Author Topic: Nitroethane ala Antoncho succes  (Read 1524 times)

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Bandil

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Nitroethane ala Antoncho succes
« on: December 29, 2001, 06:30:00 PM »
Hi!

Swim was in dire need for a small amount of nitroethane for a new dream with some 2,5-meo substituted alpha-methylated compunds. The nitroethane synthesis was modeled after

Post 233762 (missing)

(Antoncho: "Kitchen nitroalkane success!", Chemistry Discourse)
. Anyway here goes:

100 mL 96% H2SO4 was placed in a RBF with a stirring magnet and placed in a cold waterbath. 130 mL of den. 93% ethanol(44% excess compared to methanol, because of greater molar weight) was dripped in while stirring. When the mixure got to hot, the addition was discontinued, till it had cooled down. After all the ethanol had been added, the mixure was reddish. The mixture was heated with a reflux condesor attached and after 30 minutes, ether started boiling of rapidly. At this point swim let it cool down and poured in some 60 grammes of Na2SO4 and continued heating for some time.  Totally swim heated for 1 hrs.

After heating, the mixure was cooled and pulled through a lot of toilet paper(worked just fine) in a funnel, to give a reddish mixture.

120 g of Na2CO3 was slushed up in 350 mL 93% den. ethanol and poured in the cool mixture slowly, while stirring like a madman. After 30 mins the whole thing was added and CO2 evolution ceased.

This new mixure was strained through a cloth and the precipate was thrown in the oven and dried at 75 deg.

Yield: 110 grammes of ca. 60% NaEtSO4/NaSO4

So far so good...

After some days, 50 g og this powder was ground up really finely in a mortar and afterwards 50 g anhydr. sodium nitrite was ground aswell. This was ground up together in the mortar, till it resembled flour. This was placed in a 500 mL FBF and submerged in an oil bath. Swim set up for atm pres. distillation and started heating.

When the oil temp reached 150-160 degrees, the powder was still bone dry, but some reflux was seen. Shortly after, some liquid started coming over. The oil hit 190 degrees when this happened. After 40 minutes no more liquid came over and the reaction mixure was more "ugly", but not molten. Some discoloration was seen around the edges etc, but largely intact. The slightly yellowish liquid(looked a LOT like nitromethane), weighted 5.12 g. Swim was excited, as the reaction apparently had worked, but alas, swim made a huuuuuuuge mistage. He wanted to clean it a bit, so he mixed it with equal parts water and 1/2-2/3 dissolved, BUGGER! Swim looked up the soln. og nitroethane in water, and it was quite high...

After the wash about 2 g remained.

Swim has established success on this method, but there are some things that he need to improve:

1) Swim will let the ethanol / H2SO4 stand overnight with low heat applied to allow full conversion, and NOT make ether boil off.

2) Swim will not forget to add Na2CO3 to the final reaction mixure(although the Na2CO3 already present probably saved him from complete failure)

3) Swim will simply dry the crude nitroethane with CaCl2 and distill and skip the wash. To much was lost!!


All in all: A great synth, that requires few hard to get materials. Its a damn shame its so difficult to make such a small annoying molecule, that everyone should have lots of :)

now for my questions:
How pure does the nitroethane have to be, to work with the 2,5-DMBA condensation? Swim thinks its a lot easier to do the workup AFTER that reaction...  How sensitive is that reaction to water?

Rhodium

  • Guest
Dean-Stark trap for nitrostyrene synthesis
« Reply #1 on: December 29, 2001, 06:50:00 PM »
For the condensation step, the purity of the nitroethane is probably of no concern, as long as there are no reactive impurities (acids/bases/nitrites) in the solution, just use a little more nitroethane than directed to compensate for any impurities. Your simple distillation of the nitroethane should suffice if your goal is just to synthesize a certain nitropropene, and aren't obsessed with the highest yields possible.

The reaction is water-sensitive in a way that too much water may lower the yield due to Le Chatelieres principle. What method were you planning to use for the condensation?

If you dissolve the reactants (say 0.1 mole benzaldehyde, 0.125 moles nitroethane and a few mol% of an amine catalyst) in 100ml toluene or benzene, and then reflux the mixture for a few hours (3-4?) under constant removal of water from the reaction mixture (Using a Dean-stark trap*), then water in your reactants is no issue, at is continuosly removed and caught in the trap. Workup as usual, evaporate the solvent and follow the procedure used in the appropriate Pihkal entry.

* The dean-stark trap isolates all the water that is carried away as the azeotrope with the toluene/benzene and collects it in a little pocket. I guess there are many ways to improvise such an apparatus if you don't have one handy. Here is a picture of such a trap, and a websearch gives detailed descriptions of its use.




yellium

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Re: Nitroethane ala Antoncho succes
« Reply #2 on: December 29, 2001, 09:38:00 PM »
Even impure aldehyde is not that much of a problem if you got the nitrostyrene/LAH route, as long as it is the right aldehyde, with some unreacted other gunk. The final acid/base wash does wonders.


terbium

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Re: Nitroethane ala Antoncho succes
« Reply #3 on: December 29, 2001, 11:32:00 PM »
Also instructive in the photo is what they are using to insulate the arm of the Dean-Stark trap ... or, more precisely, what they are not using - they are not using aluminum foil.

Rhodium

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Re: Nitroethane ala Antoncho succes
« Reply #4 on: December 30, 2001, 12:53:00 AM »
I get all your Al foil arguments you have mentioned earlier Terbium, but in my personal experience, the tube has a very hard time on its own to transfer the vapors to the condenser, but if it is tightly wrapped in Al foil, the vapors readily reach the condenser to reflux.

Glass wool and stuff like that insulates probably better, but Al foil does a good job in my opinion.


Goodtimes

  • Guest
Re: Nitroethane ala Antoncho succes
« Reply #5 on: December 30, 2001, 05:48:00 AM »
Nice pic Chief..  always wondered what a Dean-stark looked like..

thx!  :)

"The gods are too fond of a joke."  (Aristotle)


Antoncho

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Re: Nitroethane ala Antoncho succes
« Reply #6 on: December 30, 2001, 06:53:00 AM »
Congratulations, Bandil!

Shall we call it an established victory now ;)

Just for the record - your yield was ~34%, better than in previously described attempt,
and i think it's not the upper limit - higher ethylsulfate content will certainly (IMHO) bee good for this rxn.

We now really should further optimize HEtSO4 process, i think.

My best wishes,

Antoncho