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All 5 posts   Subject: Zn/NH4Cl reduction of MDP2P Oxime - Help!   Please login to post   Down

07-13-04 05:10
No 519044
      Zn/NH4Cl reduction of MDP2P Oxime - Help!     

Hi bees... I recently read about an attempt to make MDA.HCl from MDP2P (made via standard performic oxidation of isosafrole).  The ketone was excellent (41.6g distilled MDP2P from 48g isosafrole).  The oxime was made following Chromic's and Sonson's instructions, to yeild exactly 17.8g dry oxime from 17.8g ketone.  Then, it was decided to attempt a reduction of the oxime using ammonium chloride/zinc dust as in Post 477266 (Lego: "Reduction of oximes with zinc/ammonium formate", Novel Discourse) (as ammonium formate was not immediately available, and an attempt to make it resulted in total sublimation through carelessness).  5g oxime, 3g NH4Cl and 3.6g Zn (1:2:2 molar ratio, approximately) was placed in 50mL MeOH and refluxed.  Almost as soon as reflux temperature was hit, a reaction started, significant bubbling occurred, and ammonia gas could be smelled from the condensor.  The reaction was allowed to run for 7 hours, at which time there was still significant bubbling, but there didn't seem to be too much zinc dust left in the mix.  The MeOH was evaporated off, the flask extracted with chloroform and the chlorofom dried and gassed with HCl.  No crystals formed, but it was thought that perhaps there was some water in the chloroform, dissolving the crystals... the chloroform had taken on a slight pinkish colour...

So, the chloroform was evaporated off, and left perhaps 3mL of a fairly dark brown oil (orange when seen in a thin layer).  When it cooled back to RT it became very viscous.  It smelt vaguely amine-like, and when a tiny sample was tasted it burnt the tounge.  An experienced taster suggested that it tasted rather like MDA.HCl...  A sample was taken and tested with nitric acid (the closest thing to a testing reagent available).  There was something blood red, and then what appeared to be green-brown (presumably brown from being mixed with the red).  MDA.HCl should turn green in the presence of nitric acid.

So, can anyone give any indication of what this stuff could have been?  Is there the possibility of some sort of polymerization of chloroform in the presence of the acid? (According to the MSDS, there shouldnt be a problem, but then again...).  Does chloroform not allow for absorption of HCl?  A lot of HCl gas later came out of the chloroform (it was almost a serious problem, to be honest!).  It's got me stumped...
(The Archetypical "Good Guy")
07-13-04 07:00
No 519067
      Horrible workup     

I would definately bet my money on that your problem is due to very sloppy workup. Secondly as far as I remember chloroform is not the best solvent for crystallizing amines.

Try working it up like this instead:
- Run the oxime reduction
- Filter off the Zn sludge
- Rinse with a little more MeOH
- Evaporate of MeOH
- Dissolve residue in dilute aq. HCl
- Wash 2-3X with DCM or chloroform
- Basify and extract three times with DCM or chloroform
- Wash organic phase with brine
- Dry organic phase with a suitable drying agent
- Strip solvent
- (you should distill it to ensure total purity, but that will probably give a substantial loss in yield when working with such small amounts. So simply recrystallize your end product carefully.)
- Make the salt of choice, by any method you prefer (I'd suggest using the method using azeotropical distillation I have described in the newbee forum).

Good luck!


Nuke the whales!
(Hive Bee)
07-13-04 20:59
No 519172
User Picture 
      Reagent ratios & possible zinc complex     

Thanks for trying this procedure!
Lego was waiting for a bee like you to try it.....

In the original article they use the following reagent ratios:
Oxime/ammonium chloride/zinc: 1/2-4/2

You used: 1/2/2

So one of your problems might bee the excess of zinc present in the reaction. Amines, including ammonia, tend to form complexes with zinc which have different properties than the free amines and the zinc ion. There must bee a reason why the authors used an excess of ammonium chloride compared to zinc.

Perhaps you should try this procedure again, this time again with more ammonium chloride and the work-up proposed by Bandil.

Good luck! cool

The tendency is to push it as far as you can
08-09-04 10:17
No 524415
      Hi guys, thanks for the responses...     

Hi guys, thanks for the responses... sorry it took me so long to get back here, been busy!

Anyway, first off, I would like to defend the lab technique, and criticise my posting - I was in a rush, left out a few details... the work up was exactly like that outlined in the article, with the exception of the final chloroform evaporation, with gassing being done instead.

However, since then, research has shown a new and interesting way of making ammonium formate, which may be attempted... of course ammonium chloride is just laying around, and there's enough oxime available for a few trials, so hopefully a working procedure can be devised! It was also found somewhere on the Hive that MDA.HCl is soluble (at least to a degree) in DCM, and therefore it would be reasonable to assume that it would be similarly soluble in chloroform - therefore, xylene or acetone will be attempted in the future.  Also, came across a snazzy microscale distillation apparatus, which may come in handy.

Presently time is unavaliable for labwork.  However, the project is at the top of the list, and the suggestions given here will certainly be taken into account!!  Again, thank you!!
(Hive Bee)
09-23-04 06:37
No 532802
      ha, u think thats bad...     

Couldn't make it to the store to buy xylene/toluene today, so ended up getting acetone, which wasn't a good idea... ah well... but the reaction went well ammonia is let off from the  rxn after adding the KOH to solution, acetone and water apparently mix very lol. (This probably makes u feel better). But tomrrow, is another run, and another fun time, hopefully with the appropriate solvent :)



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