Author Topic: nitropropene crystallization problem  (Read 779 times)

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Bandil

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nitropropene crystallization problem
« on: January 09, 2002, 03:52:00 AM »
Hi!

Swim made 5.5 g of crude nitroethane ala Antoncho and immediately proceeded with the 2,5-DMBA condensation to form the nitropropene. Swim did this, as described in pihkal and used acetic acid as solvent and ammoniumacetate as catalyst. The color shift proceeded excactly like swim has previously seen in the 2,5-DMBA + Nitromethane to form the nitrostyrene synth, so swim suspects that the nitroethane was just dandy.

When the reaction had refluxed for three hours, the heat was removed and the color was noted to be very dark red/black and gave yellow "stains" that slowly ran down the side of the glass, when shaken in the flask(corresponds 100% to the nitrostyrene synth). The solvent was removed at atm pressure, and swim thought, that he would be a wise bee and simply recrystallize right away as done in the nitrostyrene synth, so swim added some IPA and shaked the mixture. This was placed in the fridge and a couple of hours later it was taken out. Alas no crystals had formed :(

Swim suspects that the nitropropene was TO crude, to be recrystallized and Shulgin yet again was right and one actually have to wash the reaction mixture at first. Swim was thinking of this scheme to save his precious nitropropene:

Distill of the IPA and suspend residue in water.
Extract the water/nitropropane/gunk mixture with methylene chloride(no chloroform avavible) three times and evaporate the solvent and THEN recrystallize.

Any ideas on how to save swims dream? Is methylenechloride ok for extraction or do you have better suggestions?

Thank you so much for you help!

Regards
Peter

Bandil

  • Guest
Re: nitropropene crystallization problem
« Reply #1 on: January 09, 2002, 08:23:00 AM »
OK, swim removed the IPA via distillation and poured some water in the container. The sludge was exctracted with 3X methylene chloride, which gave a smooth dark liquid. The combined DCM wasings, were distilled and a very dark tar like liquid remained. Swim threw it in the fridge to initiate crystallization, but none was seen.

What should swim do here? How do you induce crystallization, to purify the product? Swim is quite conviced that the reaction occured correctly as the color shifts and reaction time followed the styrene reaction well!

Thanks!

Regards
Peter

Bandil

  • Guest
Re: nitropropene crystallization problem
« Reply #2 on: January 09, 2002, 09:22:00 AM »
Swim tried scratch the inside of glass with a glass and metal rod, but still nothing. Its just a REALLY thick liquid, altough it has been cooled to -15 degrees :( How about dissolving in small amounts of EtOH, could that induce some crystallization?

If everything fails, is it possible to simply do the LAH reduction on the crude product and do the A/B exctractio followed by distillation of the DMA?

Please help ASAP, as the swims product is just sitting there looking all bored :)

Regards
Peter

Osmium

  • Guest
Re: nitropropene crystallization problem
« Reply #3 on: January 09, 2002, 10:59:00 AM »
Dissolve it in some IPA or other alcohol. Place in fridge or freezer, and give it sufficient time to crystallise. If it still fails to crystallize add a few drops of water. Not too much, you don't want all the stuff to oil out again. Be patient. Alternatively you could try to put a layer of a non-solvent like pet ether on top of your nitropropene solution, and let it slowly diffuse into the alcohol layer. leave undisturbed for a day or two, hopefully something will crash out by then.

Bandil

  • Guest
Re: nitropropene crystallization problem
« Reply #4 on: January 09, 2002, 11:13:00 AM »
OK, swim will definately dissolve it in some sort of alcohol(IPA preferred??). Does a mixture with alcohol offer higher chance of crystallization, that the pure compound?

@Os> Why does a NP solvent help crystallizing the compund(not that i doubt you, just being curious :) )?

Osmium

  • Guest
Re: nitropropene crystallization problem
« Reply #5 on: January 09, 2002, 01:07:00 PM »
Not every non-polar will work here!
Solubility in alcohol is much higher than solubility in pet ether. The pet ether will slowly mix with the alcohol, creating a super-saturated solution from which the product will hopefully crystallize.

Bandil

  • Guest
Re: nitropropene crystallization problem
« Reply #6 on: January 10, 2002, 03:43:00 AM »
Swim just thought of the fact, that he has access to a -80 deg celc freezer. Would it help the petit crystals on the way, if swim threw his IPA/Nitropropene soln in a fridge like that?

Osmium

  • Guest
Re: nitropropene crystallization problem
« Reply #7 on: January 10, 2002, 04:12:00 AM »
Definitely, but don't leave it in there for too long!
You don't want to cool it down too much because if you do so the oily shit will crash out again. Slowly diminishing the solubility, either by cooling or by changing the solvent quality will produce the best results.

foxy2

  • Guest
Re: nitropropene crystallization problem
« Reply #8 on: January 10, 2002, 10:30:00 AM »
I think Os meant that you don't want to cool it too fast

I hate my government, does this mean I'm a terrorist??

Bandil

  • Guest
Re: nitropropene crystallization problem
« Reply #9 on: January 11, 2002, 08:27:00 AM »
OK, swim is getting REALLY desperate here. His damn nitropropene oil is just sitting there, laughing in his face :( Swim has lowered the temp in his fridge about 5-10 degrees and scratched the glass like a maniac. The final attempt will bee a NP soln. floating on top.

What is one to do with it, if it CANNOT crystalize? How come it is so difficult to crystallize out, when compared to Nitrostyrene, made in NM as the only solvent(swim just left this at RT and it crystallized beautifully)? Is it possible just to reduce the entire mess and do the A/B extract afterwards?

Thanks!

Regards Peter

___

  • Guest
Re: nitropropene crystallization problem
« Reply #10 on: January 11, 2002, 08:38:00 AM »
How much solvent are you trying to recrystallize <10g of nitro from?

The oil can be used, you just won't have any idea as to it's purity,.

Bandil

  • Guest
Re: nitropropene crystallization problem
« Reply #11 on: January 11, 2002, 08:55:00 AM »
It's currently dissolved in app 10 mL IPA

Osmium

  • Guest
Re: nitropropene crystallization problem
« Reply #12 on: January 11, 2002, 09:35:00 AM »
Do some TLC and compare it with the benzaldehyde, to see if there is any nitropropene it it at all.