[curiouscat]

I've read of several protocols to activate MnO2 (to be used as an oxidizing agent) and one point I'm wondering about is what happens to the spent MnO2? Is it transformed chemically and if so to what?

Reason I ask is most protocols do recommend a large excess of MnO2 (10 equivs often) and I'm wondering if it'd be possible to keep recycling and reactivating the spent MnO2 after each oxidation batch.

For a commercial process this would make a lot of sense. Would an oven drying cycle at 110 C be likely to work or would re-dissolution and re-precipitation be needed after each step?

[Archer]

Someone may correct me on this but I would assume the oxidation is to Mn(II)O.

I've only encountered MnO₂ as a nuisance finely divided mud-like solid from permanganate oxidations. I oxidise this to Mn²⁺ with bisulfite.

[curiouscat]

I've only encountered MnO₂ as a nuisance finely divided mud-like solid from permanganate oxidations. I oxidise this to Mn²⁺ with bisulfite.

I have faced this problem too in other situations! What do you use again to oxidize that pesky nuisance? Na-bisulfite you said? Or....?

Just confirming,

[Archer]

Sodium metabisulfite, yes. I used to centrifuge before I read about this little gem.

[Borek]

I've only encountered MnO₂ as a nuisance finely divided mud-like solid from permanganate oxidations. I oxidise this to Mn²⁺ with bisulfite.

MnO₂ Mn²⁺ looks like a reduction to me 

[Archer]

I've only encountered MnO₂ as a nuisance finely divided mud-like solid from permanganate oxidations. I oxidise this to Mn²⁺ with bisulfite.

MnO₂ Mn²⁺ looks like a reduction to me 

Doh! Public humiliation   

[opsomath]

The sulfite family does a great job of clearing up MnO2 leftovers. I used to have a benzylic oxidation with KMnO4 that was my least favorite reaction in the world  until I learned about that one.

Milkshake, the man the legend, had a post someplace on activating and storing MnO2 as an oxidizer. I'm getting ready for class but I'll look for it later.

[curiouscat]

Milkshake, the man the legend, had a post someplace on activating and storing MnO2 as an oxidizer. I'm getting ready for class but I'll look for it later.

@opsomath

Did you find that thread? I couldn't.

Closest I found was this:

http://www.chemicalforums.com/index.php?topic=50628.0