victornguyen
Harmless
Posts: 1
Registered: 10-3-2019
Member Is Offline
|
|
Yellow ether?
Recently synthesized some ether using ethanol and sulfuric per the article in pre pub. I then dried it over some NaOH for a few days. When I came back
to it , it had this yellow cloudiness that I didn't recognize. There was not much water in the ether since none separated out with the hydroxide, but
I'm thinking the yellow coloring was produced by the formation of sodium ethoxide from residual ethanol reacting with the lye. Do you think that could
be the case, or did something else cause the yellow coloring? I also had a small piece of copper wire in the bottle for prevention peroxide formation,
which I didn't not remove before adding the NaOH. I redistilled and it is perfectly clear now.
|
|
unionised
International Hazard
Posts: 5119
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
At a guess, traces of acetaldehyde (from oxidation of the ethanol) which polymerises in alkaline conditions to form a yellow/ brown resin.
|
|
fusso
International Hazard
Posts: 1922
Registered: 23-6-2017
Location: 4 ∥ universes ahead of you
Member Is Offline
|
|
Can H2SO4 oxidize EtOH in such conditions?
|
|
Felab
Hazard to Self
Posts: 76
Registered: 9-11-2018
Member Is Offline
Mood: :dooM
|
|
This happened to me as well. It might be sodium ethyl sulphate, acetaldehyde or maybe something else. And yes acetaldehyde is formed as a side product
in this synth by the oxidation of ethanol with sulphuric acid.
I doubt it is sodium ethoxide because the amount that would be generated should be prety minimum and it should also be colourless.
BTW sodium hydroxide destroys peroxides by itself so you don't need to ad the copper as long as you have it over the NaOH
|
|
unionised
International Hazard
Posts: 5119
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
Acetaldehyde can be formed from peroxides I think.
Air will certainly oxidise ethanol, so, unless you carefully distilled that before you did the ether synth, there will be acetaldehyde.
Of course, there could be other stuff too.
The last ethanol I bought had MEK as a denaturant and that would do a fine job of going yellow in strongly alkaline conditions
|
|
nimgoldman
Hazard to Others
Posts: 303
Registered: 11-6-2018
Member Is Offline
|
|
Yes this happened to me. I store ether over KOH and whiff a bit of argon in the bottle to make an inert pillow. It still yellowed but the peroxide
test came out negative. It was likely the ethanol (common impurity in ether) reacted with the hydroxide. Distilling the stuff removed discoloration.
|
|
CobaltChloride
Hazard to Others
Posts: 239
Registered: 3-3-2018
Location: Romania
Member Is Offline
|
|
This happened as well with ether distilled from starter fluid in my case. In order to ensure purity, I just followed the procedure in this video https://www.youtube.com/watch?v=EEXqjJd0Bak .
|
|