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Phenyl-2-nitropropene crystallization

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APOPLEX:
SWINM has big problems to crystallize the Nitrostyrene made from Benzaldehyde and Nitroethane.
He want to show you his fails so you can make it better....


Purity of used chemicals:

Benzaldehyde: ACS grade, FCC3, al least 99 %
Nitroethane: 98+ %

The chemicals are stored at RT ( 20°C ) in brown glass bottles so they should be ok.


He tried it with NaOH as the base like described in TS II in Rhodium`s Chapter about three times, sometimes with slight modifications. The temperature and the other reaction conditions were correct, but there was no crystallization. He washed the yellow - orange oil with dH2O to remove any acid/base, dissolved it in MeOH, EtOH or IPA and filtered it with a drying agent to remove any water traces. He does the same again without filtering with a drying agent. Then he put the samples in the freezer and looked at it from time to time, but even after two days in the freezer ( -18°C )
no crystals were produced. So he decided to eject this reaction.


Next he tried it with n-butylamine as the base and no additional solvent at RT:

1 mole Benzaldehyde, 1.1 mole Nitroethane and 0.1 mole n-butylamine were mixed in a beaker and set aside at RT in a dark place. After two days water begun to separate wich was floating on the top. After 10 days he sucked off about 9 ml of produced water. The solution was yellow to slightly orange at this point so he decided to wait a few more days because - in theory - 18 ml of water should be collected. But at day 14 no more water was produced and the color changed to a very deep orange. He knows this is a sight of decomposition, but he tried to crystalize it like before - with and without solvent - but no results.

Hmmm... the rxn seems to work with n-butylamine because water was separated, but the rxn time was to long and after removing the water from the top ( day 10 ) decomposition was probably accelerated because of better contact to the air....


He would try this rxn again, but with some modifications:

1 mole Benzaldehyde, 1.1 mole Nitroethane and 0.1 mole n-butylamine were mixed in a flask and the air was pumped out with vacuum to prevent decomposition while reacting. The flask was put in a warm water bath ( 40 - 50°C ) for
about 2 hours.....

But he don´t know if this will work because there are so many variables:

What is the correct temp. and rxn-time ?  Lower temp. causes longer rxn-time and versus.

Should he add some GAA to form n-butylamine-acetate wich is probably a milder base than n-butylamine ?

With solvents like GAA, MeOH or EtOH the produced water came much more in contact with the produced Nitropropene wich disturbes the rxn.

So he think it´s better to use no additional solvent in this rxn because the water can float on top. I this right ?


Please share your experiences with n-butylamine as the base in this rxn, and help him to get some fucking crystals out of that shit.... .;-)


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APOPLEX

Chimimanie:
I never tried this one, but here are a few thought:

Your starting chemicals are not a problem (just hope you didnt bought them at same source ;) )

He washed the yellow - orange oil with dH2O to remove any acid/base, dissolved it in MeOH, EtOH or IPA and filtered it with a drying agent to remove any water traces.

Plain water can be used instead of dH2O, it's cheaper... And you cannot dry a compound when it is dissolved in an alcohol, the alcohol will most likely react with the drying agent.

Then he put the samples in the freezer and looked at it from time to time, but even after two days in the freezer ( -18°C ) no crystals were produced. So he decided to eject this reaction.

Well next time dont throw it away, put it in a rbf, big enough to do a good evaporation, then distill of the alcohol in vacuum, see if you have crystal or oil remaining. Then try to work with the oil to see if it crystallise or not. Once you have crystal, continue the workup by dissolving them and putting in freezer or whatever.

But at day 14 no more water was produced and the color changed to a very deep orange. He knows this is a sight of decomposition, but he tried to crystalize it like before - with and without solvent - but no results.

Well the deep orange is not always a sign of decomposition, here i think it is your solvent getting more and more charged with nitropropene (and this is a good thing :) ).

1 mole Benzaldehyde, 1.1 mole Nitroethane and 0.1 mole n-butylamine were mixed in a flask and the air was pumped out with vacuum to prevent decomposition while reacting. The flask was put in a warm water bath ( 40 - 50°C ) for about 2 hours.....

Here i am afraid that at 40-50° with a vacuum you are evaporating your catalyst... Better make the acetate and dont use a vacuum, air will not bee that bad for those compounds at that temperature. ;)

Hell stop to think all decompose so fast too ;D  if your reaction even turn red it is good, your product is colored, dont forget. BTW you dont use any solvents in that reaction?

Well you should also try to put your benzaldehyde (20g), and nitroethane (20mL) + some catalyst (ammonium acetate or butylammonium acetate)(1-2g) in the MW oven, with a glass of cold water near, and nuke that on defrost for a few minutes (repeat the cycle 2 or 3 times, and let cool down a few minutes between the cycles too), it could work. Then evap the nitroethane off, in vacuuo, and recrystallise the oil/crystals with an appropriate solvent i dont know :P . Post result back here after.

Good luck

starlight:
well, you're not doing anything wrong.

but this nitropropene is indeed sometimes very difficult to crystallize.

if you run the reaction with ammonium acetate as a catalyst (the same is probably true for other catalysts too) then there is a trick that will allow you to induce crystallization every time. All you need to do is drop a suitably sized piece (size of a large pea or two) of dry ice into the post reaction mixture, and swirl the flask from time to time. The whole thing will crystallize. This seems to always work.

Save a couple of crystals to use as seed crystals next time you do the reaction. Dropping seed crystals into the cold post-reaction mixture (room temp) will induce crystallization.

To make dry ice all you need is a liquid CO2 cylinder with the siphon to the bottom of the cylinder, and a CO2 pellet maker.

hest:
Somtimes the 'cold' method gives a lot og dimerisation. Use the old one (reflux 2 houers, use accetic or nitroethane as the solvent) Works always, yeald in the 80's

bio:
Sometimes it is a little time consuming but will usually crys without cooling with scratching and seeding. After removing the solvent cool very slowly to RT then scratch the sides of the glass shallow container with a glass rod. Do not be afraid to actually put scratches in the glass as this helps seed crystal form. Try seeding with very tiny sand grains (only a few) if you don't have the PNP crystals. Recrys from hexanes. This always worked for me so I don't see why you are having trouble. Be patient and do not throw the stuff out as you may come back in a couple days to find it crys on it's own. Also you don't really need crystals. Just distill and use as liquid.

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