Sciencemadness Discussion Board

Reaction in Thunder in a Testube?

coccoc - 7-11-2009 at 08:27

Can you suggest how the reactants react in the experiment of thunder in a testube?

When Acetone is used, Permanganate contacted with conc. sulfuric acid to form Manganese Heptoxide, which then reacts, with acetone producing red oily liquid.

So how many reactions may actually occur in this experiment?

woelen - 7-11-2009 at 10:32

I have done this experiment with ethanol, sulphuric acid and KMnO4. It probably also works with acetone, isopropyl alcohol or propyl alcohol.

http://woelen.homescience.net/science/chem/exps/mini-expl/in...

Arrhenius - 7-11-2009 at 17:39

I think you might fairly consider every possible oxidation of the acetone molecule. I'm no expert on metals, but I imagine Mn2O7 behaves a bit like MnO4(-) or HCrO4(-). Consider the enol tautomer of acetone, and you can write an array of mechanisms to "reduce the manganese" and cleave and oxidize acetone to formic acid and acetic acid. I've proposed some manganese species that perhaps an inorganic chemist wouldn't like, but I imagine they could react further. I couldn't get MnO2 out of a mechanism :P oh well. My answer to your question would be that there are a LOT of competing reactions going on, both in manganese species present and with regards to acetone. But here are some ideas:

Mn2O7.gif - 13kB

[Edited on 8-11-2009 by Arrhenius]

coccoc - 7-11-2009 at 19:53

Quote: Originally posted by woelen  
I have done this experiment with ethanol, sulphuric acid and KMnO4. It probably also works with acetone, isopropyl alcohol or propyl alcohol.

http://woelen.homescience.net/science/chem/exps/mini-expl/in...



I have also done this experiment and make a video, I just wonder if what I think about the reactions is correct, thanks for the data.

coccoc - 7-11-2009 at 19:57

Quote: Originally posted by Arrhenius  
I think you might fairly consider every possible oxidation of the acetone molecule. I'm no expert on metals, but I imagine Mn2O7 behaves a bit like MnO4(-) or HCrO4(-). Consider the enol tautomer of acetone, and you can write an array of mechanisms to "reduce the manganese" and cleave and oxidize acetone to formic acid and acetic acid. I've proposed some manganese species that perhaps an inorganic chemist wouldn't like, but I imagine they could react further. I couldn't get MnO2 out of a mechanism :P oh well. My answer to your question would be that there are a LOT of competing reactions going on, both in manganese species present and with regards to acetone. But here are some ideas:



[Edited on 8-11-2009 by Arrhenius]


The mechanism is quite good, and I think there is some MnO2 although I don't exactly know the mechanism.:P

Fleaker - 9-11-2009 at 07:13

I wonder if it is presumptuous to think it only oxidizes the organics to their respective carboxylic acids?

Arrhenius - 9-11-2009 at 07:55

CO2 is the only higher oxidation state of carbon here, so sure, it's possible. Is that what you mean? However, it doesn't look like there's very much gas evolving.