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Author: Subject: Cell for smallscale electroreduction of nitroalkenes
Melgar
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[*] posted on 10-9-2017 at 11:14


Quote: Originally posted by HollowMan  
Anyone knows a good solvent for the TLC?
The nitropropene is good visible with PE:EA (petrolether:ethylacetate) 3:1 but the Amine wasn´t running...


Silica or alumina for stationary phase? Either way, I don't actually know. Alumina is supposed to be the easy one for TLC with amines, since it's slightly basic, but they still only barely move off the starting spot, and it could be any of the basic nitro reduction products for all I know.




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Melgar
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[*] posted on 28-10-2017 at 04:46


I guess it's okay to double post if I can't edit my last post because it's been too long.

So I hit upon the idea to just use polyester fabric, presumably sewn together, to form the membrane in a divided cell. In another thread, people were remarking on how difficult it was to hydrolyze PETE plastic, whether by acid or base. Although hot sulfuric acid and nitric acid will certainly damage it, not much else will, and PETE is the same polymer as polyester. While it's not as inert as the polyethylene used in car batteries, it's certainly good enough for any purposes that we might want to use it for.




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PHILOU Zrealone
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[*] posted on 30-10-2017 at 03:47


Quote: Originally posted by Melgar  
I guess it's okay to double post if I can't edit my last post because it's been too long.

So I hit upon the idea to just use polyester fabric, presumably sewn together, to form the membrane in a divided cell. In another thread, people were remarking on how difficult it was to hydrolyze PETE plastic, whether by acid or base. Although hot sulfuric acid and nitric acid will certainly damage it, not much else will, and PETE is the same polymer as polyester. While it's not as inert as the polyethylene used in car batteries, it's certainly good enough for any purposes that we might want to use it for.

Ammonia or strong amino bases (like diamino ethane or aminoethanol) will also damage it quite fast...especially if hot...

Synthesis of terephtalic acid from PETE and NaOH/Ethylene glycol is explained into an article of the publication section

Maybe you may focus onto the old receipe to make half permeable container for osmotic pressure...
==> Use a porous unglazed clay pot...
1) Make it wet/rinse it with demineralized water... disgard the rinsing water

2) Inside put a saturated solution of CuSO4

3) Outside put a saturated solution of NaSCN (or NH4SCN or KSCN)

==> Both solution will migrate by capilarity, diffusion and osmotic pressure into the pores...at the contact they will precipitate ultrafine Cu(SCN)2 making the pore size lower and lower until only water molecules passes through.

4) Take the saturated CuSO4 and put it into an aside recipient, do the same with the thiocyanate solution into a different aside recipient

5) Wash well the inside and outside with demineralized water...disgard the washing waters.

6) Reverse the saturated solutions... so take the set aside recipient of thocyanate and put it inside the clay pot... and put the CuSO4 outside this time...

7) Wait, pour the solutions (or take them aside for another use/clay pot/membrane), wash well the clay pot inside and outside eventually immerse for a few days into agitated demi water... disgard washing/rinsing water

8) You now have a true semi permeable membrane clay pot...only permeable to very tiny molecules like H2O, H(+), OH(-)...eventually Li(+)

Edit:
Maybe the process will work with other precipitating salts...to allow for fine tuning the properties of the membrane to better resist certain solvants, pH (acids or bases), complexing agents...

[Edited on 30-10-2017 by PHILOU Zrealone]




PH Z (PHILOU Zrealone)

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Melgar
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[*] posted on 30-10-2017 at 04:17


I thought the reduction would be under acidic conditions, no?

The only reason clay pots are so popular in the literature, is because that literature was usually written during the 1800s, before plastics were invented. There's no reason to keep revisiting that. And why would you use CuSO4? Copper would plate onto the cathode if you did, and that's something you'd want to avoid. Typical salts are things like K2SO4, that contain ions that won't damage either electrode.

If you really want to be professional about it, then use more recently-developed technology, like ion-exchange membranes. Nafion 117 is a popular choice for general-purpose use:

http://www.fuelcellsetc.com/store/N117

It's used for fuel cells and water electrolyzers, and is basically Teflon with triflic acid ion-binding sites. A 10 cm x 10 cm sheet of it is $35, which is perhaps 10 times the price of a clay pot, but it works a million times better as a divider for an electrolytic cell.




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