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{{chembox |
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| Verifiedfields = changed |
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| verifiedrevid = 443932622 |
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| Watchedfields = changed |
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| verifiedrevid = 445299286 |
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| ImageFile = Manganese(IV) oxide.jpg |
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| ImageFile = Manganese(IV) oxide.jpg |
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| ImageName = Manganese(IV) oxide |
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| ImageName = Manganese(IV) oxideMn4O2 |
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| ImageFile1 = Rutile-unit-cell-3D-balls.png |
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| ImageFile1 = Rutile-unit-cell-3D-balls.png |
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| ImageName1 = |
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| ImageName1 = |
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| IUPACName = Manganese oxide<br />Manganese(IV) oxide |
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| IUPACName = Manganese dioxide<br />Manganese(IV) oxide |
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| OtherNames = ] |
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| OtherNames = ], hyperoxide of manganese, black oxide of manganese, manganic oxide |
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| Section1 = {{Chembox Identifiers |
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| Section1={{Chembox Identifiers |
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| CASNo = 1313-13-9 |
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| CASNo = 1313-13-9 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| PubChem = 14801 |
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| PubChem = 14801 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID = 14117 |
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| ChemSpiderID = 14117 |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| ChEBI_Ref = {{ebicite|changed|EBI}} |
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| ChEBI = 136511 |
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| EINECS = 215-202-6 |
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| RTECS = OP0350000 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = TF219GU161 |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChI = 1S/Mn.2O |
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| StdInChI = 1S/Mn.2O |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey = NUJOXMJBOLGQSY-UHFFFAOYSA-N |
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| StdInChIKey = NUJOXMJBOLGQSY-UHFFFAOYSA-N |
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| SMILES = O==O |
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| SMILES = O==O |
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| EINECS = 215-202-6 |
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| RETECS = OP0350000 |
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}} |
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}} |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| Formula = MnO<sub>2</sub> |
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| Formula = {{chem|MnO|2}} |
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| MolarMass = 86.9368 g/mol |
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| MolarMass = 86.9368 g/mol |
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| Appearance = Brown-black solid |
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| Appearance = Brown-black solid |
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| Density = 5.026 g/cm<sup>3</sup> |
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| Density = 5.026 g/cm<sup>3</sup> |
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| Solubility = insoluble |
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| Solubility = Insoluble |
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| MeltingPt = 535 °C decomp |
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| MeltingPtC = 535 |
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| MeltingPt_notes = (decomposes) |
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| MagSus = +2280.0×10<sup>−6</sup> cm<sup>3</sup>/mol<ref>Rumble, p. 4.71</ref> |
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}} |
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}} |
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| Section4 = {{Chembox Thermochemistry |
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| Section3 = {{Chembox Structure |
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| Structure_ref =<ref>{{cite journal|title=Second-order rutile-type to CaCl<sub>2</sub>-type phase transition in β-MnO<sub>2</sub> at high pressure|journal=Journal of Physics and Chemistry of Solids|volume=56|issue=7|pages=965–973|doi=10.1016/0022-3697(95)00037-2|year=1995|last1=Haines|first1=J.|last2=Léger|first2=J.M.|last3=Hoyau|first3=S.|bibcode=1995JPCS...56..965H }}</ref> |
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| DeltaHf = −520.9 kJ/mol |
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| CrystalStruct = Tetragonal, ], No. 136 |
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| Entropy = 53.1 J K<sup>−1</sup> mol<sup>−1</sup> |
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| SpaceGroup = P4<sub>2</sub>/mnm |
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| LattConst_a = 0.44008 nm |
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| LattConst_b = 0.44008 nm |
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| LattConst_c = 0.28745 nm |
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| LattConst_alpha = |
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| LattConst_beta = |
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| LattConst_gamma = |
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| LattConst_ref = |
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| LattConst_Comment = |
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| UnitCellVolume = |
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| UnitCellFormulas = 2 |
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| Coordination = |
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| MolShape = |
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| OrbitalHybridisation = |
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| Dipole = |
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}} |
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| Section7 = {{Chembox Hazards |
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|Section4={{Chembox Thermochemistry |
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| Thermochemistry_ref =<ref>Rumble, p. 5.25</ref> |
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| ExternalMSDS = |
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| DeltaHf = −520.0 kJ·mol<sup>−1</sup> |
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| EUIndex = 025-001-00-3 |
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| Entropy = 53.1 J·mol<sup>−1</sup>·K<sup>−1</sup> |
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| EUClass = Harmful ('''Xn''')<br />Oxidizer ('''O''') |
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| HeatCapacity = 54.1 J·mol<sup>−1</sup>·K<sup>−1</sup> |
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| RPhrases = {{R20/22}} |
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| DeltaGfree = −465.1 kJ·mol<sup>−1</sup> |
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| SPhrases = {{S2}}, {{S25}} |
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}} |
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| NFPA-H = 1 |
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|Section7={{Chembox Hazards |
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| NFPA-F = 1 |
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| ExternalSDS = |
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| NFPA-R = 2 |
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| GHSPictograms = {{GHS07}} |
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| NFPA-O = OX |
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| GHSSignalWord = Warning |
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| FlashPt = 535 °C |
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| HPhrases = {{H-phrases|302|332}} |
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| PPhrases = {{P-phrases|261|264|270|271|301+312|304+312|304+340|312|330|501}} |
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| NFPA-H = 2 |
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| NFPA-F = 1 |
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| NFPA-R = 2 |
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| NFPA-S = OX |
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| FlashPtC = 535 |
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}} |
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}} |
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| Section8 = {{Chembox Related |
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|Section8={{Chembox Related |
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| OtherAnions = ] |
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| OtherAnions = ] |
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| OtherCations = ]<br/>] |
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| OtherCations = ]<br/>] |
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| OtherFunctn = ]<br/>]<br/>]<br/>] |
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| OtherFunction = ]<br/>]<br/>]<br/>] |
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| Function = ] ]s |
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| OtherFunction_label = ] ]s |
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'''Manganese(IV) oxide''' is the ] with the ] {{chem|MnO|2}}. This blackish or brown solid occurs naturally as the mineral ], which is the main ore of ] and a component of ]s. The principal use for MnO<sub>2</sub> is for dry-cell ], such as the ] and the ].<ref name="G&E">{{Greenwood&Earnshaw1st|pages=1218–20}}.</ref> {{chem|MnO|2}} is also used as a ] and as a precursor to other manganese compounds, such as {{chem|link=potassium permanganate|KMnO|4|}}. It is used as a ] in ], for example, for the oxidation of ] ]s. |
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'''Manganese dioxide''' is the ] with the ] {{chem|MnO|2}}. This blackish or brown solid occurs naturally as the mineral ], which is the main ore of ] and a component of ]s. The principal use for {{chem|MnO|2}} is for dry-cell ], such as the ] and the ].<ref name="G&E">{{Greenwood&Earnshaw1st|pages=1218–20}}.</ref> {{chem|MnO|2}} is also used as a ] and as a precursor to other manganese compounds, such as {{chem|link=potassium permanganate|KMnO|4}}. It is used as a ] in ], for example, for the oxidation of ] ]s. {{chem|MnO|2}} has an α-] that can incorporate a variety of atoms (as well as water molecules) in the "tunnels" or "channels" between the manganese oxide octahedra. There is considerable interest in {{chem|α-MnO|2}} as a possible cathode for ].<ref>{{cite journal|last1=Barbato|first1=S|title=Hollandite cathodes for lithium ion batteries. 2. Thermodynamic and kinetics studies of lithium insertion into BaMMn<sub>7</sub>O<sub>16</sub> (M=Mg, Mn, Fe, Ni)|journal=Electrochimica Acta|date=31 May 2001|volume=46|issue=18|pages=2767–2776|doi=10.1016/S0013-4686(01)00506-0|hdl=10533/173039|hdl-access=free}}</ref><ref>{{cite journal|last1=Tompsett|first1=David A.|last2=Islam|first2=M. Saiful|title=Electrochemistry of Hollandite α-MnO : Li-Ion and Na-Ion Insertion and Li Incorporation|journal=Chemistry of Materials|date=25 June 2013|volume=25|issue=12|pages=2515–2526|doi=10.1021/cm400864n|citeseerx=10.1.1.728.3867}}</ref> |
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==Structure== |
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==Structure== |
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Several ]s of {{chem|MnO|2}} are claimed, as well as a hydrated form. Like many other dioxides, {{chem|MnO|2}} crystallizes in the ] motif (this polymorph is called β-{{chem|MnO|2}}), with three-coordinate oxide and octahedral metal centres.<ref name=G&E/> {{chem|MnO|2}} is characteristically ], being deficient in oxygen. The complicated ] of this material is relevant to the lore of "freshly prepared" {{chem|MnO|2}} in ]. |
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Several ]s of {{chem|MnO|2}} are claimed, as well as a hydrated form. Like many other dioxides, {{chem|MnO|2}} crystallizes in the ] ] (this polymorph is called ] or {{chem|β-MnO|2}}), with three-coordinate oxide anions and octahedral metal centres.<ref name=G&E/> {{chem|MnO|2}} is characteristically ], being deficient in oxygen. The complicated ] of this material is relevant to the lore of "freshly prepared" {{chem|MnO|2}} in ].<ref name= Cahiez/> The α-polymorph of {{chem|MnO|2}} has a very open structure with "channels", which can accommodate metal ions such as silver or barium. {{chem|α-MnO|2}} is often called ], after a closely related mineral. |
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==Production== |
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==Production== |
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Naturally occurring manganese dioxide contains impurities and a considerable amount of manganese in its ] ]. Only a limited number of deposits contain the γ modification in purity sufficient for the battery industry. The production of ] also requires high purity manganese dioxide. Therefore the production of synthetic manganese dioxide is important. Two groups of methods are used, yielding "chemical manganese dioxide" (CMD) and "electrolytical manganese dioxide" (EMD). The CMD is mostly used for the production of ferrites, whereas EMD is used for the production of batteries.<ref name="ChiuZMnO2">{{citation | last = Preisler | first = Eberhard | title = Moderne Verfahren der Großchemie: Braunstein | journal = Chemie in unserer Zeit | year = 1980 | volume = 14 | pages = 137–48 | doi = 10.1002/ciuz.19800140502}}.</ref> |
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Naturally occurring manganese dioxide contains impurities and a considerable amount of ]. Production of ] and ] (two of the primary uses of manganese dioxide) requires high purity manganese dioxide. Batteries require "electrolytic manganese dioxide" while ferrites require "chemical manganese dioxide".<ref name="ChiuZMnO2">{{citation | last = Preisler | first = Eberhard | title = Moderne Verfahren der Großchemie: Braunstein | journal = Chemie in unserer Zeit | year = 1980 | volume = 14 | issue = 5 | pages = 137–48 | doi = 10.1002/ciuz.19800140502}}.</ref> |
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===Chemical manganese dioxide=== |
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===Chemical manganese dioxide=== |
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One method starts with natural manganese dioxide and converts it using ] and water to a ] solution. Evaporation of the water leaves the crystalline nitrate salt. At temperatures of 400 °C, the salt decomposes, releasing {{chem|N|2|O|4}} and leaving a residue of purified manganese dioxide.<ref name="ChiuZMnO2"/> These two steps can be summarized as: |
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:{{chem|MnO|2}} + {{chem|N|2|O|4}} {{eqm}} {{chem|Mn(NO|3|)|2}} |
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One of the two chemical methods starts from natural manganese dioxide and converts it using ] and water to ] solution. Evaporation of the water, leaves the crystalline nitrate salt. At temperatures of 400 °C, the salt decomposes, releasing N<sub>2</sub>O<sub>4</sub> and leaving a residue of purified manganese dioxide.<ref name="ChiuZMnO2"/> These two steps can be summarized as: |
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In another process, manganese dioxide is ] reduced to ] which is dissolved in ]. The filtered solution is treated with ] to precipitate {{chem|MnCO|3}}. The carbonate is ] in air to give a mixture of manganese(II) and manganese(IV) oxides. To complete the process, a suspension of this material in sulfuric acid is treated with ]. ], which forms in situ, converts any Mn(III) and Mn(II) oxides to the dioxide, releasing chlorine as a by-product.<ref name="ChiuZMnO2"/> |
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:MnO<sub>2</sub> + N<sub>2</sub>O<sub>4</sub> → Mn(NO<sub>3</sub>)<sub>2</sub> |
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:Mn(NO<sub>3</sub>)<sub>2</sub> → MnO<sub>2</sub> + N<sub>2</sub>O<sub>4</sub> |
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Lastly, the action of ] over ] crystals produces the desired oxide.<ref>Arthur Sutcliffe (1930) Practical Chemistry for Advanced Students (1949 Ed.), John Murray – London.</ref> |
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In the other chemical process, manganese dioxide ore is reduced by heating with oil or coal. The resulting ] is dissolved in ], and the filtered solution is treated with ] to precipitate MnCO<sub>3</sub>. The carbonate is ] in air to give a mixture of manganese(II) and manganese(IV) oxides. To complete the process, a suspension of this material in sulfuric acid is treated with ]. ], which forms in situ, converts any Mn(III) and Mn(II) oxides to the dioxide, releasing chlorine as a by-product.<ref name="ChiuZMnO2"/> |
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:2 {{chem|KMnO|4}} + 3 {{chem|MnSO|4}} + 2 {{chem|H|2|O}}→ 5 {{chem|MnO|2}} + {{chem|K|2|SO|4}} + 2 {{chem|H|2|SO|4}} |
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===Electrolytical manganese dioxide=== |
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===Electrolytic manganese dioxide=== |
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Electrolytic manganese dioxide (EMD) is used in ] together with ] and ]. EMD is commonly used in zinc manganese dioxide ] also. For these applications, purity is extremely important. EMD is produced in a similar fashion as ]: The manganese dioxide is dissolved in ] (sometimes mixed with ]) and subjected to a current between two electrodes. The MnO<sub>2</sub> dissolves, enters solution as the sulfate, and is deposited on the ].<ref>{{cite journal | url=https://pubs.rsc.org/en/content/articlelanding/2015/ra/c5ra05892a | doi=10.1039/C5RA05892A | title=Electrolytic manganese dioxide (EMD): A perspective on worldwide production, reserves and its role in electrochemistry | date=2015 | last1=Biswal | first1=Avijit | last2=Chandra Tripathy | first2=Bankim | last3=Sanjay | first3=Kali | last4=Subbaiah | first4=Tondepu | last5=Minakshi | first5=Manickam | journal=RSC Advances | volume=5 | issue=72 | pages=58255–58283 }}</ref> |
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Manganese dioxide is used in ] together with ] and ]. |
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==Reactions== |
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==Reactions== |
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The important reactions of {{chem|MnO|2}} are associated with its redox, both oxidation and reduction. |
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The important reactions of {{chem|MnO|2}} are associated with its ], both oxidation and reduction. |
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===Reduction=== |
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===Reduction=== |
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{{chem|MnO|2}} is the principal ] to ] and related alloys, which are widely used in the steel industry. The conversions involve ] using ]: |
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{{chem|MnO|2}} is the principal ] to ] and related alloys, which are widely used in the steel industry. The conversions involve ] using ]:<ref name=UllMn>{{cite book |doi=10.1002/14356007.a16_077|chapter=Manganese and Manganese Alloys |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2000 |last1=Wellbeloved |first1=David B. |last2=Craven |first2=Peter M. |last3=Waudby |first3=John W. |isbn=3527306730 }}</ref> |
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:{{chem|MnO|2}} + 2 C → Mn + 2 CO |
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:{{chem|MnO|2}} + 2 C → Mn + 2 CO |
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The key reactions of {{chem|MnO|2}} in batteries is the one-electron reduction: |
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The key redox reactions of {{chem|MnO|2}} in batteries is the one-electron reduction: |
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:{{chem|MnO|2}} + e<sup>-</sup> + H<sup>+</sup> → MnO(OH) |
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:{{chem|MnO|2}} + e<sup>−</sup> + {{chem|H|+}} → MnO(OH) |
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{{chem|MnO|2}} ] several reactions that form {{chem|O|2}}. In a classical laboratory demonstration, heating a mixture of ] and manganese dioxide produces oxygen gas. Manganese dioxide also catalyses the decomposition of ] to oxygen and ]: |
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{{chem|MnO|2}} ] several reactions that form {{chem|O|2}}. In a classical laboratory demonstration, heating a mixture of ] and manganese dioxide produces oxygen gas. Manganese dioxide also catalyses the decomposition of ] to oxygen and ]: |
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:2 H<sub>2</sub>O<sub>2</sub> → 2 H<sub>2</sub>O + O<sub>2</sub> |
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:2 {{chem|H|2|O|2}} → 2 {{chem|H|2|O}} + {{chem|O|2}} |
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Manganese dioxide decomposes above about 530 °C to ] and oxygen. At temperatures close to 1000 °C, the ] Mn<sub>3</sub>O<sub>4</sub> forms. Higher temperatures give MnO. |
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Manganese dioxide decomposes above about 530 °C to ] and oxygen. At temperatures close to 1000 °C, the ] {{chem|Mn|3|O|4}} forms. Higher temperatures give MnO, which is reduced only with difficulty.<ref name=UllMn/> |
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Hot concentrated ] reduces the MnO<sub>2</sub> to manganese(II):<ref name="G&E"/> |
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Hot concentrated ] reduces {{chem|MnO|2}} to ]:<ref name="G&E"/> |
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:2 MnO<sub>2</sub> + 2 H<sub>2</sub>SO<sub>4</sub> → 2 MnSO<sub>4</sub> + O<sub>2</sub> + 2 H<sub>2</sub>O |
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:2 {{chem|MnO|2}} + 2 {{chem|H|2|SO|4}} → 2 {{chem|MnSO|4}} + {{chem|O|2}} + 2 {{chem|H|2|O}} |
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The reaction of ] with MnO<sub>2</sub> was used by ] in the original isolation of ] gas in 1774: |
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The reaction of ] with {{chem|MnO|2}} was used by ] in the original isolation of ] gas in 1774: |
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:MnO<sub>2</sub> + 4 HCl → MnCl<sub>2</sub> + Cl<sub>2</sub> + 2 H<sub>2</sub>O |
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:{{chem|MnO|2}} + 4 HCl → {{chem|MnCl|2}} + {{chem|Cl|2}} + 2 {{chem|H|2|O}} |
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As a source of hydrogen chloride, Scheele treated ] with concentrated sulfuric acid.<ref name=G&E>{{Greenwood&Earnshaw1st}}.</ref> |
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As a source of hydrogen chloride, Scheele treated ] with concentrated sulfuric acid.<ref name="G&E"/> |
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::''E''<sup><s>o</s></sup> (MnO<sub>2</sub>(s) + 4 H<sup>+</sup> + 2 e<sup>−</sup> {{eqm}} Mn<sup>2+</sup> + 2 H<sub>2</sub>O) = +1.23 V |
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::''E''<sup><s>o</s></sup> ({{chem|MnO|2}}(s) + 4 {{chem|H|+}} + 2 e<sup>−</sup> {{eqm}} Mn<sup>2+</sup> + 2 {{chem|H|2|O}}) = +1.23 V |
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::''E''<sup><s>o</s></sup> (Cl<sub>2</sub>(g) + 2 e<sup>−</sup> {{eqm}} 2 Cl<sup>−</sup>) = +1.36 V |
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::''E''<sup><s>o</s></sup> ({{chem|Cl|2}}(g) + 2 e<sup>−</sup> {{eqm}} 2 Cl<sup>−</sup>) = +1.36 V |
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The ]s for the ]s indicate that the reaction is ] at pH = 0 (1 M ), but it is favoured by the lower ] as well as the evolution (and removal) of gaseous chlorine. |
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The reaction would not be expected to proceed, based on the ]s, but is favoured by the extremely high ] and the evolution (and removal) of gaseous chlorine. |
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This reaction is also a convenient way to remove the manganese dioxide ] from the ]s after running a reaction (i. e., an oxidation with ]). |
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This reaction is also a convenient way to remove the manganese dioxide ] from the ]s after running a reaction (for example, an oxidation with ]). |
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===Oxidation=== |
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===Oxidation=== |
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Heating a mixture of ] and {{chem|MnO|2}} in air gives green ]: |
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Heating a mixture of ] and {{chem|MnO|2}} in air gives green ]: |
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:2 MnO<sub>2</sub> + 4 KOH + O<sub>2</sub> → 2 K<sub>2</sub>MnO<sub>4</sub> + 2 H<sub>2</sub>O |
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:2 {{chem|MnO|2}} + 4 KOH + {{chem|O|2}} → 2 {{chem|K|2|MnO|4}} + 2 {{chem|H|2|O}} |
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Potassium manganate is the precursor to ], a common oxidant. |
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Potassium manganate is the precursor to ], a common oxidant. |
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==Occurrence and applications== |
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==Applications== |
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The predominant application of MnO<sub>2</sub> is as a component of ] batteries, so called ], or ]. Approximately 500,000 ]s are consumed for this application annually.<ref name=Ullmann>{{citation | first = Arno H. | last = Reidies | contribution = Manganese Compounds | title = Ullmann's Encyclopedia of Industrial Chemistry | publisher = Wiley-VCH | location = Weinheim | year = 2002 | doi = 10.1002/14356007.a16_123 | volume = 20 | pages = 495–542 | isbn = 3-527-30385-5}}.</ref> Other industrial applications include the use of {{chem|MnO|2}} as an inorganic ] in ]s and in ]. |
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The predominant application of {{chem|MnO|2}} is as a component of ] batteries: alkaline batteries and so called ], or ]. Approximately 500,000 ]s are consumed for this application annually.<ref name=Ullmann>{{citation | first = Arno H. | last = Reidies | contribution = Manganese Compounds | title = Ullmann's Encyclopedia of Industrial Chemistry | publisher = Wiley-VCH | location = Weinheim | year = 2002 | doi = 10.1002/14356007.a16_123 | volume = 20 | pages = 495–542 | isbn = 978-3-527-30385-4}}</ref> Other industrial applications include the use of {{chem|MnO|2}} as an inorganic ] in ]s and in ]. It is also used in water treatment applications.<ref>{{cite journal |last1=Ibrahim |first1=Yazan |last2=Wadi |first2=Vijay S. |last3=Ouda |first3=Mariam |last4=Naddeo |first4=Vincenzo |last5=Banat |first5=Fawzi |last6=Hasan |first6=Shadi W. |title=Highly selective heavy metal ions membranes combining sulfonated polyethersulfone and self-assembled manganese oxide nanosheets on positively functionalized graphene oxide nanosheets |journal=Chemical Engineering Journal |date=15 January 2022 |volume=428 |pages=131267 |doi=10.1016/j.cej.2021.131267 |issn=1385-8947 }}</ref> |
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=== Prehistory === |
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Excavations at the ] site in southwestern France have yielded blocks of manganese dioxide writing tools, which date back 50,000 years and have been attributed to ] . Scientists have conjectured that Neanderthals used this mineral for body decoration, but there are many other readily available minerals that are more suitable for that purpose. Heyes et al. (in 2016) determined that the manganese dioxide lowers the combustion temperatures for wood from above 350°C (662°F) to 250°C (482°F), making fire making much easier and this is likely to be the purpose of the blocks.<ref>{{Cite web |title=Neandertals may have used chemistry to start fires |url=https://www.science.org/content/article/neandertals-may-have-used-chemistry-start-fires |access-date=2022-05-30 |website=www.science.org |language=en}}</ref> |
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===Organic synthesis===<!--used in ind production of p-quinone from aniline--> |
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===Organic synthesis===<!--used in ind production of p-quinone from aniline--> |
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A specialized use of manganese dioxide is as oxidant in ].<ref>{{citation | last1 = Cahiez | first1 = G. | last2 = Alami | first2 = M. | last3 = Taylor | first3 = R. J. K. | last4 = Reid | first4 = M. | last5 = Foot | first5 = J. S. | contribution = Manganese Dioxide | title = Encyclopedia of Reagents for Organic Synthesis | editor-first = Leo A. | editor-last = Paquette | year = 2004 | publisher = J. Wiley & Sons | location = New York}}.</ref> The effectiveness of the reagent depends on the method of preparation, a problem that is typical for other heterogeneous reagents where surface area, among other variables, is a significant factor.<ref>{{citation | last1 = Attenburrow | first1 = J. | last2 = Cameron | first2 = A. F. B. | last3 = Chapman | first3 = J. H. | last4 = Evans | first4 = R. M. | last5 = Hems | first5 = B. A. | last6 = Jansen | first6 = A. B. A. | last7 = Walker | first7 = T. | journal = J. Chem. Soc. | year = 1952 | page = 1094}}.</ref> The mineral ] makes a poor reagent. Usually, however, the reagent is generated in situ by treatment of an aqueous solution KMnO<sub>4</sub> with a Mn(II) salt, typically the sulfate. MnO<sub>2</sub> oxidizes ] alcohols to the corresponding ]s or ]s:<ref>{{OrgSynth | author = Leo A. Paquette and Todd M. Heidelbaugh | title = (4S)-(−)-tert-Butyldimethylsiloxy-2-cyclopen-1-one | |collvol = 9 | collvolpages = 136 | year = | prep = cv9p0136}} (this procedure illustrates the use of MnO2 for the oxidation of an allylic alcohol.</ref> |
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A specialized use of manganese dioxide is as oxidant in ].<ref name= Cahiez>{{citation | last1 = Cahiez | first1 = G. | last2 = Alami | first2 = M. | last3 = Taylor | first3 = R. J. K. | last4 = Reid | first4 = M. | last5 = Foot | first5 = J. S. |doi=10.1002/047084289X.rm021.pub4 | contribution = Manganese Dioxide | title = Encyclopedia of Reagents for Organic Synthesis | pages = 1–16 | editor-first = Leo A. | editor-last = Paquette | year = 2004 | publisher = J. Wiley & Sons | location = New York| isbn = 9780470842898 }}.</ref> The effectiveness of the reagent depends on the method of preparation, a problem that is typical for other heterogeneous reagents where surface area, among other variables, is a significant factor.<ref>{{citation | last1 = Attenburrow | first1 = J. | last2 = Cameron | first2 = A. F. B. | last3 = Chapman | first3 = J. H. | last4 = Evans | first4 = R. M. | last5 = Hems | first5 = B. A. | last6 = Jansen | first6 = A. B. A. | last7 = Walker | first7 = T. | title = A synthesis of vitamin a from cyclohexanone | journal = J. Chem. Soc. | year = 1952 | pages = 1094–1111 |doi= 10.1039/JR9520001094 }}.</ref> The mineral ] makes a poor reagent. Usually, however, the reagent is generated in situ by treatment of an aqueous solution {{chem|KMnO|4}} with a Mn(II) salt, typically the sulfate. {{chem|MnO|2}} oxidizes ] alcohols to the corresponding ]s or ]s:<ref>{{OrgSynth | author = Paquette, Leo A. and Heidelbaugh, Todd M. | title = (4S)-(−)-tert-Butyldimethylsiloxy-2-cyclopen-1-one | |collvol = 9 | collvolpages = 136 | year = | prep = cv9p0136}} (this procedure illustrates the use of MnO<sub>2</sub> for the oxidation of an allylic alcohol)</ref> |
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::cis-RCH=CHCH<sub>2</sub>OH + MnO<sub>2</sub> → cis-RCH=CHCHO + “MnO” + H<sub>2</sub>O |
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::cis-RCH={{chem|CHCH|2|OH}} + {{chem|MnO|2}} → cis-RCH=CHCHO + ] + {{chem|H|2|O}} |
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The configuration of the ] is conserved in the reaction. The corresponding ] alcohols are also suitable substrates, although the resulting ] aldehydes can be quite reactive. ] and even unactivated alcohols are also good substrates. 1,2-]s are cleaved by MnO<sub>2</sub> to ]s or ]s. Otherwise, the applications of MnO<sub>2</sub> are numerous, being applicable to many kinds of reactions including ] oxidation, aromatization, ], and ] oxidation. |
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The configuration of the ] is conserved in the reaction. The corresponding ] alcohols are also suitable substrates, although the resulting ] aldehydes can be quite reactive. ] and even unactivated alcohols are also good substrates. 1,2-]s are cleaved by {{chem|MnO|2}} to ]s or ]s. Otherwise, the applications of {{chem|MnO|2}} are numerous, being applicable to many kinds of reactions including ] oxidation, aromatization, ], and ] oxidation. |
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===Pigment=== |
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===Microbiology=== |
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In '']'' sp., MnO<sub>2</sub> functions as an electron acceptor coupled to the oxidation of organic compounds. This theme has implications for ].<ref>{{cite book |doi=10.1016/S0065-2911(04)49005-5|title=Dissimilatory Fe(III) and Mn(IV) Reduction |series=Advances in Microbial Physiology |year=2004 |last1=Lovley |first1=Derek R. |last2=Holmes |first2=Dawn E. |last3=Nevin |first3=Kelly P. |volume=49 |pages=219–286 |pmid=15518832 |isbn=9780120277490 }}</ref> |
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Manganese dioxide was one of the earliest natural substances used by human ancestors. It was used as a ] at least from the ]. It was possibly used first for ], and later for ]. Some of the most famous early cave paintings in Europe were executed by means of manganese dioxide. |
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==Hazards== |
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==See also== |
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* ] |
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Manganese dioxide can slightly ] human skin if it is damp or in a ], but the stains can be washed off quite easily with some rubbing. |
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==References== |
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==References== |
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{{Reflist}} |
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{{Reflist|30em}} |
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==Cited sources== |
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*{{RubberBible99th}} |
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==External links== |
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==External links== |
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{{Commons category|Manganese dioxide}} |
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* '''' (1893) by A. J. Hopkins |
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{{Manganese compounds}} |
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{{Manganese compounds}} |
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{{Oxides}} |
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{{DEFAULTSORT:Manganese Dioxide}} |
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{{DEFAULTSORT:Manganese Dioxide}} |
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