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| verifiedrevid = 384865126 |
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| verifiedrevid = 437792124 |
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| IUPACName = potassium manganate(V)<br/>potassium tetraoxidomanganate(3−) |
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| IUPACName = potassium manganate(V)<br/>potassium tetraoxidomanganate(3−) |
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| Section2 = {{Chembox Properties |
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|Section1 = {{Chembox Identifiers |
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| ChemSpiderID = 64887110 |
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| Reference = <ref name="Mandelate">{{citation | title = Reduction of manganate(VI) by mandelic acid and its significance for development of a general mechanism of oxidation of organic compounds by high-valent transition metal oxides | first1 = Donald G. | last1 = Lee | first2 = Tao | last2 = Chen | journal = J. Am. Chem. Soc. | year = 1993 | volume = 115 | issue = 24 | pages = 11231–36 | doi = 10.1021/ja00077a023}}.</ref> |
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| PubChem = 118856760 |
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| Appearance = bright blue solid |
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| SMILES = O=(=O)(=O)=O... |
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| Formula = K<sub>3</sub>MnO<sub>4</sub> |
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| StdInChI=1S/3K.Mn.4O/q3*+1;-3;;;; |
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| MolarMass = 236.23 g mol<sup>−1</sup> |
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| StdInChIKey = BABZALCEXXHDEO-UHFFFAOYSA-N |
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| LambdaMax = 670 nm<br/>(''ε'' = 900 dm<sup>3</sup> mol<sup>−1</sup> cm<sup>−1</sup>) |
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| Section8 = {{Chembox Related |
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|Section2 = {{Chembox Properties |
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| Properties_ref = <ref name="Mandelate">{{citation | title = Reduction of manganate(VI) by mandelic acid and its significance for development of a general mechanism of oxidation of organic compounds by high-valent transition metal oxides | first1 = Donald G. | last1 = Lee | first2 = Tao | last2 = Chen | journal = J. Am. Chem. Soc. | year = 1993 | volume = 115 | issue = 24 | pages = 11231–36 | doi = 10.1021/ja00077a023}}.</ref> |
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| OtherAnions = ]<br/>] |
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| Appearance = bright blue solid |
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| K=3 | Mn=1 | O=4 |
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| Density = 2.78 g/cm<sup>3</sup> |
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| MeltingPtC = 900 |
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| MeltingPt_notes = (decomposes) |
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| LambdaMax = 670 nm<br/>(''ε'' = 900 dm<sup>3</sup> mol<sup>−1</sup> cm<sup>−1</sup>) |
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|Section8 = {{Chembox Related |
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| OtherAnions = ]<br/>] |
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'''Potassium hypomanganate''' is the ] with the formula {{chem2|K3MnO4}}. Also known as '''potassium manganate(V)''', this bright blue solid is a rare example of a salt with the ] or manganate(V) anion, where the ] atom is in the +5 ] state. It is an intermediate in the production of ] and the industrially most important Mn(V) compound.<ref name="Kirk">{{cite journal |author1=Kenneth Pisarczyk |title=Manganese Compounds |journal=Kirk-Othmer Encyclopedia of Chemical Technology |date=2005 |doi=10.1002/0471238961.1301140716091901.a01.pub2 |language=en}}</ref> |
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'''Potassium hypomanganate''', K<sub>3</sub>MnO<sub>4</sub>, also known as '''potassium manganate(V)''', is a bright blue salt and a rare example of a manganese(V) compound. It is formed: |
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*by the ] of ] with excess ];<ref name="C&W">{{Cotton&Wilkinson4th|page=746}}.</ref><ref name="G&E">{{Greenwood&Earnshaw1st|pages=1221–22}}.</ref> |
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::MnO{{su|b=4|p=−}} + SO{{su|b=3|p=2−}} + H<sub>2</sub>O → MnO{{su|b=4|p=3−}} + SO{{su|b=4|p=2−}} + {{nowrap|2 H<sup>+</sup>}} |
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*by the reduction of ] with ] in 10 M ] solution;<ref>{{citation | title = Oxidation of hydrocarbons. 18. Mechanism of the reaction between permanganate and carbon-carbon double bonds | first1 = Donald G. | last1 = Lee | first2 = Tao | last2 = Chen | journal = J. Am. Chem. Soc. | year = 1989 | volume = 111 | issue = 19 | pages = 7534–38 | doi = 10.1021/ja00201a039}}.</ref> |
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::{{nowrap|2 MnO{{su|b=4|p=2−}}}} + H<sub>2</sub>O<sub>2</sub> + {{nowrap|2 OH<sup>−</sup>}} → {{nowrap|2 MnO{{su|b=4|p=3−}}}} + O<sub>2</sub> + {{nowrap|2 H<sub>2</sub>O}} |
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*by the reduction of potassium manganate with ] in 3–10 M potassium hydroxide solution;<ref name="Mandelate"/> |
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::{{nowrap|2 MnO{{su|b=4|p=2−}}}} + C{{su|b=8}}H{{su|b=7}}O{{su|b=3|p=−}} + {{nowrap|2 OH<sup>−</sup>}} → {{nowrap|2 MnO{{su|b=4|p=3−}}}} + C{{su|b=8}}H{{su|b=5}}O{{su|b=3|p=−}} + {{nowrap|2 H<sub>2</sub>O}} |
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*by ] when ] is dissolved in a concentrated solution of potassium hydroxide;<ref name="C&W"/> |
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::{{nowrap|2 MnO<sub>2</sub>}} + {{nowrap|3 OH<sup>−</sup>}} → MnO{{su|b=4|p=3−}} + MnO(OH) + H<sub>2</sub>O |
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==Properties== |
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The hypomanganate anion is unstable with respect to disproportionation in all but the most alkaline of solutions:<ref name="C&W"/><ref name="G&E"/> estimated ]s at ] 14 are<ref>{{RubberBible62nd|page=D-134}}.</ref><ref>{{citation | title = Manganese – compounds – standard reduction potentials | url = http://www.webelements.com/manganese/compounds.html | publisher = WebElements | accessdate = 2010-06-26}}.</ref><ref name="Epot">{{citation | title = Rate of the MnO<sub>4</sub><sup>−</sup>/MnO<sub>4</sub><sup>2−</sup> and MnO<sub>4</sub><sup>2−</sup>/MnO<sub>4</sub><sup>3−</sup> electrode reactions in alkaline solutions at solid electrodes | first1 = K. | last1 = Sekula-Brzezińska | first2 = P. K. | last2 = Wrona | first3 = Z. | last3 = Galus | journal = Electrochim. Acta | volume = 24 | issue = 5 | pages = 555–63 | doi = 10.1016/0013-4686(79)85032-X | year = 1979}}.</ref> |
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Potassium hypomanganate is oxidized in water to ]:<ref name="the">{{cite thesis |degree=Diploma|last=Tupec|first=Josef|date=2001|title=Interoperational analytical control during the production of potassium permanganate|url=https://dk.upce.cz/bitstream/handle/10195/19372/D10892.pdf|type= |chapter= |publisher= |docket= |oclc= |access-date=}}</ref> |
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:MnO{{su|b=4|p=2−}} + e<sup>−</sup> {{eqm}} MnO{{su|b=4|p=3−}} ''E'' = +0.27 V |
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:MnO{{su|b=4|p=3−}} + e<sup>−</sup> + {{nowrap|4 H<sub>2</sub>O}} {{eqm}} MnO<sub>2</sub> + {{nowrap|6 OH<sup>−</sup>}} ''E'' = +0.96 V |
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:2 K<sub>3</sub>MnO<sub>4</sub> + H<sub>2</sub>O + 0.5 O<sub>2</sub> → 2 KOH + 2 K<sub>2</sub>MnO<sub>4</sub> |
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However, it undergoes ] in acidic solutions producing ] and potassium permanganate.<ref name="the" /> |
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The disproportionation is believed to pass through a protonated intermediate,<ref name="Epot"/> with the ] for the reaction HMnO{{su|b=4|p=2−}} {{eqm}} MnO{{su|b=4|p=3−}} + H<sup>+</sup> being estimated as p''K''<sub>a</sub> = {{nowrap|13.7 ± 0.2}}.<ref>{{citation | title = Studies of Manganate(V), -(VI), and -(VII) Tetraoxyanions by Pulse Radiolysis. Optical Spectra of Protonated Forms | first1 = J. D. | last1 = Rush | first2 = B. H. J. | last2 = Bielski | journal = Inorg. Chem. | year = 1995 | volume = 34 | issue = 23 | pages = 5832–38 | doi = 10.1021/ic00127a022}}.</ref> However, K<sub>3</sub>MnO<sub>4</sub> has been cocrystallized with Ca<sub>2</sub>Cl(PO<sub>4</sub>), allowing the study of the ] of the hypomanganate ion.<ref name="C&W"/><ref>{{citation | journal = J. Chem. Soc. | year = 1956 | pages = 3373–80 | doi = 10.1039/JR9560003373 | title = Structure and reactivity of the oxy-anions of transition metals. Part I. The manganese oxy-anions | first1 = A. | last1 = Carrington | first2 = M. C. R. | last2 = Symons}}.</ref> |
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In the absence of moisture, it is stable up to 900 °C. Above that temperature, it decomposes to ], ], and oxygen.<ref>{{cite journal |author1=H. Peters |author2=K.-H. Radeke |author3=L. Till |title=Über das thermische Verhalten von Kaliummanganat(V), -(VI) und -(VII) |journal=Zeitschrift für anorganische und allgemeine Chemie |date=1966 |volume=346 |issue=1-2 |pages=1-11 |doi=10.1002/zaac.19663460102 |trans-title=About the thermal behavior of potassium manganate(V), -(VI) and -(VII) |language=de}}</ref> |
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==Preparative routes== |
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The solid salt can be produced by the reaction of ] and ] in the presence of ] at 800 °C.<ref name="the" /> However, in the industrial process of producing potassium permanganate, it is produced by fusing manganese dioxide and ]. The resulting hypomanganate further reacts with water to produce manganate.<ref name="Kirk" /> |
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A solution of potassium hypomanganate is produced: |
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*by two-electron ] of ] with excess ];<ref name="C&W">{{Cotton&Wilkinson4th|page=746}}.</ref><ref name="G&E">{{Greenwood&Earnshaw1st|pages=1221–22}}.</ref> |
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:{{chem2|MnO4− + SO3(2−) + H2O → MnO4(3−) + SO4(2−) + 2 H+}} |
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*by the single-electron reduction of ] with ] in 10 M ] solution;<ref>{{citation | title = Oxidation of hydrocarbons. 18. Mechanism of the reaction between permanganate and carbon-carbon double bonds | first1 = Donald G. | last1 = Lee | first2 = Tao | last2 = Chen | journal = J. Am. Chem. Soc. | year = 1989 | volume = 111 | issue = 19 | pages = 7534–38 | doi = 10.1021/ja00201a039}}.</ref> |
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:{{chem2|2 MnO4(2−) + H2O2 + 2 OH− → 2 MnO4(3−) + O2 + 2 H2O}} |
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*by the single-electron reduction of potassium manganate with ] in 3–10 M potassium hydroxide solution;<ref name="Mandelate"/> |
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:{{chem2|2 MnO4(2−) + C8H7O3− + 2 OH− → 2 MnO4(3−) + C8H5O3− + 2 H2O}} |
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*by disproportionation when ] is dissolved in a concentrated solution of potassium hydroxide;<ref name="C&W"/> |
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:{{chem2|2 MnO2 + 3 OH− → MnO4(3−) + MnOOH + H2O}} |
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The compound is unstable due to the tendency of the hypomanganate anion to disproportionate in all but the most alkaline solutions.<ref name="C&W"/><ref name="G&E"/> |
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==References== |
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==References== |
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{{potassium compounds}} |
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{{manganese compounds}} |
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