weiming1998
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Oxidation of alcohols via KMnO4+NaHSO4, strange liquid formed?
Just before I tried oxidizing my methylated spirits (95% ethanol)
with KMnO4. Nothing happened even with stirring, the KMnO4 just precipated, so I repeated my experiment with NaHSO4 and a little water added, to form
a deep purple coloured solution. I then poured this onto a bit of ethanol, confirmed it won't burst into flames, and poured the rest into a glass
bottle holding small amounts of ethanol. I shook the flask slightly and brown MnO2 immediately precipated, which I then decanted off very easily (the
MnO2 won't mix with the liquid at all!) The liquid, which is now in another glass bottle, has a sickening smell sort of like the chloroform I made
before with Ca(ClO)2 and acetone. I cannot detect even a whiff of the smell of acetic acid. It will not burn (even though the water in this solution
will be less than 50%). The strangest of all, it reacts with a zinc coated iron wire to form bubbles, but not with CuO to form a blue solution, even
after hours of exposure! My first guess would have been acetaldehyde, but that is supposed to have a flammability rating of 4, which will probably
ignite in an aqueous solution of less than 50% water! If there was even a bit of acetic acid, it would have the smell, plus it would react with the
CuO. But I do not think aldehydes react with metals at all.
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Mumbles
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I'd bet there is excess bisulfate in that liquid. It will react with zinc selectively. You could probably confirm this by placing another galvanized
nail in it side by side with a copper wire. The patent below is for separating zinc from copper in brass scrap.
http://www.freepatentsonline.com/4482377.html
I wouldn't use the flamability test as definitive proof that you don't have acetaldehyde. It sounds to me like you do in fact have it from the smell.
You could try distilling it. Additionally reacting it with Tollen's reagent or Fehling's reagent (both fairly OTC to prepare) would confirm the
presence of aldehyde groups. If the HSO4- was somehow reduced, it may also be able to form some sulfonate adducts.
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weiming1998
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Quote: Originally posted by Mumbles  | I'd bet there is excess bisulfate in that liquid. It will react with zinc selectively. You could probably confirm this by placing another galvanized
nail in it side by side with a copper wire. The patent below is for separating zinc from copper in brass scrap.
http://www.freepatentsonline.com/4482377.html
I wouldn't use the flamability test as definitive proof that you don't have acetaldehyde. It sounds to me like you do in fact have it from the smell.
You could try distilling it. Additionally reacting it with Tollen's reagent or Fehling's reagent (both fairly OTC to prepare) would confirm the
presence of aldehyde groups. If the HSO4- was somehow reduced, it may also be able to form some sulfonate adducts. |
If that was the case, what about CuO? I thought a fairly strong acid like NaHSO4 would react quickly with CuO, unlike Cu. as CuO is an oxide, which is
the anhydride of a base, it should react with the bisulfate quickly, forming CuSO4, H2O and Na2SO4. Anyway, when I could buy some tartaric acid, I
will try your latter way of finding out.
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