Hi!
(keywords: EtNO2, nitroethane, nitroalkane, nitrite, ethylsulfate, NaEtSO4, NaMeSO4)
Well, you see… Na2SO4, of course, is needed to abdorb water….. And one mole of it absorbs 10moles of H2O, BUT.
1) The rationale beehind using 5x xcess was that Na2SO4, however thoroughly you grind it, won’t bee exactly in “finely dispersed state” and I feared that the hydrated salt on the surface of the granules might prevent it from reacting further.
2) The second rationale is that the more dehydrating agent you use, the faster the rxn goes. It seems to take long enough all by itself.
Please note that I don’t know for SURE neither of the above since neither myself nor anyone else did any analysis of the rxn thus far. SWIM just figured those proportions and durations would work and they did. You may improvize at your own risk if you want to, though
Now I want to say a couple of things that I never said earlier, although I definitely should have
Please forgive me for that, I was planning to work some more on the reaction and then submit the ‘final’ version to the Hive. I haven’t achieved what I planned yet, been too busy w/other stuff. But since you decided to do this, I’ll tell you some things that will bee undoubtedly helpful.
1) Excessive heating ruins the nitroethane. That is, you can just turn your heater ‘full throttle’ when you do this on MeNO2 and bee fine. But not w/EtNO2. If you heat it above, say, 150 C (the precise temp hasn’t been found out yet – but as the doc on Rh’s about EtONO à EtNO2 conversion suggests, that should bee the critical temp), you’ll get a product contaminated w/all sorts of shit, w/EtNO2 content <40%
2) Unfortunately, since EtNO2 has a rather high bp, it makes it rather difficult to distill it out of the rxn – although, who knows, maybee there is a thin temp margin when you can pull it out and still not ruin it. It’s just we haven’t found it yet. If you have a vacuum source, definitely use it.
Work-up of the rxn by mixing w/water and xtracting w/pet ether is feasible as well, SWIM just never got to it (yet). Probably, this is the best avenue to take at the present state of affairs. Just remember not to overheat it. Drying w/CaCl2 and re-distilling the crude product is also a must. Too bad that it takes really huge amts of salts to produce miserable qtties of the product, so you might have to do this several times bee4 you collect enough to make drying and redistilling feasible.
3) The purer NaEtSO4 you use, the better (less junk to hold the product vapours). It is probably also very important not to overbasify your ethylsulfate when you prepare it (nitroalkanes form salts w/alkalis) . Remember, you can’t overacidify it either since it will ruin all of your NaEtSO4 product rather quickly, although not as quickly if you do that in EtOH (which I advise you to do by all accounts). Lesson: at the last stages of neutralization measure pH literally every second.
4) There is another problem w/the neutralization stage. Unlike w/MeOH, EtOH dissolves significantly less NaOH and huge qtties of alcohol would bee required to dissolve the needed amt. But if you just leave alkali undissolved in the alcohol, it will form a fine suspension that will react w/the acid only gradually, making it very difficult to carefully monitor the pH. That is, the mixtr beecomes acidic and after some time turns basic again – at least, that’s what SWIM saw.
Now KOH is much better soluble in EtOH so maybee it would bee advisable to use it instead.
It is unclear how well it will beehave instead of Na salt, but comrades
Ennarkont & DMMDA reported a 54% yield of crude (rather impure, as turned later) from pure (reagent grade) KEtSO4.
5) SWIM had an idea of performing this rxn in some high-boiling solvt to circumvent the disadvantages of horrible heterogenicity (solid reacting with solid) – he tried glycerol, planning to simply xtract the rxn w/pet ether afterwards (glycerol isn’t miscible w/naphta, so isn’t DMSO. Unfortunately, DMF mixes w/it. SWIM has no DMSO, alas). Well, the only thing he can say is: use a vessel MUCH larger the the rxn contents. It will foamingly expand enormously and fill all of your apparatus, including the condenser.
Apart from that, I think this idea has a great potential, in terms of improving the yields.
6) And the last thing I want to say – when you get your EtNO2, use the ‘classical’ method in GAA to condense it w/a BA of your choice. The ‘cold’ method that works beautifully w/MeNO2 has been reported to give _oiling_out_ nitropropene even w/a reagent grade EtNO2 (that is still confusing, since evidently it can bee made to work according to the proc on Rh’s; maybee it is specific of 2,5-diMeO-Ph-nitropropene that Ennarkont and DMMDA tried to prepare. Anyhow, that won’t bee a 100% positive test for your nitroethane purity).
That’s all I have to say; bee certain to report your results!
Antoncho