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Author: Subject: Sodium from sodium methoxide electrolysis in pentane
deltaH
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[*] posted on 15-10-2015 at 21:33
Sodium from sodium methoxide electrolysis in pentane


Apparently sodium methoxide is [slightly] soluble in pentane (1). Could such an electrolysis possibly yield sodium at the cathode if you used a porous separator in the cell?

If you refluxed methanol, NaOH and CaO flakes in pentane under anhydrous conditions for extended periods of time, might you generate the required electrolyte?

References:

(1) http://onlinelibrary.wiley.com/doi/10.1002/047084289X.rs089m...





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[*] posted on 16-10-2015 at 02:30


To be honest I wouldn't take electricity anywhere near such a flammable substance. One little spark and your whole setup goes kaboom.

That's just me, though. I have no idea whether or not it would actually work.
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[*] posted on 16-10-2015 at 03:12


I looks to me like a non-ionised solution so electrolysis would not work.
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[*] posted on 16-10-2015 at 06:49


Yes. And even if it did, the conductivity would be absurdly low.



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[*] posted on 16-10-2015 at 07:07


@deltaH:

I doubt if that solution is an electrolyte.




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Little_Ghost_again
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[*] posted on 16-10-2015 at 07:44


sounds like a job for the drunkard one :D.



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[*] posted on 16-10-2015 at 11:08


What about a solution of sodium alkoxide in something like ether? It should dissolve better in it, shouldn't it? Or even solution different of sodium salt with rather inert anion, soluble in relatively unreactive solvent?
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[*] posted on 16-10-2015 at 11:22


Quote:
I doubt if that solution is an electrolyte


Quote:
sounds like a job for the drunkard one

One could always add copious quantities of weak urine at this time of night.

Should bring the resistance down a bit.




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[*] posted on 16-10-2015 at 17:43


Quote: Originally posted by Upsilon  
To be honest I wouldn't take electricity anywhere near such a flammable substance. One little spark and your whole setup goes kaboom.

That's just me, though. I have no idea whether or not it would actually work.


You greatly overestimate the danger of this. Just make a cardboard shield for the electrodes that isolates the reaction vessel from the air above, and use good ventilation.




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deltaH
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[*] posted on 16-10-2015 at 21:19


Quote: Originally posted by MeshPL  
What about a solution of sodium alkoxide in something like ether? It should dissolve better in it, shouldn't it? Or even solution different of sodium salt with rather inert anion, soluble in relatively unreactive solvent?


I think I should request this article and see what "...as well as a wide variety of other solvents." means exactly and also maybe we're lucky and some figures are given.

Initially, I was interested in sodium methoxide because Wikipedia gave a very low melting point of 127 °C so I thought of a molten cell, but after some digging, I don't think this figure is correct, it's probably a decomposition temperature. Also, sodium methoxide combusts too easily for this. Then I read the opening reference that said it's soluble in pentane. That also seemed rather surprising, but hey, it does come from a reputable source.



[Edited on 17-10-2015 by deltaH]




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MeshPL
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[*] posted on 16-10-2015 at 23:51


I have an idea: Crown ethers.

They can greatly increace solubility of salts in different solvents. If they wouldn't interfer with epectrolysis, they would be a good solution. I think Dibenzo-18-crown-6 can be even synthesised by a garage chemist.

Also I think sodium oxalate or maybe formate or acetate MAY also be good salts for such electrolysis. But they wouldn't dissolve well in inert solvents.

What about sodium salts of fatty acids? Will they dissolve well in ether/hydrocarbons?

Sodium benzoate is supposedly soluble in pyridine. Is pyridine inert enough?

And what about sodium phenoxide?



[Edited on 17-10-2015 by MeshPL]
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deltaH
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[*] posted on 17-10-2015 at 00:50


Crown ethers are not practical IMHO. Also, not so sure a crown ether holding a sodium ion would reduce easily, it is after all a caged inside the crown ether quite well.

As for the salts of fatty acids, you mean soap? Soaps in organic solvents form reverse micelles, not solutions of discrete sodium palmitate (or whatever fatty acid). Reverse micelles have tails pointing outwards and the ionic bits in the centre, usually with some small amount of water in the centre as well. Not so sure that they would work as an electrolyte because the micelle is neutral as a whole, the core forms an electric double layer.

Perhaps when sodium methoxide dissolves in pentane, a similar thing happens in which case blogfast would be correct and it wouldn't be an electrolyte.

Maybe one simply cannot form an electrolyte in non-polar solvents because ionic materials, even if you get them to dissolve, would always prefer to order into some kind of charge neutral complex within it, i.e. perhaps the only way to make it energetically favourable for this not to happen is to intercede with a solvent that has a high dielectric constant and so by definition cannot be a non-polar one.

The most polar solvents I know of that might not react with sodium are the carbonates, e.g. ethylene carbonate and propylene carbonate. There was talk of this a while ago to use for electrolyzing alkali salts, but I think it was never carried out.

These carbonates proved difficult to order IIRC and somewhat of a pain to synthesis from urea and glycols.

Anyway, I think we should simply chalk up my original idea as a crap one :mad:

[Edited on 17-10-2015 by deltaH]




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Little_Ghost_again
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[*] posted on 17-10-2015 at 01:54


Quote: Originally posted by deltaH  
Crown ethers are not practical IMHO. Also, not so sure a crown ether holding a sodium ion would reduce easily, it is after all a caged inside the crown ether quite well.

As for the salts of fatty acids, you mean soap? Soaps in organic solvents form reverse micelles, not solutions of discrete sodium palmitate (or whatever fatty acid). Reverse micelles have tails pointing outwards and the ionic bits in the centre, usually with some small amount of water in the centre as well. Not so sure that they would work as an electrolyte because the micelle is neutral as a whole, the core forms an electric double layer.

Perhaps when sodium methoxide dissolves in pentane, a similar thing happens in which case blogfast would be correct and it wouldn't be an electrolyte.

Maybe one simply cannot form an electrolyte in non-polar solvents because ionic materials, even if you get them to dissolve, would always prefer to order into some kind of charge neutral complex within it, i.e. perhaps the only way to make it energetically favourable for this not to happen is to intercede with a solvent that has a high dielectric constant and so by definition cannot be a non-polar one.

The most polar solvents I know of that might not react with sodium are the carbonates, e.g. ethylene carbonate and propylene carbonate. There was talk of this a while ago to use for electrolyzing alkali salts, but I think it was never carried out.

These carbonates proved difficult to order IIRC and somewhat of a pain to synthesis from urea and glycols.

Anyway, I think we should simply chalk up my original idea as a crap one :mad:

[Edited on 17-10-2015 by deltaH]


Why? loads of stuff on this board has been done when at first it seemed it couldnt happen. Look at the patent with potassium, nobody thought it was anything but a hoax.

I am sure someone can get access to the paper and then take a look from there, ideas are never crap often its the execution thats crap.
If you had a gut feeling on it then its worth following up




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deltaH
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[*] posted on 17-10-2015 at 01:59


I have put in a request yesterday in references, let's see if they elaborate more in the text. H ok it's here already in the usual place, nice paper, lots of info on it as a reagent...

No further mention of pentane solubility in the text body :mad:

I specifically want to know about pentane, will dig through the literature when I have some time, this must have come from somewhere...

*********

Ok found this paper that mentions using sodium methoxide in pentane to carry out the reaction:

http://pubs.acs.org/doi/abs/10.1021/ja00967a014?journalCode=...

Not so sure it dissolved per say.

[Edited on 17-10-2015 by deltaH]




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[*] posted on 17-10-2015 at 13:21


Anytime you have an Alkali Metal, in a highly flammable solvent, and electricity, you are juggling rattlesnakes.

Pentane itself is plenty touchy to work with. Should we underestimate it, because we use such things to fuel our automobiles? No.

Sodium isn't especially difficult to make by other methods. Why not go that way?

Sodium itself isn't especially dangerous. The solvent worries me.

Unless, of course, this is a theoretical discussion. In which case, my bad. I tend to trend with procedures that I might actually attempt sometime. I'll read that article, maybe it will sway me.
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