Sciencemadness Discussion Board

Stabilization of diethyl ether by the adition of ethanol

Felab - 22-2-2019 at 12:49

Some time ago, I made diethyl ether by the acid ether synthesis. It worked all right and I stored the final product in a corcked glass bottle in a fridge over potassium hydroxide.

As the days passed, the potassium hydroxide started precipitating a very flufy white powder out of the ether. At first I thought that those where impurities in my ether that I wasn't able to remove, so I tested for dissolved peroxides, which yielded a negative result and then I distilled it and stored it over potassium hydroxide again with the same bottle.

After a couple of days I started seeing the white fluffy precipitate contaminating my ether again, so that leads me to beieve that the precipitate is actualy ether peroxide being precipitated by the potassium hydroxide.

This would be good if the precipitate didn't stay in suspension. Since I don't want my ether to be contaminated with junk I am looking for ways to stabilize it. I don't have any BHT so I cannot use it. On further research I found that ether is often sold with 1% ethanol by volume for non-analytical pruposes, but I couldn't find how this is supposed to inhibit the formation of peroxides.

I also found that copper metal reduces the peroxides to form CuI/CuII.

Would storing my ether over copper wire and adding to it 1% ethanol solve the problem?
Does anyone know the mechanism in which ethanol is supposed to inhibit the formation of peroxides?

I already know there are many other threads on the stabilization of ether but no one talks about doing it with ethanol.

Any answers are apreciated as I dont want my "lab" to explode.



[Edited on 22-2-2019 by Felab]

arkoma - 22-2-2019 at 18:23

I also am interested to the answer to this question. I distilled enough to COMPLETELY fill my storage bottle to keep out air

Ether stabilisation experiment

Felab - 25-2-2019 at 13:26

Since no one seems to give an answer, I will conduct an experiment by myself:
-I have taken 10 mls of untreated ether which yielded negative for peroxide formation (as a control) and I bottled it in a 100 ml ground glass flask (to have planty of air).

I did the same in another flask but ading 200ul of absolute ethanol to the ether.

I will left them for one week in my fridge and then test for peroxides.

Hopefully my house will not explode in the process.

fusso - 25-2-2019 at 14:09

I think put it under room temp can speed things up.

SWIM - 25-2-2019 at 14:13

If peroxides form that fast, I've certainly been taking chances without knowing it.
I always make it fresh in small batches, but I sometimes keep it around for a week or even two.

I thought they formed more slowly than that.


Is there any chance that precipitate is just Koh coming out of solution from the equilibrium conditions?

Felab - 25-2-2019 at 14:22

Quote: Originally posted by SWIM  
If peroxides form that fast, I've certainly been taking chances without knowing it.
I always make it fresh in small batches, but I sometimes keep it around for a week or even two.

I thought they formed more slowly than that.


Is there any chance that precipitate is just Koh coming out of solution from the equilibrium conditions?


The thing is that the precipitate looks very yellow and nasty, so I don't think it is.

I also thinked that they formed more slowly and that is why I distilled the ether without looking how to stabilise it.

Felab - 25-2-2019 at 14:25

Quote: Originally posted by fusso  
I think put it under room temp can speed things up.


It can also cause my ether to evaporate and create pressure in the container.

Also, the point of the expeiment is testing the formation of peroxides in the conditions I will store it in.

Alucard - 26-2-2019 at 02:50

Quote: Originally posted by Felab  
Since no one seems to give an answer, I will conduct an experiment by myself:
-I have taken 10 mls of untreated ether which yielded negative for peroxide formation (as a control) and I bottled it in a 100 ml ground glass flask (to have planty of air).

I did the same in another flask but ading 200ul of absolute ethanol to the ether.

I will left them for one week in my fridge and then test for peroxides.

Hopefully my house will not explode in the process.


Diethyl ether is not a chloroform to be stabilized with 1% of ethanol addition, and I have never seen any suggestion like that before, so I doubt ethanol will work with diethyl ether, I think it only works with chloroform.

Despite I can't give any reference about my source, but I was read about that it's possible to store diethyl ether over a copper metal. From other hand, if you have ever seen a video on Youtube made by NileRed and this video was about how to prepare diethyl ether, and he suggests to store a ether over KOH or maybe NaOH, but I'm not sure that adding base to ether will really prevent it from peroxide formation.

Felab - 26-2-2019 at 06:06

Quote: Originally posted by Alucard  
Quote: Originally posted by Felab  
Since no one seems to give an answer, I will conduct an experiment by myself:
-I have taken 10 mls of untreated ether which yielded negative for peroxide formation (as a control) and I bottled it in a 100 ml ground glass flask (to have planty of air).

I did the same in another flask but ading 200ul of absolute ethanol to the ether.

I will left them for one week in my fridge and then test for peroxides.

Hopefully my house will not explode in the process.


Diethyl ether is not a chloroform to be stabilized with 1% of ethanol addition, and I have never seen any suggestion like that before, so I doubt ethanol will work with diethyl ether, I think it only works with chloroform.

Despite I can't give any reference about my source, but I was read about that it's possible to store diethyl ether over a copper metal. From other hand, if you have ever seen a video on Youtube made by NileRed and this video was about how to prepare diethyl ether, and he suggests to store a ether over KOH or maybe NaOH, but I'm not sure that adding base to ether will really prevent it from peroxide formation.


There is my source: https://www.sigmaaldrich.com/chemistry/solvents/learning-cen...

I did store over koh but the precipitating ether peroxide derivative makes my ether all cloudy and gross.

Tsjerk - 26-2-2019 at 07:55

Quote:
As the days passed, the potassium hydroxide started precipitating a very flufy white powder out of the ether.

That is an assumption ;)

I'm pretty sceptical towards your claim this precipitate being peroxide. Especially when your ether turns out negative when testing for it. I guess it is KOH.

Also I never heard about ether forming peroxides in days in a fridge, also not in days at any other temperature. It forms in many months, when not stabilized when plenty of oxygen is present.

KOH is slightly soluble in ether. I can imaging KOH precipitating out as a fluffy white haze, as suggested above.

Was your KOH anhydrous? Usually it is 15% water, 85% KOH, while being stated to be 99+% pure. The KOH part is 99+% in that case, not the whole thing. KOH is only anhydrous if specifically stated, or when you dried it yourself. If it wasn't one of either your KOH is quite useless as drying agent (that is what you used it for right?).

What do you need it for? How dry do you need it to be? I guess you are not going to do a Grignard when you are talking about adding ethanol. Add some anhydrous sulfate salt to dry it, distill it from this salt and the KOH, add 1 % ethanol and store it like that, just make sure it is stoppered tight. No need for refrigeration. -- This way; No dissolved KOH, no peroxide, dry ether. -- Or at least I would do it that way.

I like your experimentation though, well thought of and thorough! But if it turns out negative for peroxides I would just go for the drying, distillation and storing with ethanol.

[Edited on 26-2-2019 by Tsjerk]

Felab - 26-2-2019 at 11:01

Quote:

I'm pretty sceptical towards your claim this precipitate being peroxide. Especially when your ether turns out negative when testing for it. I guess it is KOH.


Of course I might be wrong, but the precipitate is a yellowish brown when it settles to the bottom so either my potassium hydroxide is extremely dirty, my ether is dirty al well and I haven't purified it enough or it is the peroxide being precipitated out of solution.

I want to use it in wet plate photography, to make the collodion. For that application ethanol isn't a problem since I will need to ad more later. But I do need it to be extremely pure as any impurities might ruin the photographs

My koh isn't anhydrous and I dont care for water contamination all that much. Although prior to distilling it I did dry the ether in CaO to make it clear. I want it since it was supposed to inhibit the formation of peroxides, but it doesn't inhibit their formation, it destroys them contaminating my ether in the process.

Also, I can't store it non-refrigerated since temperatures in my "lab" can reach 40º celsius or more during summer. Spain is unfortunatley hot.

[Edited on 26-2-2019 by Felab]

Alucard - 26-2-2019 at 12:08

Quote: Originally posted by Felab  
Quote:

I'm pretty sceptical towards your claim this precipitate being peroxide. Especially when your ether turns out negative when testing for it. I guess it is KOH.


Of course I might be wrong, but the precipitate is a yellowish brown when it settles to the bottom so either my potassium hydroxide is extremely dirty, my ether is dirty al well and I haven't purified it enough or it is the peroxide being precipitated out of solution.

I want to use it in wet plate photography, to make the collodion. For that application ethanol isn't a problem since I will need to ad more later. But I do need it to be extremely pure as any impurities might ruin the photographs

My koh isn't anhydrous and I dont care for water contamination all that much. Although prior to distilling it I did dry the ether in CaO to make it clear. I want it since it was supposed to inhibit the formation of peroxides, but it doesn't inhibit their formation, it destroys them contaminating my ether in the process.

Also, I can't store it non-refrigerated since temperatures in my "lab" can reach 40º celsius or more during summer. Spain is unfortunatley hot.

[Edited on 26-2-2019 by Felab]


Although ethanol may turn yellowish when treated with strong enough base like KOH, NaOH and even Ca(OH)2, diethyl ether must not turn yellow after being treated with KOH within at least 24 hours, while this test is performed in a bottle with ether that must be stored in a dark place only, and only bottle equipped with a glass stopper cork is valid to perform such test. Failing to perform this test means that at least aldehyde or H2O2 are present along with ether.

To detect peroxides it is possible to perform a test with potassium iodide solution in water, so one could yield such a reaction :

C2H5OOC2H5 + 2KI + H2O = I2 + C2H5OC2H5 + 2KOH

If any peroxides are present with ether, free iodine will be evolved after performing a test described above, turning an ether to yellow color as well, but adding starch will turn ether into blue color.

Felab - 26-2-2019 at 12:57

Since a picture is worth a thousand words I will post an image on how I store my ether:




IMG_20190226_212749_583.jpg - 301kB IMG_20190226_212810_534.jpg - 309kB



The bottle has frost covering it since it came right out of the fridge, but you can still appreciate the yellow colour of the KOH and the haziness of the precipitate.

BTW I dont have the ether in an amber bottle since I store it in the fridge and no light can reach it.

Tsjerk - 26-2-2019 at 13:18

Quote: Originally posted by Alucard  

Although ethanol may turn yellowish when treated with strong enough base like KOH, NaOH and even Ca(OH)2, diethyl ether must not turn yellow after being treated with KOH within at least 24 hours


Guess what this ether was made with?

Quote: Originally posted by Alucard  

Failing to perform this test means that at least aldehyde or H2O2 are present along with ether..


No, it doesn't. It could also show the presence of ethanol, hydroxide and oxygen.

[Edited on 26-2-2019 by Tsjerk]

Felab - 26-2-2019 at 13:58

Quote: Originally posted by Alucard  
Quote: Originally posted by Felab  
Quote:

I'm pretty sceptical towards your claim this precipitate being peroxide. Especially when your ether turns out negative when testing for it. I guess it is KOH.


Of course I might be wrong, but the precipitate is a yellowish brown when it settles to the bottom so either my potassium hydroxide is extremely dirty, my ether is dirty al well and I haven't purified it enough or it is the peroxide being precipitated out of solution.

I want to use it in wet plate photography, to make the collodion. For that application ethanol isn't a problem since I will need to ad more later. But I do need it to be extremely pure as any impurities might ruin the photographs

My koh isn't anhydrous and I dont care for water contamination all that much. Although prior to distilling it I did dry the ether in CaO to make it clear. I want it since it was supposed to inhibit the formation of peroxides, but it doesn't inhibit their formation, it destroys them contaminating my ether in the process.

Also, I can't store it non-refrigerated since temperatures in my "lab" can reach 40º celsius or more during summer. Spain is unfortunatley hot.

[Edited on 26-2-2019 by Felab]


Although ethanol may turn yellowish when treated with strong enough base like KOH, NaOH and even Ca(OH)2, diethyl ether must not turn yellow after being treated with KOH within at least 24 hours, while this test is performed in a bottle with ether that must be stored in a dark place only, and only bottle equipped with a glass stopper cork is valid to perform such test. Failing to perform this test means that at least aldehyde or H2O2 are present along with ether.

To detect peroxides it is possible to perform a test with potassium iodide solution in water, so one could yield such a reaction :

C2H5OOC2H5 + 2KI + H2O = I2 + C2H5OC2H5 + 2KOH

If any peroxides are present with ether, free iodine will be evolved after performing a test described above, turning an ether to yellow color as well, but adding starch will turn ether into blue color.


Acetaldehyde is a notoriously difficult to remove contamination in ether made by the acid ether synth so maybe that is causing the yellow precipitate.

Tsjerk - 26-2-2019 at 14:09

Would acetaldehyde be a problem for your purposed use?

Felab - 26-2-2019 at 14:23

Quote: Originally posted by Tsjerk  
Would acetaldehyde be a problem for your purposed use?


As long as it is in a reasonably low concentration it shouldn't be a problem, but the solids evolved by its decomposition in KOH are.

So no more KOH for storing my ether and repace it with copper metal.

The most harmfull impurities are inorganic salts disolved in the ether ( specialy iron salts)

Alucard - 26-2-2019 at 14:23

Quote: Originally posted by Tsjerk  

Guess what this ether was made with?



It ain't pure enough, of course.
Quote: Originally posted by Tsjerk  

No, it doesn't. It could also show the presence of ethanol, hydroxide and oxygen.

[Edited on 26-2-2019 by Tsjerk]


I agree, it discovers many impurities, not solely aldehyde.
Quote: Originally posted by Felab  


Acetaldehyde is a notoriously difficult to remove contamination in ether made by the acid ether synth so maybe that is causing the yellow precipitate.


Perhaps here is an option to try to drain off KOH and then treat ether residue with 5% w/w FeSO4 water solution to remove any present peroxides, then perform a distillation. It must be enough just about 100 ml of FeSO4 solution per 1 liter of an ether. FeSO4 solution must be slightly acidified with H2SO4 as well, but only slightly acidified.

You can also oxidize aldehyde to acetic acid with 0,5% w/w KMnO4 water solution. After doing that it's required to wash an ether with 5% w/w NaOH water solution, and then with water.

[Edited on 26-2-2019 by Alucard]

[Edited on 26-2-2019 by Alucard]

Tsjerk - 26-2-2019 at 14:34

Quote: Originally posted by Felab  


So no more KOH for storing my ether and repace it with copper metal.

The most harmfull impurities are inorganic salts disolved in the ether ( specialy iron salts)


Copper isn't needed as long as you add ethanol. I wouldn't use it when metal salts are your enemy.

Tsjerk - 27-2-2019 at 06:17

Or the fluffy stuff is potassium ethoxide...

Felab - 27-2-2019 at 10:05

Quote: Originally posted by Tsjerk  
Or the fluffy stuff is potassium ethoxide...


Maybe but I fractionated the ether at exactly 34.6 Cº so ethanol contamination is unikely. I also mixed it with CaCl2 before distilling it.

Tsjerk - 27-2-2019 at 13:28

I'm looking forward to the results of your week long experiment, I'm getting curious now.

S.C. Wack - 27-2-2019 at 13:58

BTW ethanol will stop turning color with base forever after enough refluxing with it. Perhaps the same can happen here. Ether for lab use at least through the 70's was often old stock of Squibb medical ether, with copper plated to the inside of the can. The cans did come with a cork but I don't think long term storage of opened cans was really the plan. This ether had been pretreated with copper, producing oxygen or CO2, surface oxide, and acid then removed with wet magnesium hydroxide. Perhaps you're getting acetate. It would be interesting to compare with the anhydrous NaOH.

[Edited on 27-2-2019 by S.C. Wack]

Experiment delay...

Felab - 27-2-2019 at 22:06

When I went this morning to check on the experiment the stopper had blown up as I didn't use a keck clip, and the ether had evaporated all too.

I replaced the contents of the flask and puted on some keck clips. The results may be delayed for two days.

Apologies.

[Edited on 28-2-2019 by Felab]

woelen - 28-2-2019 at 00:42

Storing ether in a bottle with a cork does not sound good to me. Corks are somewhat porous and ether certainly will escape through that.
Best is to store the ether in a glass bottle having a cap with Al-foil liner. You can buy bottles with such caps, but you can also make one yourself easily from folded household foil and a decent cap with a flat foam liner. I myself store my ether in such a bottle and even after years of storage I do not notice any relevant loss of ether.

Diethyl ether can be stabilized for peroxide formation with tiny amounts of BHT or benzophenone (a few tens of ppm or so). Benzophenone is not that hard to obtain, BHT may be somewhat harder to obtain.

I have doubts about storing ether with KOH or NaOH. Does this really prevent formation of peroxides? Why don't others store ether over these?

The brown crap you see most likely is due to impurities in your ether. I think that there are organic impurities, which with KOH (and possibly some water from the 85% KOH) condenses into larger polymeric species. Such stuff is very common in organics and usually it is yellow/brown at very low concentration, reddish/brown in small amounts and brown/black in larger concentrations. Especially aldehydes, ketones and unsaturated C=C bonds tend to form such condensed species.

S.C. Wack - 28-2-2019 at 14:32

The use of corks was perfectly wise. A cork was included so the ether wouldn't all evaporate from the can during the operation, if the can wasn't emptied into some fancy ether dispenser. These were quite small cans having no other way to seal them.

The Organikum (generally a good source of different directions) says "It is therefore recommended to store it over potassium hydroxide, which immediately converts the hydroperoxides produced into insoluble salts and, moreover, is a very suitable drying agent.", but my thinking was this would be on the surface of the KOH only, and would not occur with peroxide free ether. I guess if something is precipitating regardless (there are other threads and posters here noting precipitates with KOH) the K is getting into the ether somehow.