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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Dungsbars on December 23, 2008, 11:44:59 AM

Title: Permanganate, Chromium Trioxide oxidation products
Post by: Dungsbars on December 23, 2008, 11:44:59 AM

I'm not sure whether this belongs here or in the organic forum. When I oxidize an alcohol or aldehyde with a strong oxidizing agent, like those in the topic title, I get a ketone/aldehyde or a carboxylic acid. But I wonder what happens with the oxidizing agents after this reaction.
When I write out the mechanism, I arrive at H₃MnO₄ or H₂CrO₃, which both don't seem to exist. They can dehydrate to HMnO₃ and CrO₂, of which the latter exists, but I'm not sure if that's what actually happens. And what happens with the "manganite" is a mystery.

Title: Re: Permanganate, Chromium Trioxide oxidation products
Post by: UnintentionalChaos on December 23, 2008, 03:03:36 PM

Permanganate will be reduced all the way to Mn²⁺ in acid solution. In basic media, it precipitates as hydrated MnO2 when it hits the +4 oxidation state. Chromium trioxide/chromate/dichromate/PCC/PDC is reduced to Cr³⁺.

Title: Re: Permanganate, Chromium Trioxide oxidation products
Post by: Dungsbars on December 24, 2008, 05:09:52 PM

But say we oxidize a secondary alcohol to a ketone. Carbon goes from 0 to +2, so you expect Mn⁷⁺ to go to Mn⁵⁺. How does it end up at 4+ or 2+? Same for Cr⁶⁺ going to Cr³⁺.