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jimwig
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[*] posted on 28-10-2005 at 12:24
nitroethane - and again


"Expertiment 104 - Preparation of nitro.ethane,C2H5-NO2 from ethyl iodide.

The silver iodide is prepared by adding a slight excess of a lukewarm concentrated solution of potassium nitrite to a similar solution of silver nitrate and allowing the mixture to cool. The precipitate of silver nitrite is colledted on a filter, washed rapidly, and dried on a porous plate.

42 grm. of dry silver nitrite are placed in a round.bottomed flask fitted with a reflux condensor, and 34 grm. of ethyl iodide are added gradulally through the condensor tube. During the process the flask is not distrued, as it is imporant that the silver nitrite should be gradually penetrated by the iodide. The latter is admitted at such a rate that the liquid boils vigorously, but not too violently. The mixture is finaly warmed for some time on the water bath , and the products seperated by fractional distillation. Ethyl nitrite , boiling point 18C, distils over first, and afterwards nitro-ethane is collected at 110-114C. Yield 8-9grm. ie 50 percent of theory.


When pure itis a colorless liquid. Boiling point, 113-114C. D1.058"

Practical Organic Chemistry
Sudborough/James

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Any thoughts and is this book avialble online? If not I will scan in the future.
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[*] posted on 7-11-2005 at 14:04


cool! The yield is down quite a bit from the same reation done in ether, but ether is a pita, and with some recycling the yield loss may not be a big deal. At the end of the reaction and distillation, you should be left with silver iodide right? recover the silver with metallic copper and then -- heres what I'm thinking -- react the copper iodide with sulfuric acid and anhydrous ethanol to get ethyl bromide so the reaction can be undertaken again. This would seem to make this reaction very economical to my way of thinking. Any thoughts?
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[*] posted on 8-11-2005 at 06:20


I have the feeling copper(I) iodide would be produced and this would complicate things. Might be worth checking the yeild from sodium nitrite directly. This might only be useful if you can do the reaction in DMSO though.
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[*] posted on 8-11-2005 at 08:23


Nitroethane is produced in significant yield from sodium nitrite solution containing a small amount of sulfanilic acid as a surfactant / catalyst , shaken
for hours with diethyl sulfate . Niromethane is gotten by substituting
dimethyl sulfate . A mechanical shaker
must be used and a glass gallon jug no more than about one third full of the reaction mixture , with agitation conditions which cause churning of the mixture into an emulsion . A teflon closure and teflon vent line must be provided to allow for pressure relief continuously from the reaction mixture .
After several hours of the mixture being shaken , a single phase will result and
this is vacuum distilled to obtain the nitroethane or nitromethane . It is urgently important that the distillation apparatus be purged of air before any
heating is applied for the distillation ,
and even more essential that the closed
system be allowed to cool down completely and further purged of any residual vapors from the vacuum distillation before being opened to the atmosphere , or an explosion will result
which will destroy the apparatus , arising from the pyrophoric nature of the vapors .
It is believed that the residual vapors which present this danger of pyrophoric
ignition are the byproduct ethyl or methyl nitrite esters along with nitrogen oxides
mixed with of course vapors of the main product which is desired from the reaction . A good yield is produced by the reaction , but it is hazardous .
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[*] posted on 8-11-2005 at 15:52


Marvin, maybe there was some confusion, I wasn't thinking of some insitu regeneration, but merely recovering the iodide post reaction to start again, batchwise. Iodide is somewhat dear.

Rosco, excellent details you have there. Nice to know about the dangers presented by the byproducts. Is the pressure what makes your reaction more dangerous, or does it have something to do with that your reaction is aqueous and carries more byproducts to the distillation?

[Edited on 8-11-2005 by skippy]
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Rosco Bodine
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[*] posted on 8-11-2005 at 16:28


The danger resides with the notoriously unstable nitrite esters which are dangerous enough under the best conditions , and distillation aggravayes their instability greatly . The ice cold and pure nitrite esters will generate red fumes when exposed to air , and those fumes are decomposition products , nitrogen oxides mixed with vapors of the
undecomposed nitrite , which at even slightly elevated temperatures or in a
ratio and vapor density which is concentrated as in a closed apparatus ,
can be pyrophoric . You could conduct the distillation to endpoint and believe all danger is past , release the vacuum and
the rush of incoming air will result in an ignition and explosion of the vapors .

Hey , if anybody doesn't believe this ,
and you want to experiment ....go ahead and try it , but I have personally seen this happen and the color of the flash is orange at the center of the flying fragments of glassware . It will also generate a noxious dense cloud of toxic vapor and acrid smoke .
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[*] posted on 8-11-2005 at 18:32


I believe you! Does this mean that this procedure (found in google cache of old synthetikal's hive archive) is foolishly dangerous? Its workup is entirely atmospheric! Maybe the ether vapours dilute the nitrous esters and nitrogen oxide to the point where they won't spontaneously combust... but preventing pyrophoric phemomenon with ethyl ether vapours seems kind of sketchy!

For what its worth the fellow claimed to have made a liter of nitroethane following it though...

(whole thing quoted for posterity's sake)


"
karel
(Newbee)
04-25-04 10:31
No 502896

Nitroethane synthesis

I also attepted to synth nitroethane from EtBr and NaNO2 in DMSO with bad yield. I can recommend reaction of EtBr with dry AgNO2 in dry Et2O, which fully satisfied SWIM and gave him about 80 % yield.
It's not difficult to transform AgBr back to AgNO2 (you need zinc wire, HNO3, and NaNO2), SWIM made about a liter of EtNO2 from several hundred grams of AgNO3 (from which AgNO2 is produced).

"


"
karel
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04-25-04 16:29
No 503001

Nitroethane synthesis
(Rated as: excellent)

The procedure in Org. Synth., Coll. Vol. 4, 724 (http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0724) was followed with 2 mol EtBr and 2 mol AgNO2. Distillation of the reaction mixture at atmospheric pressure gave ether contamined with EtONO and NOx as a forerun and then 75-80 % yield of EtNO2 boiling at 108-112 C.

Ether containing EtONO was attempted to purify by shaking with dilute HCl and water. Drying with NaOH and then with metallic Na led to reduction of leftovers of nitrogen impurities to ammonia, which was precipitated with concd H2SO4. Ether was after drying with NaOH and then with Na suitable for using in the reaction.
I assume that low-boiling petroleum ether could be good substute for ether, but I didn't try it.

The AgBr precipitate*, which was filtered from the reaction mixture, was allowed to dry in air and suspended in 1000 ml hot water. Diluted H2SO4 was added to destroy nonreacted AgNO2 and NOx were allowed to escape. The addition of H2SO4 was repeated at times to maintain the solution acidic. To slightly acidic hot solution was then added zinc wire** of diameter 3-5 mm. It is advantageous to use this wire as a stirring rod. Immediately after the wire reached the AgBr precipitate, the reduction of black Ag occured at the point of contact. After several hours the reaction was finished; it was necessary to keep solution acidic by occasional addition of H2SO4. Reduced Ag formed characteristic light gray precipitate, which was dried in air.
This Ag was dissoved in cca 20 % HNO3, solution was shortly boiled to remove NOx and excess acid was carefully neutralized with diluted NaOH. The neutral solution was suitable for production of next batch of AgNO2 (see Org. Synth. procedure).

* The mother liquor and washing liquors from AgNO2 preparation were collected and excess of NaCl solution was added to them. Precipitated AgCl was then added to AgBr, so the overall lost of Ag at this 2 molar scale was lower than 1 g.

** Zinc wire was used in excess. It was found to be much better than zinc powder. If slight contamination of Ag with carbon doesn't matter, the steel wire could be also used, but I didn't try it.

"
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[*] posted on 8-11-2005 at 18:43


Rosco, that is an interesting procedure. I have never heard of it before and I've read plenty of articles on nitroalkane production. Is it from a patent? Something you worked out yourself? If you have more detailed notes on procedure and yield I'd be very interested in seeing them.



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Rosco Bodine
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[*] posted on 8-11-2005 at 19:53


The method was published in a major
English language journal , maybe JACS or
JOC .....I don't remember . It was a pretty
old article , but I think more recent than
1940 , maybe late 50's or early 60's , wish I could be more specific . IIRC it was a pretty detailed article with charted results of many experiments , and I believe the publication was indexed in
Chem Abstracts under a general search results for " nitroethane " . Anybody
doing some digging can find it .

But I'll level with you about all these similar methods where a certain amount of the nitrite ester which is isomeric with
the nitroalkane is produced as a mixed product to be separated by distillation .
Such distillations are inherently dangerous and not any work for the uninformed or novices who think they are handling benign materials . What is actually being done is the distillation of
an inherently unstable and explosive mixture and it must be handled as such
with proper purging and complete cooldown before exposing to atmosphere , preferably releasing the vacuum to something other than air ,
maybe CO2 or nitrogen or natural gas or propane ....anything to purge the system
before opening it . Complete cooldown
alone minimizes the risk , but personally
I'd never trust it to that alone . This is one of those times when even a small flow of nitrogen or natural gas through
a bleed tube capillary in the distillation flask , would not be a bad idea to keep
some constant ventilation throughput
to the aspirator and down the drain with
the unstable stuff , keeping its concentration lower in the system through
the entire distillation .

Glass shrapnel is generally rough on the complexion , and the babes aren't attracted by the life after napalm look :D
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[*] posted on 8-11-2005 at 20:02


I was wondering this in the past - shouldn't it be possible to convert the nitromethane (I don't know if it works for higher nitroalkanes) with NaOH to Na-nitronate, which precipitates, is filtered, washed, and converted back to nitromethane by adding the correct amount of i.e. H2SO4, which then drops out of solution as it is insoluble?
I don't know the potential reactions of alkane nitrites with NaOH, but to my knowledge it wouldn't react.

Also, I always was under the impression that the nitrite alkanes are fairly stable, i.e. isn't isopropylnitrite made for hydrazine production? Why would isopropylnitrite be safe, but not ethylnitrite?

Or am I mixing something up?

Also, please be aware of the more generic nitroalkane thread.




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Rosco Bodine
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[*] posted on 8-11-2005 at 20:19


The stability of the nitrite esters is better when they are cold pure liquids . And they are probably okay as vapors in small diameter tubes in the absence of air or oxidizing levels of nitrogen oxides . But under distillation conditions there is a hasty departure from those conditions to different conditions where the materials become dangerous . It is possible where ether is added to the mixture that the escaping fumes of ether are acting to dilute and purge any accumulation of vapors which in the absence of the ether
could be explosive .
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[*] posted on 8-11-2005 at 20:37


Another thing - at the end of the reaction between the (m)ethylsulphate with NaNO2, before destillation, maybe adding urea to eliminate NOx might be good.
Or, simply distill under very low pressure?

Anyway, I mentioned purification methods other than destillation above, although I have not tested it whether it'd work. Are there any other chemical methods? Anyone?




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Rosco Bodine
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[*] posted on 8-11-2005 at 21:08


The reaction producing the nitroethane may be continuing in the distillation flask as the distillation proceeds , so it may kill the yields to try to eliminate the nitrite ester or strip the nitrogen oxides chemically .

The article which I was following didn't
happen to mention the distillation hazard ,
just as certain details are often not covered in scientific literature or patents ,
but one learns of these things as they reveal themselves . But just because something isn't spelled out in the literature , doesn't mean there isn't more to the story than what you read . That applies to any of these references where there may or may not be all the pertinent details disclosed in publication which is in some cases deliberately kept general , or as brief as possible . There may be several pages edited out from the original
submission , which nobody but the submitters and the editors ever see .
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[*] posted on 11-11-2005 at 12:15


Is it really possible to recycle the silver iodide using magnesium? Silver iodide's solubility in water is extremely low.
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[*] posted on 11-11-2005 at 13:32


Hum, as a matter of fact you could, by Goldschmidt-style reacting it. You'll probably lose a whole lot of reagent (by which I mean ALL) because Ag is so much less reactive than Mg. Fleaker can tell you about the dynamics of the analogous reaction using oxide instead of iodide. :D

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[*] posted on 17-10-2006 at 14:11
synthesis of ethyl nitrite then conversion to nitroethane


Hello all. ok i know this is one out of 1 million nitroethane threads but i wasnt sure wich one to add onto. plus i havnt seen this idea presented yet...

my computer is acting funny so these methods may be a little messy because they are from memory.

Ethyl nitrite can be produced by running NOCl through a dilute ethanol solution (or something like that)

us pat:2615896

Ok, i havnt tried that but i got it from the merk manual. can anyone verify it? NOCl is easy enough to produce...

then running ethyl nitrite over asbestos (?) at elevated temps is suppose to isomerize it to nitroethane. does anyone know of a better method? or anyfeedback on how dificult this could be (dangers etc)

http://books.google.com/books?vid=LCCN22014438&id=jq_4_WhqQlcC&pg=PA521&dq=J.+++Chem.+++Soc.+++109,+701+(1916)


sorry if this has been brought up before.
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[*] posted on 17-10-2006 at 14:24


Actually it has all been brought up...

Check the isobutyl/isopropyl/ isoamyl/amylnitrite threads.

Nothing complicated required, just NaNO2, HCl and the alcohol, and direct esterification of the alcohol ensues to form ethyl/substitute nitrite.

Conversion to the nitro-form is never easy.. easier to start with ethylsulfate and NaNO2 ...

Merged with the nitroethane thread.




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[*] posted on 12-9-2008 at 15:25


Hmm, so I attempted the procedure detailed in the first post and had no reaction whatsoever. The EtBr was freshly prepared, as was the AgNO2. I understand EtI is slightly more reactive than EtBr, but should EtBr not show a reaction? The AgNO2 appeared to soak up the EtBr and there was no way for it to boil, any ideas?



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[*] posted on 13-9-2008 at 02:56


Dry ether is supposed to be used as a solvent.

"Cool 100 g of silver nitrite (0.65 mol) in 150 ml of dry ether to 0°C in a 3 neck 500 ml flask (in a darkened room or using yellow light). Add 0.5 moles of ethyl halide (78g ethyl iodide or 55g of ethyl bromide) dropwise over a 2 hour period while stirring constantly and maintaining the temperature at 0°C and dark conditions. Stir for 24 hours at 0°C, then 24 hours at room temp if using ethyl bromide, and 48h if using ethyl bromide.

Silver iodide (or bromide) will precipitate in the solution during the course of the reaction. Filter off the silver salt, and wash it with several portions of ether. Evaporate the ether at room temperature. (This may be substituted with distillation of the ether using a water bath at atmospheric pressure. A 2x45 cm column packed with 4 mm pyrex helices is used. A more efficient column is not used due to the instability of the ethyl nitrite formed as a by-product in the reaction. Maintain anhydrous conditions since the ethyl nitrite will hydrolyze to ethanol and will be difficult to separate.) Then vacuum distill the residue at about 5 mmHg. The ethyl nitrite will be the initial fraction, followed by an intermediate fraction, then the nitroethane will distill. The yield is about 83% of theory."

(From one of the pages on rhodium - I appreciate this is not the best source.)


[Edited on 13-9-2008 by DJF90]
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[*] posted on 14-9-2008 at 02:17


Quote:
Originally posted by Douchermann
Hmm, so I attempted the procedure detailed in the first post and had no reaction whatsoever. The EtBr was freshly prepared, as was the AgNO2. I understand EtI is slightly more reactive than EtBr, but should EtBr not show a reaction? The AgNO2 appeared to soak up the EtBr and there was no way for it to boil, any ideas?


one would imagine that either this is a case where the iodide reacts differently or not at all cf the bromide or your technique requires refinement. Bromides are poorer leaving groups but in many cases this is negated cf the iodide because of steric hinderances in sn2 reactions with iodides. Although sn2's appear very simple mechanistically nothing is ever very simple.
If i were you i would make the ethyl iodide, establish using this reagent that the reaction functions as per the paper, then move on to using the bromide and optimizing that. Remeber by switching to the bromide here you are not only changing leaving groups but solvent also.
I do not understand why they are using the ethyl iodide as a solvent instead of dry ether as is normal with silver salt based sn2's, but one could imagine a better variant on the technique would be to get everything to like -30C in a salt bath then add the two together completely, seal the flask and allow to come to temperature over about 24hrs, swirling on occasion. Another 24hrs at RT or if you are keen reflux, minding though that as nitroethane forms the reflux temperature would increase close to the sublimation point of iodine and vapour may exit.




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[*] posted on 15-9-2008 at 14:03


Would using the safer Di(M)ethyl Carbonate instead of Di(M)ethyl Sulfate on the classic DMS/DES + H2O + NaNO2 + stirring in a closed bottle, yield any nitroalkane?
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[*] posted on 15-9-2008 at 16:35


Quote:
Originally posted by Douchermann
Hmm, so I attempted the procedure detailed in the first post and had no reaction whatsoever. The EtBr


Maybe if ethyl bromide had a higher boiling point, it would react. The lack of reaction was noted in the original literature.

http://books.google.com/books?id=jegMAAAAYAAJ&pg=PA240&a...

[Edited on 15-9-2008 by S.C. Wack]
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[*] posted on 17-9-2008 at 14:11


New question then. If the reaction using ether as a solvent was not completely anhydrous, would the water prevent the reaction from proceeding? or would it just turn some of the EtONO into ethanol.



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[*] posted on 17-9-2008 at 16:07


the nitrite is a most complicated of species to attempt an SN2 with, its resonance structure indicates to every atom having some significant activity towards 'backside attack' . However the nitrogen is the favoured, but taken into account there are double the no of oxygens immediately doubling your number of collisions, also the nitrogen is somewhat sterically hindered compared with the oxygen however this is a lesser consideration. It can be seen it would not take much for the balance to shift either way.

If you look a the water site i referenced in misc you will see how complicated water is and in this instance water molecules help's hydrating the nitrite ion helps orientate the molecule to favour the oxygen nucleophiles, once substituted as the nitrite the hydrated water performs a further substitution and you end up with ethanol. In cases where there is gross amounts of water the nitrite substitution would be limited completely in favour of water. There is a italian paper published this decade which claims to make short chain alkyl nitro compouinds with the inclusion of water but this to me seemed ridiculous and obviously leaving out something, there work as all done on a microscale with one .1molar scale up to confirm it scaled, note that was on one compound only. How lovely for them, GC the reaction matrix, no workups, thirty compounds a day, well at least 5.

So it is essential to remove that water and besides there is nothing worse than performing an experiment that fails and because you haven't isolated your variables you have also learnt nothing.




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[*] posted on 17-9-2008 at 19:29


Well, would CaCl2 satisfactorily dry the ether and ethyl bromide? My sodium is of limited quantities at the moment and I would prefer not to waste it on drying ether. There shouldn't be a large amount of water, both sat over CaCl2 overnight, and the AgNO2 was in a MgSO4 desicator for a couple days, I just don't think it will be perfectly anhydrous as specified. Also, what signs should I notice if the reaction is working. After 6 hours it's still a clear solution (slightly yellow due to a rubber stopper) above a fine, lightly colored ppt. I, however, am not employing magnetic stirring though, as I dumped my last stir bar down the drain accidentally so I'm just swirling the flask every hour or so if possible.



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