Electrochemical reductions of 1-R-Nitropropenes --> 1-R-Isopropylamines
So I am attempting the reduction of a 1-R-2-nitropropene. I say 1-R because I feel this can be applicable to many others through my trial and errors,
and at this point its complete errors. For the purposes of this discussion I am working on phenyl-4-nitropentadiene, and want to discuss some of the
things that have occured. I chose electrochemical reduction as most reagents for reductions of nitro groups or double bonds are very dangerous or
inadiquate, ie LiAlH4 (very nasty stuff, had one too many ether fires with this one), Fe/HCl (never works except for nitrobenzenes), NaBH4 (never
liked this chemical... or it doesnt like me). I looked to this board and searched for electrochemical reductions and pulled up some guys Flower pot
reduction design.... Amateur hour imho no offense, but it developed an intrigue that lead to more reading.
First thing... ripping open a car battery.... not the brightest idea, however the bags could be very useful. I have done research and the best
membrane ie the one used by chemists worldwide, and most battery manufacturers is something called Nafion made by Dupont, at 30 dollars a sq ft I have
ordered and waiting to receive in the post. I say the car battery is a bad idea because I have opened two, and maybe its because they were both used,
maybe its the way I got inside, but all of the separators, I mean all have some small leak. This results in mixing of the anolyte and catholyte and
can create some funny side reactions. For example if using Vitus's rough synth you will get chlorine gas as the HCl will leak into the cathode and
get oxidized... this itself has happened once and made me order the Nafion
My setup is a variable Amp/Volt lab power supply that can supply 0-15V/0-40A. I know this is a HUGE amount of power and I really only want 40 A/dm,
but it gives me the option of having a bigger anode allowing for faster reduction.
The power supply is connected by 8 gauge wires crimped to the proper rated alligator clips, and connected to Pb electrodes.
The electrodes are made from 4#/sq ft sheet lead, and I have tried anodizing them the way Vitus specifies, but its seems like that is not so important
since this is 99% lead sheet from the mill.
Upon reading the flower pot thread one person had an issue with a an orange color appearing, and I have an explanation, back to the mixing of the
electrolytes, and polymerization. In my experiments I have noticed that if the temperature is not carefully kept at room temperature or below
intermolecular deils alder reactions leading to polymerization will occur.
This polymerization naturally occurs in my o chemist mind as the sulfuric acid accelerates this reaction at some degree no matter what temperature,
along with air oxidation, so this makes me ask the question how best to view the reaction from inside, as waiting for it to go colorless relys on
perfect conditions, and relying on the amateur hour of when the bubbles start to increase isn't really a chemists view. I say this because depending
on what phase of the reaction is completed
nitropropene-oxime-hydroxylamine-amine
the bubbles will increase steadily until done. I am blessed to have TLC plates, and for those that read a recommendation on solvent system would be
great!!
At the moment I am using a PPE separator from one of the batteries, and the lead electrodes in a pyrex beaker immersed in an ice bath. My solvent
system is 4:4:1 EtOH:AcOH:HCl (37%) for the anolyte and 10% H2SO4 for the catholyte. The equipment that I am working with is sparse so I am looking
for a better way to work up the product isopropylamine that doesnt require any distillation or organic solvent. A rotovap would be great but not in
my budget.
My questions
What TLC system for reaction monitoring that would give clear separation of all four compounds?
Is the mild leak in the PPE separator that much of a problem is this their design?
Would going above 40A/dm current density that frowned upon? would this further accelerate the intramolecular deils alders?
what kind of workup would be best to minimize the idea of stripping solvents?
Also mods I noticed that the flowerpot thread is closed so if this is offensive forgive me, delete, give me a chance
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