TheChemiKid
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Removing Permanganate from reaction mixure
I recently attempted this reaction. In the video, it recommended refluxing for about 2 hours. After refluxing for over 8 hours, some permanganate has still not reacted
with the toluene. I do not know of a good way to remove this.
I also still have lots of toluene left over, but that is easy to remove.
PS: I UTFSE, but couldn't find a good thread to post this in.
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Galinstan
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This could be because you have used up all the acid in your reaction so therefore no more permanganate will react so you could try adding more acid
and reflux. or to remove the permanganate wash it with a weak reducing agent such as a solution of sodium thiosulphate to reduce it to Mn2+
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Hexavalent
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Add ethyl acetate, followed by water. The benzoic acid and toluene will enter the organic phase, whereas the permanganate will enter the aqueous
phase. The MnO2 will remain undissolved. Then, filter off the manganese dioxide, and put the filtrate into a separatory funnel, retaining
the organic layer.
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TheChemiKid
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Can I replace ethyl acetate with anything?
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Hexavalent
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Anything fairly polar that is immiscible with water.
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TheChemiKid
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Ok, thanks. Could I add lots of salt to the water, then use isopropanol?
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Hexavalent
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Quite possibly, although you'll have to be careful not to saturate the water so that it cannot dissolve any of the permanganate.
Go to virtually any supermarket and buy a bottle of non-acetone nail polish remover that lists ethyl acetate as the primary component: it is a very
useful solvent with a wide variety of uses.
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TheChemiKid
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The problem with that is that I cannot find any of this easily in my area, and I do not wish keep the mixture around for a while.
I have two last propositions. One is chloroform, this should probably work. The other is xylene. This is unlikely to work in my opinion, but it does
have a slightly higher polarity index than toluene.
EDIT: Can I add some hydrogen peroxide to reduce to manganese (IV)?
[Edited on 23-11-2013 by TheChemiKid]
[Edited on 23-11-2013 by TheChemiKid]
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Hexavalent
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Chloroform should work, although if you have it, I'd advise you to save it for a more worthy purpose. Xylene(s) may work, although you'd have to be
careful about oxidation to the respective corresponding carboxylic acids. I don't know how fast this would proceed at room temperature, but avoiding
solvents which react with your substrates is generally preferred.
Yes, the hydrogen peroxide idea should work, but if you have difficulty acquiring reagents, you may wish to consider trying to preserve the
KMnO4. If this is not a priority, though, then try this method and report back.
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Galinstan
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If you perform a liquid liquid extraction make sure to acidify everything first to make sure none of your benzoic acid is the potassium salt which of
course would remain in the aquas phase 
and yes the peroxide would reduce the permangnate and i don't think it would effect your product but i could be wrong.
[Edited on 24-11-13 by Galinstan]
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UnintentionalChaos
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Were you stirring the reaction mix? If not, then that is why it isn't reacting. you have a water-insoluble reactant (toluene) and a water-soluble
reactant with no solubility in the organic material. The reaction rate is wholly dependent on the surface area between the two phases, the only place
where the reaction can be happening. Boiling by itself does not usually provide much mixing of immiscible phases. Vigorous magnetic stirring can
however, stir the two into an emulsion with hundreds, if not thousands of times the surface area of the unstirred phases. I am aware that the original
video doesn't do this, but I have run an analogous reaction with o-xylene.
Also keep in mind that potassium permanganate has a very high molar absorptivity (basically, really dark color). A saturated solution is damned near
impossible to see through and it isn't even particularly concentrated. Light purple color can be achieved with the tiniest bit of solid in a lot of
water. If the filtered water solution is very light purple, just add the acid. The color will vanish and a tiny bit of chlorine gas will form (do it
outside). If it is a medium or dark shade of purple, don't do this unless you want to gas yourself.
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TheChemiKid
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Yes, I was stirring the reaction mixture.
The hydrogen peroxide method is very messy. I have to still separate my final product.
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TheChemiKid
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After 5 Hydrogen Peroxide additions, and 5 filters, I finally have a clear product. I have added H2SO4, and a small amount of
benzoic acid has formed (I tested pH), but I still have to boil it down.
Here is a picture during the final filtration.
[Edited on 24-11-2013 by TheChemiKid]
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