Author Topic: Wet Reduction problem: unknown crstyals  (Read 1821 times)

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ephemeral

  • Guest
Wet Reduction problem: unknown crstyals
« on: April 20, 2004, 11:39:00 PM »
Following the  "Improved Really Wet Reductive Alkylation", all went accroding to description and performed perfectly.
 Unfortunately, having been exhausted and not thinking, Swim reached the final stage wherein the toluene should be distilled off to yield the freebase oil.
   Rather than distill off the toluene at atmospheric, swim mistakenly applied vacuum while the toluene/oil was somewhat warm.
  The vac pulls 9 mbar, and it boiled immediately.  This was held for a few minutes until the error was realized and the vac removed.
  At this point a pile of white/dirty brown  crytals had formed at the bottom of the flask.  The oil (product) that had been there was now a mass of crystals, and the toluene all there.
  Swim tried heating the toluene thinking the oil had temporarily solidified due to the lower temp, but this did nothing.
 Help! Swim is at a total loss in both ways.  What has happened, and what can been done?
    Much help is needed, please advise.  Thanks

ApprenticeCook

  • Guest
adding a touch more toly any good?
« Reply #1 on: April 21, 2004, 02:07:00 PM »
adding a touch more toly any good? try and dissolve the crystal mass...??? or you may have made a whole fuck load of goop.
Add some more toly and stir it up, see if the crystals dissolve and then try again...

Anyone anything else??

ephemeral

  • Guest
Shit, shit, shit. Tried dissolving a small...
« Reply #2 on: April 21, 2004, 04:27:00 PM »
Shit, shit, shit.  Tried dissolving a small amount of xtals in boiling 99%IPA.  The brown tint disappeared and the "xtals"  solvated and then became an undissolved  (at least partially) white powder.
  Will add more toluene to the original mass and see what happens.  Thanks.  Add this one to really stupid lab mistakes, heh?

RepVip

  • Guest
Just Wondering...
« Reply #3 on: April 22, 2004, 03:05:00 AM »
Just Wondering...
What was your starting material? P2P? MDP2P?
Certainly not 1-(2,4-dimethoxyphenyl)-2-propanone  ;D

Sorry, I don't have any advice as I don't know much about vacuum distillation. It seems to me the product might possibly have distilled over with the toluene... instead of salting out.

ephemeral

  • Guest
The starting material was MDP2P from a ...
« Reply #4 on: April 22, 2004, 05:06:00 PM »
The starting material was MDP2P  from a buffered performic following Labtops proceedure. There is a brief post on this under another topic.
     Tried adding more toluene and stirring.  The result was, after 7 hours, a  brownish/white  "blob",  almost a gummy conglomeration.  THe original xtals were gone, but who knows what now.
   The confusion stems from the fact that the temp was never very elevated, even during the vac mistake.  Yes, it boiled, but at around  50 C.  Very confusing  for this neophyte.
 Will rerun bisulifte test on suspected ketone to assure.

 Thanks for any input, all.

XrLeap

  • Guest
any update for this dream?
« Reply #5 on: July 15, 2004, 10:26:00 PM »
any update for this dream? SWIX is interested to find out about the "wet" dream:)


r2e3

  • Guest
had same prob
« Reply #6 on: July 15, 2004, 10:31:00 PM »
basifying - it sucks...
is it necessary or is it merely to maximise base recovery? -in which case extraction is better - ie DCM?

the use of toluene is limited - panickity chemist going on about impurities - use dcm 40C bp - if it is really that crap can always recrystalise

endo1

  • Guest
"basifying" is of course necessary...
« Reply #7 on: July 16, 2004, 10:22:00 PM »
"basifying" is of course necessary otherwise your product will stay in the water layer. When you add your sodium hydroxide solution the product will fall out of the water as an oil. When you see oil fall out you should be happy to know that you have product there. In what way does basifying suck?

r2e3

  • Guest
from other info
« Reply #8 on: July 17, 2004, 05:14:00 PM »
i have received - the step after reductive amination NaBH4/Menh2 - you basify only to retrieve the trace amounts of oil that remain in the aqueous phase.

Would it not be better and a whole lot easier just to include a further dcm wash of the aqueous phase to get the last traces. mdp and the free base are oils at all times after all..

point is - so i have been lead to believe is that basifiying is mainly to recover trace aqueous amounts dissolved as an emulsion.

I say all this cause on a couple of occassions - after basifying my FB - after what seemed a successful reduction - ie co2 gen + heat rise - i add the 5% NaOH and end up with sludge - very annoying after 2 days of nurturing.

i have yet to try this other method but 'saponifying' is not what i want to do to my lovely honey.

so yeah - any thoughts on the subject are indeed welcome as  i have a batch planned for the next week or 2 and want damned success :-)

also - one - method described suggestes addition of hcl to reaction mixture post reduction (neutralise excess NaBH4)and then distillation, whilst another suggests basifying and then gasing followed by recrystalisation - nice and dirty as well as time consuming

i have my own protocol forming as it seems that the 'experts' use widely different methods to reach their endpoints. a learning process  i guess but a lot of it seems to come from pure experience rather than from someone who claims to know what they are doing.

i will try the non basifying route suggestested to me by a fellow member of the community - makes sense to me - i will let you know how it goes...

the sludge refered to in the first post of this thread is the direct result of basifying being the point.

endo1

  • Guest
Not a wet reduction
« Reply #9 on: July 17, 2004, 09:38:00 PM »
Ephemeral was originally talking about a step in the improved wet reduction workup hense the name of this thread. In his case the base is required.

I think r2e3 is talking about flooding the post reaction mix of the non aqueous reduction in which case plain water should be fine here as long as no HCl was used either.

XrLeap

  • Guest
SWIM had a similiar dream, only that in SWIM's
« Reply #10 on: July 22, 2004, 09:00:00 PM »
SWIM had a similiar dream, only that in SWIM's dream, no vacuum was used to distill the toluene. After the toluene was stripped off, all under atm lower, a junk of brown crystals fromed as well as oil.

Tried to isolate the formed crystal bfore adding muriatic acid, kept them aside. These brown crystals just wouldn't dissolve in boiling IPA, thus could not do a recrystallization....... bad dream.

The dream went to to show that ethanol was used to dissolve the oil, 5N Muriatic Acid/IPA(dried with silica beads) was added to the oil to form crystals.

The dream went on to become nightmare when muriatic acid was added to the oil(dark colored), some crytals formed and washed with acetone, and failed to dissolve under dry boiling IPA agian. They seem quite white, but with a lot of reading, SWIM thought that they were not pure. Anyway, SWIM dreamt on with FOAF and being stoopid to try the product and no effect was noted even with 1g dosage(the salt tasted very salty, where SWIM tested before some very nasty and bitter salt which gave good feeling). This was really a nightmare, in the process broke a 1L RBF with 50g ketone loss, not to say that another similar dream happened where no crystal was in sight at all.

Can any experience bee tell SWIM that what color at what stage should SWIM expect in the Barium's wet dream. please?