My Synthesis of Nitroethane via a AgNO2 Packed Column

Good day all,

It's bean rather exhaustively discussed on these boards and elsewhere for the better part of 25 years, and the consensus seems to be that it's a pain to make. That's because it is a pain to make.

Chemplayer's great video was still unfortunately a ton of setup and time for a relatively small yield. Silver being part of this reaction complicates it further from a monetary point of view as well.

I have recreated Chemplayer's Victor-Meyer style synthesis using anhydrous THF in lieu of Ether, and Bromoethane in lieu of Iodoethane, with similar (albeit worse) results.

Those who have read the literature know of course about the industrial methods using propane and ethane at 400 C and vapourized nitric acid etc etc; these industrial processes are best left alone. KABOOM comes to mind when I even think of trying one on a lab bench scale.

(As an aside, I did find one nitration of ethane that runs at 100 C, using UV light as the catalyst, paper attached below)

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Now, radiochemistry is not really something done in a home chemistry setting, which is why this method and it's paper might have slipped through the cracks a bit:

https://www.thevespiary.org/rhodium/Rhodium/Vespiary/talk/in...

About half way down the page there is a post by "no1uno" detailing an interesting method. I gave it a try, results below:


A jacketed Liebig condenser was lightly packed with a 90/10 AgNO2/Silica sand mix and a glass wool plug was inserted in the bottom. A glass takeoff adapter with a long glass hollow rod was led into Distilled H2O. About 1 Mole of AgNO2 was used (+/- 10% to make sure the Liebig was topped off)

A 1000 ml RBF was charged with 6 moles of Bromoethane (freezer stored, synthesized 1 year ago, dried using 3 Angstrom Molecular Sieves). A stir bar was inserted and the flask placed in a heating mantle. One neck of the flask was then connected with a 3 way distillation adapter, and the AgNO2 packed Liebig was connected to this adapter giving it a slight downward angle which helped facilitate product collection (IMO).

I did not use an N2 or a CO2 stream of dried carrier gas as per the paper. I settled on a 24/29 12 inch 3.3 boro tube packed with CaCl2 and a small aquarium style air pump to bubble dried room temp air into the Bromoethane as it was being heated and help push it into the AgNO2 packed Liebig.

The AgNO2 packed Liebig had its jacket connected to a small pressure cooker that was delivering steam to the jacket to keep it at approximately 100 Degrees C for the entirety of the run. A Jacketed HPLC column would have been even more ideal however I do not own a jacketed one and the Liebig seemed a good compromise.

Steam was introduced to the AgNO2 packed Liebig, and the heating mantle was turned on. Bromoethanes boiling point is 38.4 C, so not much heat was required to vapourize it. The air pump was turned on (very light flow, basically enough to keep positive pressure and encourage the Bromoethane to flow into the AgNO2 packed Liebig).

About 1.5 hours were required to send a majority (approx 25 ml left in the distilling flask) of the Bromoethane through the AgNO2 packed Liebig, and the dried air positive pressure flow helped to push the effluent reaction mix down into the Distilled H2O. I used a conical 1000 ml flask with a take off side arm as the receiving flask, and then ran the take off into another 1000 ml conical flask just to ensure I captured as much as possible. The paper uses DMSO to capture the nitroalkanes, but I am all out of DMSO currently.

The pressure cooker, mantle and air pump were turned off and the entire setup was allowed to come back to room temperature.

The Distilled H2O receiving flask (Just the first one in the train) had 2 semi-opaque layers. This was put into a sep funnel, and the top aqueous layer retained and extracted with 50 ml of DCM once.

The organic layer was pooled with the DCM extraction, and dried over CaCl2 for several hours in the fridge. The flask was rigged for fractional distillation on a hotplate with stir bar added.

The Bromoethane came off intermixed with the DCM (their boiling points are basically the same). I chose DCM because I would rather contaminate my cheap and easily made Bromoethane than face a toluene azeotrope / pure toluene boiling point(s) of 80/110 C respectively, the latter which would definitely co-mingle with any Nitroethane coming off at circa 114 C. In hindsight I would not have pooled my DCM extract with my main organic layer and worked it up separately.

After removing approximately 350 ml of seemingly unreacted Bromoethane and DCM (very volatile so no doubt mechanical losses as well as evaporative losses as well throughout the process) through fractional distillation, the temperature climbed past 110 C and around 112 C a slightly yellow oily liquid came over.

The collection flask was changed out and approx 10 ml of what was assumed to be Nitroethane was collected. Its characteristic smell was compared to a known authentic sample (briefly, as its..... you know.... toxic.....).

This yield is a very poor 14% based on starting silver nitrite, with a 6 x molar excess of Bromoethane thrown in to boot.

HOWEVER, given the cost of Bromoethane and the ease of this solvent-free setup, I feel that if I tweak this procedure to be more in line with the paper, coupled with all the potentially unreacted Bromoethane recovered during workup, we could have a very viable source of Nitroethane!



The next time I run this experiment I will take and post photos of the entire thing. Questions and comments are welcome!



Sources:





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[Edited on 16-4-2020 by Johnny Windchimes]

It's nice to see someone posting results. Everyone talks about nitroethane syntheses but no one ever posts results.

Have you ever tried the bromoethane and sodium nitrite in DMSO reaction? https://www.hyperlab.info/inv/index.php?s=61ad7dd3930f684e12... (Run it through Google translate.) I plan on running this in the coming months. I've heard a lot of people fail miserably with this reaction but then there are a few -- not many -- posts which show it works quite well for how cheap the reagents are. This reaction is all based on the work of Kornblum, see the following links:

DOI: 10.1021/ja01588a059
DOI: 10.1021/jo01355a612
DOI: 10.1039/B805985C

Quote: Originally posted by chemplayer...

The holy grail is finding the conditions or OTC solvent that can do this with sodium nitrite. We wondered if acetonitrile might work, but never got the time to try it out.

Two steps forward.....

Although it might be going in the wrong direction insofar as OTC goes....

These two papers use Polymer suspended nitrite to get the job done. This is prepared from Sodium Nitrite as opposed to the pricey Silver Nitrite as well.

I have nothing against Iranian chemistry, or the Journal of The Chinese Chemical Society per se (re: Zarchi 2005), but it seems in line with Gelbard 1977 in relation to the theory at least. The polymer Zarchi use's is a tad more exotic, but I found it easily on Alibaba once typing in the CAS number. Some people I've noticed don't trust out of the way journals or chemistry at face value, for perhaps good reason.... but it looks legit (in my infinite wisdom haha).

Worth mentioning is Zarchi also in his paper directly synthesizes Nitroethane (among other Nitroalkanes) as opposed to everyone else who makes longer chain Nitroalkanes and only allude to their methods short chain Nitroalkane application(s).



And I'll throw in Ballini & Palmieri's 2018 Nitroalkane Review paper too for kicks. It's nice to know these boys are dedicated over the years....


If the PEG-400 Synthesis fails I'll give the polymer ones a try as well. I'm kinda addicted to finding a reasonably working method at this point!

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[Edited on 18-4-2020 by Johnny Windchimes]

Quote: Originally posted by chemplayer...

The holy grail is finding the conditions or OTC solvent that can do this with sodium nitrite.

Quote: Originally posted by clearly_not_atara

Quote: The holy grail is finding the conditions or OTC solvent that can do this with sodium nitrite. Anethole is way cheaper than silver and nobody ever seems to think about the anethole pseudonitrosite method. Only sodium nitrite is required. The only other difficult chemical needed for the pseudonitrosite rxn is diethyl ether. Shulgin demonstrated the retro-Henry reaction using alpha-methylbenzylamine but I imagine you could get pretty similar results with beta-phenethylamine or any of the other known methods for hydrolysing a nitroalkene. There is also a direct anhydrous cleavage of nitroalcohols: https://www.thieme-connect.com/products/ejournals/pdf/10.105... I am not sure if copper in wet conditions could catalyze the same thing but it seems interesting. [Edited on 19-4-2020 by clearly_not_atara]

Interesting, I saw that you advocated for this method in another Nitroethane thread in 2019. Let me see if I can dig it up....

http://www.sciencemadness.org/talk/viewthread.php?tid=40137&...

There we are. Yeah looks interesting I'll dive into that one too. It's a quiet Sunday so I'll start with this great piece on Nitroso compounds by Gowenlock.

Attached below~


Unfortunately if anyone was to need gallons of Nitroethane they would need to rely on one of the industrial processes miniaturized. Bubbling propane through heated Nitric Acid and then shoving it all into a 450 C heated tube sounds super safe and fun to me.... But I don't think my wife would want that device in our garden shed.... or anywhere on the property in general.

These boys tried a mini propane heated nitration and man what a ton of work. Paper attached below~

I don't need gallons, but it would be nice to find a reasonably scalable synthesis!~



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[Edited on 19-4-2020 by Johnny Windchimes]

Quote: Originally posted by draculic acid69

Firstly nice write-up. The price of silver salts and brominating ethanol make this a pretty expensive experiment.

Quote: Originally posted by outer_limits

Quote: Originally posted by draculic acid69   Firstly nice write-up. The price of silver salts and brominating ethanol make this a pretty expensive experiment. I'd say that it's expensive only because of silver and it's salts prices. But sometimes you can buy some good quality silver fairly cheap and make silver nitrite on your own. So the costs could be reduced.

Quote: Originally posted by clearly_not_atara

Quote: I can get silver at a great price but buying silver and whatever else to make it takes time and the costs add up.i don't think it is as easy as nitrate.then making 6+ moles of bromoethane =more time and money. If there is one thing that seems to be the rule with nitroethane, it is that lazy people get no yield. The ethyl sulfate route works well when it is performed with a well-planned setup and careful technique. Antoncho's method is news to nobody. Of course, the anethole route is still much easier. I plan to type that sentence approximately five thousand times over the next ten years.

500 ml of Anethole oil ordered as well It wasn't too bad of a price.

This thing, as you've posted it (and I've looked into as well), is rather "Hivey".... like you did mention. Nothing wrong with that at all, but some stuff there is a bit shaky on the details.

This one seems decently descriptive though. I can see the Nitropropene angles for their purposes, and I suppose by decomposing / hydrolysing at the end I'd essentially be "ruining" the proposed drug synthesis and ending back up with the 'starting' nitroethane, insofar as 'starting' can be ascribed.

I like the idea of using bisulfite to adduct out the aldehyde right in the same pot too, then filtering, seems slick.

If you add in the electro-synthesis of nitroethane (oh yes, I'm totally going after these 2 sentence throwaway blurbs from 1895 involving sodium propionate and sodium nitrite I saw in a google book search baby!!), I'll have my hands full!!

I've attached Hofer's Electro paper. It's in German. I'll havta have it translated to get the experimental procedure with a hope of recreating it, any helpful German volunteers?

PEG-400 first!








[Edited on 23-4-2020 by Johnny Windchimes]

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[Edited on 23-4-2020 by Johnny Windchimes]