Barium manganate
Chemical compound
From Wikipedia, the free encyclopedia
Barium manganate is an inorganic compound with the formula BaMnO4. It is used as an oxidant in organic chemistry.[2] 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.
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3D model (JSmol) |
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| ECHA InfoCard | 100.029.190 |
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CompTox Dashboard (EPA) |
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| Properties | |
| BaMnO4 | |
| Molar mass | 256.26 g/mol |
| Appearance | light blue to dark blue and black powder |
| Density | 4.85 g/cm3 |
| insoluble[1] | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
GHS03, GHS07: oxidizing, skin and eye irritant |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Properties
The manganate(VI) ion is a d1 ion and is tetrahedral with bond angles of approximately 109.5°. The Mn−O bond lengths in BaMnO4 and K2MnO4 are identical at 1.66 Å. In comparison, the Mn-O bond length in MnO2−4 is longer than in MnO4− of 1.56 Å and shorter than the Mn−O bond found in MnO2, 1.89 Å.[3][4] Barium manganate is isomorphous with BaCrO4 and BaSO4. Barium manganate can appear as a dark blue or green to black crystals.[5] Barium manganate is indefinitely stable, active and can be stored for months in dry conditions.[5]
Preparation
Barium manganate can be prepared from potassium manganate and barium chloride by salt metathesis to give insoluble barium manganate:[6]
- BaCl2 + K2MnO4 → 2 KCl + BaMnO4↓
Applications
Barium manganate oxidizes a number of functional groups efficiently and selectively: alcohols to carbonyls, diols to lactones, thiols to disulfides, aromatic amines to azo-compounds, hydroquinone to p-benzoquinone, benzylamine to benzaldehyde, hydrazones to diazo compounds, etc.[7] It does not oxidize saturated hydrocarbons, alkenes, unsaturated ketones, and tertiary amines. Barium manganate is a common substitute for MnO2. It is easier to prepare, reacts more efficiently, and the substrate:oxidant ratios are closer to theory.
Another use for barium manganate was as a component of the inorganic pigment manganese blue, which is no longer produced on an industrial scale.