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Author: Subject: Synthesis of thioacetone?
macckone
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[*] posted on 4-3-2022 at 11:39


Fery,
Interesting paper on the working conditions.
glove box and destroying any vapors in situ.
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[*] posted on 5-3-2022 at 00:28


Hi macckone, I'm not so brave to crack the trimer to monomer, but maybe I will try to synthesize the trimer. Cracking requires quite strong conditions. I found in literature that during the synthesis of trimer, there is a lot of side product propane-2,2-dithiol "with an intensely powerful, disagreeable odor" (60-70% trithioacetone and 30-40% propane-2,2-dithiol, see the experiment in the attached pdf, they had to perform vacuum distillation to separate them). This side product (geminal dithiol) worries me more than the trithioacetone itself which is quite stable and hard to crack to monomer. My friend who already does organic chemistry business (still studying PhD) told me, that the trimer is in equilibrium with monomer so traces of monomer are always present. He also told me that he is specialized in organosulfur chemistry and performed a lot experiments in organosulfur syntesis. In university lab they finally always washed equipment with methanol or isopropanol, but once his schoolfellow mistakenly used acetone to wash a glass with remainders of P2S5 so the thioacetone "was cooked". It happened inside fume hood but the whole building was full of very bad odor. My friend also pointed me out, that using P2S5 is best with pyridine complex, otherwise P2S5 is very strong dehydrating agent because P2O5 is formed.
Yet I still did not succeed with preparation of thioformaldehyde trimer (I tried Na2S2O3 to avoid H2S but it did not work in my case). My first step would be trimer of thioformaldehyde = 1,3,5 trithiane and I will have to bubble the nasty H2S into the reaction (or drip solution of Na2S but that will introduce sulfur contamination as my Na2S is not colorless but yellow so with impurities of disulfide/polysulfides which would decompose to sulfur in solution with excess of HCl). Maybe only then I'll try the trimer of thioacetone somewhere in wood few kilometers away from civilization, maybe not (distillation of propane-2,2-dithiol is quite distractive for me, but maybe it could be separated by creating its Na salt by reaction with NaHCO3 or Na2CO3? which should be soluble in water unlike trithioacetone which is almost insoluble).

https://sci-hub.ee/10.1002/pol.1970.150080826

Attachment: pol.1970.150080826.pdf (728kB)
This file has been downloaded 566 times




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Lionel Spanner
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[*] posted on 10-3-2022 at 04:13


Quote: Originally posted by Keras  
What’s funny about thioacetone is that it seems to stink more in a diluted form (so far away from the source). I suspect, like H₂S, some sort of overload of the olfactory nerves when the concentration is too high.

Good target for a microscale experiment :p


Could also be down to its vapour pressure, i.e. it evaporates more quickly when diluted.




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Tsjerk
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[*] posted on 10-3-2022 at 04:50


No, because it is already evaporated when diluted. Also vapour pressure only starts playing a role in high relative concentrations, which I really hope no one is experiencing with thioacetone.
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[*] posted on 27-12-2022 at 02:14


I suppose it was inevitable that someone like NileRed would try to make it and post a video on it:

https://www.youtube.com/watch?v=LmAG8-V_WQY

Apparently not the first youtuber. LabCoatz beat him to it:

https://www.youtube.com/watch?v=E_wboFJZBTU&t=0s

PS:Happy new year everyone

[Edited on 12/27/2022 by wg48temp9]




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[*] posted on 27-12-2022 at 02:42


The famous NileRed that rents an island to make the stuff but later admits the nearest houses are only a couple hundred meters away...
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[*] posted on 27-12-2022 at 22:06


It should be possible, but please don't. You'll stink up your entire neighborhood.
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[*] posted on 28-12-2022 at 02:05


i like this topic.
i really want to make it
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[*] posted on 16-1-2023 at 20:34


Both NileRed and LabCoatz did not follow the original procedure that produced the infamous odor. In both the Freiburg incident [1] and Whitehall Soap Works [2] the procedure was to bubble H2S into a mixture of Acetone and HCl. It is likely the next step was taken immediately after which is to steam distill the trithioacetone. This is important because free thioacetone is not stable [3] and will likely polymerize shortly in storage.

Another error is smelling it up close. It is reported to smell worse in more dilution so it would be better to have a person far away walk towards where it is being produced to have a true sense of the odor.

I will attempt the synthesis when I can with both of these in mind and report the result.

An alternate method to produce monomeric thioacetone that does not involve cracking is bubbling H2S into an acidic solution of acetone ketal [3] [4]. Produces more monomer than cracking and seems easier.

Quote:

For each mole of the corresponding ketal or enol ether, double the amount by weight of glacial acetic acid and about 1 g of hydroquinone are added, 3 drops of concentrated sulfuric acid are added and a trickle of hydrogen sulfide is introduced until the theoretical amount is absorbed. As a rule, the reaction is completed after 15-20 min. Final temperature about 35 deg. The mixture is then poured into ice water, the insoluble organic phase is rapidly taken up in petroleum ether, purified and distilled in a column. The following aliphatic thioketones are extremely unpleasant and pervasive smelling, indeterminate, deep red oils. We report separately on thioacetone and on the chemistry and spectroscopic properties of the thiones.
[4]


[1] https://www.sci-hub.se/10.1002/cber.188902202151
[2] https://books.google.com/books?id=MSDOAAAAMAAJ&pg=RA3-PA... pg. 219
[3] https://www.sci-hub.se/10.1002/anie.196402771
[4] https://sci-hub.se/10.1002/cber.19630961139
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[*] posted on 16-1-2023 at 22:27


Hi zero, very useful information! Starting from acetone + HCl + H2S there is a side reaction producing 2,2 propanedithiol (30-40% dithiol while trimer of thioacetone 60-70%). As you wrote - it is necessary to column distil, otherwise you could smell this dithiol with a false hope that it is monomer of thioacetone. One of the mentioned youtubers whose knowledge as well practical skills in chemistry were inversely proportional to his courage even did not distill either did not apply vacuum to crack the trimer. The other who was more careful and has years of practical chemistry skills, at least used steam distillation in lab, but I do not know whether his vacuum pump running on electrical battery on the island produced sufficient vacuum level to crack the trimer (if the steam distillation was not sufficient to get rid of gem dithiol and vacuum level too weak then he could again smell the propane-2,2-dithiol instead of monomer of thioacetone). Anyway I appreciate that both were brave enough to try this experiment! One PhD student who is focused on organosulfur chemistry discouraged me to do such experiments if I would like to avoid contact with a team of professionals dressed in spacesuits arriving in big red truck with loud siren horn. He also told me a story how his university schoolmate mistakenly used acetone to clean a glass with remainders of P4S10-pyridine complex, the washings were poured into a waste container with acetone so an undesired product was cooked spontaneously. Acetone is the most commonly used solvent to clean a glass but in organosulfur chemistry I should use methanol.
If the reaction from acetone ketal you mentioned produces more monomer, that could be very interesting route.
Personally I would be more happy for the trimer of thioacetone which should have scent of some tropical fruit and is used in some candy. So far I was brave to synthesize only trimer of thioformaldehyde which I did outside of my house during night when there were no passersby on street and neighbors were inside their houses. The scent of H2S produced at 0,5 mol scale during few hours from which circa one half did not react and was vented into atmosphere, was terrible. I did not bother to trap the H2S into an alkaline / hypochlorite / permanganate solution and just did the trithioformaldehyde synthesis outside.
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[*] posted on 17-1-2023 at 02:14


I suppose thioacetone acts on the smell receptors the same way hydrogen sulphide does: at too high a concentration, the receptors become saturated and ‘pass out’. That would explain why the smell is worse at low concentrations, where the receptors are still fully functional.
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[*] posted on 17-1-2023 at 07:49


Fery: Saw your synthesis of thioformaldehyde, very nice! Do you know how far you could smell the H2S from?
You are correct that the gem-dithiol is formed but it is only mentioned with the ZnCl2 modification, not with the original HCl. Not saying it wouldn't be formed, but the references I have only mention it when using ZnCl2. [1]
Another reason I doubt both Nilered and Labcoatz succeeded is also in [1]:
Quote:

Thioacetone was prepared by pyrolyzing hexamethyl-s-trithiane on hot quartz rings under reduced pressure with subsequent quenching of the product as quickly as possible to -78°C. The pyrolysis temperature was fairly critical. Within the pressure range of 5-20 mm, a temperature below about 500°C permitted much of the trimer to survive. Above 650°C, decomposition to simpler compounds became excessive, and allene and hydrogen sulfide became important products. Under favorable conditions, 80% yield of red-orange, clear liquid monomer could be obtained, which could be redistilled quantitatively in a vacuum system.

The odor they describe is more like H2S, a thiol, or even the trimer evaporating unchanged. I don't think a blowtorch without argon or a vaccuum will produce much monomeric thioacetone.
According to the Esso researchers:
Quote:

Two of our chemists who had done no more than investigate the cracking of minute amounts of trithioacetone found themselves the object of hostile stares in a restaurant and suffered the humiliation of having a waitress spray the area around them with a deodorant.

Surely if either Nilered or Labcoatz made thioacetone, they would have a similar experience with family or friends? To be clear these researchers were working in a fumehood so imagine how tiny the amount of thioacetone got on them. In both the Freiburg incident and the Esso researchers mention the smell travelled about 0.5 km. Nilered was much closer than that to houses which likely would have complained and Labcoatz reported the smell only travelled 200 ft. Again, more consistent with H2S or a thiol.

Keras: Agreed, it does seem to overpower much like H2S.

I will be focusing on producing monomeric thioacetone from the ketal method since it should bypass the temperature control issues and the hydroquinone will prevent polymerization.

[1] https://sci-hub.se/10.1002/pol.1970.150080826

[Edited on 17-1-2023 by zero]

[Edited on 17-1-2023 by zero]
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Fery
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[*] posted on 17-1-2023 at 09:33


zero - my trithiane was not completely odorless, I smelled something a little sulfurous, but definintelly only veeeeery weak... that could also be some impurity... traces of organosulfur compounds have strong enough scent...
you can scent H2S from distance, it just depends on its concentration (amount and how fast are you releasing it into air) and the direction of wind... there is some threshold of H2S which could be found in some literature, below this threshold you do not scent it (in my synthesis I scented it from few meters already and circa 0,25 mol was released into air during few hours)... you can avoid that by trapping gas into alkaline solution / hypochlorite / permanganate etc... the last 2 trap and oxidize also escaping organosulfur compounds which have worse scents than H2S but I was just lazy to trap H2S because I did the reaction outside
you are right, cracking thioacetone trimer into monomer is not so easy... strong enough vacuum, narrow window of temperature, quickly cooling into very low temperature - otherwise polymerization occurs quickly:
https://sci-hub.ee/10.1016/0032-3861(67)90069-9
Attachment: 0032-3861(67)90069-9.pdf (1002kB)
This file has been downloaded 182 times

anyway if any of the 2 youtubers yield of monomer was something like 0,00000001% they would be able to notice its scent at this very low but sufficient concentration



[Edited on 17-1-2023 by Fery]
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[*] posted on 28-7-2023 at 04:39


Found another acetal based procudure. Uses anhydrous ethanol instead of GAA and no hydroquinone.

https://sci-hub.se/10.1016/S0040-4039(00)60029-1

Quote:

A solution of acetal (30-70 mmol) and zinc chloride (0.05-0.1 equivalent) in ethanol
(40 ml for 50 mmol) is cooled to 0°C. H2S is bubbled through the solution over 30 min.
After a few minutes a red colour appears. The extraction is executed by partition
between pentane and a 0.1 N HCl solution. The organic solution is then washed with
water, dried on MgSO4 and concentrated. The crude material is purified by flash
chromatography with pentane as eluent. Thioketones 3 are characterized by their NMR
spectra (2).

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[*] posted on 30-7-2023 at 00:14


There is a tendency: selenium and tellurium compounds smell worse than sulfur. If we already talking about something which requires evacuaction of a small village and stable only on low temperatures why not try with more potent chalcogens which could show less tendency to trimmerisation? If it would be microscale experiment it probaly will not lead to disaster, but who knows, may be it have a potention also to engrave a human history ...

[Edited on 30-7-2023 by teodor]
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[*] posted on 30-7-2023 at 11:14


teodor - firefighters would arrive...
my friend who has a company focused on organic synthesis told me, that their neighboring company doing inorganic syntheses attracted rescuers when synthesizing AlBr3 (they are suppliers of one big company with this compound) - one guy broke 2,5 L flask with bromine, he ended up in hospital (few operations - skin transplantation, few dialyses) and the sanitation of the factory was done by specialized firefighters... it happens also to professionals... my friend discouraged me to synthesize thioacetone so I synthesized trithiane instead (trimer of thioformaldehyde)... btw during university studies and now PhD he is focused on sulfur organochemistry... he also told me more stories, like that he always had to clean the apparatus with methanol, never with acetone, but his schoolmate once mistakenly used acetone (first as well last time) and poured it into waste container with remainders of sulfuration agents (like P4S10-pyridinium complex, Lawesson's reagent etc) so the undesired product "was cooked" (his exact words he used) and the people in building noticed it.
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[*] posted on 30-7-2023 at 12:28


Selenoketones dimerize, and telluroketones are very unstable so thioketones are easier to make.

The simplest experiment is recreate initial one by Fromm and Baumann that caused Freiburg incident.
Bubble H2S into cooled concentrated HCl (aq) + acetone (equal parts of each). After 10-12 hours no weight change, dilute with water and steam distill oil at the bottom. During this steam distillation is when the incident happened. Simple easy procedure. Possibly done in-situ by dropping a sulfide into mixture.
https://www.sci-hub.se/10.1002/cber.188902201224

The issue with the youtube experiments is that not steam distilled immediately. Thioacetone monomer degrades in the acidic conditions and by the time they distilled was all trimer. Only the tiniest trace of monomeric thioacetone will be present under the steam distillation conditions. Can be done at the 1g scale instead of 100g Fromm and Baumann used.
If I continue having issues making acetone acetals I will do this procedure in a remote area.
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[*] posted on 30-7-2023 at 20:08


There is also a sideproduct 2,2-propanedithiol. Youtubers very likely smelled this. Cracking trimer of thioacetone into monomer is very hard and keeping it in monomer form also not so easy.
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[*] posted on 31-7-2023 at 00:42


Do you think dithioacetic acid (C2H4S2) calcium salt will not give thioacetone on heating like calcium acetate gives acetone? The bubbling gasses and steam distillation are not simplest manipulations to be planned on microscale. But heating some dithioacetate with alcohol burner you can do in the middle of nowhere not be worring about firefighters.

[Edited on 31-7-2023 by teodor]
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[*] posted on 31-7-2023 at 05:12


If ketonic decarboxylation worked probably only get trithioacetone because of high temperature and acid conditions.

Bubbling gas is the difficult part. "Steam distillation" in this experiment can be boiling in an open container. This is easy with minimal equipment.
A modification with lower chance of success is instead of bubbling H2S, add FeS to the acidic acetone solution. H2S is generated in situ. With this modification the experiment can be done with only one or two containers and a heat source. Should fit in a backpack.
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[*] posted on 31-7-2023 at 05:44


Acid conditions?

I don't think saturation with H2S is a complex part, there is well known techniques how to do that even on micro scale. (I don't believe you need bubbling, I think saturation would be enough). Micro-scale steam distillation/purification is a complex part. Fery wants to get a pure compound to understand how it really smells.

Well, I can imagine 2 options:
1. Making an adduct. There are acetone adducts. Why shouldn't thiacetone monomer adducts be exist.
2. Zeolites or similar structures with pore sizes big enough for monomer but small for trimer.

[Edited on 31-7-2023 by teodor]
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[*] posted on 31-7-2023 at 06:55


During ketonic decarboxylation is there no free acid at all? Even so the high temperature will instantly trimerize the thioacetone unless it is so high it cracks it.

For isolation the ideal route seems the acetal one since the isolation is straightforward. The HCl + acetone + H2S route only makes enough thioacetone monomer to smell, not enough to isolate. Even on the 100g scale the monomer is not possible to isolate never mind microscale.
The idea was to "isolate" using large volume of air. Can set up reaction then run away down wind. At the right distance the only smell will be the thioacetone. Acetone, HCl, water will not smell from the distance. Trithioacetone smells fruity will not be confused. Thiols, dithiols, H2S may smell from a distance so need to go far. Thioacetone smells much stronger still so it will be the first component smelled.

Thioacetone and acetone behave differently, acetone adducts do not necessarily apply.
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[*] posted on 31-7-2023 at 07:45


Quote: Originally posted by zero  
During ketonic decarboxylation is there no free acid at all? Even so the high temperature will instantly trimerize the thioacetone unless it is so high it cracks it.


Fast heating with e.g. filament / electric current could be the option. After evaporation to air there is a little chance for it to trimerize.

OR drop a microgram of solid on something heated to a red-heat.


[Edited on 31-7-2023 by teodor]
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[*] posted on 14-8-2023 at 10:25


Found a reference to stop selenoketone and telluroketone speculation. Instead of more odor, seems less.


Quote:

Selenoketones also possess a very striking odor. It is, however, neither indescribably frightful nor does it contaminate whole sections of cities...
The odor is somewhat similar to that of garlic and mercaptans...
Recently four telluroketones have been prepared by the action of H2Te on the ketones...
The odor is disagreeable, but apparently less so than that of the selenium analogs.

https://www.sci-hub.se/10.1021/ed012p363
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[*] posted on 9-1-2024 at 10:51


Have not found suitable location for thioacetone experiments, but have more than enough materials (ketals) to attempt a microscale reaction.

Looks like Labcoatz will beat me to it, they will attempt to make thioacetone by Lawesson's Reagent. See description here: https://www.youtube.com/watch?v=ia4aEJvuiY4

Once I do find a location, will try but have low chance of success since I fail to get dry reagents like in my other experiments. Very excited to see Labcoatz results.

Even if I'm beat on this, have many more stinky projects ahead.
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