Author Topic: Phenyl-2-nitropropene crystallization  (Read 3894 times)

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  • Guest
Phenyl-2-nitropropene crystallization
« on: August 29, 2003, 06:55:00 PM »
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.... .;-)



  • Guest
« Reply #1 on: August 29, 2003, 07:38:00 PM »
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


  • Guest
it is difficult but easy
« Reply #2 on: August 31, 2003, 05:21:00 AM »
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.


  • Guest
« Reply #3 on: August 31, 2003, 05:45:00 AM »
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


  • Guest
Phenyl-2-nitropropene crystallization
« Reply #4 on: August 31, 2003, 09:11:00 AM »
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.


  • Guest
Thank´s for your responses Bee´s...!
« Reply #5 on: August 31, 2003, 10:51:00 AM »
He will try it soon ala Shulgin, but with n-Butylamine.

1 mole Benzaldehyde and 1.1 mole Nitroethane are mixed with 200 ml GAA. Then about 10 ml n-Butylamine is added while stirring. The whole mix is then brought to a mild reflux for about 2 hours in a water bath until the color changes to a light orange yellow. After slowly cooling to RT a piece of dry ice is dumped into the post reaction mix. * Cool idea, starlight !  ;) *

The hopefully produced crystals will then recrystalized with a suitable solvent to get clean crystals.


He will use a glas jar with a vent on the top as rxn vessel, because his dist. setup is broken a whil ago !   :(
He think this should work for a mild reflux, and probably produced pressure could be released with the vent.

He don`t know if the rxn-time of 2 hours is correct for this catalyst (n-butylamine-acetate).

He has made 3,4,5-Trimethoxy-beta-nitropropene in the past with GAA as solvent and Cyclohexylamine as the base and about 4 hours rxn-time without any problems to crystalize the Nitropropene. This was probably because of the higher bp. of the M-nitropropene than of the Phenyl-2-nitropropene.

The n-Butylamine is a little bit stronger base than the Cyclohexylamine. So about 2 hours rxn-time shoul be enough. What do you think ?

Yields and hopefully success will be reported in a few weeks because now he has absolutely no time to do this...



  • Guest
Thank´s for your responses Bee´s...!
« Reply #6 on: August 31, 2003, 01:03:00 PM »
Following the method of Susie and Heider in an old JOC (can't find it now) I always got easy crystals without removing the solvent. Yields are excellent even w/o a Dean Stark tube (but at least use a drying tube). The solvent was benzene, NButylamine 20ml/mole (i've heard 25 is better)and about 5 or 6 hour reflux. Maybe some bee can find this ref for you. You can also use PhCH3 solvent per Org. Syn and reduce insitu w/o separating.


  • Guest
it is difficult but easy
« Reply #7 on: August 31, 2003, 02:45:00 PM »
starlite.....Am using another method now but will try the PNP with ammonium acetate in a little while. How much should be used? I always used the BuNH so don't know. Check out this patent for EtN02 from EtOH (US4431842)Will use the new furnace tube I'm making to try it out. By the way does anyone know a good way to remove O2 from air? I once read a procedure using rusting steel wool but can't find it now. Fe makes several oxides you see. I need a way that will make a small continuous flow relatively O2 free to eliminate the inert gas bottle.

Also I used PhCH3 in a similar tube to make PhCHO in high yield using CeMo catalyst before. It really is quite easy and is found in the Journal of Chemical Education (around 1950"s). I had to ditch my library a couple years ago so lost all my refs which took hundreds od hours to copy on the machine at the library. I just love the internet. Didn't have it then.


  • Guest
« Reply #8 on: August 31, 2003, 11:50:00 PM »
Don't estimate the reaction time. Use TLC !


  • Guest
not sure if its optimal
« Reply #9 on: September 01, 2003, 04:33:00 AM »
but 10g of ammonium acetate for 60g benzaldeyde works ok.


  • Guest
some experience....
« Reply #10 on: September 01, 2003, 08:06:00 AM »
i've read of more than half a dozen tries of the 'cold method' on both straight BA and 2,5-diMeO-BA and NITROETHANE and neither of them has ended in a success.

With nitromethane it seems to work OK every time.

So i suggest we put a small question mark beeside that doc on Rh's site - obviously it needs to bee at the very least optimized.

Stralight - you report seems to bee quite interesting. Could you give us more details, please? (the yield, time, temp, solvt ratio etc.) Curiously, there hasn't been, i beelieve, a published/posted success w/straight BA and NH4AcO - at the very best yields achieved ~50%. IMHO/AFAIK.



  • Guest
General suggestion
« Reply #11 on: September 07, 2003, 08:34:00 AM »
SWIM has had some problems with BA's in the past. Especially nitropropene's made from 2,5-DMBA. It was even worse(of course) when the starting materials was less pure. SWIM is using the following method which has worked for ALL compounds tried so far, no matter how pure/impure the materials have been:

The benzaldehyde and nitro(m)ethane are reacted ala barium with methylamine as catalyst. When the reaction is over the product rarely crystallizes if the starting materials have been less pure. When the whole lot has cooled, the GAA is added and the whole thing is dissolved in small amounts of DCM. This is washed 2-3 times with water and then stripped of solvent. With some following cooling and maybe a little scratching followed by recrystallization if the crsytals aren't nice enough, this provides SWIM with yellow-beautifull crystalls every time!

Good luck.



  • Guest
Phenyl-2-Nitropropene crystallization
« Reply #12 on: September 08, 2003, 07:21:00 PM »
Wash the whole post-reaction mixture with vigorous shaking with 1/3 its volume of water, followed by 1/3 its volume of conc. sodium chloride, and if it doesn't crystallize already in the sepfunnel, drain it into a beaker, scratch the inside of the beaker with a glass rod, and then recrystallize it from methanol or isopropanol.

If all else fails, make a seed crystal of phenyl-2-nitropropene using this method:

Then add such a crystal to your liquid phenyl-2-nitropropene - it will crystallize immediately. Always save a seed crystal for future use of all hard-to-crystallize compounds, you will never regret it!


  • Guest
a little more detail (not much)
« Reply #13 on: September 09, 2003, 07:27:00 AM »

Time ~6hrs
Temperature: reflux
Solvent: None, just equimolar BA and Nitroethane
Yield: <50% as you guess (not sure exactly, will measure for you next time)

Will provide a full writeup when done next time.


  • Guest
« Reply #14 on: September 09, 2003, 08:16:00 AM »
This is an ongoin storry.
Reflux in accetic acid for 2-3houer usual gives 70-80%
Reflux in nitroethane usual gives 75-80%
MW is a bit trickey, iff you stop before the polimerisation begins(lot's of TLC), then yeald is in 75-80%, else in the 50%
3,4,5-trimethoxybenzaldehyde and bnitromethane is notorius hard to work with (yeald 30-60%), rhodium have posted a synth with KF ect. haven't trye't yet.
2,5-dimethoxybensaldehyde works alwayes greath, yeald in th 80-90%
Mu personal eksp. with differen catalysators is that it dosen't matter much.


  • Guest
Bawoosh....success !
« Reply #15 on: September 18, 2003, 04:36:00 PM »
Here are the results - and belive me - they are gooood..!  8)

1 mole Benzaldehyde and 1.1 mole Nitroethane were mixed with 100 ml wf/EtOH. While stirring 20 ml n-Butylamine were added dropwise with a Pipette and stirred for another 5 minutes or so.
This was then refluxed for 2 - 2.5 hours until the solution becomes orange and more viscous.
Let it slowly come down to RT in the RBF and then pour it into a large Beaker. Bawoosh....the whole thing crystallized after a few seconds without cooling in the fridge !!!

The solid mass was filtered with suction and washed with a little bit of cold EtOH to remove catalyst.

After recrystallization with boling EtOH SWINM got very light yellow needle like clean crystals.

Yield: 142g or 87% of theory.

Full range success !!!  :)

And that´s not all:

You remember SWINM´s try with BA/NE and n-Butylamine without solvent at RT ??? He put some GAA (just to neutralize the amine) and about 50 ml water on it and stirred it for a minute. The water/GAA floats on the top of the now deep red almost black solution. No crystals appeared - so he decided to throw it into the toilet. But the whole thing now solidified to a deep red chunk !?! He recrystallized this mess twice with boiling EtOH. And even at this stage of decoposition (it now stands over five weeks !) he got about 55% of wonderful crystals like above !!!

So the BA/NE/n-BA route at RT works !!

Yields should increase dramatically with shorter rxn-time... this

1 mole BA, 1.1 mole NE, 10 ml n-BA, mix, let stand for about 2-3 weeks in a dark place until orange and more viscous. Netralize with GAA/water and pour it in a large volume of cold water. Yield should be in the 80`....



  • Guest
You retrieved phenyl-2-nitropropene from the...
« Reply #16 on: September 18, 2003, 05:52:00 PM »
You retrieved phenyl-2-nitropropene from the toilet bowl???


  • Guest
« Reply #17 on: September 19, 2003, 12:31:00 AM »
hmm an aprote titel will bee toiletchemist, thank's for a good laugh.  ;D


  • Guest
Gives the term "shitty drugs" an...
« Reply #18 on: September 19, 2003, 01:27:00 AM »
Gives the term "shitty drugs" an entirely new meaning  8)


  • Guest
Shit happens....
« Reply #19 on: September 19, 2003, 05:33:00 AM »
...but luckily not in this toilet at this day...  ;)



  • Guest
RE: Starlight: not sure if its optimal...
« Reply #20 on: February 16, 2004, 12:47:00 PM »
I think you are absolutely right about that, starlight!
From SWIMs experience, 1.1 grams ammonium acetate works perfectly with 6ml (about 6.5 grams) benzaldehyde and an excess of 18 ml nitroethane. Refluxing this for 6 hours yields a dark cherry-red, viscous oil, distilling off the excess nitroethane and EXCESSIVE washing (up to 4 or 5 times!) with plain tap water will almost surely produce loads of crude orange crystals at some point of the procedure (even in the separatory funnel, while being drained! watch out..) The weight of this raw nitropropene amounts to 6.4 grams, recrystallisation would probably reduce the yield, but I don't know as SWIM usually keeps his raw P2NP in the freezer until needed for further investigations (they are reXtalized from boiling iPrOH as needed ;)

(yes, some of you will think that using that much nitroethane is a bad idea cuz its too precious to them, but hey, I found a source for it right around the corner in my home depot - sorry but I won't tell you! For you poor bees who don't share my knowledge, supposedly isopropyl alcohol as solvent will work as well (as long as its anhydrous)I asked SWIM 'bout that too, but he said that he never tried it... :P  ;)


  • Guest
nitro TLC
« Reply #21 on: February 18, 2004, 10:43:00 AM »
After some thought (not to much) and Hest’s suggestion, TLC is looking more and more indispensable, as starting material (3,4,5-BA) is severely limited. Any bee have some thoughts concerning suitable solvents for a TLC (commercial, on plastic) of a 3,4,5-p2np synth (cyclohexane in GAA). She doesn’t really have the option of experimenting as this is a one time event. Iodine will be used for visualization.

Is there some magic table (library/WWW)of different chromatography (TLC, column, high pressure) solvents/rates for different compounds (or “like” compounds or functional groups…) that she’s oblivious too?

Sorry if this off topic.



  • Guest
« Reply #22 on: February 18, 2004, 11:27:00 AM »
1: Get some UV-light/Blacklight.

2: Read the Paragraph "Chromatography" at Rhodium page (ner to the bottom.

3: When you have read it all ask some more, wee will still bee here


  • Guest
Try propylamine, much faster than n-butylamine
« Reply #23 on: February 19, 2004, 02:45:00 AM »
Try propylamine, much faster than n-butylamine and boil it with the benzaldehyde and the nitroethane without solvent.. when the reaction turns deep orange (1/2 h) this crystallise easily when the temperature is lovered, after the water is seperated out with a sep funnel!! the sep funnel induce crystalls from the drop drying in on the opening, just scrape this into your beaker.. this also work with ammoniumacetate and i have also did several mix with both propylamine and ammoniumacetate.. But dont put in solvent because this have to be removed before crystallisation..


  • Guest
Re: Propylamine catalyst
« Reply #24 on: February 24, 2004, 10:32:00 AM »
Grignard: could you please post some reaction details for the condensation of benzaldehyde w/nitroethane using Propylamine/NH4OAc as catalyst, especially ratio/amount of reactants, time/temperature (reflux?)? I would greatly appreciate it...

THX :)

(Doh, just overread, seems you already answered my 2nd question, 30 minutes at reflux... sorry!)


  • Guest
Nitropropene crystallisation
« Reply #25 on: February 24, 2004, 10:51:00 AM »
Oh, and since this is the "probs w/Xtalisation"-thread about nitropropenes:

If your post-reaction mixture doesn't behave like it should in terms of producing crystals, try to pour it over crushed ice, let that melt and filter to recover P2NP crystals...

I think it's the combined effects of sudden cooling, giving impurities a possibility to be "washed out" (perhaps they even "creep" into the ice? dunno..) and exposing the P2NP oil to a surface of solid crystal working as seeding crystals that makes Xtalisation happen here...

For SWIM this always works as a last effort before thinking he's fucked up and throwing away the whole shit; 'cuz workup is a bit hard due to the crystal size being very small, clogging filters, but it's always worth a try before discarding what you prepared in hours of lab work, breathing toxic fumes... :(  ::)  :)  ;D

Offline futurealchemist

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Re: Phenyl-2-nitropropene crystallization
« Reply #26 on: January 28, 2017, 04:30:55 AM »
nitro compound and aldehyde into IPA with ethylenediamine diacetate as a catalyst. allow to react at room temp for a few days and set into fridge to crystallize. voila.

Offline Tsathoggua

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Re: Phenyl-2-nitropropene crystallization
« Reply #27 on: January 28, 2017, 02:15:00 PM »
One could try TETA (triethylenetetramine) as amine catalyst, using GAA, and once the reaction is complete.

This was done with 2,5-dimethoxy-4-methylnitrostyrene, and when complete, the entirety of the reaction fluid was poured onto ice. The result, crystallized near instantly, after which, filtration at the Buchner, and then washing with H2O cleaned it up nicely. Did a final recrystallization from ice-cold MeOH, and that removed the very last traces of pumpkin-orange, which in any case formed only a slight halo around the exterior of the mass of crystals, which were filtered off from the ice/traces of ice water from its melting, in this case, whilst Tsath' has never done it with a nitropropene, formation of crystalline product was immediate.
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I'm hyperbolic, hypergolic, viral, chiral. So motherfucking twisted my laevo is on the right side.