ChemicalSolution (Hive Bee)
02-22-02 08:27
No 271880
      nitroethane density problems  Bookmark   

SWIM has made 2 batches of nitroethane from etBr/NaNO2 in DMSO.  In both cases, the product was distilled under reduced pressure.  The density is around 2g/ml!!?!?!?

So SWIM fractionally distilled again under atmospheric pressure.. Now she has around 40mL of nitroethane that weighs (still!) 80g.

What the heck is going on here?

xoxo
julia
 
 
 
 
    Rhodium
(Chief Bee)
02-22-02 14:21
No 271998
      Re: nitroethane density problems  Bookmark   

Strange! Nitroethane has a density of 1.05 and ethyl bromide 1.46 - you must have something really interresting in your flask, or a broken scale.
 
 
 
 
    hypo
(Hive Bee)
02-22-02 14:25
No 272000
      Re: nitroethane density problems  Bookmark   

that brings me to a question: i heard of a guy who washed his EtBr with conc. H2SO4. but the EtBr definitely formed the lower layer. how can this be?
 
 
 
 
    Rhodium
(Chief Bee)
02-22-02 14:41
No 272002
      Re: nitroethane density problems  Bookmark   

Either the sulfuric was dilute (and thus lighter), or somehow there is a really heavy contaminant in your ethyl bromide, like polyhalogenates.
 
 
 
 
    hypo
(Hive Bee)
02-22-02 14:49
No 272004
      Re: nitroethane density problems  Bookmark   

right. i forgot about the possibility that the crude EtBr was full with EtOH and maybe some Et2O, which dissolved in the H2SO4 layer making it lighter. (some heat evolved when adding the H2SO4).
 
 
 
 
    ChemicalSolution
(Hive Bee)
02-23-02 09:37
No 272433
      Re: nitroethane density problems  Bookmark   

SWIM's scale is on the money.. 25ml of water weighs 25g and a nickle weighs 5g..

This one is some kind of mystery..

So, bees, what do you think?  Should she use this stuff in a Knoevenagel reaction?  If she does, she'll use the nitroethane by volume, and not by weight.

Julia
 
 
 
 
    terbium
(Old P2P Cook)
02-23-02 10:27
No 272453
      Re: nitroethane density problems  Bookmark   

Should she use this stuff in a Knoevenagel reaction?
Nope. If your density measurements are correct then you definitely don't have nitroethane or any other nitroalkane.

You need to go back and figure out where things went wrong. How do you know that you had ethyl bromide? What was the density of your ethyl bromide?
 
 
 
 
    ChemicalSolution
(Hive Bee)
02-24-02 00:24
No 272664
      Re: nitroethane density problems  Bookmark   

The ethylbromide was purchased...

This product boils around 114,  and is an oily, water-white liquid that coats the flask when swirled.  It has a somewhat sweet scent that reminds SWIM if nitromethane, only a little stronger..

Forget about the Knoevenagle, SWIM is just curious to find out just what is in her flask.  Density of 2g!!!  This stuff is more dense than sulfuric...  What could it be?

Julia
 
 
 
 
    Antoncho
(Official Hive Translator)
02-24-02 06:50
No 272791
      Re: nitroethane density problems  Bookmark   

..... definitely smth w/a bromine atom or two in it....

BTW, is there any reported successes at all w/this route? I know, SWIRitter did it w/some phloroglucinol, but IIRC, there has been several failure reports when using no nitrite scavengers (Julia, can you bee more precise on what you did? We need to find out what's happened, after all!)

Antoncho
 
 
 
 
    ChemicalSolution
(Hive Bee)
02-25-02 06:24
No 273192
      Re: nitroethane density problems  Bookmark   

The reaction went by adding etBr to a stirred solution of NaNO2 in DMSO.  This was stirred @ room temp until an thick emulsion formed.

Two different scales were used-- no difference was found between larger and smaller scales as far as reaction details and product.

No catechol was used... But in the JOG article, none was used either.

This is really blowing SWIM's mind!!  A double-distilled liquid that has all the properties of nitroethane right down to the oily texture and fruity smell.. EXCEPT the density..

Speaking of smell, can anyone confirm that nitroethane has a sweet smell that is a little stronger than nitromethane?

To all the brains:  Any ideas on how to 'purify' this dense nitroethane???  Fractional distillation did not help one bit.

xoxo
Julia
 
 
 
 
    Mountain_Girl
(Stranger)
02-25-02 09:39
No 273255
      Re: nitroethane density problems  Bookmark   

As a rule of thumb, organic compounds usually have a density between 800 and about 1000 kg/m3, unless they are halogenated or have some other heavy atom. Therefore your "nitroethane" may contain quite a bit of some other brominated compound that has increased the density of the mixture to 2 g/l. But I guess we've already figured that out...
I'm thinking that this alien compound may also be adding insult to injury by forming an azeotrope with the nitroethane. If this is the case then maybe you can add water to the mix and distill off the nitroethane/water azeotrope (bp 87C, 71% nitroethane). Hopefully the contaminant will remain behind and the distillate can be dried afterwards with MgSO4 or something. In other words, an analogous process to that used for removing water from ethanol by using C6H6 to break the azeotrope.
 
 
 
 
    Antoncho
(Official Hive Translator)
02-26-02 08:24
No 273658
      Re: nitroethane density problems  Bookmark   

Sorry for not mentioning this earlier, but - a nice way to purify your nitro would bee to dissolve it in alkali - it forms a salt, then carefully acidifying which you'll get it back.

A usual test for aliphatic nitrothings is addition of ethanolic NaOH - i'm not sure, but i think the salt thus formed is insoluble in EtOH, so may bee separated.

Of course, there'll bee some loss in the rxn - but the lowest yield they get when doing this w/any nitroalkane is 80% - of course, when inversely done - adding nitrosalt to acid will result in its coversion to aldehyde - Nef rxn.

Hope that helps - keep us informed, please!wink

Antoncho
 
 
 
 
    ChemicalSolution
(Hive Bee)
02-26-02 12:02
No 273728
      Re: nitroethane density problems  Bookmark   

Antoncho--  It would bee GREAT if you could give Julia a detailed procedure of this method of purification!!

xoxo
Julia
 
 
 
 
    Antoncho
(Official Hive Translator)
02-26-02 13:53
No 273759
      Re: nitroethane density problems  Bookmark   

Oh dearest Julia!

I can't give you a detailed proc. - in fact, i never heard anyone use this route to purify nitroalkane. But it definitely must work. All nitroalkanes are acidic in nature and react w/alkalis, forming water-soluble salts (explosive when dry!). I ain't sure 'bout the alc. NaOH test - but i frequently seen mentions of it in the old Russian books - unfortunately, they never said what is actually the result of the test, but it's been my impression that a precipitate.

The whole idea is to slowly w/stirring and cooling drop nitro into aq. alkali (the experimental part for that can bee found in the link below), clean out the impurities (like by xtraction or separation or whatever) and then carefully acidify it, also w/good stirring, salt out, separate. The competing rxn is Nef rxn of the nitro to (acet)aldehyde - it is the prevalent one when adding salt to acid. See ../rhodium/chemistry /nef.html for the details.

Anyway, testing this on a small qtty of your product won't hurtwink

Antoncho

P.S. Rhodium, if you're reading this - the link at your page says 'nitroalkenes', not 'nitroalkanes' as it should beeblush
 
 
 
 
    cheeseboy
(cheese head)
02-27-02 08:06
No 274111
      Re: nitroethane density problems  Bookmark   

Mt.Girl sounds like she knows what's going on. Did you try a slough of different tests on it to see what happens? Brainstorm...this can bee solvented, solved.Try freezing it and seeing what happens and at what temps.

         May The Source Bee With You...Always.