P2NP Question

[wolfram]

The procedure here come from www.rhodium.ws thank you all mighty Rhodium.


First some NO2Et..

https://www.thevespiary.org/rhodium/Rhodium/chemistry/nitroalkane.html

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"1.5 mole sodium nitrite (103.5g) is intimately mixed with 1 mole of sodium ethyl sulfate (158g) and 0.0625 moles of K2CO3 (8.6g). The mixture is then heated to 125-130°C, at which temperature the nitroethane distills over as soon as it is formed..."
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Q.1: What is the K2CO3 doing there?

W: One mole of of sodium ethyl sulfate is 148g not 158g!


Now P2NP...

https://www.thevespiary.org/rhodium/Rhodium/chemistry/phenyl-2-nitropropene.html

"A solution of benzaldehyde (6.4 g) and ammonium acetate (1.0 g) in nitroethane (20 mL) was heated to reflux for 5 h...."

Q.2: As I can see the amount of NO2Et over BzA is 4 times greater in moles why?? NO2Et is not very aviable for most people.. What would happen if the procedure was modified to unimolar amount of BzA and NO2Et? With maybee some EtOH or HAc as solvent?

[Bandil]

Swim has tried that nitroalkane synth, and it is quite difficult to get proper(if any) yields from.

Anyhow, they simply use the nitroalkane as a solvent, which is quite a waste seen from a basementchemists viewpoint. A nice way to get around this is to either do the reaction in GAA with ammoniumacetate as catalyst or use the IPA/methylamine scheme. Both give decent yields with approximately 1.1 eq of the nitroalkane.

There are lots of information about this topic on this site, so search away!

Regards
Bandil

[Antibody2]

K2CO3 is your catalyst (you will cry when you see how liitle the yeild from that reaction is especially if you made your own sodium ethyl sulfate, which is LOTS of work) the key to increasing yeilds is that it is very well mixed and finely ground.

When swim wants to condense an aldehyde with a nitroalkane Ab2 uses the NaOH catalyzed rxn in MeOH. It is high yeilding and hard to screw it up.

https://www.thevespiary.org/rhodium/Rhodium/chemistry/mdp2np.html

(never understood why bees make that rxn more complicated than it needs to bee using all manner of exotic catalysts, reflux et al.)

[Antoncho]

That 'cold' method of condensation never worked neither for SWIM, nor for several HyperLab bees when it came to nitroethane.

In

https://www.thevespiary.org/rhodium/Rhodium/chemistry/nitrostyrenes.gairaud-lappin.html

they say:

...alcoholic potassium hydroxide gave generally poor results with most substituted benzaldehydes in the reaction with nitromethane and was completely unsuccessful with nitroethane and 1-nitropropane.

...and i'm pretty much convinced at this point that it is indeed the case. I also want to point out that in ALL literature sources to that rxn i ever saw they used strictly nitromethane, that doc at Rh's being the only confusing exception.



Antoncho

P.S. And one more thing - that NaEtSO4 EtNO2 preparation does produce miserable yields, the highest one achieved thus far being ~16%

[Antibody2]

Ab2 never triied it with nitroethane, only with nitromethane as you mention antoncho, BUT aqueous NaOH was used and the yeilds were always impressive (ca 80%) with both 2,5-DMNS and 2,3-DM,4,5-MDNS.

Ab2 just assumed that since the ref on Rhodiums site used nitroethane that it worked equally well for nitropropenes. thanks for the heads up

[Grignard]

I have always used the benzaldehyde and nitroethane in 1:1 molar ratio, but i use nitroethane in 10% exess to get rid of most of the aldehyde. then ads ammoniumacetate and boil under reflux to the solution gets clear orange/red. But the problem with the whole prosess is the reduction of this f.... styrene.    

[hest]

This might bee an interesting thread.
For the condensation all the reactions work, but it’s the 95% yield there is a problem (and if you have made the aldehyde from scratch it’s quite important)
My personal experience is. (wit the DOM TMA-2 TMA-6 Aldehyde.) [for some reason 2,5-BA goes in 95% no mather how bad you doo it.)
Reflux in nitroethane 70-90%
Reflux in GAA 60-70%
IPA and ultrasound 40-80% (40 in large scale)
1:1 MW 50-95%, but polymerization is fast (you have to stop at the right point)
50° 1:1 with some IPA and MeAm 50-95%

The reduction is done by the nitropropene ->Nitropropane->Amine.
Reduction off the dob.bond with NaBH4 in Alcohole or two phase system works great.
Red of the nitro with Pd/C and H2 works from time to time(95%) with Zn/GAA every time (50-70%)

The safe way is refluxing the aldehyde in nitroethane, reduce the dob.bond with NaBH4 and reduce the nitro with Zn/GAA. Yield not high but it works.


I would love to here from some other’s bee’s about this subject

[Grignard]

I also observed the polymerisation, but i always stop the rx before it gets to red. maybe a litle unprofessional but it works.. I Tryed to condesate with propylamine instead of ammoniumacetate, it`s very fast but its a lot of polymerisation and its wery important to stop at the right moment, but the yeld is pretty good (no exact % yet). The sodium borohydride is a great reduction, but it`s very very hard to get an hold of that stuff .

[silenziox]

IPA and ultrasound 40-80% (40 in large scale)
1:1 MW 50-95%, but polymerization is fast (you have to stop at the right point)

Ive never experienced any polymerization when sonicating and the yeilds corresponds to the literature even in large (over 50mol scale):

https://www.thevespiary.org/rhodium/Rhodium/chemistry/nitrostyrene.ultrasound.htm

(Works great with nitropropenes also...)

... But then again, I've never used IPA  

[starlight]

hest is referring to microwaves, not sonication when he talks about polymerisation.

[hest]

And don't miss this post, it all about aldehyde + nitro(m)ethane

Post 419399

(Barium: "High-yielding nitrostyrene catalyst", Methods Discourse)

[starlight]

hest is right to point you to barium's method. After some initially poor results, but continuing encouragement from others, I have found this to be the best approach for many substrates.

Have however found poor yields and purity when using 20% aqueous methylamine, but excellent yields and purity with alcoholic methylamine made with KOH/MeNH2.HCl