Author Topic: Al/Hg Reductive amination under pressure results  (Read 2487 times)

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  • Guest
Al/Hg Reductive amination under pressure results
« on: October 06, 2004, 03:21:00 AM »
Tried this with a few modifications and it worked.

 smokemouth 04-11-00 No 108238

 This is the experimental from the patent.

 French Patent 844228
To 14 g phenylacetone dissolved in 50 g ether is added 15g  20% alcoholic methylamine solution, another 50g ether, 5g water and 2g activated aluminum. The mixture is put under a hydrogen pressure of 3 atm. The reaction is done when all the aluminum has been consumed. The aluminum hydroxide is removed by filtration and the filtrate is extracted with hydrochloric acid. By neutralising with alkalic solution 14 g of crude base is obtained. Distillation gives the pure

 This is what bio did.........

 13.4g P2P (100mm) + 4.7g MeNH2 (150mm) in 30ml Abs EtOH + 100ml 96% EtOH (to arrive at the water amount in the patent). + 4.0g  Al(150mm)..2g for reaction..2g for pressure in situ was the theory  which did  NOT test out btw.
Started with 20PSI H2 pressure but was only able to develop 2 atm insitu (which is the EtOH pressure at 97deg.) in a 100deg water bath. This was partly due to technical problems  with the H2 generator rig, so I just heated the whole shebang.

 Anyway got 11.1g base product which ain't too shabby for a first run  with numerous problems. Also did a nitromethane reduction in the same  rig to get the MeNH2.


  • Guest
Nice! What kind of vessel did you use to ...
« Reply #1 on: October 06, 2004, 05:25:00 AM »
Nice! What kind of vessel did you use to contain the overpressure?


  • Guest
Overpressure Vessel
« Reply #2 on: October 06, 2004, 10:28:00 AM »
A 30lb freon can was used and evacuated at the start. Am thinking of going with a small bladder tank like they use for water pressure systems. This would hold much more in the same volume if the bladder side was pressurized to say 150PSI and hydrogen could be used instead of the standard compressed air.  It can be done without an expansion tank if continuosly monitored as there were no sudden extreme changes in pressure. It should be possible to run a whole mole with 20g Al in a 4 or 5 liter vessel.

BTW I tried the 2 liter soda bottle rig in a dry run w/o P2P and forget it bottle shrunk below the alcohol level and just plain gave me the creeps, even behind my improvised "blast shield"..........More later.


  • Guest
If the reaction is allowed to sit for six to...
« Reply #3 on: October 07, 2004, 12:43:00 PM »
If the reaction is allowed to sit for six to twelve hours at RT after it is theoretically finished, sealed and preferable under some hydrogen pressure (2-3 bar), the yields improve significantly.
It is no problem if the reaction vessel loses slowly the overpressure over the time by small leaks or so.
"Let sit under hydrogen" is the where the emphasis is on.


  • Guest
better idea for the hydrogen generator ?
« Reply #4 on: October 08, 2004, 06:17:00 AM »
Thanks for the suggestion Organikum,btw way do you have a better idea for the hydrogen generator than Al and NaOH? (have some zinc dust laying around) The method used per the patent (US934036) and was too hard to control by dripping in the water onto the ground Al dry lye mix. The 100mm reaction was still bubbling a little after 4 hours with no visible Al so I went a little longer. Will certainly try your idea with stirring I assume. Used extra heavy foil and ground up a little tighter than usual. Did the amalgam at 50deg insitu then dumped in the imine which had been sitting chilled a few hours.

Rhodium if you meant the reaction vessel it was a never used (tested of course) 500ml 24/40 heavy wall short neck round bottom boiling flask.
I wanted to see what was going on with the reaction (with the intention of not exceeding 40PSI), especially the stirring effectiveness, which was easy with so little sludge. Total liquid volume was 164ml and this could be reduced if less Al was used. A 3 liter 18/10 stainless reactor with a heavy tempered glass lid was modified and is  currently being pressure tested (asparagus steamer). The big magnet works great through it. It is difficult to find truly non-magnetic stainless cookware regardless of what they stamp on the thing as all 300 and 400 series stainless steels are supposed to be non-magnetic. Was thinking of maybe trying that new Teflon coating with the low temp (250deg) oven cure.


  • Guest
Hydrogen Generator
« Reply #5 on: October 09, 2004, 11:59:00 AM »
Al/NaOH is my method of choice too, but not with Al-powder/NaOH premixed but with chunks of scrap-aluminium thrown into concentrated lye and sealing the vessel. Evolution of hydrogen can be controlled by temperature, some caustic fumes coming over dont matter in this reaction as long a slight excess of amalgamated aluminium is used.

But thats still a work in progress.  :)


  • Guest
« Reply #6 on: November 08, 2004, 02:25:00 AM »
I think its a good idea to add this link to the thread:

Post 187921 (missing)

(xtaldoc: "Re: presurrised reductive amination", Chemistry Discourse)