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The chemical knowledge of Potassium dichromate

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The chemical knowledge of Potassium dichromate

Post  gill on Thu Dec 09, 2010 4:17 am


Potassium dichromate, K2Cr2O7, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications.
In organic chemistry,
potassium dichromate is a mild oxidizer compared with potassium permanganate. It is used to oxidize alcohols. It converts primary alcohols into aldehydes, or into carboxylic acids if heated under reflux. In contrast, with permanganate, carboxylic acids are the sole products. Secondary alcohols are converted into ketones — no further oxidation is possible. For example, menthone may be prepared by oxidation of menthol with acidified dichromate. Tertiary alcohols are not oxidized by potassium dichromate.
In an aqueous solution the color change exhibited can be used to test whether an aldehyde or ketone is present. When an aldehyde is present the chromium ions will be reduced from the +6 to the +3 oxidation state, changing color from orange to green. This is because the aldehyde can be further oxidized to the corresponding carboxylic acid. A ketone will show no such change because it cannot be oxidized further, and so the solution will remain orange.


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