electrochem reduction of 1-nitroalkenes to amine Success! :)

loki · guinea pig

it would be good to get a series of TLC plates done taken from the tank at some period through the reaction to establish exactly how many coulombs are required to do the reaction. then once the approximate point is established run it at normal amps up until the point of the plate just before it's done and then wind the amps back to like 1/4 of the normal and do a set of plates, try and establish the numbers within a very narrow margin. i'm not sure what method of visualising the plates would be most appropriate.

i'm quite fond of electrolytic chem cos of the fact that it doesn't use many chemicals, but the thing of getting the wattage right makes it tricky.

Vitus · Psychoscientist

Vitus · Psychoscientist

This was emailed to me recently. I hope the sender doesn't mind me posting it here.

bio · Working Bee

..........Why is it that with the 3 different PC power supplies I've tried the 12V line gives up to 5-6A while the 5V line gives about 2A under the same conditions?
The 3.3V line on the newer models can deliver up to 30A and more, yet only 1A at most is delivered under these conditions. What am I missing here? My knowledge of electricity is still a bit lacking Embarassed .....................

V=IR means Volts = Current X Resistance therefore

12V/6A=2 Ohms ........This is the cell resistance

5V/2 Ohms = 2.5A.........And so on and so forth

An easy way to adjust the current, lacking proper equipment, is to adjust the electrodes spacing. Farther apart more resistance and heating losses so overheating can also be controlled to some extent this way as well.

Since current efficiency is never 100%, especially in crude setups, more than the calculated Faradays must be passed, as much as 150% in many cases.

An LM317 voltage regulator can be made into a constant current regulator by mearly adding a variable resistance on the output and connecting the sense line downstream. These regulators have only 3 leads and a current regulator can be made with only one (1) external part (the potentiometer 25 OHM 5 watt) A 5A LM317 can be had for about $5-9.

Vitus · Psychoscientist

In the previous post I have been confusing overall cell voltage with electrode potential measured to the reference electrode. Thanks for pointing out that the delivered current depends on the cell resistance.

In the experiment the electrodes were placed as close to each other as possible, but overheating is still a main issue when the flowerpot is used.

Maybe simple refrigeration technology a la https://www.wetdreams.ws/forum/topic.asp?TOPIC_ID=2059 could be used for cooling especially in case of larger scale reductions?
Or just performing it in a freezer? Smile

In the Slotta and Szyszka J.Prakt.Chem article (https://www.synthetikal.com/Rhodiums_pdfs/chemistry/electromesc.txt) 3.5 h at 6 A are theoretically needed to achieve complete reduction. The authors let it run for 12 h, which accounts for a current efficiency of 342%.

bio · Working Bee

Try using a membrane made from an auto battery bag. They are polypropylene (the gray ones) allow closer spacing and work quite well. The maintenance free higher quality ones have the best bags.

.......The authors let it run for 12 h, which accounts for a current efficiency of 342%...

That would be more like 29% but you get the idea. Losses with clay pots are HUGE so this would not be surprising.

hose PP wet wipes for glass would probably work as a membrane if doubled up and ironed. I use the bags cut up and glued to a frame for easy cleaning. Hey you could buy some Nafion! Just don't forget to send me a piece.

Vitus · Psychoscientist

Argh I'm getting mathematically dyslexic Smile

mmm how do the car battery PP bags differ from regular PP bags or sheet? I'll try to locate a car battery soon and give it a try.

Have also been thinking about glass fibers or fritted glass.

I can't immediately imagine what "hose PP wet wipes for glass" are.

bio · Working Bee

The plastic needs to be semipermeable not just a fine filter! The battery ones are maybe 20mils thick and if filled with water, for example, it just slowly seeps out if held in the air. Plastic bags don't leak.

A super fine frit is still too coarse yet could work for some things. Good luck cleaning it though. Membranes tend to get gunked up and the bags are easy to clean with a toothbrush. Clay pots went out with the dinosaurs but ceramic semipermeable plates are available, maybe try JMatthey (Alpha/Aesar)

Those polypropylene glass wipes have about half the area fused and by using several together and ironing the porosity can be adjusted. Higher heat shrinks and partially fuses the fabric. I make them for clean in place filters on an electrolytic lead acetate production tank.

Vitus · Psychoscientist

So the divider had to be semipermeable to let through ions but not molecules, except water.

Then Fester's condoms must be as thrustworthy as his books I guess Smile

The_Dude · Sat Jul 16, 2005 6:03 am

Hope this helps.

Properties for Polypropylene Film

Permeability to Carbon Dioxide @25C x10-13 cm3. cm cm-2 s-1 Pa-1 6 @ 30C
Permeability to Hydrogen @25C x10-13 cm3. cm cm-2 s-1 Pa-1 30
Permeability to Nitrogen @25C x10-13 cm3. cm cm-2 s-1 Pa-1 0.3
Permeability to Oxygen @25C x10-13 cm3. cm cm-2 s-1 Pa-1 1.7 @ 30C
Permeability to Water @25C x10-13 cm3. cm cm-2 s-1 Pa-1 16
Permeability to Water @38C x10-13 cm3. cm cm-2 s-1 Pa-1 70

http://www.msu.edu/~aurasraf/permeability.htm

http://www.devicelink.com/mpb/archive/98/09/005.html

http://www.freepatentsonline.com/4237526.html

Medical supply houses might be a good place to look at.

http://www.chemplex.com/Section-1/Microporous-Polypropylene-Film.html

BTW, great work.