Author Topic: Problem forming the oxime  (Read 4725 times)

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angryscientist

  • Guest
Problem forming the oxime
« on: August 06, 2004, 10:08:00 PM »
a friend was trying to form the oxime in sonson's method, followed all instructions, made his procedure x20 with distilled water, fresh methanol, fresh hydroxilamine and sodium acetate.3h2o - everything seemed perfect except his ketone which looked a little green. Anyways, this ketone works fine with the nitromethane method, he says. at the end of the procedure, he noticed the ketone separated out of the mixture. HE WAS SHOCKED!
he added water, and part of the ketone might have reacted, since crystals formed. BUT, when he separated the ketone in a separation funnel, he had the brilliant idea of extracting everylast drop of it by adding some DCM.
well, needless to say, he separated out the oil and DCM, and when he filtered there was nothing in the filter paper, although mixture was water-white.

Why did the ketone separate out? can one not scale up this procedure successfully? was it the DCM who robbed the little bit of oxime he might have gotten??
what can he do to recover the possible formed oxime and the MDP2P?

he knows he is stupid, but stupid people need help too, so I came to you for him. please help
:(

angryscientist

  • Guest
speculation of the problem
« Reply #1 on: August 07, 2004, 03:24:00 PM »
My friend was thinking the whole night about the problem he had, and he came up with a hypothesis.
In case his reflux setup was not so efficient, he would loose some methanol. If the methanol evaporated out, would the oil separate? does this sound like a reasonable explanation? He tried again with clear, yellow ketone and same thing happened - 0 filtrate. Note that that the second try was done in the very same setup.

Osmium

  • Guest
> made his procedure x20 Maybe the angry...
« Reply #2 on: August 07, 2004, 11:41:00 PM »
> made his procedure x20

Maybe the angry one should do smaller batch size.

> at the end of the procedure, he noticed the ketone separated out of the mixture.

How did you identify the substance that separated out? By looking at it?
Have you considered the possibility that the oil that separated out might have been the (impure) oxime?

What happened after you evaporated the DCM? Found anything?


angryscientist

  • Guest
nope, never came to his mind
« Reply #3 on: August 08, 2004, 06:02:00 AM »
no, the possibility of this `oil` that came out to be the impure oxime never came to his mind. the DCM was added after most of the supposed-ketone (which looked exactly like the in-coming one) already was separated out. After this wash, the supp. ketone + dcm mixture did turn a little reddish, but my friend has done nothing to it yet.
If he should do only small batches, the method does not interest. As he mentioned, he tried it again, only twice the batch and using beautiful yellow ketone. same thing happened.
He insists on the fact that maybe his reflux was not efficient, and if this is in fact a possible mistake which would push the oil out of the solution inhibbiting reaction.
He would like to mention that quite a while ago he got a few needles out of this procedure, but it was so long ago he doesn´t remember what went differently.

OcoteaCymbarum

  • Guest
Question for knowing bees
« Reply #4 on: August 09, 2004, 02:49:00 AM »
I've been reading about oxime formation and I feel like trying it. Im just wondering about something, reading Chromic's posts. He says a white sludge will settle to the bottom, and this is not oxime. Some sorts of inorganic salts. But where does the salt go when the oxime is shaken to crystalize??? Will it be washed away with the water wash??
Im looking to pointers to look for while trying it. Can anybody help me so i dont waste any ketone?

angryscientist

  • Guest
GOT SOME RESULTS
« Reply #5 on: August 11, 2004, 10:41:00 PM »
well, you lazy bees arent interested at all in the oxime method...
anyways, I will post my friend´s results, and hope to have someone around with experience
in forming the oxime to make precious MDA.

From the last post, he got back to his lab and opened the freezer only to find
nice crystals in the smaller (2x) entirely and beautifully crystallized!! Not only that!
all his not-washed equipment contained crystals as well! He found this so amazing he
got on drying the dcm from the batch he thought went wrong and got MORE CRYSTALS!!!

He has repeated the 20x procedure 4 times, with good, beautiful reflux and the oxime oiled out
everytime, but in the morning he consistently got nice crystals in his freezer.
Anyone has the same experience?

He put most of his batches in vacuum to dry and will leave there a few days, but he tried to
light-dry one of them and he got SCARED!!! it seemed to melt, but it was definitely not 80C.
He supposes the oxime re-dilluted into the solvent (water) that was still around. does this
sound reasonable?? is there a faster way to dry this baby? (NOTE: he put this batch in vaccum
too and although he didn´t check, it looks like has crystallized again.)

thank you all 4 your time and knowledge
;D

OcoteaCymbarum

  • Guest
Not many seem to try this route
« Reply #6 on: August 12, 2004, 03:36:00 AM »
Usually, someone around has some sort of answers.
It doesnt seemto be the case here so I just might ask you the questions.
How can you separate the inorganic salt that precipitates and the oxime crystals that you are suppose to see when u shake???
Should you cool everything down. Filter off the salt, then take the filtrate and shake to see crystals forming???
What would happen if the solution is left to cool for a longer period. Would crystals spontaneously form?

hypo

  • Guest
purify your MDP2P
« Reply #7 on: August 12, 2004, 09:43:00 AM »
if the oxime oils out then with a good chance it's your MDP2P that is dirty.
don't collect 50°C fractions! try the HCl rearrangement which seems to produce
less byproducts (for whatever unknown reason!).

> How can you separate the inorganic salt that precipitates and the oxime crystals
> that you are suppose to see when u shake???

you've got that wrong.

there is some inorganic precipitate after the reaction, but it goes away when you dilute
with water. after adding water you get a clear / slightly turbid solution. put that in
the freezer overnight to get nice crystalls.


OcoteaCymbarum

  • Guest
Thanks for that input
« Reply #8 on: August 12, 2004, 02:12:00 PM »
I have no experience doing the oxime and I am trying to understand exactly before I use the ketone. I am certain of its purity so It should work fine.
So adding that extra 40 ml of water like in Chromic's posts is enough to dilute the salt or should I had even more???

Pots

  • Guest
I also had trouble forming the Oxime when I...
« Reply #9 on: August 12, 2004, 04:08:00 PM »
I also had trouble forming the Oxime when I started and I found that putting the solution in the freezer for an hour or so is not enough.....you need to keep it in the freezer overnight and then be patient enough to sit back and let it dry for a few days afterwards. The ketone used here is pale green.


angryscientist

  • Guest
pots... did it oil out too?
« Reply #10 on: August 12, 2004, 05:46:00 PM »
Pots, my friend has the exact same situation, but what he wants to know is if  your oxime oiled out too, or did it just hang around in the solution? His oiled out as soon as the reaction cools dow and water is added. He is pretty sure his ketone is pure, it not only looks pure, but other reactions run very smoothly with this ketone. It is fres, and beautifully yellow. The green ketone he used in earlier trials gave less yield and a brown oil he doesn´t know what it is. might even be ketone. he will try to redistill it sometime just to see what comes, if something comes at all.

>How can you separate the inorganic salt that precipitates >and the oxime crystals that you are suppose to see when u >shake???

Hypo is right. If you throw in the water, and immediately filter the solution absolutely nothing stays in the filter paper.

My friend filtered out crystals and put the solution back in the freezer to get more crystals in the next day. this happened consistently too. He is not sure if it has to be filtered real cool or if the last of the oximes just take a long time to come out. he will cool future batches 03 days before filtering to check on this.

>if the oxime oils out then with a good chance it's your >MDP2P that is dirty.
>don't collect 50°C fractions! try the HCl rearrangement >which seems to produce
>less byproducts

He doesn´t believe the MPD2D is dirty. It is distilled, and for test reactions he always collects the best parts of his ketone. He also has no idea of what you mean  by 50° fractions or HCL rearrangements... he is cOnFuZeD

From the wise ones who posses a lot of oxime, do they usually form beautiful needles or just regular crystals? what would possibly interphere in this difference?

My friend is no longer angry. he is happy to know he can count on his friends  ;)

calcium

  • Guest
HCl rearrangement
« Reply #11 on: August 12, 2004, 09:09:00 PM »
Search for Chromic's thread on using acids other than sulphuric for post-peracetic rxn work up. Oh, here it is...

Post 476034 (missing)

(Chromic: "Rearrangement with other acids", Chemistry Discourse)


HCl gives better yields. Especially, it seems, for those who seek TMA-2... just my two cents.

hypo

  • Guest
and it is dirty
« Reply #12 on: August 13, 2004, 10:14:00 AM »
> He doesn´t believe the MPD2D is dirty.

he would be surprised!
look: the oxime is a solid, so why would it oil out? either it's forming a layer with
the alcohol, for some kinetic reasons, or it's impure. i think we can rule out the
first two possibilities, so it must be impure. why is it impure? either the reaction
was not complete, there were side products or the GIGO principle applies (the MDP2P
was dirty). with this reaction, we can pretty much rule out the first two possibilities,
so chances are big that the ketone is the culprit

> It is distilled, and for test reactions he always collects the best parts of his ketone.

how does he determine the best parts?

> From the wise ones who posses a lot of oxime, do they usually form beautiful needles
> or just regular crystals?

fine shiny crystalls (needles?), but it can be recrystallised into bigger crystalls.

> what would possibly interphere in this difference?

impurities, solvent system, kinetics.


angryscientist

  • Guest
So what would the suggestion be?
« Reply #13 on: August 13, 2004, 03:19:00 PM »
As I posted earlier, after a night in the freezer my friend gets crystals. What could they possibly be if not oxime?
He is drying his supposed oxime real hard and will try the reduction to see what happens.

When he mentions needles, he means that the crystals formed are needle-like, forming 2-4 cm, thin structures - real beautiful.

The "best ketone" for him is the middle fraction of the distillation. Meaning the first to come out is separated and the last too. Doesn´t look reasonable? Would re-distill all ketone be a good option for further purification? He is sad to loose valuable ketone.
This reaction looks simple, ans he is pretty sure his solvents are good. even the water he is using is distilled (sonson does not mention it).

after reduction trials, he will tell me his results.

angryscientist

  • Guest
he should change the method
« Reply #14 on: August 13, 2004, 04:04:00 PM »
guys...
My friend uses benzo wacker, and is thinking about dmf o2.
This method substitutes his old fashioned wacker, but...
you mean to tell me his ketone is useless to make oxime?

hypo

  • Guest
go on already :)
« Reply #15 on: August 13, 2004, 04:07:00 PM »
it's the oxime alright, stop talking and reduce it. the worst that can
happen is that the reaction jumps out of the flask and eats you alive.

i was just pointing out that there are impurities in the ketone, not that
it's unuseable.


OcoteaCymbarum

  • Guest
Lots of side products
« Reply #16 on: August 13, 2004, 04:16:00 PM »
in a wacker. the aldehyde, the carboxylic acid, even chlorinated by-products.
Even if some seems to imply something else, I strongly believe that pure ketone is yellow, no other color. This is not to say neon green(often seen in a wacker) or blue or whatever doesnt contain ketone, merely that its not pure.

Pots

  • Guest
When I add water everything oils out and I end
« Reply #17 on: August 15, 2004, 08:11:00 AM »
When I add water everything oils out and I end up with nothing in the filter. If I don't add water I end up with some offwhite granular precipitate, certainly not like the nice crystals described in this thread. I don't doubt the quality of my ketone because it always works perfectly in the Al/Hg reduction for MDMA. I have failed on a number of occasions so I am looking forward to seeing what others have to say about it.
Only once did I end up with enough of the solid precipitate to do anything with so I followed through and tried to reduce it to the Amine but all I got was a very mild reaction with the Al/Hg amalgum producing some bubbling but nothing like the runaway reaction you should get. Now I am licking my wounds and thinking how to go about my next attempt.


hypo

  • Guest
wrong
« Reply #18 on: August 15, 2004, 11:05:00 AM »
> I don't doubt the quality of my ketone because it always works perfectly in
> the Al/Hg reduction for MDMA.

then think again. Al/Hg works even with mega-dirty ketone, because non amine-impurities
are removed during acid base extraction. you don't have this luxury when forming the oxime.
it's actually a good test for ketone purity.

> but nothing like the runaway reaction you should get.

hogwash. you shouldn't get anything like a runaway reaction. best is to use no acid and reflux.


Pots

  • Guest
OK Hypo thanks for the tip re the ketone.
« Reply #19 on: August 15, 2004, 03:31:00 PM »
OK Hypo thanks for the tip re the ketone. However,according to Antibodys recipe non acidic solvent systems all fail to reduce the Oxime so now your confusing me. Could you please elaborate further to enlighten me.