construction of electroreduction cells?

Synthon · Wed Sep 21, 2005 9:36 pm

SWIM found the following ref on rhods site a while ago:

1 mol of phenyl-2-nitropropene, C6H5CH=C(CH3)NO2, is dissolved with a solvent prepared by mixing 1000ml of ethanol with 500ml of acetic acid and 500ml of 12 N sulfuric acid. The resultant solution is placed in the cathode compartment of a divided electrolytic cell containing a metallic cathode of mercury, copper, or other metal of similar nature. Current is passed, using a current density of ~0.2 amp/cm2 of cathode surface. The temperature is kept at about 40°C during the electrolysis which is continued until at least eight Faradays of electricity have been passed.
When the reduction is completed, the amphetamine may be separated from the solution. A convenient way of doing this is by removing the ethanol and ethyl acetate present by evaporation and then making the residual solution strongly alkaline by addition of caustic alkali. The basic layer thus formed is separated from the aqueous solution and contains the desired amphetamine freebase.

The yield seems to be around 50-60% when using this method to reduce P2NP to
desoxyephedrine. Not comparable with other reduction methods but sounds interesting though.

SWIM isn´t very sophisticated in electrochemistry and he has no clue how to construct such a device.

Despite the fact that this method was very popular in the past, I found no more detailed descriptions than the one posted above.

If someone has experience with this electro method please give SWIM some hints how to build a electroreduction cell of sufficient size.

joe_aldehyde · huxleys associate

there is an electroreduction thread by bumblebee. UTFSE.
porous cells could be...clay pots for flowers with the bottom hole sealed, for example.

bio · Working Bee

The cathode polypropylene bags in car batteries make good diaphragm/membranes.
With cleaning they can be used repeatedly.

The high quality maintenance free types have the best bags which can be cut and welded together if mounting on a large removable frame for example.

icecool · Insistent Chemist

Maybe it is a very stupid question but in car battery's I've opened.
There are plates of lead and leadoxide seperated by some kind of wadds and the total is drained in 37% H2SO4.
So where could I find these bags, or am I using the wrong car batteries?
And can one also use polypropylene sheet if it is available to him just in the store.
Because those little baggies where one puts his sandwiches in and stuff that goes into the freezer aren't those polypropylene.

bio · Working Bee

Cheaper batteries use just a separator of a white PP fabric or even kraft paper.
The maintenance free ones have the gray bags which are seam welded and totally enclose the cathode plates, so 6 in each 12V battery. The top of the line have heavier bags.

You may be able to get dead batterries for the hauling at auto parts stores and garages. In fact many of these have only one bad cell, the positive post link inside breaks.

Baggies are LDPE (low density polyethylene). The polypropylene must have specific
porosity to pass ions of a certain type and I've found that the battery bags work well in everything I've tried. Regular sheet is only slowly porous to gasses. The battery bags if filled with water slowly ooze the liquid evenly over the entire surface. HDPE plastic would also work but takes a lower temperature about 100deg PP will survive 130deg.

A filter paper membrane < 1 micron might also work but the battery bags are specifically designed for electrochemical dividers and are free and easy to get given a little DIY effort.