a volumetric flask

A major application of KMnO₄ is as a reagent for the synthesis of organic compounds. Significant amounts are required for the synthesis of ascorbic acid, chloramphenicol, saccharin, isonicotinic acid, and pyrazinoic acid.

KMnO₄ is used in qualitative organic analysis to test for the presence of unsaturation. It is sometimes referred to as Baeyer's reagent after the German organic chemist Adolf von Baeyer. The reagent is an alkaline solution of potassium permanganate. Reaction with double or triple bonds (R
2C=CR
2 or R−C≡C−R) causes the color to fade from purplish-pink to brown. Aldehydes and formic acid (and formates) also give a positive test. The test is antiquated.

Baeyer's reagent reaction

KMnO₄ solution is a common thin layer chromatography (TLC) stain for the detection of oxidizable functional groups, such as alcohols, aldehydes, alkenes, and ketones. Such compounds result in a white to orange spot on TLC plates.

 الاستخدام التحليلي

Potassium permanganate can be used to quantitatively determine the total oxidizable organic material in an aqueous sample. The value determined is known as the permanganate value. In analytical chemistry, a standardized aqueous solution of KMnO₄ is sometimes used as an oxidizing titrant for redox titrations (permanganometry). As potassium permanganate is titrated, the solution becomes a light shade of purple, which darkens as excess of the titrant is added to the solution. In a related way, it is used as a reagent to determine the Kappa number of wood pulp. For the standardization of KMnO₄ solutions, reduction by oxalic acid is often used. In agricultural chemistry, it is used for estimation of active carbon in soil.

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

In histology, potassium permanganate was used as a bleaching agent.

 الحفاظ على الفواكه

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.

The chemical reaction, in which ethylene (C₂H₄) is oxidised by potassium permanganate (KMnO₄) to carbon dioxide (CO₂), manganese oxide (MnO₂) and potassium hydroxide (KOH), in the presence of water, is presented as follows:

3 C₂H₄ + 12 KMnO₄ + 2 H₂O → 6 CO₂ + 2 H₂O + 12 MnO₂ + 12 KOH

 Survival kits

Potassium permanganate is sometimes included in survival kits: as a hypergolic fire starter (when mixed with glycerol antifreeze from a car radiator); as a water sterilizer; and for creating distress signals on snow.

 مكافحة النيران

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. Both handheld helicopter- unmanned aircraft systems (UAS) or boat-mounted plastic sphere dispensers are used.

 استخدامات أخرى

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 hessian cloth (burlap), ropes, timber and glass.

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.

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

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.

 التاريخ

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. 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. 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. According to Varlam Shalamov, potassium permanganate solution was used as a catch-all treatment for dysentery, frostbite and ulcers in the Gulag camps of Kolyma.

Early photographers used it as a component of flash powder. It is now replaced with other oxidizers, due to the instability of permanganate mixtures.

 التحضير

Potassium permanganate is produced industrially from manganese dioxide, which also occurs as the mineral pyrolusite. In 2000, worldwide production was estimated at 30,000 tonnes. The MnO₂ is fused with potassium hydroxide and heated in air or with another source of oxygen, like potassium nitrate or potassium chlorate. This process gives potassium manganate:

2 MnO
2 + 4 KOH + O
2 → 2 K
2MnO
4 + 2 H
2O

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.

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

2 K
2MnO
4 + 2 H
2O → 2 KMnO
4 + 2 KOH + H
2

 Other methods

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

2 K
2MnO
4 + Cl
2 → 2 KMnO
4 + 2 KCl

and the acid-induced disproportionation reaction may be written as

3 K
2MnO
4 + 4 HCl → 2 KMnO
4 + MnO
2 + 2 H
2O + 4 KCl

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

3 K
2MnO
4 + 2 CO
2 → 2 KMnO
4 + 2 K
2CO
3 + MnO
2

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 alkenes into diols. This behaviour is also used as a qualitative test for the presence of double or triple bonds in a molecule, since the reaction decolorizes the initially purple permanganate solution and generates a brown precipitate (MnO₂). In this context, it is sometimes called Baeyer's reagent. However, bromine serves better in measuring unsaturation (double or triple bonds) quantitatively, since KMnO₄, being a very strong oxidizing agent, can react with a variety of groups.

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

CH
3(CH
2)
17CH=CH
2 + 2 KMnO
4 + 3 H
2SO
4 → CH
3(CH
2)
17COOH + CO
2 + 4 H
2O + K
2SO
4 + 2 MnSO
4

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

5 C
6H
13CHO + 2 KMnO
4 + 3 H
2SO
4 → 5 C
6H
13COOH + 3 H
2O + K
2SO
4 + 2 MnSO
4

Even an alkyl group (with a benzylic hydrogen) on an aromatic ring is oxidized, e.g. toluene to benzoic acid.

5 C
6H
5CH
3 + 6 KMnO
4 + 9 H
2SO
4 → 5 C
6H
5COOH + 14 H
2O + 3 K
2SO
4 + 6 MnSO
4

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. Its sterilizing properties are another reason for inclusion of KMnO₄ in a survival kit.

 Ion exchange

Treating a mixture of aqueous potassium permanganate with a quaternary ammonium salt results in ion exchange, precipitating the quat salt of permanganate. Solutions of these salts are sometimes soluble in organic solvents:

KMnO
4 + R
4NCl → R
4NMnO
4 + KCl

Similarly, addition of a crown ether also gives a lipophilic salt.

 Reaction with acids and bases

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

2 KMnO
4 + 16 HCl → 2 MnCl
2 + 5 Cl
2 + 2 KCl + 8 H
2O

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 alkaline solution to give green K₂MnO₄:

4 KMnO
4 + 4 KOH → 4 K
2MnO
4 + O
2 + 2 H
2O

This reaction illustrates the relatively rare role of hydroxide as a reducing agent.

Addition of concentrated sulfuric acid to potassium permanganate gives Mn₂O₇. Although no reaction may be apparent, the vapor over the mixture will ignite paper impregnated with alcohol. Potassium permanganate and sulfuric acid react to produce some ozone, which has a high oxidizing power and rapidly oxidizes the alcohol, causing it to combust. As the reaction also produces explosive Mn₂O₇, this should only be attempted with great caution.

 Thermal decomposition

Solid potassium permanganate decomposes when heated:

2 KMnO
4 → K
2MnO
4 + MnO
2 + O
2

It is a redox reaction.

 Safety and handling

Potassium permanganate poses risks as an oxidizer. Contact with skin can cause skin irritation and in some cases severe allergic reaction. It can also result in discoloration and clothing stains.

 وصلات خارجية

• بطاقة السلامة الكيميائية العالمية 0672
• National Pollutant Inventory: Manganese and compounds Fact Sheet
• The use of potassium permanganate in fish ponds
• Sugar, NaOH and KMnO4