Sciencemadness Discussion Board

Nitroethane synthesis trouble

Ormarion - 13-8-2023 at 02:19

Hello, i decided to create this post to maybe gather some opinions about the last test i did on nitroethane and its synthesis

I have been spending a few weeks on trying to improve its synthesis following different procedure without real success
(My goal would be to obtain enough in order to perfome some tiffeneau demjanov test)

I obviously tried the sodium ethyl sulfate pathway but the yeild obtained are really terrible

The second test i have done were to react ethyl bromide with NaNO2 using DMF as a solvent (all reagent were dried correctly). The reaction seem to perfom well as it heat up for several hours on its own (at around 40°C) and a very obvious precipitate form (NaBr i presume). After overnight stirring the mixture was added to 2 time its volume of ice cold water and extracted with DCM, the organic layer was then removed with my rotavap and the obtained liquid was shortpath distilled

In the end i obtained a yellow liquid with a density of 0,95 (DMF density basically) boiling between 115 and 130°C. I tried to do a flame test and surprisingly after a bit of heating it produce a weak white flame (I must also precise the liquid definitely have this acrid smell characteristic of nitroethane). I then tried to do mix the liquid in water but no phase separation occured... (maybe could attemp a extraction using LiCl ?)

Apparently im not the first one to who it happened to have issues during purification (some friends of mine got the same issues), someone i know also reported negative result using DMSO instead of DMF

My next try would probably involve using silver nitrite but even if you can recover the silver in the end it seem quite a lost to me

Any help would be welcome ! Thanks for reading

Fery - 13-8-2023 at 20:54

Yes these nitroalkanes burn with white flame. Nitroethane has very nice fruity scent. AgNO3 is too expensive. I cannot find from where I got nitroethane (it was years ago). I just found in documents that I got nitropropane from es-drei.de, SKU S1000710.25, but not nitroethane.
https://shop.es-drei.de/alkane/6637/1-nitropropan-min.-98?nu...
Someone is selling nitroethane from Italy (your neighboring country) on ebay, but the price seems to be unfair high for me:
https://www.ebay.com/sch/i.html?_nkw=nitroethane
https://www.ebay.com/itm/184636411795

Ormarion - 14-8-2023 at 08:20

Well i ended up ordering some from S3 as they are trusted seller i have even if it was pretty expensive. I just dont rly want to order such chemical from shady seller on ebay. However if anyone have proposition to improve the synth i would rly appreciate

Fery - 14-8-2023 at 10:16

You are right, I found that it could be misused as a precursor to illegal drugs, you do not know who is that ebay seller.
I found the synthesis you did in DMF solvent, by my opinion it looks like wasting a lot of solvents in 20-fold excess than the amount of the product so the price of solvents exceeds the price of the product significantly. Attached the pdf.

Attachment: jr9440000024.pdf (152kB)
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Then I found this:
https://erowid.org/archive/rhodium/chemistry/nitroethane.htm...
experiment 18 - someone tried to oxidize alanine with KMnO4 and decarboxylate the acid. They encountered well known problem for me, how nasty is fine MnO2 freshly produced from KMnO4 (I did few oxidations of oleic acid into azelaic so I really know not theoretically but practically and decades ago toluene into benzoic acid and naphthalene into phthalic acid). And the worse that they do not mention whether ever they got some yield.
Quote:

Method 18: Oxidation of alanine with permanganate followed by decarboxylation

Nitroethane via oxidation of alanine?

Theory

MeCH(NH2). COOH + 3(O) --> MeCH(NO2). COOH + H2O.

MeCH(NO2). COOH + NaOH --> MeCH(NO2). COONa.

MeCH(NO2). COONa + H2O --> MeCH2(NO2) + NaHCO3.

Procedure

A solution of potassium permanganate (0.3 mol) in water was made by dissolving 47.41 g KMnO4 in 400 mL hot water in a 1 L 3-necked flask fitted with a reflux condenser, a stirbar[note 1], thermometer, and a 100-mL addition funnel. As the solution cools to room temperature fine crystals of KMnO4 crystallise out of solution[note 2]. A solution of alanine (0.1 mol, 8.91 g) in 65 mL of water was placed in the addition funnel and added dropwise with stirring over a 20 minute period. The temperature slowly rose. When the addition was complete, the reaction mixture was heated to 60º over a period of approximately 2 hours. 40 mL of acetone was added [note 3] and then the reaction mixture maintained at 70-85º [the sludge was extremely viscous and the stirbar was of no use] for 2 hours. 0.1 mol sodium hydroxide in 20 mL of water was then added through the addition funnel.

Pause (to be completed).
The flask showed no sign of heating up after addition of the NaOH. By now the black/brown sludge will not mix (with the stir-bar). The next step is to heat to 80-100C to decarboxylate any nitro-propionic acid and then to steam distil.

Notes:

1. An overhead stirrer is essential - the stirbar will get clogged with MnO2.

2. KMnO4 solubility is 1 in 3.5 parts of hot water and 1 in 14 parts of cold water.

3. The acetone was added to try to clear the sludge. I would have added more but I had second thoughts.

Refs:

1. Synthesis Of Aliphatic And Alicyclic Nitro Compounds; Org. Syn. p 131-132 [The Oxidation of Amines]

2. Organic Syntheses, Vol. 52, pp 77-82, 2-Metryl-2-Nitrosopropane and its Dimer, A. Calder, A. R. Forrester and S. P. Hepburn.

3. Vogel's Practical Organic Chemistry, 4th ed. P 564 'Nitromethane'.

Questions:

1. Is it safe to heat this mixture to 90C without a stirrer? [the next step to make sure that nitro-propionic acid is decarboxylated]

2. Should I improvise an overhead stirrer to finish this off?

3. Nitroethane will steam distill won't it?

4. Should the permanganate have been buffered?

5. I think the NaOH should have been in there from the start. The sodium salt of alanine would have been a better idea?

6a. Would the reaction benefit from taking place in an organic solvent?

6b. If so, what solvents are suitable apart from acetone?

I will repeat this - with an overhead stirrer and the addition of sodium salt of alanine rather than alanine followed by NaOH.


then I found this video and the guy got some yield:
https://www.youtube.com/watch?v=vLArJ30X1_g

and there are of course few threads in our forum, the first one looks viable route and in the second one there are some useful suggestions:
http://www.sciencemadness.org/talk/viewthread.php?tid=15837
https://www.sciencemadness.org/whisper/viewthread.php?tid=73...

So I would vote for buying the product. But I understand the beauty of chemistry and sometimes it is more satisfying to synthesize something than just buying.

Ormarion - 14-8-2023 at 11:38

Thanks a lot this is a procedure i never saw before ! i will definitely give it a try on small scale

Also i must precise i didn't used the quantity of solvent they claimed, if i remember correctly thety used 600ml of DMF for 30g of NaNO2 and EtBr, i only used 200 without issues on the way it went i believe

Fery - 15-8-2023 at 01:50

I found that alanine + KMnO4 gives something else: CO2, oxalic acid, ammonia, nitric acid.

Attachment: 1-s2.0-S0021925818914390-main.pdf (195kB)
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Grizli7 - 13-12-2023 at 09:10

I got it from bromoethane via dimethyl sulfoxide - I didn’t really like the reaction. The yield is about 30% but I don’t remember exactly.

zed - 5-1-2024 at 16:22

Nitroethane is tough to make. Unfortunately, here in the USA, its sale is restricted.

Some of the guys here have suggested oxidizing Acetaldehyde Oxime, with
Sodium Perborate, in glacial Acetic Acid.

clearly_not_atara - 8-1-2024 at 14:40

Kornblum's method suggested EtBr and NaNO2 in DMF with catalytic urea and phloroglucinol or resorcinol. Since then, dozens of people have posted reports of attempting the method without phloroglucinol or resorcinol and usually also without urea. They then complain that it doesn't work.

Urea is OTC but phloroglucinol is not. The green tea polyphenol "EGCG" is reputed to cause various health effects by supplement vendors even though studies show it is not actually absorbed by the body. EGCG should mimic phloroglucinol or resorcinol at a 1:3 molar ratio (1 mole EGCG = 3 moles phloroglucinol).

So one possibility is EtBr and NaNO2 in DMF with catalytic urea and EGCG. You will try this method without the catalysts and come back to complain that it doesn't work. Don't say you weren't warned ;)