I am a fish
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Decomposition of Sodium Ethoxide
Several months ago, I prepared an ethanolic solution of sodium ethoxide, by dissolving sodium in an excess of ethanol. (The ethanol contained 4%
water, and so some sodium hydroxide would also have been produced.) Whilst the solution was initially colourless, it gradually, over a period of
weeks, gained a yellow tint, which intensified into a strong orange-red colour. When I inspected it yesterday, it had formed a brown-black oily
precipitate, leaving a yellow supernatant. The solution was sealed in a boiling tube throughout, and there was no noticable evaporation of solvent.
Neither the precipitate, nor the supernatant reacted in any noticable way when added to water.
Can anyone explain what happened, and what was produced?
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IPN
Hazard to Others
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How pure was the ethanol? Some denaturising (?) agents might cause that.
Camping fuel around here contains approx. 90% ethanol. The rest is isopropanol, methyl ethyl ketone, methyl isobutyl ketone and probably water.
Those colours sound quite similar to what you get when you treat acetone with NaOH.
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I am a fish
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The ethanol was (to the best of my knowledge) laboratory grade ethanol/water azeotrope (i.e. 96% ethanol, 4% water).
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garage chemist
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Even laboratory grade ethanol is denatured, otherwise it is very expensive because of taxes.
MEK is your problem here.
Dissolve about 5-10% solid NaOH in your ethanol, reflux it for 12 hours (the longer the better) and distill (not too much, , 40% should be left as a
residue). Most of the MEK is now gone.
[Edited on 12-6-2005 by garage chemist]
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unionised
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Not all lab alcohol is denatured but, since It's a bit tricky to think of any reaction here that might generate a chromophore I think this stuff
might have been. The other posibillity is that it has attacked the lid of the tube. What's the stopper made from?
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I am a fish
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The tube was sealed with a bung made from standard laboratory orange rubber. Although this may have reacted with vapour, I am pretty sure that the
liquid never came into contact with it.
I am fairly sure that the alcohol wasn't denatured, but I will check my sources.
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