Английская Википедия:Chromium(VI) oxide peroxide
Шаблон:Chembox Chromium(VI) oxide peroxide or chromium oxide peroxide or more accurately chromium(VI) oxide diperoxide is an inorganic compound with the chemical formula Шаблон:Chem2 or more accurately Шаблон:Chem2. It is an unstable dark blue compound. This compound contains one oxo ligand and two peroxo ligands, making a total of five oxygen atoms per chromium atom.
Preparation and properties
Chromium(VI) oxide peroxide is formed by the addition of acidified hydrogen peroxide solutions to solutions of metal chromates or dichromates, such as sodium chromate or potassium dichromate. The generally yellow chromates or orange dichromates turn to dark blue as chromium(VI) oxide peroxide is formed. Chromate or dichromate reacts with hydrogen peroxide and an acid to give chromium peroxide and water.
With this method, the chromium(VI) oxide peroxide will decompose after a few seconds, turning green as chromium(III) compounds are formed.[1]
To avoid this decomposition, it is possible to stabilize chromium(VI) oxide peroxide in water-immiscible organic solvents such as diethyl ether, 1-butanol, ethyl acetate or amyl acetate by adding a layer of the organic solvent above the chromate/dichromate solution and shaking during the addition of hydrogen peroxide. In this way, the chromium(VI) oxide peroxide (unstable in the aqueous phase in which it is newly formed) is dissolved in the immiscible organic solvent. In this condition, it can be observed over a much longer period.Шаблон:Cn
Шаблон:Chem2 is unstable and decomposes on standing to form Шаблон:Chem2. It is incompatible with ketones and primary alcohols, as it oxidizes them to aldehydes and carboxylic acids while being itself reduced to Шаблон:Chem2. Therefore, Шаблон:Chem2 is a good oxidizing agent, even better than chromates and dichromates due to the presence of two reactive peroxo ligands, but due to its low stability it is not used in organic syntheses.Шаблон:Citation needed
Derivatives
The etherate, bis(pyridine) and pyridine complexes of this compound have been found to be effective oxidants in organic chemistry.[2]
The structure of the pyridine complex has been determined crystallographically.[3]
Gallery
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An aqueous solution of chromium peroxide
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A very dilute solution of chromium peroxide
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chromium(VI) oxide peroxide stabilized in ether phase (above) and chromium(III) aqueous solution (below).
See also
- Tetraperoxochromate - an similarly-synthesized analogous chromium(V) peroxide complex
References
External links
- Experimental details and photo Шаблон:In lang
- Шаблон:YouTube (8 November 2012). Professor Martyn Poliakoff of the University of Nottingham demonstrates the synthesis on Periodic Videos.
- ↑ Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils; (1985). "Chromium" (in German). Lehrbuch der Anorganischen Chemie (91–100 ed.). Walter de Gruyter. pp. 1081–1095. Шаблон:ISBN."
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
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