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Author: Subject: How bad is the smell of thiols?
theAngryLittleBunny
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[*] posted on 19-12-2021 at 02:34
How bad is the smell of thiols?


Hello, so I would need some small alkylthiols (like ethanthiol, propanthiol, so on) because I wanna make some thioether compounds.

Thiols seem easy to make, however I'm worried about the smell, especially since they are added to gas in tiny amounts so people can smell if there is a gas leak. I don't wanna make all my neighbors think that there is a gas leak for obvious reasons. Even worse, I've also heard a case where a little bit of thioaceton was spilled and the smell made people hundreds of meters away sick. I don't know if thiols smell nearly as bad as thioaceton though.

I only need tiny amounts, a few milliliters. An easy way to make them is apparently heating a bromoalkane with thiourea and hydrolyzing the resulting compound with alkali hydroxide.
Another method would be to react alkyl bromides with lithium to make alkyl lithium and then reacting this with sulfur to get the lithium thiolate salt. I would then react that thiolate directly with an aryl bromide to form the ether, that way I wouldn't have to deal with thiols at all. I think I could also store any thiols just as the thiolate salt to avoid the smell and risk of spilling it. I also have KMnO4 to destroy any thiols in waste solutions.

Are thiols comparable to H2S? As far as I the odor threshold for H2S for humans is 0.2ppb, and the odor threshold for small thiols is in the single digit ppb area, so it shouldn't be worse then H2S, right? I hope someone who worked with thiols can tell me more, I'd appreciate it.
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[*] posted on 19-12-2021 at 04:47


We had to analyse a gasket that was contaminated with ethanthiol once.
When we opened the steel tin that it had been sealed in two things happened.
One was that we closed the tin again.
The other was that people in the area started to call the emergency services to report a gas leak.
The fume cupboard vents had done a fine job of spreading the stuff about.

Eventually we worked out that we could quickly hack a sample off the gasket and soak it in bleach for a few days, then analyse it and confirm that it was made from a polymer that you shouldn't use to seal a tank of ethyl mercaptan.

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[*] posted on 19-12-2021 at 04:49


Quote: Originally posted by theAngryLittleBunny  


I only need tiny amounts, a few milliliters.

I don't think you really need it at all.

Do you have access to an open area a mile or so across?
If not, you are asking for trouble.
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Tsjerk
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[*] posted on 19-12-2021 at 05:13


I could be a bit off, but a quick calculation tells me 1 gram ethanthiol can be smelled in an area of 600x600 meters if it is nicely dispersed in the bottom 2 meters. Of course that would also mean 3000 x 120 meters, given a bit of wind.

You should have a look at other ways for making thioethers, without needing the free thiol.

[Edited on 19-12-2021 by Tsjerk]
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[*] posted on 19-12-2021 at 05:29


theAngryLittleBunny this is not exactly thioether, but maybe something less risky, the trimer of thioformaldehyde = 1,3,5 trithiane
https://en.wikipedia.org/wiki/1,3,5-Trithiane
here a one pot method from formaldehyde + Na2S2O3 + HCl:
https://www.sciencemadness.org/whisper/viewthread.php?tid=11...




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BromicAcid
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[*] posted on 19-12-2021 at 07:08


The smell of the thiol depends of course on the R-group attached to it. I've worked with methyl mercaptan through some of the heavier dodecyl mercaptans. Honestly thiol has never bothered me near as much as the smell of isonitriles. But a little does go a long way and it's crazy easy for the wind to change direction and a tiny amount of mercpatan goes towards a neighbors home and suddenly the gas company is making the rounds. There was a thio silane we used at work for an operation, a single drop of it placed in the production bay generated a detectable smell on the street outside the building during testing.



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theAngryLittleBunny
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[*] posted on 19-12-2021 at 07:29


Oh shit okay that sounds pretty bad, the odor threshold of propanethiol is 30 to 500 times lower then that of bromine.

I don't need the free thiol, I need it as a thiolate salt, like sodium propanethiolate for instance. If I would make it from alkyl lithium I would get the lithium salt and I would react that directly without isolating it, or do the thioalkoxide salts give of a significant amount of thiol?

But yeah I'll see if I find another way to do it, which sucks because using thiols would be the easiest way.
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[*] posted on 19-12-2021 at 07:30


Quote: Originally posted by Fery  
theAngryLittleBunny this is not exactly thioether, but maybe something less risky, the trimer of thioformaldehyde = 1,3,5 trithiane
https://en.wikipedia.org/wiki/1,3,5-Trithiane
here a one pot method from formaldehyde + Na2S2O3 + HCl:
https://www.sciencemadness.org/whisper/viewthread.php?tid=11...


Thanks, but I don't just wanna make any thiolether, I wanna attack an alkylthiogroup onto an aromatic ring.
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[*] posted on 19-12-2021 at 08:40


Quote: Originally posted by unionised  
Quote: Originally posted by theAngryLittleBunny  


I only need tiny amounts, a few milliliters.

I don't think you really need it at all.

Do you have access to an open area a mile or so across?
If not, you are asking for trouble.


I have fields nearby where I could be over 1Km away from any populated area, if I go a bit further I would even be at least 1Km away from any street and train track. I thought about preparing everything and then going there at night to do the reactions involving any thiols. Then I'd just destroy any remaining thiol with KMnO4 and bring it back home. The fact that it's winter here atm is also an advantage.
I'm sure I could fit everything I need for this reaction in a backback. Maybe I'll get a small tent to have the full camping experience lol.
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[*] posted on 19-12-2021 at 08:45


I recently had the displeasure of working with thiophenol, which smells quite despicable. Take the generic stinky gas smell of ethanethiol that we all know and add some notes of burning tires and rotten meat.

Even so, I had to work with selenophenol after that, and that was far worse. Take every unpleasant quality of thiophenol and multiply it tenfold. Even working in a hood and taking great care not to remove it without first neutralizing it with bleach, everyone in the lab still managed to catch a whiff. The awful smell lingered in my nose too, until I could go home and take a hot shower to steam it out.




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[*] posted on 19-12-2021 at 08:55


Quote: Originally posted by Tsjerk  
I could be a bit off, but a quick calculation tells me 1 gram ethanthiol can be smelled in an area of 600x600 meters if it is nicely dispersed in the bottom 2 meters. Of course that would also mean 3000 x 120 meters, given a bit of wind.

You should have a look at other ways for making thioethers, without needing the free thiol.

[Edited on 19-12-2021 by Tsjerk]


I got similar numbers, a bit over 1000 cubic meters per gram of ethanthiol or propanethiol if I use the lowest reported odor threshold. However 1g of ethanthiol vapour wouldn't stay near the ground for long, especially if there is any wind. It would quickly disperse in any direction. And if you work properly you can easily keep the amount that evapourates far below 1g. But a spill would be quite bad.
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[*] posted on 19-12-2021 at 09:09


Do you guys know some older appartment houses which for some reason always tend to smell like boiled cabbages?
Especially in those eastern european style highrise building styles, oh I see its even called "plattenbau" in english.

Thats actually the smell of decades of thiols which likely really stem from boiled cabbages that get adsorbed into the buildings material.
Do you want to do this inside?
You might turn the whole building into becoming cabbagey-smelling over night! :D




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[*] posted on 19-12-2021 at 11:24


Thiols are pretty bad. A very old bottle of ethane-1,2-dithiol was horrendous. The smell escaped the hood and seemingly lingered for days, like a war flashback. 1-propanethiol, also not a new bottle, wasn't as bad (almost didn't really smell it using it in the hood) but it's still very gross. Burnt rubber, gas leak, metallic death stench, and cabbage fart all apply I think.

Thiouroniums from the alkylation of thiourea works great, another advantage is the thiol can sort of be generated "in situ" for some reactions with the thiouronium salt.

[Edited on 19-12-2021 by myr]
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[*] posted on 19-12-2021 at 11:31


Quote: Originally posted by theAngryLittleBunny  

I don't need the free thiol, I need it as a thiolate salt, like sodium propanethiolate for instance. If I would make it from alkyl lithium I would get the lithium salt and I would react that directly without isolating it, or do the thioalkoxide salts give of a significant amount of thiol?


Thiolates don't smell, just be damn sure not to add any acid. What would the reaction conditions be? And how do you work up the product?
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[*] posted on 19-12-2021 at 12:12


Quote: Originally posted by Tsjerk  
Quote: Originally posted by theAngryLittleBunny  

I don't need the free thiol, I need it as a thiolate salt, like sodium propanethiolate for instance. If I would make it from alkyl lithium I would get the lithium salt and I would react that directly without isolating it, or do the thioalkoxide salts give of a significant amount of thiol?


Thiolates don't smell, just be damn sure not to add any acid. What would the reaction conditions be? And how do you work up the product?


Okay, I thought the CO2 and water from the air would react with it. I still might go outside on the fields to try it just to be sure. After reacting the alkyllithium with sulfur to the lithium thiolate I would evapourate the solvent and add DMF and an aryl bromide and let it react for a day, this should form the aryl alkyl thioether. I would then dilute the reaction mix with water and extract the product with an organic solvent. Then I add an oxidizer like KMnO4 to the aqueous solution to destroy any excess thiolate dissolved in it.
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[*] posted on 19-12-2021 at 12:47


Thiols are about as acidic as phenols (pKa around 10), so a sample of the thiolate will slowly absorb CO2 from the air and start to smell.

Cleaning everything up with bleach should get rid of it- no need to resort to KMnO4.




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Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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[*] posted on 19-12-2021 at 12:50


Quote: Originally posted by DraconicAcid  
Thiols are about as acidic as phenols (pKa around 10), so a sample of the thiolate will slowly absorb CO2 from the air and start to smell.

Cleaning everything up with bleach should get rid of it- no need to resort to KMnO4.


Thanks, and I have no bleach, but I could use calcium hypochlorite.
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[*] posted on 19-12-2021 at 12:55


You can't buy bleach cheaply and easily in any grocery store? Any household cleanser containing hypochlorites would work- I just can't see wasting real chemicals on cleaning.



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[*] posted on 19-12-2021 at 13:04


Years ago I was given a mixture of thiols, it was added to propane and butane. It was in the PET bottle, I put it in a few plastic bags and snatched it well. I finally found that the platic bag I was holding in my hand smelled of thiols that did not go away even after washing, the smell was so pungent and unpleasant that I did not even put a lid on the bottle, I have never used it and threw it away.



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[*] posted on 19-12-2021 at 13:07


Recently I obtained small bottle of 2,3-dimercapto-1-propanol, which is an antidote against Lewisite, As, Hg, Bi, Sb, Tl, Pb poisoning.
Now I'm a little afraid to even touch it. The flask has special cover to prevent shattering the glass.
Is this stuff so bad too or is it less unpleasant than monomercaptanes (thanks to much higher boiling point)? Why should it be stored in fridge at 4 C?


IMG_20211219_215537_9_sm.jpg - 34kB IMG_20211219_215608_4_sm.jpg - 29kB

[Edited on 19-12-2021 by Fery]




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[*] posted on 20-12-2021 at 06:04


Accident on an industrial level involving thiols:

https://www.bbc.com/news/world-europe-21147361

The factory burned in a separate incident since then...




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[*] posted on 26-12-2021 at 08:51


theAngryLittleBunny, I found this one pot synthesis of thioethers
https://library.sciencemadness.org/library/books/Weygand_and...

Quote:
page 637
Diethyl sulfide: Finely powdered thiourea (86g, 1.1 moles) is boiled with ethanol (50ml) and
ethyl bromide (109 g, 1 mole) under reflux for 6 h; towards the end of this time the thiourea
dissolves. The solution is evaporated in a vacuum on the water-bath and, without waiting
for the residue to crystallize, water (100 ml) is added through a dropping funnel, followed
by a solution of sodium or potassium hydroxide (4 moles) in water (200 ml) during 10 min
with stirring. This mixture is boiled for an hour under a very efficient reflux condenser; it
is then cooled, ethyl bromide (164 g, 1.5 moles) is dropped in during 30min, and gentle boiling is
renewed for 5 h. The reflux condenser is replaced by a descending condenser, and the mixture
is distilled until 1 L of distillate has collected; the volume of liquid in the distillation flask
must be kept constant by continual addition of water, so as to avoid separation of potassium
or sodium bromide. The distillate is acidified, with cooling, by concentrated hydrochloric
acid and again similarly distilled (1 L of distillate). The diethyl sulfide is separated in a separatory
funnel, washed with 10% sodium hydroxide solution and then with water, dried over calcium
chloride, and distilled through a 20-cm Vigreux column, then having b.p. 90-92° (65 % yield).
Dimethyl and dipropyl sulfide are obtained similarly in 60% yield.
Mixed sulfides can be prepared by reaction of alkyl or aryl halides with
thiols or better, because of their greater reactivity, with thiolates:
RSNa + R'Cl -> RSR' + NaCl
The reaction is most satisfactory with alkyl and aryl bromides, since the chlorides
are mostly insufficiently reactive.


I'm not so skilled to know whether during reflux with hydroxide some small quantities of free thiol couldn't be released - I would perform the first attempt at microgram scale in a closed apparatus from which I would lead a tube into solution of Ca(OCl)2 to capture everything escaping.




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[*] posted on 1-1-2022 at 13:54


I always wanted to get into sulfur chemistry, but unfortunately their smell is potent enough that even with a big property, several households in a mile radius could call 911 to report a gas leak and get you in big trouble.
Think about the fact that one skunk spray can make a radius of several miles smell gross for hours.
Would it be sufficient if you used an air-tight apparatus in which all outgoing air is bubbled through bleach to neutralize the thiol?

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[Edited on 1-1-2022 by MichaelBijanAfghani]




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