05-26-02 16:43
No 314564
suppose there was no hydroxylamine hcl to be had for a given oximation. suppose there was hydroxylamine sulfate available. but no proceedure. would this work
0.6M ketone
0.4M (HONH2)2.H2SO4 (to yeild 0.8M HONH2)
0.5M Na2CO3
dissolve 0.5M sodium carbonate (62g) in 90 mls H2O, add 475 mls MeOH, 0.6M ketone and 0.4M hydroxylamine sulfate (67g). heat to reflux for 1.5 hours, cool and crash out oxime with 225mls dH2O.
look alright? anything overlooked?
only thing wonder is if the sodium sulfate should be filtered off before the reflux or simply left behind, knowing the H2O quench at the end will dissolve it, so it won't crystallize w/ the oxime when refridgerated. comments?
(Pioneer Researcher)
05-26-02 17:13
No 314578
The only problem I see is the solubility of the hydroxilamine sulfate in the alcoholic solvent, if it doesn't dissolve completely the rxn won't take place, and may be you can't distingish it due the simultaneous precipitation of sodium sulfate. Perhaps it would be better to release the hydroxylamine in water, then add the methanol, filter the sodium sulfate and then add the ketone.
(Hive Addict)
05-26-02 20:44
No 314641
Sorry to be a bitch, but read:
../rhodium /alhg.ox
My calculations say:
Start stirring, add, in this order, to a 1L rb flask:
1" magnetic stirbar
89ml dH2O
42.9g Na2CO3 (810mmol base)
61.6g (NH2OH)2.H2SO4 (750 mmol hydroxylamine salt)
Allow this to stir until uniform, then add:
461ml MeOH
600mmol phenylacetone (slowly)
Reflux 1.5 hrs on water bath, then add:
240ml cold water
Move to freezer for 1hr. Suction filter, wash oxime with up to:
1200ml water
If you don't have either sodium carbonate or hydroxylamine sulfate, you can use one of these instead:
110.2g NaOAc.3H2O
52.1g NH2OH.HCl
If you don't have 95% EtOH, substitute with MeOH and it will work fine as well.
The above procedures have been tested by SWIC (they are not just "in theory" calculations), and worked fine!
Btw, the H2O quench might not dissolve it, but the H2O wash certainly will. I've always seen that "slime" of sodium sulfate, and I think it's mentioned in other threads as well... but it seems to dissolve away no problem...
(Rehabilitated)
05-26-02 21:05
No 314650
the stuff says "washing soda" assuming that's the sodium carbonate hydrate, it might acount for the disparities in our math
. (no fancy anhydrous reagents)what do you think about filtering off the sodium sulfate chromic?
(Hive Addict)
05-27-02 11:56
No 314851
The fancy anhydrous sodium carbonate I've got was made by heating baking soda in an oven for an hour or so at 500F.
Although I've never done it, filtering sounds like a good idea as the desired hydroxylamine will be soluble in the aqueous alcoholic mix and filtering should help to remove solid impurities.
(Distinctive Doe)
05-28-02 17:58
No 315388
I think there is a thread around here on converting hydroxylamine sulfate to HCl.
Those who give up essential liberties for temporary safety deserve neither liberty nor safety
(Hive Addict)
06-10-02 09:48
No 319451
Question: Can anyone who's cleaned up oxime before, please recommend some amounts of some solvents to use to recover the most oxime (ie >75%) while removing the most impurity? (ie recrystallization or washing)
Background: Someone who would never make such a mistake, reacted 10g of mdp2p with the appropriate amounts of H2O, MeOH, Na2CO3 and (NH2OH)2.H2SO4. Well, he fitted the flask with a condenser, and although he turned his water on and it flowed into the condenser, it never ended up circulating... he didn't realize this. As a result, he evaporated most of his MeOH... he did detect this before things got dry in the flask. So some water was added, moved to the freezer, no oxime. Shit.
So the mixture was flooded with water, extracted 2x with DCM. Then the DCM distilled off. More H2O, MeOH, Na2CO3 and (NH2OH)2.H2SO4. This time everything goes alright. He adds some water, allows to sit for a day, and then filters the mixture. He washes what he gets with 150ml of water or so, then noticed that the crystals are BEIGE! At least the crunchy crystals seem to be the oxime (water insoluble, melt when heated). The recovery looks a bit low, less than the 10.9g of expected ketoxime (weighs 8g after sitting in the dessicator for an hour or so, maybe perhaps 5-7g when bone dry?) However it's still lots for his purposes and want to recover it as he's used up the last of his mdp2p.
What should be done to clean them up? Should they just be dried them and used as is? Or should he recrystallize them from IPA... wash with acetone something like that?
Thanx: Thanx!
(Rehabilitated)
06-10-02 11:57
No 319495
after washing w/ water a couple times i wouldn't bother recrystallizing unless it was for a melting point. A little Na2SO4 in an Al/Hg isn't going to hurt anything
(Hive Addict)
06-10-02 16:51
No 319579
I don't think there's any Na2SO4 in it because it was washed with water, but he was wondering what produced that light biege color. Anyways, I'll tell him to throw it into an Al/Hg while reciting a few prayers.
Thanx.
(Stranger)
06-10-02 18:43
No 319619
Here is the reference:
Gribbs; Barnes Tetrahedron Letters 1990, 31, 5555