Author Topic: Low Yield on Wacker-O2-->Cyanoboro, plz help!  (Read 3653 times)

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hmx777

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Low Yield on Wacker-O2-->Cyanoboro, plz help!
« on: May 06, 2001, 08:08:00 PM »
SWIM did the wacker O2 method.  The ketone came over at
about 130-140 deg. C @30 PSI vacuum. It smelled like the
stuff and was a yellow with a very slight hint of greenish
to it.  It definately didnt smell like safrole.  Does
isosafrole smell very similar to safrole?
SWIM tried a bit of it with the bisulfite addition
method,it wasnt an instant reaction, but SWIM got some
crystals.  SWIM found the bisulfite method isnt always
accurate, sometimes SWIM gets precipitate, sometimes not
(even though the ketone always smells like it should).
Anyway....  The yield from this step was decent for
starters, around 50% ketone.

SWIM Proceeded to do a sodium cyanoborohydride reduction:
175g MD-P2P, 1.5L Methanol, 605g Ammonium Acetate.
Slowly added 82g Sodium Cyanoborohydride.
Maintaned pH at around 6-7 with concen. HCl.
Added some silica gel to keep water out of reaction
(promote better imine formation).
Kept stirring for about 3 days.
---
Evaporated off methanol.
Added HCl till pH 1-2.
Extracted off unreacted ketone with DCM.
Added cold NaOH till pH was around 10-11.
Color changed to a lightish brownish with some weird waxy
looking precipitate floating around.  No amber oil was seen
even after letting sit in ice bath for 1 hour.
Continued with DCM extraction to get freebase...
Boiled off DCM, a very small amount of oil was seen.
Turned freebase into HCl salt.
Yield was around 4%!!  That is four percent, very low!

Some extra info:
The sodium cyanoborohydride was fresh, SWIM has little
reason to believe that it was inactive.
SWIM didnt put N2 inert atmosphere when reacting for 3
days, but come on guys...  That would not inpact yield to
4% !! SWIM expected at least 40% and up!
SWIM wonders if the ketone was in fact the ketone?  Like
SWIM said, it smelled nothing like safrole.  Had that
definate smell of ketone.  What else can it have been
anyway?
There wasnt much unreacted ketone leftover from DCM
extraction after reduction.  Leads SWIM to believe that
something must have been formed!  Is it still in solution
after pH is brought to 10-11?  For the hell of it SWIM put
it to almost 14 after just to see, nadda.
Is there a better method for taking that freebase oil out
of solution?  Keeping it in fridge 24hours didnt help.  Is
NaOH solvating the MDA?  Could SWIM have used bicarbonate
to get it out?

SWIM tried this 4 times.  Same results!
SWIM has been searching on hive for a while now, no posts
people have put seem to give SWIM any ideas.
Any help would be appreciated, thanks in advance.


terbium

  • Guest
Re: Low Yield on Wacker-O2-->Cyanoboro, plz help!
« Reply #1 on: May 06, 2001, 09:05:00 PM »
A couple of points:

You can't really mean 30 psi of vacuum. You probably mean 30 inches of mercury which implies that you are using a mechanical guage. With a mechanical quage you have no way of knowing what your vacuum was. The vacuum levels needed for this distillation are low enough that they are out of the range of this type of guage. Since you don't know what you vacuum was the boiling point you metion is meaningless and doesn't give any indications of what it was you were distilling.

The bisulphite test works well with MDP2P. If all you are getting is a few crystals then I have to question if you are getting any ketone. I don't know what you mean by "the bisulfite test isn't always accurate". I think it more likely that you are just not getting any ketone.

I am not certain that an O2 Wacker even works. In the half hearted attempts that I made I could not seem to get any ketone - perhaps just a bit of an aldehyde. Note that aldehydes will also give a bisulfite product. Perhaps your weak bisulfite reaction was just from some byproduct aldehyde.

There is no need for an inert atmosphere.

Excess NaOH will not redissolve your freebase. You can take the pH up to 14 with no problem.

hmx777

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Re: Low Yield on Wacker-O2-->Cyanoboro, plz help!
« Reply #2 on: May 06, 2001, 10:23:00 PM »
Yes, I meant 30 inHg.  I am using an aspirator and the tap
water is around 10deg. C., this should give a decent vacuum
for distillation purpose.  This translates to about 760mmHg
less than atmosphere.  I suspect I'm getting around 20-30
mmHg.  I will test the exact vacuum soon by checking what
temp. water(or any solvent) comes over and look it up in a
chart to see what vacuum.

I dont think the vacuum is the problem, my pure safrole is
coming over at around 110 deg. C.  Sounds about right to me.

I really believe the O2 wacker works(not neccessarly saying in my case it did).  But, the product smells exactly like
the ketone I smelled made from performic route I smelled way in the past.

I dont think there is anything wrong with the cyano reduction part of the experiment.  It is tried and true and
not too much can go wrong there.  Must be the ketone phase.
There must be some ketone being formed by the wacker if I do get some product(tested and a wonderful product ;-) )

Should I try a knoevanegal condensation route to ketone?
I dont like benzoquinone wacker (that shit is nasty).
I dont like Performic either.
Perhaps you are right with the o2 wacker.
Any other ideas?

DiethylEtherMan

  • Guest
Re: Low Yield on Wacker-O2-->Cyanoboro, plz help!
« Reply #3 on: May 07, 2001, 12:15:00 AM »
My grandmother has tried a dozen O2 wackers with different solvents, and none have worked beyond 20-25% yields...EVER. Her and my mother would distill the o2 wacker ketone, and not realizing this until a couple months back, they discovered they were also distilling the aldehyde. It is very hard to catch the temp difference, and it is certainly a good possiblity that the boiling point differs with the varying water pressure/temp using water used for water aspirators. After re-distilling they're mixture after each o2 wacker, and paying really close attention to the temp everything was comming over at (using the benzo/tone temp as a guildline) realized most of they're product was in-fact not tone at all. The al/hg yields they used the O2 wacker tone in, were always horribly low, and/or contaiminated, therefore producing yellow/orange xtals.

Also, the O2 (supposed) tone, did smell somewhat like tone, but also still had that safrole smell to it. Don't kid yourself into thinking it smells like tone. Thats what my grandma did, although, she has alzhimers.

But if you really want to be sure, re-distill 3/4's of your mixture and use the 1/4 that is left over. Don't forget to smell the difference between the two.



If some of us were not so far ahead, the rest of you would not be so far behind!

KrZ

  • Guest
Re: Low Yield on Wacker-O2-->Cyanoboro, plz help!
« Reply #4 on: May 07, 2001, 12:40:00 AM »
If you can setup a bleeder between the pump and gauge, you can regulate vacuum.  If you set it to 26 or 27 in. Hg you will still be able to distill without charring, but, more importantly, you should be able to determine your vacuum to within +/-20mmHg (If you are using a good quality mechanical gauge, such as a spirahelic, which is accurate to +/- 15 mm Hg).  Unfortunately, you won't be able to distill MDMA freebase at that pressure, as the bp would be too high, so you would need a better gauge.

scram

  • Guest
Re: Low Yield on Wacker-O2-->Cyanoboro, plz help!
« Reply #5 on: May 07, 2001, 10:03:00 AM »
"The al/hg yields they used the O2 wacker tone in, were always horribly low, and/or contaiminated, therefore producing yellow/orange xtals."

There is a skill to getting dark amber oils mixed with your liquid mdma.hcl to get it emulsified into white crystals. It involes adding clean toluene to the red oil paste, or viscous liquid while stirring. When it becomes paste, quickly add acetone (4-6 times to toluene volume). It must stirr vigoursly for 2 minutes allowing the crystals to form without locking in the impurities. Once the impurities are locked in, you will get pink or beige crystals. The same with gassing using undistilled oil. You want the crystal matrix to form without locking in impurities.

hmx777

  • Guest
Re: Low Yield on Wacker-O2-->Cyanoboro, plz help!
« Reply #6 on: May 07, 2001, 08:30:00 PM »
Was wondering...
Is there any difference in using Ammonium acetate (NH4+) ion or dry NH3 for the
cyanoboro reduction?  Since the ketone is on in ionic form, is there any
hinderance of the NH4+ getting close enough to the ketone?  Since the NH4+ is in
equilibrium: NH4+ -OAc <->NH3 + HOAc.  Doesnt the imine formation really require
a neutral amine?  It is the the neutral amine's lone pair of electron that attacks
the carbonyl group.  Imine formation must be pretty bogged down if one has to also
compete with Ammonium acetate forming neutral amine in solution.  Why not use
dry NH3 bubbled in?

terbium

  • Guest
Re: Low Yield on Wacker-O2-->Cyanoboro, plz help!
« Reply #7 on: May 07, 2001, 11:21:00 PM »
If you have access to chemicals then why not use hydroxylamine to form the oxime and then reduce that?